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

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

Ole Skov, and Janni B. Lund,, 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


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



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


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


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 +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-


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