Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech

agrotech.dk

Article. Energy in fokus - from Kyoto to Copenhagen. - AgroTech

ENERGY IN FOCUS

EnErgy in Focus

- From Kyoto to copenhagen

Institute for Agri Technology and Food Innovation

gartner

tidende


NOT ONLY GREEN

ON THE OUTSIDE

For further information about business development

and sustainable greenhouses of the future please

visit our website agrotech.dk/plantpower.

Institute for Agri Technology and Food Innovation


Jesper Mazanti Aaslyng

Head of Department, AgroTech

– Institute for Agri Technology

and Food Innovation

We need PlantPower

Energy is one of our most important resources, and it will continue to be so in the future.

We’ve been hearing this for a long time, so what’s different now?

The greenhouse sector, technology companies and knowledge institutions have been reducing energy

consumption for many years. Several projects are extremely promising. Now we are in a phase moving from

research to innovation. Development is still necessary, but we must also reap the rewards of our experience so

far, and results must be implemented.

We believe that the time is ripe to bring into use many of the technologies which have been developed

and which are still being developed. External factors such as high energy prices and government demands for

reduced energy consumption by the sector are also calling for this change process.

We must think innovatively and reduce energy consumption in every way conceivable. Changes in climate

regulation, LED lights, new sensors, new plant species, new curtains, and better climate screens are just some

of the possibilities. We have to adjust ideas from the closed greenhouse concept, and continue harvesting and

exploiting the surplus energy generated in greenhouses during the summer.

Under the PlantPower banner, the Danish company AgroTech – Institute for Agri Technology and Food

Innovation, has initiated several projects aiming at creating the sustainable, energy-producing greenhouse.

Many enterprises and knowledge institutions are involved, as only through concerted efforts can we meet this

challenge.

It must be possible to build the greenhouse of the future with the same pride as CO2-neutral towns are

being built today throughout the world. Greenhouses should not be mere CO2-neutral production areas, they

must also have a positive CO2 account and they must be a high-quality product which is an integral part of a

biological cycle. This must be the long-term goal of the sector.

Several projects have already started to achieve this goal and ’Energy in focus, from Kyoto to Copenhagen

is providing some of the first results of these projects. Let us together harvest PlantPower for the future.

The projects are sponsored by the participating companies and institutions, Region South Denmark, the European

Regional Fund and the Danish Agency for Science, Technology and Innovation under the Ministry of Science.

4 Hjortebjerg greenhouse nursery

6 Towards a semiclosed greenhouse

8 Development of future greenhouse climate control

10 Optimisation of climate management with Climate Check and Plant Check

11 Environmental sensors for harsh environments

12 Energy savings in Danish greenhouse production

14 Ventilators save energy

16 Energy extraction from greenhouse companies with district heating

17 What can we use NIR curtains for?

18 Dynamic management of supplemental light

19 Artificial lighting and lighting control of the future

20 The sun as a potential source of energy

22 Purchase electricity when it is cheapest – automatically

23 Renewable energy and the storage issue

24 Dynamic climate control works – worldwide

28 Two organizations working for the same cause

30 Plants on wheels reduce the carbon footprint

33 Intelligent us of Energy in Greenhouses

Mini symposium / Workshop 6-7 October 2009 Odense

Publisher: AgroTech A/S, Udkærsvej 15, 8200 Aarhus N, Denmark • Production: Gartner Tidende / MarkTing a/s • Print: Rosendahls


Ole Skov, oes@agrotech.dk and Janni B. Lund, jbl@agrotech.dk, consultants, AgroTech

Hjortebjerg greenhouse

– a demonstration facility for new energy technologies

What can we do right now to reduce

the consumption of fossil fuels in

the greenhouse sector? What technologies

should we concentrate on in the future?

Researchers, consultants and technology

enterprises working with the greenhouse

sector have tried to answer these questions

in collaboration with the sector.

An innovation consortium, a demonstration

project and various other cooperation

projects have been started in this

connection, and these mean that today a

4,000 m2 demonstration greenhouse has

been set up at Hjortebjerg. Furthermore,

an exhibition has been set up at Hjortebjerg

which shows the technologies which

can be used right now and in the future.

Our short-term goal is energy savings

of 60 percent and the long term goal is to

make the greenhouse sector a net energy

producer.

The owners of Hjortebjerg would like

to make production more energy friendly

- But it must also be financially viable

and we won’t compromise on the quality

of the plants, says Steen Thomsen, joint

owner and responsible for energy management

at the production plant.

The demonstration greenhouse is

located as an extension of the production

sections. The greenhouse is a standard

Venlo Block with single glazing in the

roof surfaces and two-layer channel plates

in the sides and gables, supplied by

Viemose-Driboga.

Exhibition

at Hjortebjerg

Extraction and storage

of surplus heat

We know that if the heat from the summer

could be stored until the winter, greenhouses

could be self-sufficient in energy.

The challenge is to store the heat as energy

which can be reused. There are several

energy-storage possibilities, and for this

project it was decided to store the energy

underground.

Studies show that much of the Danish

subsurface could be used for this type

of storage. The Netherlands has a lot of

experience with this type of plant. In

Denmark, in order to install such a plant,

a permit must be obtained from the local

authorities.

The plant at Hjortebjerg can be considered

a semi closed system because experience

has shown that it is best not to have

the windows closed all the time which

would also require a very large cooling

capacity on hot summer days.

The climate inside the greenhouses is

managed according to principles developed

over a number of years, such as

dynamic climate control, which will provide

the possibility for optimal plant production

and energy reductions in heating

of at least 50 %.

It is usually necessary to drill down to

70-100 m, but at Hjortebjerg 40 m was

enough. Drilling was carried out by a

Danish firm, Enopsol, while the extraction

units, comprising 24 JSK units located bet-

From October to January, there is an exhibition

at Hjortebjerg of the technologies currently being used,

as well as future technologies such as LED lighting.

It is possible to arrange a visit to Hjortebjerg

Contact: Janni B. Lund, project manager

jbl@agrotech.dk +45 2338 0559

ween the columns in the greenhouse, were

supplied by the Dutch company Wilk van

der Sande.

In order to extract as high temperature

as possible, ‘chimneys’ were built from

the extraction plant and up to the ridge,

where the temperature is more than 40°C

for long periods. The energy extracted is

stored in the underground magazine at an

average temperature of 30°C. When the

energy extracted is to be reused, the water

is heated from the 30°C to 70°C via a CO2

-based heat pump, supplied by Advansor.

New types of curtains

Two curtains have been set up in the

demonstration greenhouse. Both curtains

are from Ludvig Svensson. One curtain

is for insulation and shade (LS16), and

the other is a new curtain, an NIR (Near

Infrared Reflecting) curtain, which reflects

large parts of the heat radiation in the

near-infrared area of the spectrum (heat

radiation) and allows the photosynthesisactive

light to pass through.

LS 16 has a shade rate of 60 % for the

whole spectrum, while the NIR curtain has

a shade rate of 20 % for photosynthesisactive

light and 80 % t for heat radiation

from 800 nm to 1200 nm. The curtains

are controlled so that they ensure optimal

climate conditions for the plants, and so

that, during extraction, the air circulation

creates optimises the extraction of heat

from the air. During extraction, the NIR

curtain must be used to separate the layer

above and below the curtain. The curtain is

opened with slits of at least 15% t in order

to ensure the required air circulation.

Optimal climate control

A climate control computer (LCC Completa)

from Senmatic was installed in the

new section, with software developed in

a collaboration between Senmatic, The

University of Southern Denmark, Aarhus

University and AgroTech.

The new software is to ensure optimal

use of the energy with respect to plant

growth. In order to optimize management,

better measurements of the climate con-

4 ENERGY IN FOCUS


nursery

ditions for the plants are required. In the

demonstration house, new sensors are

being tested which are under development

at Danfoss IXA Sensor Technologies

in cooperation with Senmatic, DELTA and

AgroTech. The aim is to make cheap, reliable,

durable cordless sensors, and these

are expected to be commercially available

in a few years.

Other initiatives at Hjortebjerg

In addition to taking part in the projects

involving the demonstration greenhouse,

Hjortebjerg have also reduced the energy

costs by having a Climate Check carried

out by AgroTech.

This resulted in reductions in energy

consumption of 35 % from 2007-2008.

Moreover, one of the three Caterpillar

motors in Hjortebjerg’s combined heat

and power plant has been replaced with a

more energy-efficient motor.

What the future will bring for Hjortebjerg

is as yet uncertain but, as Steen

Thomsen says, “we will keep a watchful

eye on solar cell technology, which we

expect we will be able to combine with

underground energy storage. We are also

keeping an eye on the increasing demands

to minimise resources, which in the future

will involve far more than just energy”.


Hjortebjerg I/S

The history of Hjortebjerg goes back

to 1933 and today it is one of Denmark’s

largest suppliers of the pot

plants Saint Paulia and Euphorbia

milii. Five-six million pot plants are

produced each year on about 51,000

m 2 , of which 80 % are exported. The

plant is extremely modern, with a

high degree of automation. The enterprise

is owned by Jørgen Thomsen

and his sons, Gert, Alex and Steen.

The Danish Nursery Hjortebjerg has taken

a huge step into the future with the establishment

of a demonstration greenhouse for testing

of new energy saving technology

ENERGY IN FOCUS 5


Silke Hemming, Wageningen UR Greenhouse Horticulture, The Netherlands, silke.hemming@wur.nl

Towards the semiclosed

The liberalisation of the energy market

has increased the awareness of

the energy consumption. This free market

implies that growers do not pay a fixed

price per unit of natural gas anymore, but

that prices are greatly determined by the

maximum supply capacity of the gas contract.

Therefore, it is important to reduce

peaks in energy use.

Improved energy efficiency

In view of the Kyoto protocol several

governments have set goals for energy use

and CO2 emission. In the Netherlands, the

horticultural sector and government have

agreed to improve the energy efficiency

(production per unit of energy) by 65% in

2010 compared to 1980 and to increase

the contribution of sustainable energy to

4%. Over the period 1980 - 2005, energy

efficiency in Dutch greenhouse industry

has more than doubled. However, total

energy use per square meter of greenhouse

hardly changed. Efficiency improvement

resulted from a more than doubling in

yield per m 2 caused by amongst others

improved greenhouse transmission, cultivars

and cultivation techniques.

The use of fossil energy can be reduced

by limiting the energy demand, higher

insulation and by intelligent control of climate,

by increasing the energy efficiency

and by using sustainable energy sources.

Energy saving of

greenhouse systems

Energy losses occur through the ventilation

but also greenhouse covering. Greenhouse

covers with higher insulating values and

energy screens highly limits the energy

loss. Increased insulation can be obtained

by modern greenhouse materials, where

new coatings (low emission and antireflection)

are applied. Energy saving of

25-30% seems to be possible with the

new materials without loss of light. If additional

CO2 is applied production will not

decrease, in spite of considerable energy

savings.

In current greenhouse horticulture, next to high production,

levels, quality and timeliness of production are important.

6 ENERGY IN FOCUS


greenhouse

If screens are used almost permanently,

they can reduce the energy use by more

than 35%. Due to restrictions for closing

in commercial practice, reduction in

energy use by thermal screens is restricted

to 20%. Efficient screening strategies can

save energy while maintaining crop production

level.

Semi-closed greenhouse concepts

The last years several greenhouse concepts

were developed. It started with using the

greenhouse itself as solar collector (solar

greenhouse “Zonnekas”), followed by fully

closed greenhouses, towards energy producing

greenhouses (“Kas als energiebron”)

and latest developments toward electricity

producing greenhouses (“Elkas”). In closed

greenhouses, the excess of solar energy

in summer is collected and stored e.g. in

aquifers to be reused in winter to heat the

greenhouse. These concepts result in a

reduction in primary energy use of 33%.

But to reduce investment costs, growers

tend to choose a semi closed system.

Cooling capacity of this system is lower

and insufficient to keep the temperature

below the maximum, so ventilation windows

will be opened. CO2 emission in

(semi)closed greenhouses is considerably

lower than in open greenhouses. In a

recent experiment, in which tomatoes

were grown at a maximum concentration

of 1000 ppm, the open greenhouse used

54.7 kg CO2 m-2 in contrast 14.4 kg CO2

m-2 in the closed greenhouse.

Sustainable greenhousees

Specific characteristics of climate in (semi)

closed greenhouses are: high CO2 concentrations,

vertical temperature gradients,

high humidities, combined conditions of

high light intensity and high CO2 concentration

and increased rates of air movement.

Yield increase is due to the effects

of elevated CO2 concentration at high

irradiance, and the optimum temperature

for crop photosynthesis increased with

CO2 concentration.

The following concepts are shown at

the Innovation and Demonstration Centre

in Bleiswijk and investigated by Wageningen

UR Greenhouse Horticulture. These

and future concepts might even create a

surplus of energy to be used in the surroundings.

Sunergy Greenhouse

The objective is to obtain the greatest possible

light transmittance. A double screen

traps heat to reduce the greenhouse’s own

heat consumption. This greenhouse combines

the best of the existing technologies

now being applied in horticulture. The

roof of the greenhouse is anti-reflective

glass (GroGlass). The greenhouse is seven

metres with an ultra-lightweight substructure

(Twinlight) but no roof vents. Heat loss

is limited by a double screening system

with a new sliding system preventing

leaking gaps. The concept is developed

by Wageningen UR and P.L.J. Bom greenhouse

builders.

Sun Wind Greenhouse

Many pot plants are shade plants that

require a high degree of screening during

the summer. An innovative paneled screen

installed in the Sun-Wind Greenhouse collects

energy in the form of warm water and

prevents direct sunlight from entering. The

warm water is then stored in a special buffer

under the greenhouse but with a conventional

climate control. The greenhouse

roof faces south and consists of adjustable

solar collector panels sandwiched between

double glazing at a 35° slope. The

north side of the greenhouse consists of

acrylic sheets with a slope of 60° and onesided

continuous roof ventilation. The post

height is three meters, ridge height nine

meters and trellis girder 11.80 meters. This

concept is developed by Thermotech and

Gakon greenhouse builders.

FlowDeck Greenhouse

The greenhouse roof consists of hollowcore

polycarbonate sheeting through

which water flows from the gutter to

the ridge and back. Light transmittance

through Flowdeck is equal to conventional

acrylic sheeting but when filled with

water is equal to normal single horticultural

glass. The greenhouse has a Venlo

structure with a gutter height of 7 metres

and an extended span of 6.40 metres. The

greenhouse has roof vents on the sheltered

side. An air-handling unit is connected to

an air distribution system with perforated

flexible pipes installed under the cultivating

systems. Forced-air heating/cooling

units are installed. The greenhouse is also

equipped with a single shade cloth. This

concept is developed by Climeco Engineering

and Maurice greenhouse builders.

Energy efficient

climate control

Within semi-closed greenhouse concepts,

an energy efficient climate control leads to

further reduction in energy consumption

and/or increase of production. New growing

strategies are currently developed for

several crops. The aim of such concepts is

to reduce energy consumption dramatically

without production losses. In the new

growing strategy for tomato e.g. the energy

consumption has to drop from 40 m 3 to

26 m 3 gas per m 2 greenhouse area. Other

concepts are developed for other crops.

There are several possibilities to decrease

energy consumption in greenhouse

horticulture in the future. The challenge is

to reach it with low-cost solutions.

Semi-closed greenhouse concepts are

permanently in development in order to

optimize the systems concerning costs and

performance. In order to apply new greenhouse

concepts and growing strategies

into horticultural practice cooperation, an

active exchange of knowledge between

growers, horticultural industry, extension

service and research is necessary.


ENERGY IN FOCUS 7


Oliver Körner, consultant, AgroTech, oko@agrotech.dk • Mads Andersen, Senmatic, DGT Volmatic, maa@senmatic.com

Bo Nørregaard Jørgensen, The Maersk Mc-Kinney Moller Institute, University of Southern Denmark, bnj@mip.sdu.dk

Development of future

greenhouse climate control

Next to production of high quality plants, the greenhouses of the future

will have to produce energy too. In order to ensure optimal output,

there should be improved automation of the climate control system

Such automation requires climate control

software based on models that can

predict the actual plant reactions to the

ongoing changes in the greenhouse climate

(as a consequence of combined plant

and energy production), and the complexity

of this issue demands a different way of

planning and thinking when designing the

climate control software.

In a cooperation including AgroTech,

University of Southern Denmark (SDU),

and Senmatic DGT Volmatic, future climate

control software will be planned,

built up and tested.

The system

Future greenhouses will at least be CO2

neutral and they will also produce energy.

Research has shown that climate conditions

in closed and semi-closed greenhouses

demand new climate strategies.

Luckily, in parallel with the development

of these types greenhouse, there have been

rapid developments in greenhouse climate

control. The long discussed speaking-plant

approach to fill the greenhouse with a lot

of sensors, measure everything possible on

and around the plants, and then control

the greenhouse climate to meet the needs

of the plants, is coming closer. Development

of inexpensive wireless microsensors

is well on the way, and the quality of

calculation models for interpretation and

further use of the measured data has been

greatly improved.

The system is modular

All these possibilities place high demands

on the climate control software platform.

The platform must be flexible so that new

options can be added as soon as they are

available from research.

In order to achieve the necessary flexibility,

the climate control software must be

based on independent control modules,

and the individual commands from these

modules for the greenhouse climate must

be coordinated by a higher integrating

decision unit.

The decision unit is programmed with

goals for plant quality, energy consumption

and so on. The higher integrating

decision unit coordinates and decides for

any given situation, which of the modules

are to control the greenhouse actuators.

The modules may be physical sensors, soft

sensors or soft controllers.

Different modules can send conflicting

commands to the actuators and thus

coordination is necessary. Without a well

structured unit this would result in serious

errors. Consequently, the system asks

for clearly defined stand-alone modules,

as interdependency among the modules

induces a high risk that the whole system

will not work correctly.

At the Mærsk McKinney Møller Institute

at SDU, research is being carried out into

software technologies that can handle

these so-called feature interactions. The

use of independent modules is in the long

run a basic need to utilise and implement

international research results in climate

control without re-designing the system.

The future climate control platform thus

enables faster implementation of research

into practice.

Models for climate control

The modules for the future greenhouse

climate control platform are typically sensors,

soft sensors or soft controllers. Soft

sensors will be developed in areas where

physical sensors are not appropriate, are

too expensive, or do not exist, or where

basic measurements need to be analysed

further. Soft sensors are typically mathematical

models that are used to further

compute measured data for more value

usage.

Soft sensors are under development for

a number of processes in the greenhouse

such as plant temperature or condensation.

For climate control, continuous data

are necessary, and appropriate sensors are

often not available.

For example, measuring photosynthe-

8 ENERGY IN FOCUS


sis is routine, but it is impossible to get

detailed photosynthesis measurements of

the whole greenhouse, and at any given

time, without investing in very expensive

measuring equipment.

In this case, a model can produce

a photosynthesis soft sensor by calculating

actual photosynthesis from measured

microclimate point measurements. Such

a soft sensor implemented in the control

circuit is called a soft controller.

A typical and simple soft controller

used in daily practice is temperature integration.

A typical soft sensor/controller

system is an early warning system for

stress. Soft-sensors can help to identify

plant stress before it can be seen and actually

damage the plant. The greenhouse

actuators can then be controlled in order

to avoid crop damage.

AgroTech develops these model-based

soft sensors and soft controllers. They have

been implemented in co-operation with

SDU and Senmatic.

Interpretation

of measurements

Models are not only used in soft-sensors

and soft controllers. Soon there will be

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many new sensors available and with the

new software systems, it will be child’s

play to fit these to the climate control

platform.

But, what should we do with the sensor

data when their interpretation is somewhat

unclear? The danger is that we will make

the wrong decisions. How can we be sure

whether a measurement is good or bad?

Here, models are very helpful for data

interpretation.

Everybody knows when temperature,

relative humi-dity, light or CO2 is too

low or too high. But how can we use

measurements of stomata conductance,

photosynthesis or transpiration? What is

low and what is high and when is it as it

should be? In these questions, models can

help to find the right interpretation of the

measurements.

When will the future

climate control be available?

A part of the ongoing projects focuses on

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in practice. The actual projects include:

• Intelligent Energy Management

in Greenhouses, Greenhouse

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ENERGY IN FOCUS 9

Energy

costs

• Technology for sustainable greenhouse

production, PREDICT – Towards

spreading of intelligent climate

control to the greenhouse

horticultural industry.

These projects are based on different elements

of research within dynamic climate

control and the aim is to create a substantial

reduction in energy consumption

without compromising plant quality. New

developments within dynamic climate

control are being transferred to practice

in all the projects. The newly created climate

software is continuously being tested

in the participating greenhouse production

plants. Software developed within the

scope of the projects will be available for

evaluation by other producers when the

projects terminate.

In general, in the future Danish greenhouse

producers will experience the

benefits of new features in climate control

software when the ongoing flux of

research, development and new knowledge

is implemented in coming versions

of existing software packages.


Energy

savers


Peter Rasmussen, per@agrotech.dk • Jens Rystedt, jor@agrotech.dk • Jakob Skov Pedersen, jap@agrotech.dk, consultants, AgroTech A/S

Optimisation of climate management

with Climate Check and Plant Check

Is the greenhouse nursery spending more money than necessary on energy?

What will happen if we change to dynamic climate management?

Should I inject more CO2 and cut down on growth lighting instead?

Is it worth investing in new curtain systems or lights?

There is a lot of questions, and the decisions

are often hard to make, but there

is money to be saved, if you make the

right decisions. Many people are reluctant

to change cultivation practices or climate

strategy because it is difficult to see how

changing a setting will affect heating bills

or how well plants grow. However, the

high energy prices in summer 2008 caused

many producers to look for quick savings,

and at AgroTech we saw a need to develop

services to optimise greenhouse production.

We came up with Climate Check and

Plant Check.

Climate Check and the

new opportunities

In brief, Climate Check involves collecting

all the relevant data in the greenhouses, for

example data on climate management and

energy consumption. This data is entered

into a model which uses the data to calculate

ongoing energy consumption. The

calculations are adapted to the individual

greenhouse and they can be carried out

at short intervals, for example every five

minutes. This makes it possible to look

more closely at the climate management

settings in relation to energy consumption.

It also makes it possible to simulate alternative

climate management strategies with

new settings, and it is possible to calculate

the new energy consumption figures and

the new climate.

AgroTech has implemented Climate

Did you know that ...

Climate boxes at KU Life being used for Plant Check. The boxes here

are being used to study cucumbers.

Check at ten greenhouse companies with

a total of 500,000 m 2 under glass. On

average, proposals for energy savings of 12

per cent have been put forward.

Since autumn 2008, AgroTech has

developed Climate Check further with

a greenhouse simulation model known

as AgroClimate. This makes it possible

to simulate plant growth, photosynthesis,

temperature, humidity as well as energy

processes in the greenhouse. With

much better time resolution than previous

models, the new model can analyse the

complex relationship between humidity,

transpiration, ventilation and dosage of

CO2. The aim is to be able to predict

• Heat loss from greenhouses increases exponentially with the difference between

inside and outside temperature?

• If the greenhouse curtain is opened at low light limits early in the morning, a

significant proportion of the daily energy consumption is used immediately after?

It is important to find the right balance between light and energy consumption.

• It is a good idea to log climate data - it may be worth its weight in gold! A climate

check makes optimal use of climate data going back over up to two years.

• Plants have a higher rate of photosynthesis with diffuse light than with direct light.

new strategies for a specific production

and to ensure compliance with growth

requirements for humidity, temperature

and light.

Plant Check

But climate management and energy

consumption is one thing. Quite another

aspect is the plants. When do they grow

best? How much light, heat or cold can

they tolerate? This is where Plant Check

comes into play. Plant Check can establish

the plants’ limits for optimal growth,

for example tolerance limits for cold

and heat. It also establishes how plants’

photosynthesis and growth are affected

by the cultivation climate and lighting.

Plant Check can be anything from advanced

cultivation trials in climate cham-

bers or climate boxes to simpler proces-

ses to measure photosynthesis on indivi-

dual leaves under various climate con-

ditions. Imagine what would happen if

energy prices rose to the same levels as in

August 2008. Wouldn’t it be nice to know

how much you can reduce the temperature

at night? A few degrees can easily

mean savings of 15-20 per cent.

If you would like to find out more, you

are always welcome to contact us.


10 ENERGY IN FOCUS


Jens Møller Jensen, CTO, Danfoss IXA A/S, jensen@danfoss.com and Bent S. Bennedsen, Agrotech A/S, bsb@agrotech.dk

Environmental sensors

for harsh environments

– a novel approach to multiple parameter sensors for greenhouses

Sensors for environmental parameters are numerous and widespread, and the

number of applications in which such sensors are applied is constantly rising.

One application of interest is greenhouse production, in which the application

of multiple distributed sensors can serve to drastically reduce energy

consumption and improve growth control

However, this approach implies

requirements that are not fulfilled

with existing sensors, namely requirements

that the sensors function continuously

and stably and with little or no maintenance

requirement in a harsh environment

likely to contaminate the sensors.

Additional requirements are that the sensors

can operate wirelessly in order to

enable use of multiple sensors without

obstructions and expensive cabling, and

that they can do so at an energy consumption

level low enough to be powered by

energy harvesting, avoiding the need for

recurrent battery exchange.

New sensors needed

Currently available sensors are in general

not specifically designed for harsh environments,

and in most cases standard

sensors are therefore applied with various

additional measures to protect them and

with limited positioning options to compensate

for the harsh environment impact.

Moreover, different sensors

are needed for the various

environment parameters. This

means the sensors are even less

applicable, less durable and less

accurate than needed in order

to efficiently provide measurement

data for optimum energy

management and environment

control.

Such control requires monitoring

of the environment in close

proximity to the plants, and the

sensors therefore should be placed

amongst the plants, preferably

on a multiple distributed

basis. The sensors should be able

to withstand close impacts from

the various plant-care activities

while at the same time not requiring

tedious time and effort consuming installation

and maintenance, which impedes

daily work routines.

Obtaining these features requires

sensors that are actually designed for

the purpose. They must be reliable and

durable and designed for maximum usability

in the specific application, and they

must require no or very little service and

maintenance. They must also be able to

communicate data wirelessly in order to

facilitate easy and dynamic positioning

and handling.

Novel approach

All this calls for a novel approach to

greenhouse sensors in technology, conception

and design. Danfoss IXA A/S,

together with partners of the Greenhouse

Concept 2017, is developing such sensors,

based on novel and patented optical principles

incorporating nanotechnology.

Danfoss IXA A/S has developed and

patented a novel optical measurement

principle and novel nano-coating principles

which, together with application

targeted design, enable sensors with all

the required properties. The sensors simultaneously

measure CO2, absolute and

relative humidity, including dew point,

various temperatures and light; they are

faster than existing sensors, they are self

cleaning and hermetically sealed, they

are powered by energy-harvesting, and

they communicate wirelessly in a multiple-node

network which enables huge

improvements in both greenhouse energy

consumption and growth control. At the

same time the sensors impose no additional

maintenance and service requirements

on the users. The sensors can withstand

direct exposure to the various daily plantcare

activities and handling and they

are specifically designed for optimum

usability and efficiency in professio-

nal greenhouse production plants.


ENERGY IN FOCUS 11


Ole Skov, oes@agrotech.dk and Jens Rystedt, jor@agrotech.dk, consultants AgroTech

Energy savings in Danish

greenhouse production

For a number of years, there has been focus on energy savings in greenhouse

nurseries, and this has led to a general reduction in energy consumption

of 25-30 percent over the past 10 years. Today, the average annual

energy consumption per m 2 of greenhouse is about 400 kWh

The large reduction in energy consumption

is due to a wide range of initiatives

from researchers, advisors, and not least

the greenhouse producers themselves.

Despite great efforts, however, energy

consumption remains high and increasing

prices for energy and CO2 allowances

can have significant consequences.

If energy prices again exceed USD 140 per

tonne, energy consumption will have to be

halved in a very few years, as a minimum,

if competitiveness is to be retained.

Therefore, it is proposed that greenhouse

companies launch and carry out an

action plan to make energy consumption

more efficient.

This should be over a number of years,

with gradual utilisation and introduction

of the newest technologies and initiatives

from research and development. Most

important are making the greenhouse climate

more efficient, energy improvements

to the climate screens in greenhouses, and

exploitation of surplus heat.

More efficient greenhouse

climate (Climate Check)

This could be via the greenhouse nursery’s

own climate data, where the interaction

between temperature, curtain control,

growth lighting and so on is analysed using

a modelling program which tests the existing

management strategy.

This provides knowledge about when

energy is used in the greenhouse. On this

basis, a number of suggested changes to

the management system are listed which

will lead to reduced energy consumption.

Experience so far shows a savings potential

of 10 to 30 percent.

Improvements of the climate screens

in greenhouses (Energy Check)

This is primarily about installing new

mobile curtain equipment. Preferably two

types; one thick curtain for insulation at

night, and another for shade with a maximum

shade effect of 20 percent.

It is also about replacing single-glazed

panes in the greenhouse with channel

plates with several layers of glazing. This

will lead to a reduction in heat transmission

through the new plates of about 60

percent, as well as a reduction in the influx

of light as channel plates with several layers

have somewhat lower light transmission

than single-glazed panes.

However, replacement in many of the

greenhouse surfaces will not lead to significant

reductions in the influx of light,

for example gables and outer walls. With

respect to older DEG standard greenhouses

with leaky or draughty glass rails, it

is suggested that the glass in roof surfaces

facing north also be replaced with channel

plates with several layers, while the

glass in the south-facing surfaces should

be replaced with new four-sided supported

glass rails.

Such replacement will give reductions

in energy consumption of more than 50

percent. However, you should beware of

the reduction in light conditions.

Exploitation of surplus heat

When the surfaces of a greenhouse are

insulated, more effective management of

the greenhouse climate is required, particularly

humidity can be a problem. It might

be necessary to fit ventilation equipment

which can rapidly even out differences in

temperature and humidity in the greenhouse.

And this could be the start of a full

extraction system, where surplus heat from

the influx of sunlight and growth lighting

can be extracted, stored and reused when

the energy is needed. Such systems have

several stages, depending on how much of

the surplus energy is to be stored and for

how long. With the right dimensions, the

greenhouse nursery could become almost

independent of fossil fuels.

There is no single solution to the energy

challenge. Several balls must come into

play and it is important to set a long-term

strategy for how the individual greenhouse

company can make itself independent of

expensive energy.


12 ENERGY IN FOCUS


Pottemaskine

Pottemaskinen består af

en basisenhed, som kan

monteres med magasiner,

boreenhed og transportbånd.

Magasiner og boreenhed

fremstilles til forskellige

pottetyper og fabrikater.

For eksempel runde, støbte

potter, termoformede potter,

Jiffy potter og firkantede,

støbte potter.

Pottemaskinen har en stor

kapacitet og er opbygget som

en kompakt og arbejdsvenlig

enhed.

På fotoet er vist en pottemaskine

med boreenhed,

transportbånd og stativ

til småplanter.

Topfmaschine

Die Topfmaschine besteht

aus einer Basiseinheit, die mit

Magazinen, Bohrsystem und

Förderband ausgestattet werden

kann.

Magazine und Bohrsystem

werden für verschiedene

Topftypen und Topffabrikate

hergestellt, wie z. B. runde

Spritzgusstöpfe, Thermoform-

Töpfe, Jiffy-Töpfe und viereckige

Spritzgusstöpfe.

Die Topfmaschine verfügt über

eine große Kapazität und ist als

kompakte und arbeitsfreundliche

Einheit konzipiert.

Das Bild zeigt eine Topfmaschine

mit Bohrsystem, Förderband und

einem Ständer für Jungpflanzen.

Potting machine

The potting machine consists

of a basic unit which can

be fitted with magazines, a

drilling unit and a conveyor-

belt.

Magazines and drilling unit

are made for different pot

types and makes.

For example round, moulded

pots, thermoformed pots, Jiffy

pots and square, moulded

pots.

This high-capacity potting

machine is designed as a

compact, work-friendly unit.

The photo shows a potting

machine with a drilling unit, a

conveyorbelt and a frame

for small plants.

Bekidan a/S

Erhvervsvangen 18

DK-5792 Årslev

Telefon +45 65 99 16 35

Telefax +45 65 99 16 90

E-mail: bekidan@bekidan.dk

www.bekidan.dk

ENERGY IN FOCUS 13


By: Lotte Bjarke, editor, Gartner Tidende, post@lottebjarke.dk

Ventilators save energy

Experiences from this growing season proves that it is possible to save

about 10 percent of energy for tomato growing by the use of ventilators in the

greenhouse and at the same time achieve a better climate in the greenhouse

Normally ventilators in greenhouses

consume energy. But in the Danish

tomato nursery, Alfred Pedersen & Son, a

set of new ventilators actually helps the

nursery to save energy.

The ventilators were installed in week

6 this year and have since proven that by

a minor energy consumption to keep the

ventilators running it is actually possible

to achieve so big advantages regarding

the greenhouse climate, that substantial

savings on the total energy consumption

is achievable.

Traditionally ventilators are installed

under the greenhouse roof, but these are

installed under the plants and that is what

makes the difference.

In the nursery the tomatoes are grown

in trenches thus making it possible to

install the ventilators below the tomato

crop and thereby to create movements of

the entire greenhouse atmosphere.

- We have placed the ventilators at

intervals throughout the greenhouse. They

are each connected to inflatable tubes

along the rows of plants. The tubes have

holes in the sides which adds to the movement

of the air, explains Poul Erik Lund,

who is production manager of the nursery.

Moving the air

The trick is that the ventilators are placed

with interchanging direction of air intake.

This creates an s-shaped movement of

the air horizontally and thanks to the air

blown, out through the holes in the tubes

this movement is transmitted also to the

vertical plane. In short all the air in the

nursery is constantly moving but without

any feeling of wind in the greenhouse.

- The idea originates from the Dutch

closed-greenhouse projects. They have

ventilators under each single row of plants

while we only have placed them with a

certain interval, says Poul Erik Lund, who

is pleased with the improved climate in

the greenhouse following the installation

of the ventilators.

- We mainly expected that we could

achieve savings on the energy consumption

in wintertime when we produce toma-

toes by additional lightning, because the

movement of the air let the heating surplus

created by the lamps come to the benefit

of the plants thus making less demands

for the heating system, explains Poul Erik

Lund.

But actually there is also potential energy

savings to achieve in summertime.

- We use quite some energy to keep

the humidity under control in the morning

even in summer. Heat is necessary

to remove humidity in order to get the

evaporation of the plants going and in

order to lower the risk of diseases. But the

movement of the air now means that it is

possible to control humidity with far less

use of heating, underlines Poul Erik Lund.

Plants at work

Alfred Pedersen & Son expect that a total

saving of about 10% of the energy consumption

will be possible thanks to the

ventilators.

- We now have to learn how to optimize

the use of the ventilators. For instance we

must learn how much we can lower the

heat for humidity control in the morning.

But I am quite confident that the potential

is big, says Poul Erik Lund who even

expects possible raise of production thanks

to the improved climate of the greenhouse

also on grey and rainy days.

- It is all about getting the plants to work

as much as possible and apparently the

constant movement of the air is making

them keep up the work because the humidity

is continuously removed from the

plant surface thus optimizing evaporation,

he explains.

So far the ventilators have been installed

in a greenhouse where winter tomatoes

are produced by artificial lightning.

But a new project is coming up and the

nursery will also use the achieved experience

for production of winter cucumbers

by artificial lightning.

- We believe in the potential in tomatoes

as well as other plants but there is a

need for more experience since different

plants respond differently as well as different

growing systems mean different

potential, underlines Poul Erik Lund.


14 ENERGY IN FOCUS


A C

D

ACF

F

ENERGY IN FOCUS 15

D C

C E

C

AC

F E

F

F

D E AC

• Here, suppliers in the sector present their companies,

products and new items.

• This is where your customers will gain an overview of what

the market has to offer in the way of possibilities.

• This is the showcase for contemporary trends to provide

inspiration for future investments.

This is the place where all the new items are presented, trends

for the new gardening season are revealed in earnest and the

sector’s buyers meet to plan the upcoming season and gain

new inspiration to take away with them.

Dan-Gar-Tek was held under the same roof as the Fagmessen

for the first time in 2006. Bringing them together has

created a new, inspiring forum across the horticulture

industry throughout the Nordic region.

F

D E AC

It’s easy to

get to Denmark

by plane or

by train!

Come and be part of creating the future of horticulture in

Denmark, Norway, Sweden and Finland.

Telephone +45 65560284 | Fax +45 65560299 | e-mail: jbm@ose.dk | www.dan-gar-tek.com | www.fagmessen.dk

D E AC

D

You can find out more at www.dan-gar-tek.com,

www.fagmessen.dk, or by calling +45 6556 0284


Jan Hassing, Gartneriernes Fjernvarmeforsyning,

janhassing@energifyn.jay.net

(organization of producers with district heating) •

Jan Strømvig, FjernvarmeFyn (Funen district heating),

js@fjernvarmefyn.dk •

Jens Rystedt, AgroTech, jor@agrotech.dk

Energy extraction

from greenhouse

nurseries with

district heating

A research project is focusing on how

it is possible to use the surplus energy

from greenhouses thus making the

greenhouse nurseries energy producers

rather than energy consumers

Over a single year, a greenhouse

receives more solar energy than it

needs for heating and controlling humidity.

So, every year there is an energy

surplus in a greenhouse. The problem is

just that so far it has not been possible to

extract the surplus energy and store it for

later use, for example from day until night,

or even better, from summer until winter.

In recent years, new technologies have

made it possible to extract surplus energy.

The energy conditions in an “average

greenhouse” can be outlined as below:

When the energy is extracted, it must

be possible to either use it immediately

or to store it, for example in a groundwater

aquifer or energy storage ponds.

The investment required for storage is very

high, however, and not all locations are

suitable for underground storage.

The district heating area around Odense

Energy conditions in an “average greenhouse”

has 151 greenhouse producers with a total

of 1.8 million m² under glass. These greenhouses

are all connected to the district

heating network.

An obvious question is whether it is possible

to send the surplus energy directly

out to the district heating network, instead

of storing it in expensive seasonal storage

facilities.

Energy for 20.000 households

This year, the district heating company

on Funen, (Fjernvarme Fyn), Gartnernes

Fjernvarmeselskaber and AgroTech are

looking at the possibilities of exploiting

the surplus heat from nurseries. Preliminary

calculations show that the total potential

energy extraction from the nurseries

amounts to about 2.2 million GJ per year,

corresponding to the energy consumption

of about 20,000 households. However,

KWh per m2 Radiation out

greenhouse per year

1040

Radiation influx to a greenhouse 900

Energy consumption in a greenhouse (standard year) 400 – 450

Energy surplus 450 – 500

Potential energy extraction 350 - 400

this assumes that all nurseries extract all

their surplus energy and that the district

heating network can take all the energy.

The calculations show more realistically

that if 25 percent of the nurseries practice

energy extraction, the district heating

network will immediately be able to take

all the energy without storage for longer

periods.

Before this can become a reality, however,

there are some technical challenges to

be overcome - most importantly that the

temperature from the energy extraction by

the nurseries is too low to be immediately

sent into the district heating network. The

temperature must be increased from 35°C

to about 70°C, using either solar heating

plant, heat pumps or the existing boilers at

the nurseries.

The whole issue of financing, costs and

taxation has not yet been resolved.

Nevertheless, the greenhouse companies

do have an energy surplus which could

be recovered and which could transform

greenhouses from energy consumers to

energy producers.

The project is being funded by Gartneribrugets

Afsætningsudvalg, a foundation to

enhance development of the horticultutral

sector, and will be completed with an

overall analysis at the end of 2009.


16 ENERGY IN FOCUS


Anker Kuehn, AgroTech, ank@agrotech.dk • Eva Rosenqvist, KU-Life, ero@life.ku.dk •

Hans Andersson, LS, haa@ludvigsvensson.com and Jørn Rosager, jr@dgssupply.dk

What can we

use NIR curtains for?

NIR curtains are the newest type of curtain from Ludvig Svensson.

Near infrared reflecting curtains that reflect some of the heat radiation

and allow almost all photosynthesis-active light to pass through.

Can plants tolerate more light when the heat radiation is reduced?

When we shade plants from

high influxes of radiation from

the sun, it is usually not to reduce the

amount of light, but rather to avoid scorching

the plants. When the influx of

visible light is high, the level of invisible

NIR is also high. NIR radiation is

heat radiation that plants cannot utilise in

their photosynthesis and because, in most

cases, greenhouses are warm enough as it

is, the heat is a waste product.

In principle most plants can withstand

high exposures to light, as many of the

species grown in Danish greenhouse

nurseries love the sun, however they

must be kept cool during exposure. If the

leaf temperature becomes too high, the

plant cannot keep up with the vapour

pressure, meaning that the water that

evaporates from the leaves is not replaced

quickly enough. The plant protects

itself from dehydrating by closing its pores,

leading to the arrest of photosynthesis. If

the plant is exposed to increased vapour

pressure, the outer layer of cells on its leaves

will be damaged; what we call leaf

scorch. When the pores are closed, temperature

increases can lead to scorching

of the middle part of the leaf.

We can prevent this damage to leaves

if we provide shade for the plants,

and regular curtains, e.g. XLS16, block

64% of the radiation influx and reflect it

out from the greenhouse. Unfortunately

this type of curtain also blocks 64% of

the visible (and photosynthesis-active)

light out, thereby preventing photosynthesis.

NIR curtains

The new NIR curtain differentiates between

the visible part of the spectrum

(380-750nm, where plants use 400-700nm

in the photosynthesis) and the near infrared

(NIR) area (800-1200nm). The NIR

area also makes up a large part of what we

call heat radiation.

So, these curtains can block out up to

80% of heat radiation while at the same

time only blocking out 20 % of the visible

and photosynthesis-active light.

This means that we block out less photosynthesis-active

light while at the same

time preventing overheating of the greenhouse.

In this way CO2 can be administered

over a longer period, and we can

achieve more photosynthesis and growth.

The curtains look like regular lightshading

curtains because the shade rate

is for the part of the spectrum that we

cannot see.

We expect NIR curtains will allow for

increased growth without risk of scorching.

Hopefully we will also see lower

leaf temperatures under NIR curtains.

Testing NIR curtains

Together with a diffuse curtain, NIR

curtains are currently being tested at

KU-Life in cooperation with Ludvig Svensson.

The tests will be looking at room and

leaf temperatures under the different curtains.

First chrysanthemums, potted roses,

begonias and kalanchoë are being used

as test plants, as they have different types

of leaves and therefore their water balance

and control of leaf temperature with regard

to radiation also differs.

NIR curtains have also been installed

in the demonstration facility at Hjorte-

bjerg greenhouse nursery, where they are

on public display. See the article about

the Hjortebjerg plant – a demonstration

facility for new energy technologies.


ENERGY IN FOCUS 17


Carl-Otto Ottosen, Department of Horticulture, Aarhus University, co.ottosen@agrsci.dk •

Bo Nørregaard Jørgensen, The Maersk Mc-Kinney Moller Institute, University of Southern Denmark, bnj@mip.sdu.dk

Dynamic management

of supplemental light

As the natural light even in winter a sunny day might be adequate to substitute

supplemental light, we have decided to combine information about the weather

forecasts, the actual forecasted electricity prices and the photosynthetic

performance of the actual species into one context

This is the core of an R&D project between

Department of Horticulture and

The Maersk Mc-Kinney Moller Institute

with funding from regional energy producers

(Energy Fyns Fond) and more recently

commercial growers and national funding

(The Danish Food Agency Services).

Optimal gain of photosynthesis

To reach this target a software package has

been developed that installed on a PC connected

to the Internet and with access to a

climate computer will calculate the most

efficient time to turn on the supplemental

light based on the weather forecast, the

energy prices and the photosynthesis sum

from individual plant species.

In this way we not only overcome the

traditional rather conservative set points

for use of supplemental light, but also

secures that the use of supplemental light

takes place in periods where the gain in

terms of photosynthesis per light hours is

the best.

The control of supplemental light is

predictive rather than the traditional retrospect

analysis of light sums. The consequence

is that light use is moved from

peak to low load periods.

The decision support in the program is

based of the IntelliGrow concepts of dynamic

climate management, but added more

knowledge about the different species

ability to cope with fluctuations in light

and perhaps even use supplemental light.

The software requires currently Super-

Link4 (Senmatic), but we are testing methods

to communicate with Priva systems.

Results

Experiments with different photosyn-

thesis sums using dynamic light control

vs. traditional light controls based of set

point of supplemental light and photosynthesis

sums, have been performed in

spring 2009.

The dynamic supplemental light control

was used in combination with dynamic

climate control using potted miniature

roses, Hibiscus rosa-sinensis and

Euphorbia milii showed that a reduction

of more than 10% of the supplemental

light use was possible. If it was combined

with dynamic climate control both the cost

for heating and electricity was reduced

with an improved plant performance (often

more compact plants).

Photosynthesis measurements of the

species reveal large differences in response

times to light, which indicate several

additional possibilities for reducing

electricity costs using different igniting

patterns for the lamps. This knowledge

will be included in the software and ongoing

work on the software will include a

better prediction of the climate to improve

the photosynthesis calculation, but also

include suggestion for different uses of the

installed supplementary light in different

situations.

Testing supplemental light

use on the web

The results are developed with the involved

nurseries, but a novel web based

application is available for all. If growers

upload climate date on the homepage

http://SoftwareLab.sdu.dk/DynaLight information

about possible energy savings will

be shown.


The screen shows an example of

supplemental light control, where the

light is on 6 hrs during the night (lower

left). The graph shows times of light on

(red), price of electricity (light blue)

and working light (yellow). The green

line is natural light and light green line

is the photosynthetic activity.

18 ENERGY IN FOCUS


Anker Kuehn, AgroTech, ank@agrotech.dk, • Eva Rosenqvist, KU-Life, ero@life.ku.dk • Stig Gejl, Philips Lighting, stig.gejl@philips.com

Artificial lighting and

lighting control of the future

Lighting diodes are becoming increasingly efficient. In a few years time they

are expected to be even more efficient than SON-T lights, and prices will have

dropped so much that they can compete with other types of lighting.

It should also be mentioned that LED lights have a longer life-time

So there are many advantages to using

lighting diodes. The question is, are

there other advantages to using LED

lights? One of the advantages is that you

can change the colour composition and

thereby affect the growth of plants. For

example, colour composition affects the

way a plant stretches and when it flowers.

Effectiveness of photosynthesis

Chlorophyll is the most important pigment

and its function is to absorb light in plants’

photosynthesis. It absorbs most light in the

red and blue area. Plants are green because

they reflect much of the green light and

absorb other colours in the light spectrum.

In principle, a plant can use light of any

colour in its photosynthesis because light

is absorbed by different pigments, and

energy from the light is then transferred to

the photosynthesis reaction centre.

Blue light contains more energy than

red light, although both colour wavelengths

contribute equally to photosynthesis.

In terms of energy, the same amount of

Watts will render more red light rays than

blue. That is, as regards photosynthesis, it

is “cheaper” to use red light than blue.

Flowering

The flowering pattern of many plants is

governed by the available light. Some

plants flower when there is enough light,

that is when there is a photosynthesis

“surplus”, while the flowering pattern of

other plants is regulated by the length of

daylight. In plants that are regulated by

daylight, the length of night is the most

important. Plants contain a substance called

photochrome that can appear in two

forms, active and inactive, and it is this

substance that determines whether the

plant will flower. Photochrome can be

converted between its active and inactive

forms by using light in the red and farred

region. We know that we can bring

poinsettias to flower a week early if we

draw the curtains before the sun sets.

This is because the amount of light from

the far-red region that normally shines on

the plants just before the onset of night is

reduced.

Shape and height

There is much more far-red light than red

light in a woodland area (the leaves in the

tree crowns are very efficient at absorbing

red light), and this acts as a signal to the

photochrome in the leaves below, leading

these plants to stretch toward the light. We

also see this in plants that are exposed to

incandescent lamps, as these also irradiate

a lot of far-red light.

In addition to this phenomenon, blue

light also affects the shape of plants. Plants

that are exposed to more blue light are

more compact and produce more side

shoots. This is due to the similar conditions

to plants growing freely under a blue sky.

Correspondingly, plants that are exposed

to UV light thus stretch less.

Artificial lighting can

be controlled but it is only

supplementary lighting

When we know how plants react, we

can control the light and the colours of

the light, to match the plants’ needs. This

means that we do not need the same light

composition all of the time; sometimes

only extra photosynthesis is needed, and

in such situations it would be cheaper to

use red light, while at other times we need

to affect the shape of the plant and therefore

other light colours are needed.

The question is, how do we make this

work in practice, given that most of the

current knowledge has been obtained from

climate chambers and experiments in the

lab? In the Innovation Consortium project,

Greenhouse Concept 2017, we are testing

the LED technology in the greenhouse.

However, there are lots of light combi-

nation possibilities, and lots of different

plant reactions, so we will probably see

many different LED combinations, possibly

in the same lamp cabinet.

We must remember that daylight is

the most important light source and that

artificial light is merely supplementary

light. We know from SON-T lights that

yellow-orange light is a useful supplement

to daylight, however it does not work

very well on its own because it results in

undesirable stretching. When we use the

lights as supplementary lighting, they must

be well suited for photosynthesis, but we

can achieve even more by using new light

colour combinations. And the expected

increase in efficiency and the longer lifetime

of the LED lights is added bonus.

ENERGY IN FOCUS 19


The sun

as a potential source of energy

In the long term there are likely to be demands for CO2-friendly or perhaps

even CO2 neutral production. There is no simple method of solving this

problem. Several solutions have to be brought into play at the same time,

and exploiting the heat from the sun is a strong contender

Ole Skov oes@agrotech.dk, and Jens Rystedt jor@agrotech.dk, consultants, AgroTech

Solar radiation is potentially an enormous

source of energy, and in a greenhouse

the annual influx of energy is about

850 kWh/m2 (measured on a horizontal

surface inside the greenhouse); approximately

twice as much as the greenhouse’s

own energy consumption.

In principle, a greenhouse is one big

solar panel, and it will become increasingly

common to collect some of the

surplus energy from the greenhouse and

store it for later use. However, so far the

investment required has been too big to

make this possible. Storage of the large

amounts of energy for use in the winter is

a great challenge.

Perhaps better insulation of greenhouses

would be a good start, as this would

reduce the amount of energy which would

have to be stored. With better insulation, it

is not unrealistic to halve the energy need.

After this we can tackle exploitation of the

sun’s energy, either directly in the greenhouse,

or by using solar panels, or through

a combination of the two.

Harvest of solar energy

Great challenges have to be overcome

before we can meet all our needs using

solar energy: How is the energy to be harvested,

and how is it to be stored?

The plants seen so far, mostly in the

Netherlands, uses ventilation units to harvest

the energy by transferring it from the

air in the greenhouses to water, which is

often stored underground. This method

works at relatively low temperatures, especially

in the storage facilities. The energy

has to be transferred back to the greenhouse

from the water to the air.

The surplus energy from the sun can

be harvested and stored in many different

ways. The method to be chosen depends

on the existing equipment and on the

percentage of the energy consumption to

be covered initially by the surplus energy.

At many sites, buffer tanks and other

types of water storage have been installed

which can be used as energy stores for

short periods – e.g. from day to night or

over a few days. For example, if the surplus

energy is collected on a daily basis via a

ventilation plant in which the water temperature

is heated to 70°C and then stored

in a 500 m 2 buffer tank, this can be enough

to cover the energy consumption of a 5000

m 2 greenhouse for four to five summer

months. This corresponds to about 20 percent

of the annual energy consumption.

Water is either heated using traditional

solar panels, or using a heat pump.

New possibilities

So, even with a small heat storage facility,

it is possible to reduce the use of fossil

fuels. In combination with installation of

ventilation equipment, this provides new

opportunities to secure energy supplies,

and ventilation equipment in the greenhouse

means it is possible to control and

adjust the greenhouse climate by evening

out the differences in temperature and

humidity.

If we want to increase the percentage of

our energy which comes from solar heating,

we have to think in terms of larger storage

capacity. For example, underground

storage, or in heat storage ponds, which

are like large rainwater basins covered

with insulating material.

There is still some way to go before we

can say that we are independent of fossil

fuels, but energy directly from the sun is

certainly one of the possibilities we should

keep our eye on.


20 ENERGY IN FOCUS


Energiforbrug

Dækmaterialer

• Glas

• Dobbeltglas

• Termoglas

• Polycarbonat

• Termopaneler

Gardiner

• Et eller to lags

• Stoftyper

Der kan bygges

på mange måder

Dæklister

• Gummitætningslister

ved glas

Grønnegyden 105

DK-5270 Odense N

Phone: +45 6614 5070

Telefax: +45 6614 5084

E-mail: gpl@gpl.dk

http:/www.gpl.dk

Lad os se på

dit væksthusprojekt

Applikation and administration of:

Plant Breeders’ Right / Plant Patents

Trade Marks and Utility Patents

Odensevej 38 • Verninge • 5690 Tommerup • Tlf. +45 6475 2000 • Fax: +45 6475 2470 • info@viemose-driboga.dk • www.viemose-driboga.dk

ENERGY IN FOCUS 21


Jan Agnoletti Pedersen, Vikingegaarden A/S, jap@vikingegaarden.com • Mads Andersen, Senmatic, DGT-Volmatic, maa@senmatic.dk •

Jens Rystedt, AgroTech, jor@agrotech.dk

Purchase electricity when

it is cheapest – automatically

More than 20 percent of the energy consumption in Denmark is covered by wind

turbines, and it is estimated this will increase dramatically in the future. The successful

implementation of a high coverage of green electricity presents some huge challenges,

but it also opens up for some great opportunities. The wind turbines produce electricity

when the wind is blowing, no matter if there are consumers who can use it or not.

To obtain the balance between electricity

production and electricity consumption,

a “balance” system has been

set up with decentral standby electrical

consumers/producers and varying electricity

prices as the essential elements.

When purchasing electricity on the

spot market, it is possible to purchase

the electricity at the actual market price,

which varies hour by hour. The variations

are huge, ranging from free of charge to

very expensive in periods with high consumption.

The free of charge periods are typically

periods where the wind is blowing and

consumption of electrical power is at a

minimum. Consumers with an electrical

consumption which can be moved from

one period of the day to another, and with

a minimum of disturbance, can profit from

this system.

As a rule of thumb it is possible to save

up to 10-15 percent on the electricity bill,

as the electricity prices can vary from free

of charge to EUR 0.9-1.0 per kWh. This

large variation gives great opportunities for

significant savings on operating costs.

Change time of consumption

One condition to exploit the variations in

the electricity prices is that it must be possible

to change the hours in which electricity

is consumed, with no loss of production.

Many industrial companies are

locked to working hours, as the production

must run when the personnel is present.

However, there is a vast number of

industries with the option to change their

consumption pattern. For example cold

stores, industrial processes and pump units

can benefit from changing their consumption

to the hours with cheap electricity.

Vikingegaarden A/S manufactures webbased

control equipment, including a

module enabling the possibility to utilize

electricity when it is cheapest - Elspot.

The module can be programmed to

switch on a plant for the eight cheapest

hours, or only to switch on when the price

is below a certain price level.

Elspot system for growth light

Senmatic, AgroTech and Vikingegaarden

A/S have teamed up and are in the process

of adapting and integrating the Elspot

system so that it can be used in connection

with growth light and optional electrical

heaters.

The system from Vikingegaarden A/S

retrieves the hourly prices of electri-

city by means of the GSM/GPRS net work.

Those hourly prices are transferred to the

SuperLink 4 from Senmatic for use in the

advanced control system.

This means that electricity prices are

part of the optimization program, assuring

the most optimum match between the

lowest possible electrical prices and the

maximum growth of the plants, assuring

the horticultural sector the most profitable

business.

The systems from Senmatic and Vikingegaarden

A/S are now being implemented

and will later be tested at a nursery to

determine functionality and the financial

benefits.

The system is expected to be launched

on the market later this year, for use in the

forthcoming growth light season.


22 ENERGY IN FOCUS


Flemming Ulbjerg • Chief consultant, Rambøll, fu@ramboll.dk

Renewable energy

and the storage issue

Full conversion to renewable energy requires innovation and development.

For example, “production” and “consumption” do not always go hand in hand for

renewable energy. If we want to use more renewable energy than we do today, we have

to be able to store energy over long periods of time; and this presents a challenge

The Danish Government’s long-term target

is to be able to cover most Danish

energy consumption requirements with

renewable energy.

The renewable energy sources currently

commercially available are large-scale

solar heating and wind power both offshore

and onshore. In addition, biomass in

the shape of chippings and straw etc. is a

well known energy source, although supplies

are limited.

Large scale solar heating

Large scale solar heating has been installed

at a large number of district heating

plants supplying natural-gas fired heating.

Partly because of the taxes on natural gas,

solar heating is an extremely profitable

alternative to current supplies from natural

gas.

The cost of heat from a large solar heating

plant for the first year can typically

be around DKK 250 per MWh heat, compared

with natural gas which costs about

DKK 500 per MWh, including tax.

These solar heating plants usually cover

between 15 and 20 percent of annual

energy consumption.

Not until heat-storage technologies are

commercially mature and tested will the

way be paved to expand these solar heating

plants to cover somewhere between 50

and 75 percent of the annual consumption

of heat at a specific district heating plant.

Geothermics as a storage method

Today, geothermics are usually associated

with direct heat supply such as that in

Copenhagen, for example, in which hot

water is obtained from very deep boreholes

- often around two kilometres deep

- and then used for direct heating.

However, geothermics are also a promising

storage method. In some green-

houses heat is stored in aqueous sand

layers at a depth of about 100-200 metres.

Dutch greenhouse companies are increasingly

using this method. The heat is

extracted from the greenhouse in the summer

using a heat pump, and it is led back

in the winter via the same heat pump.

Underground storage is not possible

everywhere, so short-term storage in steel

tanks is attractive, and just as effective

as geothermic storage. However, both

geothermic storage and other forms of

storage in lagoons or heat storage ponds

must be further developed before they can

be used commercially.

Need for innovation

It is likely that future heat supply for

greenhouses and heating other buildings

will come from a combination of different

sources, with wind and solar energy playing

a large part. However, before we get

there, there is a great need for innovation

in the development of cheap heat storage.

ENERGY IN FOCUS 23


Ole Bærenholdt-Jensen • Advisor, Danish Advisory Service, obj@landscentret.dk

Dynamic climate control works

– worldwide

The international GreenSys 2009 Conference in Canada in June contained new

research results from all around the world. A major part of the conference

was about the latest developed ideas concerning energy savings. One method

for saving energy, Dynamic Climate Control, which gets a lot of attention

in Denmark, was backed up by several presentations

Some presentations from the conference

revealed that many people are

researching the same elements which are

included in the Danish Dynamic Climate

Control Concept.

Results from the “Intelligrow” project

research going on in the period 1998-2002

gave an idea of the potential for energy

saving from this kind of climate control.

The Intelligrow research has created a base

for a great part of the later development

concerning climate control in Denmark.

One important element in Dynamic

Climate Control is to allow bigger fluctuations

in the temperature in the greenhouse,

which gives you the highest possible part

of the heat from the irradiation, and as

little as possible from heating unit based

on fossil fuel (nature gas, coal, oil).

Modest, aggressive and extended

control in Great Britain

Steve Adams, Great Britain presented

results from his research in energy savings

using different levels of flexible temperature

control, based on TI, Temperature

Integration. There was calculated on three

levels: Modest, aggressive and extended

TI.

Results and explanation from the calculations

of energy use can be seen on

monthly base in figure 1.

Trials were made using these methods

in tomatoes, pot-chrysanthemum, pansy

and petunia, on Warwick research station.

The results in tomato production were

good using TI with a day temperature setpoint

on 14°C, and the yearly harvest was

not affected.

Also in pot plants the results were good,

with only 1-2 days extension in production

time using temperature setpoints at 12°C

and ventilation setpoint at 26°C.

Low temperature three

hours post-night

From Canada Mr. X. Hao et. al. reported

from trials in Ontario in tomatoes. Low

Figure 1. Calculated monthly energy consumption. Conventional control (black) day/

night 18/18°C, ventilation at 20°C. You see 8% energy saving at modest TI control (light

grey, d/n 16/16°C, vent 23°C), 13% by aggressive TI control (White, d/n 12/12°C, vent

26°C), and 18% energy saving by extended TI control (dark grey, control as the former

plus fixed low day temp setpoint). Note that only at the extended TI control it is possible to

save energy in November-February. And in June-august you can see energy consumption

at almost zero at aggressive and extended TI control.

temperature late night, combined with

temperature integration gave an increased

temperature during daytime to compensate

for the night time period with low

temperature.

The conventional treatment weas 17°C

during the three hours, to compare with

the treatment in the trial with 13,5°C

during the three hours.

There was no energy saving in February,

but 6-8% saving in march-may. Dew point

temperature at the 13,5°C treatment was

lower compared to conventional, so there

was no humidity problems concerning the

treatment. The trials did not show major

differences in harvest level (except for one

variety).

Dynamic tomatoes in France

Trials in tomato growing in West-France

using Dynamic climate control (Temperature

integration and higher/lower setpoints)

was described by Serge le Quillec

et. al. There was references also to the

Danish Intelligrow concept.

Description and results are seen in figure

2. You can see energy saving around 5%

- 15% without loss of harvest, if you assure

that the temperature don’t get lower than

13°C and not beyond 29°C. The weight

pr fruit becomes 10% higher. It was also

stated that you get higher CO2 level during

the day, having a slightly lower consumption,

because of more closed windows.

But it was also pointed out that you

have to be aware of using an effective

humidity control because of Botrytis risk,

and that you should look for more temperature

tolerant varieties, to reach bigger

energy saving results by using dynamic

climate control.

Several Dutch trials

J. A. Dieleman et. al. described in a wide

range presentation the research going on

in the latest years in Holland, concerning

energy saving from greenhouse technique,

climate control and plant physiology.

24 ENERGY IN FOCUS


Figure 2. Dynamic climate control tomato trials in France. Energy

consumption and saving in 2006-2007. At IT1 the Temperature

integration had 2-5°C extra space from highest/lowest setpoints,

compared to control. At IT2 it was 3-8°C.

She described that the essential element

in energy effectiveness by change in

climate control is to allow big difference

between highest and lowest temperature

in a “band-width”, to allow higher humidity

level, and to use dynamic changes of

the setpoints in the control.

It was stated that results from several

trials where many different cultivars were

used, show that most cultivars are tolerant

to temperature fluctuations, if you assure

to keep track of the average temperature

by using temperature integration control.

This is well known knowledge, but here

Anja Dielemann said that this assumption

is based on documentation from research,

and not just a “rule of thumb”. Results

from some trials show energy saving from

3% to 13% using a band-width on 10°C

in the temperature integration control, as

an example from the research in Holland.

Low temperature for Anthurium

grown in Belgium

If you want to use dynamic climate control

you have to decide the limit for the

allowed, lowest temperature. This can be

due to the danger of leaf wetness caused

by high humidity, if the humidity control

can’t catch up with the temperature

fluctua-tions. It can also depend on which

temperature tolerance the cultivars are

“born with” from their origin, and still not

loosing quality.

Trials that should help to state the

lowest acceptable temperature were

described on a poster from Els Storme et.

al. from Belgium.

Growing Tropical plants often requires

fairly high temperatures, therefore energy

use can be high. Therefore it is especially

important to try to save energy, for

example by using dynamic climate control

with low temperature setpoints. But how

low? The trials were made on Anthurium

‘Limoria’ (C3 plant), set in different temperature

regimes, from high to low. Measuring

on different processes in the crop,

they found that temperatures under 12°C

did affect the processes negative.

High temperature for poinsettia

On the other hand you also have to get

to fairly high temperature, especially in

Research from different places shows that it is also possible to use dynamic

climate control in tomatoes if you choose appropriate setpoints.

Anthurium. Research shows that the processes in the

plant are affected at temperatures below 12°C.

the middle of the day, where you can harvest

more free energy form the sun if you

allow high temperatures. But you can also

decide to use high temperatures if you can

buy cheep energy in certain periods.

In Germany there has been trials on this

for Poinsettia. N. Gruda et. al. used day/

night setpoints fixed on 25°C/16°C, plus

a period in the morning using even lower

temperature (12°C).

The control day/night were 18°C/16°C.

Results were good. Plant quality was good,

with bigger leaf area and same height

development, although they became a

little higher. Conclusion was that it is possible

also to use higher temperatures to

produce good quality poinsettia, in periods

where you have “luxury heat”, cheap

or free, and thereby save energy and/or

money.

Dynamic climate control

will remain

The elements from dynamic climate control

are described in an article by the

present writer in Gartner Tidende no. 12

from June 2009. A wide range of results

from research in other countries supports

that dynamic climate control works, gives

energy savings and states that the climate

control course in Denmark is right.

In several of the projects, described in

other articles in this magazine, is dynamic

climate control involved. One example

is from the project “Intelligent use of

energy”, where the climate control in

the demonstration greenhouse at “Hjortebjerg”,

Funen, is including the “Intelligrow”

climate control concept.

In my opinion we are going in the right

direction, but to be backed up by research

results from all over the world confirms

the concept. Dynamic climate control has

come and will remain.


ENERGY IN FOCUS 25


New

Leona

New

Tosca

Osteospermum

For years Dalina have been breeding Osteospermum,

and we are happy with the results they

have achieved.

There are now 15 Dalina® Osteospermum

cultivars available, in beautiful colours.

The Dalina cultivars are grower friendly, with

good garden performance.

Young Flowers present –

New

Olympia

6-Packs

Meet us at

Horti Fair

Hall 7 stand 0816

Young Flowers A/S is a global trading company,

specialising in delivering young plants, cuttings,

half-grown and seeds for nurseries and wholesalers.

We have a wide range of products in our

assortment, and we are always happy to make

you an offer.

26 ENERGY IN FOCUS


The World of Dalina® 2010

Midi+

Maxi

Dahlia

As a result of Dalina’s intensive breeding

programme, they have created a number of

beautiful and grower friendly cultivars.

Dalina® Dahlia cultivars are both healthy and

vigorous, minimising production problems.

The short production time optimises efficient

use of the available facilities.

There are now four different strains to choose

from:

Mini. 6-11 cm pots

Midi. 10-12 cm pots

Midi+. 12-14 cm pots

Maxi. 15-30 cm pots

ENERGY IN FOCUS 27

Tel.: +45 6317 0495 · info@youngflowers.dk · www.youngflowers.dk


Lotte Bjarke, editor, Gartner Tidende, post@lottebjarke.dk

Two organisations

working for the same cause

Danish Horticulture and the largest trade union in Denmark, 3F,

are in close dialogue with each other and often back up each other’s views.

Safeguarding the future of the horticultural business and preserving

jobs are some of the organisations’ common goals.

When the future of the horticultural

business is threatened, Danish Horticulture

and 3F move closer together as

was the case in the early spring when the

two organisations received the Tax Commission’s

proposal for a new Tax reform.

- We have no doubt that a quick reaction

and a joint statement from our two

organisations made a difference so that

the final result of the tax proposal ended

up not being as bad as expected, agrees

Jesper Lund-Larsen, 3F’s consultant for

environment and working environment,

and consultant in Danish Horticulture, Leif

Marienlund.

Involve staff

The two consultants can give several

examples of cases where the organisati-

ons have mutual interests among which

the most important ones are climate and

energy.

- Obviously, the energy issue is very

crucial for the greenhouse nurseries.

We are more than willing to take part

in fulfilling the climate goals set out by

the Danish State. Long-term survival is

dependent on future reductions of the

energy level. But at the same time we must

remember that the horticultural business

has already reducet its energy consumption

by 26% from 1996 to 2008, says

Leif Marienlund, who points out that this

reduction is due to close and focused cooperation

between management and staff

in the individual greenhouses. This is a

very important issue for 3F.

- It is of great significance that the staff

is involved in the whole process as this

will result in bigger profits and happy

employees, and it helps valuable experience

to be passed on from one nursery to

the colleagues in the other nursery, says

Jesper Lund-Larsen.

Common conditions in the EU

The organisations are keeping a sharp eye

on the present development on tax changes

in Denmark.

- There is no doubt that the energy

bill will increase, and it is important that

the greenhouses keep focus on energy

savings. We would like to take part in

discussions on how to reduce energy

consumption, but at the same time we

have to ensure that we are not punished

afterwards. If this situation becomes reality,

the whole Danish horticultural sector

will be closing down, Jesper Lund-Larsen

points out.

- It is a fundamental problem to provide

funds for development and one of our

greatest challenges. We are very pleased

that the Danish Minister for Food, Agriculture

and Fisheries Eva Kjer Hansen has

made a contribution of DKK 50 million

to the horticultural sector (“gartnerikonvolutten”)

to support projects concerning

innovation, energy, water consumption

etc. But it is a bit disappointing that di-

strict heating is not included in this grant,

says Leif Marienlund. He adds that of course

new technology can create jobs, but at

the same time it is important to remember

to use and develop already existing technologies.

Leif Marienlund and Jesper Lund-Larsen

wish the Danish and the European horticultural

industry all the best and hope

that the future will bring uniform working

conditions for all growers within

the framework of the EU to avoid Da-

nish growers looking upon their Dutch

colleagues in the future with envy when

they are receiving state guaranteed loans

and other means of subsidies.


28 ENERGY IN FOCUS


Pindstrup products are sold

worldwide and delivered in

bulk, Big Bales, compressed

bales or loose-filled bags.

Transport arranged by trailer,

containers or shiploads as

required by the customer.

Pindstrup · DK-8550 Ryomgaard · Denmark

Tel.: + 45 89 74 74 89 · Fax: + 45 89 74 75 70

www.pindstrup.com · E-mail: pindstrup@pindstrup.dk

ENERGY IN FOCUS 29


Af: Søren Møller Sørensen • COO (Chief Operations Officer), Container Centralen a/s, s.sorensen@container-centralen.com

Plants on wheels reduce the

Since 1976, pot plants in Europe have increasingly been transported

on trolleys – the CC Containers from Container Centralen (CC).

This has optimised horticultural logistics tremendously

In the beginning, transportation costs

and waste due to damaged plants and a

lot of one-way packaging were the major

concerns.

In the 21st century, the environmental gains

of reusable transportation items have also

become a focal point on the agenda.

Standard for plant logistics

To optimise horticultural logistics, the largest

plant exporters in Denmark came

together in the mid 1970s to develop a

transportation unit and a complementary

management system. This resulted in the

reusable CC Container and the CC Pool

System, which is now the leading transportation

system for pot plants in Europe,

including inter-continental flows, e.g. from

Asia or Latin America. CC Containers are

produced in Asia, and they are loaded

with young plants on their maiden voyage

to Europe. Transportation of empty CC

Containers is avoided, and combining

the transportation of new CC Containers

and young plants reduces CO2 emissions

immensely.

The CC Container was developed to

fully use the space in a cooled truck. At

the same time, the introduction of the CC

Pool System made it possible to exchange

empty containers for full and vice versa.

sThis decreased the need for transportation

of empty containers. When empty

containers now and then have to be transported

– e.g. when sent for repair and

maintenance – they can be disassembled

and condensed to a fraction (1/10) of their

loaded volume.

Further improvements

Needless to say, the CC Containers can

be used over and over again, eliminating

the need for one-way packaging that contributes

negatively to the CO2 account

due to more production, waste disposal,

and a poorer utilisation of space in cooled

trucks.

Also, space utilisation in warehouses is

better since there is no need to allow for

space for the forklift handling, reducing

energy for light, heating, etc.

Thus the CC Pool System, including the

When the CC Container was developed in the mid 1970s, the aim was to reduce costs in the logistic chains.

An extra bonus of optimised logistics is the reduction of the carbon footprint. The CC Container has contributed to this since 1976.

30 ENERGY IN FOCUS


carbon footprint

CC Container, has contributed to a reduction

in CO2 emissions long before climate

changes became a global concern.

From February 2010, all CC Containers

will be equipped with RFID tags (Radio

Frequency IDentification). Using RFID for

Track & Trace further improves logistics,

leading to even larger CO2 – and cost

savings in the future.

More information:

www.container-centralen.com

www.cc-rfid.com

This is how the CC Container

reduces the carbon footprint

in horticultural transportation

• Since the CC Container is a returnable transport item, continuous production

and waste of disposable packaging are avoided.

• The introduction of RFID on CC Containers in 2010 will optimise logistics and

thus reduce CO 2 emissions further.

• The CC Container has been developed to utilise all available space in cooled /

traditional “flower” trucks to avoid transportation of “air”.

• CC Containers can be exchanged full for empty and vice versa in the CC Pool

System, and therefore don’t have to travel empty over long distances.

• Container Centralen also ensures that the trucks don’t travel empty on their

return trips. Average utilisation of truck space on CC controlled transportation

of CC Containers is about 97% (including empty trucks in transit), versus the

Danish average of only 38% (source: A recent analysis published by e.g.: http://

www.dr.dk).

• Whenever empty CC Containers have to be transported, they can be condensed

to a fraction of their loaded volume (1/10).

• New CC Containers are loaded for the first time already in their country of origin

for their maiden voyage – so right from the start they don’t travel empty.

Complete horticultural

engineering

Wilk van der Sande is specialised in heating, greenhouse cooling, electrical engineering, irrigation

and closed greenhouses. Wilk van der Sande is a very innovative company, continuously

developing new solutions for improved energy saving systems. You will nd no other supplier

with such vast expertise, particularly in the eld of closed greenhouses. The combination of

disciplines takes a lot of work off your hands.

ENERGY IN FOCUS 31


Optimal Irrigation Solutions

Years of experience and

advanced new products

make us a leader

in customized

irrigation systems

in Northern Europe

Optimal Irrigation Solutions ensure precise and correct amounts

of water and energy in environmental friendly applications

Vestre 32 Kongevej 7 • 8260 Viby J. Denmark • Tel: +45-86 10 71 37 • Fax: +45-86 10 71 67 • Mobile: ENERGY +45-26 IN 74 FOCUS 71 37

• www.orev.dk • post@orev.dk

SpinNet SD application photo by OREV PTS09


Mini symposium / workshop

Intelligent use of Energy

in Greenhouses


6 - 7 October 2009

at

University of Southern Denmark, Odense, Denmark

THE EUROPEAN UNION

The European Regional

Development Fund

Investing in your future


Welcoming message

The greenhouse horticulture sector is under pressure of the huge energy expenses.

The sector’s energy consumption needs to be reduced, and efforts are being made

to find solutions, which will both reduce costs and benefit the environment. Reducing

energy consumption often reduces the quality of plants, and new technological

solutions and increased understanding of the physiological reactions of plants

will be necessary to achieve energy reduction while maintaining plant quality but

actually also to increase and diversify the production

In Denmark there has been a long history of research and development within

the area of energy saving. Most of the Danish work has been centred on the physiologically

based ideas of dynamic climate management (IntelliGrow), which has

been one of the causes of the decline in energy use in Danish nurseries.

Two projects have been granted, “Greenhouse Concept 2017” and “Intelligent

Use of Energy in Greenhouses”. The technologies, which will be investigated as

part of these projects, include storage of surplus energy in an aquifer, physiology of

plants dynamic climate control, light-emitting diodes and a number of other technologies,

which may contribute to energy efficiency in greenhouses. Results are

tested and demonstrated at Hjortebjerg Nursery in Søndersø. “Greenhouse Concept

2017” was established as an innovation consortium financed by the Danish

Agency for Science, Technology and Innovation under the Ministry of Science,

and the “Intelligent Use of Energy in Greenhouses” project is sponsored by Region

South Denmark and the European Regional Fund.

In the future, the horticultural sector, universities, ATS companies (Authorised

Technology Service) and other technological companies need work together to find

a solution for the industry and associated businesses. This will require novel use of

ideas and methods that currently is not in use in the greenhouse industry.

On the other hand the potential for energy production from the five million

square meter might be important in the longer scale, but will require more interaction

between growers, energy and technology suppliers.

On behalf of the Danish partners in the project behind the workshop – welcome

Carl-Otto Ottosen

Convener

34 ENERGY IN FOCUS


Program

Tuesday October 6

9.30 Opening

Carl Holst, Chair of Region South Denmark

9.45 Keynote

Towards the semi-closed greenhouse? Dr. Silke Hemming, WUR, NL

10.30 Coffee

10.50 Topic 1: The closed or semi closed greenhouse

Moderator Carl-Otto Ottosen, DK

10.50 Novarbo – Closed Greenhouse Cooling, Huttunen, Finland

11.10 The intelligent greenhouse concept, Lund et al, DK

11.30 Themato air heating monitoring study, Chin-Kon-Sung et al. NL

11.50 Using Novarbo cooling with cucumber, tomato and sweet pepper in summer 2009,

Kaukoranta et al. Finland

12.15 Lunch

13.20 Topic 2: Climate control in the future

Moderator, Janni Lund, DK

13.40 Improving productivity of cucumber, tomato and cut rose in semi-closed greenhouse

in Finland, Särkkä et al. FI.

14.00 Predict – climate management software for dynamic climate control, Nørregård Jørgensen et al. DK

14.20 How do we pass on new ideas like Dynamic climate control and new greenhouse

ICT to the grower? Bærenholdt-Jensen, DK

14.45 Coffee

15.15 Topic 3: Technology in greenhouses

Moderator: Andreas Ulbrect, DE.

15.15 Multilayer screening system in greenhouse with screen materials with different properties

to enhance energy saving, Andersson & Skov, DK

15.35 Innovative roofing materials for increased plant quality and energy consumption, Lambrecht et al. DE

15.55 Environmental Sensors for Harsh Environments – a Novel Approach to Multiple Parameter

Sensors for Greenhouses, Jensen & Bennedsen, DK

16.15 Dynamic management of supplemental light, Ottosen et al. DK

16.35 The effect of screen material on leaf and air temperature, Rosenqvist et al. DK

17.00 General discussion – how can we link the greenhouses to the energy grid?

18.00- Dinner at SDU

Wednesday October 7

9.00 Departure to Hjortebjerg Nursery (on your own or organized by the workshop)

10.00 Exhibition and presentation of projects in the commercial nursery and exhibition

of technical equipment associated with energy saving

11.30 Quick lunch and return to city

ENERGY IN FOCUS 35


Silke Hemming, Wageningen UR Greenhouse Horticulture, P.O. Box 644,

6700 AP Wageningen, The Netherlands. E-mail: silke.hemming@wur.nl

Towards the semi-closed greenhouse?

In current greenhouse horticulture, next

to high production levels, quality and

timeliness of production are important.

This can be reached by optimal control

of greenhouse climate for which energy

is of major importance. More conditioned

greenhouses are preferable. Next to

that the need for (energy) cost reduction

has become higher, since with increasing

prices of natural gas in the last decade,

energy forms a substantial fraction of the

total production costs. The liberalisation of

the energy market for Dutch growers since

2002 has increased the growers awareness

of the energy consumption of their cropping

systems. This free market implies that

growers do not pay a fixed price per unit

of natural gas anymore, but that prices are

greatly determined by the maximum supply

capacity of the gas contract. Therefore,

it is important to reduce peaks in energy

use. In view of the Kyoto protocol several

governments have set goals for energy use

and CO emission. In the Netherlands, the

2

horticultural sector and government have

agreed to improve the energy efficiency

(production per unit of energy) by 65% in

2010 compared to 1980 and to increase

the contribution of sustainable energy to

4%. Over the period 1980 – 2005, energy

efficiency in Dutch greenhouse industry

has more than doubled. However, total

energy use per square meter of greenhouse

hardly changed. Efficiency improvement

resulted from a more than doubling in

yield per m2 caused by amongst others

improved greenhouse transmission, cultivars

and cultivation techniques.

Energy in the greenhouse is primarily

used for temperature control, reduction

of air humidity, increase of light intensity

and to a lesser extent for CO supply.

2

The use of fossil energy can be reduced

by limiting the energy demand of the

system and decreasing energy losses (higher

insulation), by intelligent control of

(micro)climate, by increasing the energy

efficiency of the crop and by replacing

fossil energy sources by sustainable ones.

In this paper, recent developments concerning

reduction of energy consumption

in greenhouse production systems will be

presented, as well as the consequences for

crop management.

Energy saving of

greenhouse systems

Energy requirement of the greenhouse can

be lowered by reducing energy losses.

Energy losses occur through the ventilation

as sensible and latent heat, but also

through the greenhouse covering by convection

and radiation. Using greenhouse

covers with higher insulating values and

the use of energy screens highly limits

the amount of energy losses. Increased

insulation can be obtained by modern

greenhouse materials, where new coatings

(low emission and anti-reflection) are

applied. Energy saving of 25-30% seem to

be possible with the new double materials

compared to a greenhouse with single

glass and energy screen. A prerequisite is

that new insulating materials should not

involve considerable light loss, since this

would result in a loss of production, since

1% additional light results in 0.8-1% more

production. With new double materials

loss of light is not to be expected. If additional

CO 2 is applied and attention is paid

to humidity control, production will not

decrease, in spite of considerable energy

savings.

Thermal screens add an additional barrier

between the greenhouse environment

and its surroundings. When movable, it

has less impact on the light transmission

compared to fixed screens. If they are used

almost permanently, screens can reduce

the energy use by more than 35%, depending

on the material. In practice, movable

screens are closed only part of the cropping

season depending on the criteria for

opening and closing. Due to restrictions

for closing, generally enforced by criteria

related to humidity and light, in commercial

practice reduction in energy use by

thermal screens is restricted to 20%. Efficient

screening strategies can save energy

saving while maintaining crop production

level. Delaying the screen opening to out-

side radiation levels above 50-150 W m -2

energy savings can be reached in practice

without production losses.

Semi-closed greenhouse concepts

Semi-closed greenhouse concepts contribute

to energy saving. The last years

several greenhouse concepts were developed.

It started with using the greenhouse

itself as solar collector (solar greenhouse

“Zonnekas”), followed by fully closed

greenhouses, towards energy producing

greenhouses (“Kas als energiebron”) and

latest developments toward electricity producing

greenhouses (“Elkas”). In closed

greenhouses, the excess of solar energy

in summer is collected and stored e.g. in

aquifers to be reused in winter to heat the

greenhouse. These concepts result in a

reduction in primary energy use of 33%,

based on 1/3 of the area with closed

greenhouse and 2/3 with traditional greenhouse

with ventilation windows. Besides

aquifers for seasonal energy storage, the

technical concept consists of a heat pump,

daytime storage, heat exchangers and air

treatment units which either bring the cold

air directly into the top of the greenhouse

or do so via air distribution ducts below

the gutters. In this concept, ventilation

windows are closed. Thereby, CO 2 levels,

temperature and humidity can be controlled

to the needs of the crop. To reduce

investment costs, in practice growers

tend to choose for a semi closed system.

Cooling capacity of this system is lower

than that of a closed greenhouse. Therefore,

when the active cooling capacity is

insufficient to keep the temperature below

the maximum, ventilation windows will

be opened. CO 2 emission in (semi)closed

greenhouses is considerable lower than in

open greenhouses. In a recent experiment,

in which tomatoes were grown with a CO 2

supply capacity of 230 kg ha -1 h -1 up to

a maximum concentration of 1000 ppm,

in the open greenhouse 54.7 kg CO 2 m -2

was supplied whereas in the closed greenhouse

this was 14.4 kg CO 2 m -2 .

Specific characteristics of climate in

36 ENERGY IN FOCUS


(semi)closed greenhouses with cooling

ducts under the gutters are: high CO 2

concentrations, vertical temperature gradients,

high humidities, combined conditions

of high light intensity and high

CO 2 concentration, and increased rates

of air movement. Investigations showed

that air circulation did not change the

photosynthesis light-response curves. Yield

increase was therefore attributable only to

the instantaneous effects of elevated CO 2

concentration. It was also shown that at

high irradiance, the optimum temperature

for crop photosynthesis increased with

CO 2 concentration.

The higher humidities cause a reduction

in transpiration, and thereby increased

temperatures of the top of the canopy. In

systems where cooling ducts are below the

gutters, temperature differences of 5°C between

roots and top of the plant can occur.

This affects the time necessary for fruits to

mature. At lower temperatures, fruits need

more time to ripen. Tomato fruits were

found to be more sensitive to temperature

in their later stages of maturation at which

they are at lower temperatures in (semi)

closed greenhouses.

Development of new greenhouse concepts

is ongoing. Current examples are

greenhouse systems which even create

a surplus of energy to be delivered to

neighbor greenhouses, other industries or

houses. Concepts like Sunergy Greenhouse,

Sun Wind Greenhouse or Flow-

Deck Greenhouse are examples for that.

With different technological concepts an

energy surplus has to be generated. Currently

these three concepts are shown at

the Innovation and Demonstration Centre

in Bleiswijk. The innovations are intended

to inspire commercial operations to take

advantage of sustainable solutions for climate

neutral production. The performance

of the systems is currently investigated by

Wageningen UR Greenhouse Horticulture.

Sunergy Greenhouse

The sunlight that enters the greenhouse is

absorbed by plants and heats the greenhouse

air. During the summer, this energy

can be collected from the greenhouse air

by means of heat exchangers. The heated

water is then stored in an aquifer until it

can be used during the winter to provide

energy to a heat pump of the greenhouse

and those of third parties. The objective

of the Sunergy Greenhouse is to obtain

the greatest possible light transmittance.

A double screen traps heat to reduce

the greenhouse’s own heat consumption.

This greenhouse combines the best of the

existing technologies now being applied in

horticulture.

The roof of the greenhouse is equipped

with anti-reflective glass (GroGlass).

The greenhouse is seven metres in height

and has an ultra-lightweight substructure

(Twinlight). There are no roof vents. The

climate is controlled by means of pipe rail

heating, an air-treatment unit with slurves

under the gullies, and overhead cooling

units (1/100 m 2 ). Heat loss is limited by

a double screening system consisting of a

transparent screen (XLS 10 ultra plus) and

an aluminized screening material (XLS

18). A new sliding system prevents leaking

gaps. The transparent screen is closed at

night and during cold days. The aluminized

screen is closed during the night and

when the outside temperature drops below

12 0C. Dehumidification is accomplished

by drawing in outside air. This greenhouse

concept is based on storing heat collected

during the summer in an aquifer.

The concept is developed by Wageningen

UR and P.L.J. Bom greenhouse builders.

Sun Wind Greenhouse

Many pot plants are shade plants that

require a high degree of screening during

the summer. A shade cloth can prevent

solar energy from entering the greenhouse,

and light not transmitted into the greenhouse

can be collected with a screen that

acts as a solar collector. An innovative

paneled screen installed in the Sun-Wind

Greenhouse collects energy in the form of

warm water and prevents direct sunlight

from entering the greenhouse. The warm

water is then stored in a special buffer

under the greenhouse for re-use during

the winter.

The greenhouse roof faces south and

consists of adjustable solar collector

panels sandwiched between double glazing

at a 35° slope. The north side of the

greenhouse consists of acrylic sheets with

a slope of 60° and one-sided continuous

roof ventilation. The post height is three

meters, ridge height nine meters and trellis

girder 11.80 meters. Climate control

is conventional. When heat is required,

the greenhouse is heated with water from

the buffer delivered by means of a standard

heating system. For a commercial

operation, a wind turbine will generate

the electricity for the pumps. The excess

electricity will be delivered to the power

grid. During calm periods, electricity will

be drawn from the power grid.

This concept is developed by Thermotech

and Gakon greenhouse builders.

FlowDeck Greenhouse

During cold periods, the greatest loss of

heat occurs through the greenhouse roof

and sides. During the summer, the reverse

occurs and the greenhouse collects a great

deal of solar energy. A roof consisting of a

double layer ‘Flowdeck’, is better insulated

than a standard glass greenhouse. During

very sunny periods, pre-treated water can

flow between these layers to improve

light transmittance to benefit the crop.

The greenhouse roof also collects heat;

this keeps the greenhouse climate cooler

and promotes the dehumidification of the

greenhouse. The heated water is stored in

an aquifer for re-use during the winter.

The greenhouse roof consists of hollow-core

polycarbonate sheeting through

which water flows from the gutter to the

ridge and back. The supply and drainage

system is integrated into the gutter. Light

transmittance through a Flowdeck is equal

to that of conventional acrylic sheeting but

when filled with water is equal to normal

single horticultural glass. The greenhouse

has a traditional Venlo structure with a gutter

height of seven metres and an extended

span of 6.40 metres. The greenhouse has

ENERGY IN FOCUS 37


oof vents on the sheltered side. Humidity

is controlled by the ClimecoVent system.

An air-handling unit for heat recovery

(the Regain unit) is connected to an air

distribution system with perforated flexible

pipes installed under the cultivating

systems. This enables dehumidification by

means of heat recovery. The greenhouse is

equipped with pipe rail heating and wall

heating. Forced-air heating/cooling units

are installed over the aisle. The greenhouse

is also equipped with a single shade cloth

(LS 10).

This concept is developed by Climeco

Engineering and Maurice greenhouse builders.

Energy efficient climate control

Within semi-closed greenhouse concepts,

an energy efficient climate control leads

to further reduction in energy consumption

and/or increase of production. Possibilities

are: temperature integration, drop

strategies, reduction of transpiration by

reduction of leaf area, higher setpoints

for relative humidity and using diffuse

light. New growing strategies are currently

developed for several crops. The aim of

such concepts is to reduce energy consumption

dramatically without production

losses. In the new growing strategy for

tomato e.g. the energy consumption has to

drop from 40m 3 to 26 m 3 gas per m 2 greenhouse

area. This is done by high insulation

using a double screen. The first screen is a

transparent screen, which is closed until

250 W/m 2 outside radiation. The second

screen is aluminized and highly insulating.

It is closed when the outside temperature

is below 8 o C. The heating temperature is

lowered by 1 o C, the ventilation setpoint is

Jukka Huttunen, Biolan Oy, PL 2, FI- 27500 Kauttua, Finland, jukka.huttunen@biolan.fi

increased. Above 85% humidity the ventilation

is opened. It seems that the goal can

be reached in a demonstration trial. Other

concepts are developed for other crops.

There are several possibilities to decrease

energy consumption in greenhouse

horticulture in the future. The challenge

is to reach that with low-cost solutions.

More conditioned greenhouse are certainly

necessary in the future. Semi-closed

greenhouse concepts are permanently in

development in order to optimize the

systems concerning costs and performance.

In order to apply new greenhouse

concepts and growing strategies into horticultural

practice cooperation and active

exchange of knowledge between growers,

horticultural industry, extension service

and research is necessary.


Novarbo – Closed Greenhouse Cooling

Keywords:

High yield, CO 2 , condensation

Abstract

High CO 2 during high light conditions is

possible in a closed greenhouse. Closing

also helps plant protection and prevents

the heat loss, which occurs when ventilating

excess humidity, especially when

using artificial lightning in a cold climate.

The result of closing is increased yield and

decreased energy use per product.

Novarbo is a novel cooling method for

closed greenhouse. Inside the greenhouse

is a water droplet curtain, which transfers

the energy directly from the warm and

humid greenhouse air to the cooling water

by condensation of the latent heat and

conductivity of the sensible heat. Only

the heated water is then led out, where

an evaporator sprays water through outside

air, evaporating and thus cooling the

water, which is then pumped back to cool

the greenhouse.

Two years of commercial use shows

the coefficient of performance in inside

cooling (COP) was 60 –200, which is very

high, compared to normal heat pump COP

3-8. The Finnish Agrifood Research center

has growing results with cucumbers: better

crop +(25-41) %, with cut roses: +

25 % with tomatoes +10 %. This method

maximizes the growth and minimizes the

environmental impact, especially in wellequipped

greenhouses.


38 ENERGY IN FOCUS


Janni Bjerregaard Lund, Ole Skov and Bent S. Bennedsen, AgroTech A/S

The intelligent greenhouse concept

The vision behind our concept is a 60%

reduction in energy from fossil fuel

when producing potted plants in a one

layer greenhouse and without any negative

effect on the quantity or quality of the

produce.

This objective will be achieved through a

combination of;

• Improved strategies for climate

control

• Extraction of surplus heat and

storing it in ground water reservoirs

• Improved curtain systems

• Introduction of a novel wireless

sensor system

• Further improvements of the

climate control software, in order

to utilize the potentials in the

new sensor technology, heat

extraction, LED lighting, and curtains.

The concept is being implemented and

tested on the greenhouse production

plant “Hjortebjerg” located 23 kilometres

north-west of Odense at Funen Island

(Latitude 55° N). The main production is

potted Euphorba milii Des. Moul.

The first step was carried out in 2007

and consisted of a climate check. This

involves construction of a mathematical

model, which simulates the greenhouses,

and computes the energy consumption

at different climate control strategies. The

result was that by introducing dynamic

climate control, an energy reduction of

at least 21% could be obtained. During

2008, the actual reduction was 35%, from

375 kWh/m 2 in 2007 to 241 kWh/m 2 in

2008.

Calculations have shown, that the irradiance,

received by a greenhouse over

the year, is twice the energy requirement

during the same period. However, there is

a surplus during the summer, which is lost

through ventilation and a deficiency in the

winter, which is supplemented by heating.

In our concept, we extract heat from hot

air, collected below the roof ridge of the

greenhouses, and store it in groundwater

reservoirs. During the summer, ground

water of 10 o C is passed through an air to

liquid heat exchanger, which raises the

water temperature to an average of 30 o C

with a maximum of 35°C.

The water is then pumped back into

the ground water reservoir, at a depth of

40 m, where it will maintain its temperature,

albeit with a slight loss, until winter.

The process is reversed during winter by

pumping the water up and cooling it by

means of heat pumps. This generates 70

– 80 o C water for heating the greenhouses.

The system is not able to fully extract heat

on hot summer days and will be comparable

to what is known as the semi-closed

greenhouse.

The combined effect of optimized climate

control and heat storage will be a

50% energy reduction.

Further reductions will be achieved by

introducing new curtains and improved

sensor technologies for more accurate

climatic information and further improved

climate control.

A system of two layers of curtain will be

introduced to improve the insulation and

thereby reduce heat radiation. The “NIR

curtain” and a LS16 curtain (AB Ludvig

Svensson) will be installed in the demonstrations

house at Hjortebjerg.

The new sensor system, which is being

developed by Danfoss IXA Sensor Technologies,

will comprise a relatively large

number of small, wireless sensors, which

will measure temperature, relative humidity,

CO 2 level, radiation and leaf temperature.

The sensors will be located in the

foliage of the plants, and hence give more

accurate and detailed information about

the actual conditions, which the plants are

experiencing. This will permit the grower

to fine tune his climate control, and thus

reduce the energy input.

The projects will continue until 2012,

by which time, we are confident that the

objective of a 60% energy reduction will

be achieved for the Hjortebjerg plant.

Further, based on the knowledge acquired

during the projects, other greenhouse production

plants will be able to achieve the

same amount of reduction of energy and

CO 2 emission.


ENERGY IN FOCUS 39


Roël Chin-Kon-Sung, TNO Bouw en Ondergrond, The Netherlands

Themato air heating monitoring study

Introduction

TNO is a Dutch knowledge institute that

applies scientific knowledge to strengthen

the innovative power of industry and

government. Our core areas are: Quality

of Life; Defence, Security & Safety;

Science & Industry; Built Environment &

Geosciences; ICT. By encouraging effective

interaction between knowledge areas,

we generate creative and practical

innovations in the form of new products,

new services and new processes.

Greenhouse horticulture is a major engine

of the Dutch economy. The sector also

enjoys a leading international position,

which has been built through constant

innovation. TNO and Horticulture is

making an active contribution to innovation

in the greenhouse horticulture sector

in cooperation with various players, inclu-

ding growers, suppliers, machine builders

and advisors.

Our mission has been described as

follows: TNO and Horticulture applies

scientific knowledge from various disciplines

within and outside the agrarian sector

with the aim of strengthening the competitive

power and innovative character of

industry in greenhouse horticulture.

In horticulture, the use of installation

techniques to achieve climate control in

greenhouses is increasingly widespread.

Due to rising energy prices, greenhouse

horticulture is always looking for new

energy-efficient climate concepts. The

knowledge of installation concepts used in

commercial and industrial buildings such

as air-conditioning and dehumidification

is now being applied in greenhouses. Such

a new climate concept is now being tested

at a grower’s enterprise. Together with the

tomato grower, an instalation manufacturer

and a plant research institute, TNO is

evaluating this system. The climate factors

temperature, relative humidity, CO2 concentration

and air movement in the greenhouse

are monitored.

The main project goal is to achieve

energy saving and increased tomato production.

The climate control system registers

measured and calculated data such as vent

position, heating, energy consumption etc.

and setpoints. The greenhouse climate factors

are monitored according to a detailed

measuring plan. Preliminary results are

presented.


40 ENERGY IN FOCUS


Timo Kaukoranta and Juha Näkkilä, MTT Agrifood Research Finland, Horticulture

Toivonlinnantie 518, 21500 Piikkiö, Finland, e-mail: timo.kaukoranta@mtt.fi, juha.nakkila@mtt.fi

Using Novarbo cooling with cucumber,

tomato and sweet pepper

in summer 2009

key component of an energy efficient

A greenhouse is a system that removes

humidity and heat from the greenhouse

to allow it to operate without ventilation

when deemed economically meaningful.

Novarbo system by Biolan Company, Finland,

performs that task by creating a

curtain of falling, cool water droplets that

extract from greenhouse air sensitive heat

by convection and humidity by condensation.

In the configuration installed at our

greenhouse at MTT Agrifood Research Finland,

at Piikkiö, the droplets are led to an

outside basin to be re-cooled by a Waterix

evaporative water cooler. The basin serves

also as a buffer in the system that allows

the droplet curtain and water cooler to

operate separately. Electrical energy is

consumed by the system for pumping cool

water from the basin into the greenhouse

and for operating the Waterix cooler.

In an experiment in 2009 we aimed to

fully closed greenhouse, constantly high

carbon dioxide concentration (CO 2 ), and

high radiation, supplemented by moderate

inter-row (169, 175, 125 W/m 2 ) and

over-top lighting (169, 175, 125 W/m 2 ) by

HPS lights whenever total solar radiation

outside falls below 200 W/m 2 except for

a break in the night. In the table below

is summarized total cooling (sensitive +

latent), electricity consumption of the

Novarbo droplet curtain, and electricity

consumption of the Waterix cooler in three

different weather periods and three crops,

each grown in a compartment of 130 m 2 .

The goal of fully closed greenhouse

lead to rather high electricity consumption,

which however could be economically

justified. High maximum temperature (28-

30°C) and humidity (85%) settings led

to clearly lower energy consumption in

Cucumber Tomato Sweet pepper

Weather 2009 Ctot Drops Wix Ctot Drops Wix Ctot Drops Wix

Cool dry, May 12-18 - - - 2.0 0.03 0.15 2.1 0.04 0.16

Cool rainy, Jun 7-13 3.4 0.06 0.10 5.3 0.13 0.13 5.1 0.06 0.13

Warm humid, Jul 21-27 4.8 0.13 0.12 5.6 0.17 0.14 6.5 0.14 0.16

cucumber production than lower settings

in tomato (27°C, 75-80%), and sweet pepper

(28°C, 80-90%) production. Aiming at

fully closed greenhouse with cucumber

and pepper may not be economically the

most optimal goal. In fact, it is often not

even practical. Temperature can be quite

easily controlled by cooling but humidity

control is less straightforward. In a sunny

morning, ventilation with some heating

is needed for moving air to prevent condensation

of humidity on fruits. During

daytime, lowering humidity and temperature

to ensure pollination of tomato

flowers can lead to a control spiral where

absolute humidity and temperature fall

simultaneously with no decrease in relative

humidity. To cut the spiral, ventilation

is needed.


Table 1. Daily mean of sum of sensitive and latent heat extracted from a greenhouse compartment by Novarbo

(Ctot), electricity consumption by droplet curtain (Drops) and by Waterix water cooler a (Wix) allocated to each

crop. All units kWh/day/m 2 of greenhouse. During cool weather daily maximum temperature was 12 to 15°C, during

warm weather 20 to 25°C.

ENERGY IN FOCUS 41


Liisa Särkkä, Eeva-Maria Tuhkanen, Tiina Hovi-Pekkanen and Risto Tahvonen

Improving productivity of cucumber,

tomato and cut rose in semi-closed

greenhouse in Finland

Improving

M

productivity of cucumber, tomato and cut rose in semi-closed greenhouse in Finland

TT Agrifood Research Finland, Plant

Liisa Särkkä, Production Eeva-Maria Research, Tuhkanen, Toivonlinnan- Tiina Hovi-Pekkanen and Risto Tahvonen

tie 518, 21500 Piikkiö, Finland, e-mail

MTT liisa.sarkka@mtt.fi Agrifood Research Finland, Plant Production Research, Toivonlinnantie 518, 21500 Piikkiö,

Finland, Despite e-mail the good liisa.sarkka@mtt.fi

light environment for

plants, a year-round greenhouse produc-

Despite tion suffers the good from lower light environment yields in summer for plants, a year-round greenhouse production suffers from

lower than during yields the in other summer times than of the during year. Tra- the other times of the year. Traditional climate control in the

greenhouse ditional climate with control roof vents in the is greenhouse not sufficient and this weakens growth factors. A new cooling system

was

with

developed

roof vents

allowing

is not sufficient

the roof

and

vents

this

to be closed most of the time. Therefore carbon dioxide

concentration could be kept high and both air temperature and air humidity could be controlled in

weakens growth factors. A new cooling

a proper way.

system was developed allowing the roof

Cultivation vents to be trials closed were most made of the with time. cucumber, The- tomato and cut roses. In semi-closed greenhouse the

yield refore of carbon cucumber dioxide increased concentration in the could first summer by 24 % and in the second summer by 40 % compared

be kept to the high traditional and both climate air temperature control (Fig. 1). The reduced need for ventilation in semi-closed

greenhouse and air humidity allowed could maintaining be controlled of in constant a higher CO2 concentration (cucumber average 1000

ppm, proper tomato way. and cut rose 700-800 ppm) than in traditional greenhouse (cucumber and cut rose

average Cultivation 400 ppm, trials tomato were 500 made ppm) with (Fig. 2). In semi-closed greenhouse, the summer yield (weeks

23-35) cucumber, of tomato and was increased cut roses. In while seminot

the spring yield (weeks 13-22). The yield quality of cut

roses closed was greenhouse improved the but yield not of the cucumber number of flowers compared to traditional greenhouse. All trials

were increased illuminated in the first year summer round by by 24 HPS % and lamps. Moreover, tomato had 31% interlighting of 170 W/m

in the second summer by 40 % compared

to the traditional climate control (Fig.

1). The reduced need for ventilation in

2

Fig 2. 2. Climate for for cucumber in in the the semi-closed (cooling) (cooling) greenhouse greenhouse and in and the traditional in the greenhouse

traditional

(control)

greenhouse

in August

(control)

as mean values

in August

of each

as mean

hours of

values

the days.

of each hours of the days.

semi-closed greenhouse allowed maintai- greenhouse (cucumber and cut rose ave-

installed lights.

ning of constant higher CO concentration rage 400 ppm, tomato 500 ppm) (Fig. 2).

2

(cucumber average 1000 ppm, tomato and In semi-closed greenhouse, the summer

Photosynthesis measurements showed that plants benefited from high carbon dioxide concentration.

The plant structure was also affected by

cut

the

rose

semi-closed

700-800 ppm)

greenhouse

than in traditional

environment.

yield (weeks 23-35) of tomato was increased

while not the spring yield (weeks

Further trials are needed to optimize the greenhouse climate. Our cooling system makes 13-22). it possible The yield quality of cut roses was

to find out the most beneficial climates to each plant species for optimal production. improved but not the number of flowers

compared to traditional greenhouse. All

trials were illuminated year round by HPS

lamps. Moreover, tomato had 31% interlighting

of 170 W/m2 installed lights.

Photosynthesis measurements showed

that plants benefited from high carbon

dioxide concentration. The plant structure

was also affected by the semi-closed

greenhouse environment.

Further trials are needed to optimize the

greenhouse climate. Our cooling system

makes it possible to find out the most

beneficial climates to each plant species

for optimal production.


Fig 1. Yield of cucumber in semi-closed (cooling) greenhouse and traditional roof

Fig 1. Yield of cucumber in semi-closed (cooling) greenhouse and traditional roof ventilated

ventilated greenhouse (control). Summer yield in the first year was from 12 weeks

greenhouse (control). Summer yield in the first year was from 12 weeks and second year from 14

and second year from 14 weeks. The lower case shows statistical difference of the

weeks. The lower case shows statistical difference of the same classes in different treatments. Block

letters same classes show difference in different between treatments. total Block yields. letters show difference between total yields.

42 ENERGY IN FOCUS


Martin Lykke Rytter Jensen and Bo Nørregaard Jørgensen, University of Southern Denmark, The Maersk Mc-Kinney Moller Institute,

Campusvej 55, DK-5230 Odense M, Denmark

Oliver Körner, AgroTech, Højbakkegaard Allé 21, DK-2630 Taastrup, Denmark, Carl-Otto Ottosen, University of Aarhus,

Faculty of Agricultural Sciences, Department of Horticulture, Kirstinebjergvej 10, Postboks 102, DK-5792 Aarslev, Denmark

is caused by lack of CO2. The graph also shows the maximum photosynthesis we can expect in the

near future (green dashed line). This photosynthesis is continuously calculated based on irradiation

data from the most current weather forecast. When a cloudy day is expected, the control system wil

automatically turn on artificial light earlier in an attempt to achieve a specified light sum. The

PREDICT – A component-based

software platform for

dynamic climate control

grower can use the forecast to see how much artificial light will be needed and potentially adapt the

light strategy before it is executed. The transition of this version of the PREDICT software into

commercial greenhouses was planned as a three-phase process. In the first phase, the software was

tested and demonstrated to growers in a greenhouse research facility. Here, the software gives the

growers advice on optimal climate control with respect to production rate. In the second phase, the

software was installed at Danish Growers. To start with, the software runs in simulated mode; that is

the software only computes the climate set points, it does not effectuate them. The primary purpose

of this phase is to allow the growers to become familiar with the software, how it operates, and understand

the effect of dynamic climate control. The final phase is active control where the PRE-

DICT software takes control of the climate based on overall goals set by the grower. Through the

The dynamic model-based development climate of COa new that maximises component-based photosynthesis software at the platform Proven for successful dynamic in climate small setups, control, the the PRE-

2

control concept IntelliGrow DICT has project been has present contributed light level with in the extended greenhouse. knowledge The next of step the was implication to try the of IntelliGrow increasing conthe

ab-

developed in Denmark since straction 1996. The level result of climate is then control. translated This to set knowledge points appli- is crucial cept in for commercial developing greenhouses. the next Howe- generation of

concept aims at improving intelligent the energy climate-control cable by the components.

specific climate computer. ver, whereas the original IntelliGrow soft-

efficiency of greenhouse production by Combined with temperature integration ware was designed as a research prototype

adjusting the greenhouse climate References dynami- control, this optimization reduces the use applicable to an experimental setting, the

cally to the present weather Hansen situation. JM, To Ehler of additional N, Karlsen heating P, Høgh-Schmidt of the greenhouse. K, Rosenqvist move towards E. (1996). full-scale A computer production controlled in

do so, IntelliGrow incorporates chamber a determisystem

The designed concept has for been greenhouse proved to microclimate work in commercial modelling greenhouses and control. required Acta a Hort. new

nistic leaf-photosynthesis model 440:310-315.

based on climate-chamber experiments (Hansen et software platform. For this reason, the

Farquhar et al. (1980) and Gijzen Aaslyng, (1994) J.M., al., Lund, 1996) J.B., as well Ehler, as in N. small and Rosenqvist, greenhouse E. PREDICT (2003) project IntelliGrow: was undertaken a greenhouse in 2006. compo-

as presented by Körner (2004) nent-based to ensure climate experiments control with system. many different Environmental cultivars Modelling The primary & goal Software of the 18: PREDICT 657-666 project

maximum photosynthetic performance. Gijzen H. By (1994) of pot Ontwikkeling plants (Aaslyng van et al., een 2003), simulatiemodel resul- was voor to provide transpiratie such a en software wateropname platform. en van

using this model, it is possible een to integral deter- gewasmodel. ting in energy (Development savings up to 40%, of a depen- simulation A primary model design for transpiration concern of the and PREDICT water uptake

mine the combination of temperature and an and integral ding crop on model), the season. AB-DLO, Wageningen, The project Netherlands. focused on advancing pp. 90. the original

Farquhar G.D., Von Caemmerer S., Berry J.A. (1980) A biochemical model of photosynthetic CO2

assimilation in leaves of C3 species. Planta 149:78-90.

Körner O. (2004) Evaluation of crop photosynthesis models for dynamic climate control. Acta

Horticulturae 654:295-302.

Figure 1.

ENERGY IN FOCUS 43


IntelliGrow concept to include weather

forecasts in the computations of climate

set points. Where the IntelliGrow concept

uses historical sensor-data readings

for irradiance, temperature and CO 2 , the

PREDICT concept should use weather

forecasts as well. Thus, in the PREDICT

project, special emphasis is put on design

that utilizes local weather forecasts for

energy- saving purposes while ensuring

timing of the production. Another important

design concern of the PREDICToncept

focused on elaborating the idea of modularity

in climate control. In the IntelliGrow

project, the responsibility of controlling

the climate is assigned to different components.

In the PREDICT project, this idea

has been developed further in order to

allow for new climate-control components

to be easily added. The idea is to allow

growers to download new climate control

components from a central server when

these are available. However, this openness

towards new climate-control components

may make it harder for growers to

understand who is to be held responsible

for a decision and therefore the PREDICT

software is not only a control system, it

is also a decision support system. In the

short run the control system can make

sound decisions - start ventilation when it

becomes too hot, add CO 2 when it limits

plant photosynthesis etc. However, the

many decisions made by a mixture of

climate-control components are far too

complicated to be made automatically in

the long run. It is, therefore, essential that

PREDICT is capable of not just executing

but also explaining those decisions.

The goal of such explanations is to support

the grower in taking long-term decisions

beyond the reasoning capabilities of

the control system. To facilitate explanation

of control decisions, the system is open

not only to new control components, but

also to new portals capable of explaining

various aspects of the climate control. The

photosynthesis portal shown in figure 1 is

an example. The speedometer in the top

right corner of the portal shows the current

photosynthesis rate – the current photosynthesis

as a percentage of the maximum

photosynthesis possible under the cur-

rent light conditions. The control system

attempts to achieve a target rate specified

by the grower. Since the calculated temperature

optimum for leaf photosynthesis at

elevated CO 2 is often above the plant temperature

accepted for high quality plant

production, the theoretical maximum of

100% photosynthesis is commonly reduced

to around 80% to 90% and the lower

temperature value is chosen for control.

In the figure the system currently achieves

66.9% which is below the target rate.

This information encourages the grower to

take a closer look at the system. The graph

at the bottom shows the actual photosynthesis

achieved in the past (blue line) and

the maximum photosynthesis that could

theoretically have been achieved using the

light conditions at the time (green line).

The bigger the distance between the

two lines, the lower photosynthesis optimization

rate was achieved at the time.

When the grower does not understand a

pattern in the graphs, he can select a point

in time and get a detailed textual description

of relevant control decisions.

That is, if he selects 2:30 AM he will see

that the increase in photosynthesis during

the night was caused by the artificial lights

being turned on. If he selects current time

he will see that the low photosynthesis

rate is caused by lack of CO 2 . The graph

also shows the maximum photosynthesis

we can expect in the near future (green

dashed line). This photosynthesis is continuously

calculated based on irradiation

data from the most current weather

forecast. When a cloudy day is expected,

the control system will automatically turn

on artificial light earlier in an attempt to

achieve a specified light sum.

The grower can use the forecast to see

how much artificial light will be needed

and potentially adapt the light strategy

before it is executed. The transition of this

version of the PREDICT software into

commercial greenhouses was planned as

a three-phase process. In the first phase,

the software was tested and demonstrated

to growers in a greenhouse research facility.

Here, the software gives the growers

advice on optimal climate control with

respect to production rate. In the second

phase, the software was installed at Danish

Growers. To start with, the software runs in

simulated mode; that is, the software only

computes the climate set points, it does

not effectuate them. The primary purpose

of this phase is to allow the growers to

become familiar with the software, how

it operates, and understand the effect of

dynamic climate control. The final phase is

active control where the PREDICT software

takes control of the climate based on overall

goals set by the grower. Through the

development of a new component-based

software platform for dynamic climate

control, the PREDICT project has contributed

with extended knowledge of the

implication of increasing the abstraction

level of climate control. This knowledge is

crucial for developing the next generation

of intelligent climate-control components.

References

Hansen JM, Ehler N, Karlsen P, Høgh-

Schmidt K, Rosenqvist E. (1996). A computer

controlled chamber system designed

for greenhouse microclimate modelling

and control. Acta Hort. 440:310-315.

Aaslyng, J.M., Lund, J.B., Ehler, N. and

Rosenqvist, E. (2003) IntelliGrow: a greenhouse

component-based climate control

system. Environmental Modelling & Software

18: 657-666.

Gijzen H. (1994) Ontwikkeling van een

simulatiemodel voor transpiratie en wateropname

en van een integral gewasmodel.

(Development of a simulation model for

transpiration and water uptake and an

integral crop model), AB-DLO, Wageningen,

The Netherlands. pp. 90.

Farquhar G.D., Von Caemmerer S.,

Berry J.A. (1980) A biochemical model of

photosynthetic CO2 assimilation in leaves

of C3 species. Planta 149:78-90.

Körner O. (2004) Evaluation of crop

photosynthesis models for dynamic climate

control. Acta Horticulturae 654:295-

302.

44 ENERGY IN FOCUS


Ole Bærenholdt-Jensen, Advisor, Horticultural Advisory Service, Denmark. obj@landscentret.dk

Company / address: Dansk Landbrugsrådgivning, GartneriRådgivningen, Hvidkærvej 29, 5250 Odense SV.

How do we pass on new ideas like

Dynamic climate control and

new greenhouse ICT to the grower?

In Denmark, there has been energy

saving projects in the last many years

with results, that should be implemented

as much as possible at the grower. In The

Horticultural advisory service we have

been the partner in most of the project to

make the information and implementation

part. We have also been a part of the

development in the projects - the best possible

background for giving Information.

Information has been done with articles

in Growers Magazine, information days,

and by meetings in more than 100 nurseries

to give them results and presentations

adjusted to the specific nursery – their

cultures and energy saving possibilities.

Implementation: The results are an integrated

part of the advice we give at the

grower, and in climate control courses we

are giving. Therefore ideas from e.g. the

dynamic climate control project already

are adapted at many growers. The results

during the years has also been implemented

in the Danish greenhouse “energy

manual”, that most of the growers have

followed, because they have made an

“energy agreement”, with the government.

Example on information/ implementation

for the coming period is: AgroTech

and GartneriRådgivningen are releasing a

brand new www energy information platform

this autumn.


ENERGY IN FOCUS 45


N.E. Andersson 1 and O. Skov 2 , 1 University of Aarhus, Faculty of Agricultural Sciences, Department of Horticulture,

Kirstinebjergvej 10, DK-5792 Aarslev, Denmark, Phone: +45 89991900, Fax: +45 89993490, e-mail: Niels.Andersson@agrsci.dk

2 AgroTech, Højbakkegård Allé 21, DK-2630 Taastrup, Denmark, Phone: +45 87438400, Fax: +45 36440533, e-mail: oes@agrotech.dk

Multilayer screening system

in greenhouse with screen materials

with different properties

to enhance energy saving

Mobile screens in greenhouses play an

important role in energy saving and

the control of the radiation environment in

the greenhouse. The control of the screens

is base on light, a factor which makes

control for both energy saving and shading

possible. A single layer screen is common

in greenhouses because the screen

material has the properties that make it

applicable for energy saving and shading.

However, such materials are not optimal

for both shading and energy saving and the

performance of the screening system could

be enhanced by a multilayer system.

A test set-up consisting of 5 frames of

1×2×0.25 m was build of plywood and

stacked together to a total height of 1.25

m and with a ground area of 2 m2 . On the

top frame was placed a glass pane with a

thickness of 4 mm m and in the bottom

frame was a sand layer with a thickness

of 0.15 m. In the sand layer was placed a

heating cable with a length of 20 m and

with a heat dissipation of 15 Wm-1 . In the

three frames in the middle of the test setup

different combinations of screen materials

were installed. The screen materials

were XLS Obscura A/B+B/B, XLS Obscura

Fig. 1. Heat loss (Q) from the uppermost frame in regard screen combinations.

Fig. 1. Heat loss (Q) from the uppermost frame

in regard screen combinations.

Firebreak A/A+B/W, XLS NIR, XLS 10

Ultra, and XLS 55 Harmony. The test set-up

was placed in a greenhouse compartment

at a minimum air temperature of 5°C. The

experiment was conducted at two internal

temperatures in the test set-up of 15 and

20 °C and data was collected every 5

minutes, but only data during night was

used in the analysis.

The energy loss (Q) from the uppermost

frame depends on the difference in air

temperature between inside and outside

the test set-up. A high insulation effect of

the screen combination results in a low

temperature in the uppermost frame of the

test set-up and the temperature difference

between inside and outside becomes

small. Increasing number of layers reduced

the heat loss from the test set-up, but the

reduction in energy loss from the uppermost

part of the test set-up was not equal

for the different combinations of screen

materials (Fig. 1). The heat loss depends

on the set point and was always highest

at the highest set point of 20 °C. At a set

point of 20 °C the heat loss for the combination

XLS Obscura A/B+B/B and XLS NIR

is not significant different for a triple layer

combination consisting of the same two

materials together with a shading screen

type of material (XLS 10 Ultra or XLS 55

Harmony). However, the lowest heat loss

from the test set-up was always obtained

by a triple layer system independent of the

set point.

Increasing the number of layers decreased

the heat transmission coefficient (U),

but introducing a second layer did not

always result in a significant lower heat

transmission coefficient (Fig. 2). There was

always a significant lower heat transmission

coefficient with a triple layer system

compared to a single layer system.

The individual screen material has different

ability to reduce energy loss, and

the differences should be found in the

transmittance of the materials. Some of

the materials are opaque while others are

transparent, which influences the long

wave radiation heat loss. Another possible

factor that might influence the energy loss

is the permeability of the screen materials.

A higher permeability will increase mass

and heat transport.


Fig. 2. The heat transmission coefficient (U) of the system in regard to screen combinations.

Fig. 2. The heat transmission coefficient (U)

of the system in regard to screen combinations.

46 ENERGY IN FOCUS


1 S. Lambrecht, s.lambrecht@fz-juelich.de

1 S. Tittmann, s.tittmann@fz-juelich.de

2 H. Behn, helen_behn@uni-bonn.de

2 G.Reisinger, grei@uni-bonn.de

1 A. Walter, a.walter@fz-juelich.de

3 T. Hofmann, Thomas.Hofmann@centrosolarglas.com

4 H.-J.Tantau, tantau@bgt.uni-hannover.de

4 B. von Elsner, elsner@bgt.uni-hannover.de

Innovative roofing materials

for increased plant quality

and reduced energy consumption

Introduction

Light is a determining factor for optimum

quality in plants. Scientific and commercial

plant cultivation takes place in part

in greenhouses, which involves reduced

light quality and high energy consumption.

Energy consumption in greenhouses

can be almost halved by using innovative

roofing materials. In contrast to the past,

energy savings and high transmissions can

be achieved simultaneously. Our goal is

to obtain low energy consumption and

increased quality of plant products at the

same time.

Principles of glass-film

combination (GFC)

In contrast to double and triple layers of

roofing materials consisting of the same

components (only glass or only film),

Forschungszentrum Jülich has created an

innovative roofing system with different

materials. This system combines a microstructured

white glass (Centrosolar) and

an ethylene tetrafluoroethylene (ETFE) film

(Asahi Glass). The film is either pinched

or glued to the edge of the glass. By using

a ventilation system, an air cushion is

created which separates the film from the

glass. The air cushion of approximately

25mm represents an insulation layer which

results in lower energy consumption.

Fenstertechnik at Rosenheim (ift; Institute

for Window Technologies). The applied

investigation was conducted in a model

system, the so-called “hot box”, which

represents similar greenhouse conditions

with respect to air humidity and heating.

Basically, the GFC was tested in different

fixation systems (glued and pinched with

PVC profile) under both sets of conditions

in comparison to single-layer glass (i.e.

float glass).

The U-value for single layer glass (5.9

W/m 2 K) according to the manufacturer`s

2 G. Noga, nogag@uni-bonn.de

1 U. Schurr, u.schurr@fz-juelich.de

1 A. Ulbrich, a.ulbrich@fz-juelich.de

1 Forschungszentrum Jülich, Phytosphere Institute

2 University of Bonn: INRES,

3 Centrosolar, Fürth

4 Leibniz University Hannover, BGT

information is twice the value of GFC

(PVC profile) under laboratory conditions

(2.9 W/m 2 K). From an energetic point of

view, double-layer glass (manufacturer`s

information: 3.0 W/m 2 K) and GFC (PVC

profile; laboratory conditions, 2.9 W/m 2 K)

display very similar U-values. The glued

variant of the GFC has a lower effect on

energy savings. The heat transmission coefficient

is 3.6 W/m 2 K. The laboratory conditions

do not reflect the real conditions

of a greenhouse (e.g. air humidity, heating,

wind velocity). Investigations under

Heat transmission coefficient

To verify the energy efficiency potential of

the GFC, the heat transmission coefficient Figure Figure 1: Determination 1: Determination of of the the heat heat transmission coefficient “ U” “ U” on on the the basis basis of of the the manufac-

“U” was determined. With respect to the turer’ Figure turer’ s 1: information s Determination information and and investigations of investigations the heat transmission under under laboratory coefficient as well as “ well U” as applied as on applied the basis conditions of the for manufac- for different

problem of evaluating the heat transmissi-

roofing turer’ roofing s information materials. The and The manufacturer`s investigations manufacturer`s under information laboratory represents as well average as average applied values values conditions for for commercially

for different

Figure available roofing available 1: Determination

materials. glazings (Pilkington, The (Pilkington, manufacturer`s

of the Saint-Gobain, heat Saint-Gobain, transmission

information Glas Glas Trösch, coefficient

represents Trösch, Interpane, average

“U” on Arcon). values

the Arcon). basis

for Measurements commercially

of the manu- at the at the

on coefficient in commercial greenhouses, facturer’s Institut available Institut für information glazings für Fenstertechnik (Pilkington, and investigations at Rosenheim at Saint-Gobain, Rosenheim (ift) under (ift) Glas can can laboratory be Trösch, be found found Interpane, in as the in well the laboratory as Arcon). applied section. Measurements section. conditions The The section at for the on on

we decided to examine the U-value under different applied Institut applied roofing für conditions Fenstertechnik materials. represents at The Rosenheim measurements manufacturer`s measurements (ift) in can a in hot be information a hot found box box to in simulate to the simulate represents laboratory environmental average section. conditions values The conditions section for on

laboratory and applied conditions. The comparable

commercially

applied comparable conditions to those to those

available

represents of of a greenhouse. a greenhouse.

glazings

measurements

(Pilkington,

in

Saint-Gobain,

a hot box to simulate

Glas Trösch,

environmental

Interpane,

conditions

Arcon).

comparable to those of a greenhouse.

laboratory testing was performed accor- Measurements Light Light transparency at the Institut für Fenstertechnik at Rosenheim (ift) can be found in the

ding to German industrial standards (EN laboratory Basically, Light Basically, transparency section. both both materials The section (microstructured on applied white white conditions glass glass and and represents an an ethylene measurements tetrafluoroethylene in a (ETFE) hot (ETFE)

ISO 12567-1:2009-09) at the Institut für box

film) Basically,

to

film)

simulate

display both increased

environmental

materials increased transparency (microstructured transparency

conditions

to photosynthetically to white photosynthetically

comparable

glass and

to

an active

those

ethylene active radiation

of

radiation tetrafluoroethylene

a greenhouse.

(PAR; (PAR; approx. (ETFE) 92 92 per per

cent), film) cent), display UV-A UV-A radiation increased radiation (above transparency (above 80 80 per per cent) to photosynthetically cent) and and UV-B UV-B radiation active (up radiation (up to 80 to 80 per (PAR; per cent) cent) approx. in comparison in comparison 92 per to to

single-layer cent), single-layer UV-A glass radiation glass roofing (above (approx. 80 per 90 cent) 90 per per cent, and cent, UV-B 70 70 per radiation per cent cent and and (up 0 per 0 to per 80 cent, cent, per respectively). cent) respectively). in comparison The The comcom- to

bination single-layer bination of of the glass the two roofing two materials (approx. (into (into a 90 GFC a per GFC system cent, system 70 as per described as described cent and above) 0 above) per leads cent, leads to respectively). a to light a light transparency The com-

ENERGY IN FOCUS of bination of the the photosynthetically of photosynthetically the two materials active active (into radiation a radiation GFC of system of almost almost as 90 described 90 per per cent, cent, above) and and UV-A leads UV-A to of a of approximately light approximately transparency 47 70. 70.

These of These the values photosynthetically values are are comparable active with radiation with the the ones ones of of almost of floatglas. 90 per The The cent, UV-B UV-B and transmission UV-A transmission of approximately values values for for float float 70.

glass These glass are values are 0 in 0 are comparison in comparison comparable to 17 to with 17 per the per cent ones cent for of for GFC. floatglas. GFC. All All measurements The measurements UV-B transmission were were conducted values under for under float greengreenhouse glass house are conditions. 0 conditions.

in comparison to 17 per cent for GFC. All measurements were conducted under green-


applied conditions make this difficulty

very clear. The U-values for both GFC

variants are higher under applied conditions

compared to laboratory conditions.

Nevertheless, the energy saving potential

represents approximately 40 per cent in

contrast to float glass.

Light transparency

Basically, both materials (microstructured

white glass and an ethylene tetrafluoroethylene

(ETFE) film) display increased

transparency to photosynthetically active

radiation (PAR; approx. 92 per cent), UV-A

radiation (above 80 per cent) and UV-B

radiation (up to 80 per cent) in comparison

to single-layer glass roofing (approx.

90 per cent, 70 per cent and 0 per cent,

respectively). The combination of the two

materials (into a GFC system as described

above) leads to a light transparency of

the photosynthetically active radiation of

almost 90 per cent, and UV-A of approximately

70. These values are comparable

with the ones of floatglas. The UV-B

transmission values for float glass are 0

in comparison to 17 per cent for GFC.

All measurements were conducted under

greenhouse conditions.

Plant product quality

After confirming the improved light conditions

under GFC roofing, it is necessary

to verify the influence of the increased

transparency of PAR and UV-A as well as

UV-B on plant growth and development.

Investigations on plant development were

made under single-layer roofing consisting

of white glass, ETFE and float glass. These

examinations were conducted in commercial

greenhouses as well as in small

research units. The improved light conditions

led to the desired optimization of

plant growth and product quality both in

research greenhouses and also at a commercial

plant grower’s. The example of

red leaf lettuce plants showed the decisive

influence of the UV-B transmission properties

of the roofing material. This led to a

reduction in leaf length and width, which

brought about a more compact growth

form altogether.

With respect to product quality, a considerably

more intensive colouration of the

plants was visibly identifiable. The analysis

of the plants confirmed this impression

based on an increased content of significant

secondary metabolites. For instance,

the anthocyan content of red leaf lettuce

showed a significantly higher value under

UV-B-transmitting roofing material (white

glass and ETFE film).

Outlook

Further investigations are necessary to

evaluate the energy saving potential in

commercial greenhouses considering the

problems of relative air humidity. In this

context, it is important to develop an intelligent

regulation and control algorithm for

operating the air cushion.

For example, there is no air cushion

without ventilation, so the film attaches to

the glass. This state is comparable to single

layer roofing which enables condensation

and the relative air humidity decreases.

But the consequences are reduced energy

savings.


48 ENERGY IN FOCUS


Jens Møller Jensen, CTO, Danfoss IXA A/S, jensen@danfoss.com, Bent S. Bennedsen, Agrotech A/S, bsb@agrtech.dk

Environmental Sensors for Harsh

Environments - a Novel Approach

to Multiple Parameter Sensors

for Greenhouses

Sensors for environmental parameters

are numerous and widespread, and

the number of applications in which such

sensors are applied are constantly rising.

One application of interest is greenhouse

production, in which the application of

multiple distributed sensors can serve to

drastically reduce energy consumption

and improved growth control. However,

this approach implies requirements that

are not fulfilled with the currently existing

sensors, namely those of the ability of

the sensors to function continuously and

stable and with little or no service requirement

in a harsh environment likely to

contaminate the sensors, the ability to

operate wirelessly in order to enable use

of multiple sensors without obstructing

and expensive cabling, and the ability to

do so at a energy consumption level low

enough for powering by energy harvesting,

avoiding the need for recurrent battery

exchange.

Currently available sensors are in general

not specifically designed for harsh

environments, and in most cases standard

sensors are therefore applied with various

additional measures taken in terms of

artificial protection and limited positioning

options to compensate for the harsh

environment impact. Moreover, different

sensors are needed for the various environment

parameters. This leaves the sensors

still less applicable, less durable and less

accurate than needed in order to efficiently

provide measurement data for optimum

energy management and environment

control. Such control requires monitoring

of the environment in proximity of the

plants, and the sensors therefore should

be placed amongst the plants, preferably

on a multiple distributed basis, and be

able to withstand close impact from the

various nursing activities while at the same

time not requiring tedious time-and-effort

consuming installation and maintenance

which impede daily work routines and

business. Obtaining these features require

sensors that are really designed for the purpose.

They must be reliable and durable

and designed for maximum usability in the

specific application, and they must require

no or very little service and maintenance

and must communicate their data wire-

lessly in order to facilitate easy and dynamic

positioning and handling.

This all calls for a novel approach to

greenhouse sensors in technology, concept

and design. Danfoss IXA A/S together with

partners of the Greenhouse Concept 2017

is developing such sensors, based on novel

and patented optical principles incorporating

nanotechnology.

Danfoss IXA A/S has developed and

patented a novel optical measurement

principle and novel nano-coating principles

which together with application

targeted design enable sensors with all the

required properties. The sensors simultaneously

measure CO 2 , absolute and relative

humidity, including dew point, various

temperatures and light, they are faster than

existing sensors, they are self-cleaning and

hermetically sealed, they are powered

by energy harvesting and they communicate

wirelessly in a multiple-node network

which enables huge improvements

in both greenhouse energy consumption

and growth control. At the same time the

sensors impose no additional maintenance

and service requirements on the users. The

sensors can withstand direct exposure to

the various daily nursing activities and

handling and they are specifically designed

for optimum usability and efficiency

in professional greenhouse production

plants.


ENERGY IN FOCUS 49


Carl-Otto Ottosen, Department of Horticulture, Kirstinebjergvej 10, 5792 Aarslev, Aarhus University DENMARK, co.ottosen@agrsci.dk

Bo Nørregaard Jørgensen, The Maersk Mc-Kinney Moller Institute, University of Southern Denmark, Campusvej 55

DK-5230 Odense M, DENMARK, bnj@mip.sdu.dk

Dynamic management

of supplemental light

Introduction

Even the most advanced control in greenhouse

does not include species differences

adjustment. In terms of supplemental light

use, the plant species might differ dramatically

in terms of light response – both in

level and in time. In an attempt to address

not only the challenges of efficiency of

light use we have tried to combine physiological

knowledge, weather forecast

and actual energy prices to control the

light use.

The state-of-the-art dynamic climate

control system IntelliGrow is based on

the photosynthesis response of plants has

hitherto not included the control of supplemental

light control besides fixed set

points. While the initial aim was to reduce

the heating costs as much as possible,

so a natural step is find solutions to the

increasing use of electricity for the supplemental

light use in commercial green-

houses – both vegetables and ornamentals.

As the natural light even in darkest part of

the year on a sunny day might be enough

we have decided to combine information

about the weather forecasts, the actual

forecasted electricity prices and the photosynthetic

performance of the actual species

into one context.

Idea

To reach this target a software package has

been developed, that installed on a PC

connected to the Internet and with access

to a climate computer will calculate the

most efficient time to turn on the supplemental

light based on the weather forecast,

the energy prices and the photosynthesis

sum from individual plant species. In this

way we not only overcome the traditional

rather conservative set points for use of

supplemental light, but also secures that

The screen shows an example of supplemental light control, where the light is on 6 hrs

during the night (lower left). The graph shows times of light on (red), price of electricity

(light blue) and working light (yellow). The green line is natural light and light green line

is the photosynthetic activity.

the use of supplemental light takes place

in periods where the gain in terms of photosynthesis

per light hours are the best. The

control of supplemental light is predictive

rather than the traditional retrospect analysis

of light sums.

Results

Experiments with different photosynthesis

sums using dynamic light control vs. traditional

light controls based of set point

of supplemental light has been performed

in Spring 2009. The dynamic supplemental

light control was use in combination

with dynamic climate control using potted

miniature roses, Hibiscus rosa-sinensis and

Euphorbia milii showed that a reduction of

more than 10% of the supplemental light

use was possible. If it was combined with

dynamic climate control both the cost for

heating and electricity was reduced with

an improved plant performance (often

more compact plants).

Photosynthesis measurements of the

species reveal large differences in response

times to light, which indicate several

additional possibilities for reducing electricity

costs using different igniting patterns

for the lamps. This knowledge will

be included in the software and on going

work on the software will include a better

prediction of the climate to improve

the photosynthesis calculation, but also

include suggestion for different uses of the

installed supplementary light in different

situations.

Conclusions

The software that enables the link between

actual costs of electricity and the weather

forecast is as such an effective tool for

greenhouse growers to reduce the energy

cost as it illustrates clearly the actual costs

for providing light for the plants. When it is

combined with the species specific information

about the required photosynthesis

and the response rates of the plants it will

enable growers to reduce the energy costs,

by moving energy use from peak to low

peak periods, which on the other hand is

beneficial for the energy providers.


50 ENERGY IN FOCUS


Eva Rosenqvist 1 , Anker Kuehn 2 , Jakob Skov Pedersen 2 , Per Holgersson 3 and Hans Andersson 3

1 Dept. of Agriculture and Ecology, University of Copenhagen, Højbakkegård Allé 9, 2630 Tåstrup, Denmark, ero@life.ku.dk

2 Agrotech, Højbakkegård Allé 21, 2630 Tåstrup, Denmark, 3 AB Ludvig Svensson, 511 82 Kinna, Sweden

The effect of screen material

on air and leaf temperature

The present development of greenhouse

production is much focused on new

climate control strategies and new technical

solution for energy management.

Here the development of new screen

material will play an important role since

the screens have a great impact on both

the micro climate experienced by the crop

and the temperature distribution in the

greenhouse, which will be important for

the possibilities for heat extraction aiming

at storing energy harvested during warm

periods of time for use during cold periods

of time.

In an experiment run during June – September

2009 we have compared radiation

and temperature parameters under three

permanently closed screens: (1) a traditional

ventilated screen with one aluminium

strip, on clear transparent strip and two

open strips, (2) a dense prototype of NIR

screen, with clear strips that transmits less

near infra-red radiation than the traditional

transparent strips does and (3) a dense

diffusing screen with one white and two

diffusing transparent strips. Each screen

was sewn into a tent measuring 1.8 x 6.2

m, being 1.2 m high to the south and 1.6

m high to the north, towards the wall (fig.

1). In the tents and (4) on a control bench

without any screen the following climate

parameters were measured; global radiation,

photosynthetic active radiation (PAR),

air temperature and leaf temperature by

four thermocouples inserted into the leaves.

The leaf temperature was measured

on Chrysanthemum, pot roses, Begonias

and Kalanchoë.

Data from June show that the three

permanent screens decrease the global

radiation by 33–36 %, i.e. they all have

comparable filtration in the spectral range

of 400–1100 nm. In the PAR region screen

1 and 3 removes 27–30 % of the light

while the NIR screen (2) only removes

19 % of the light thus potentially increasing

the rate of photosynthesis in the

crop compared to the other screens. The

screens decreased the mean air temperature

in the range 0.3–0.9 °C while the

mean leaf temperature of Chrysanthemum

only varied with +/- 0.3 °C i.e. the effects

of the different screens on the two mean

temperature parameters were limited. It

should be kept in mind, though, that the

screens were permanently on and not

ventilated more that what the screen material

itself allowed. However, when looking

at the daily temperature course several

interesting patterns are revealed where

the screens can decrease the leaf temperature

with up to 5 °C, compared to the

control, and these differences and the

effect of the various screen materials will

be shown and discussed.


Fig. 1. The experimental setup in a greenhouse at University of Copenhagen, Tåstrup. From left are screen (1) a traditional

ventilated screen with one aluminium strip, on clear transparent strip and two open strips, (2) a dense prototype of NIR

screen, with clear strips that transmits less near infra-red radiation than the traditional transparent strips does, (3) a dense

diffusing screen with one white and two diffusing transparent strips and (4) a control bench to the east without any screen.

ENERGY IN FOCUS 51


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