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
implementing research and development
in practice. The actual projects include:
• Intelligent Energy Management
in Greenhouses, Greenhouse
Concept 2017
Mindre energi - Lavere omkostninger – Øget indtjening.
Cool Crops – Energy savers.
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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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