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GEO T Expo will show potential for geothermics in horticulture

Fruit and vegetables prosper with geothermics

Plants love heat. Because that is expensive in greenhouses, the Dutch underglass sector is placing its faith in geothermics and is heating gigantic greenhouses with natural resources. There are initial approaches in Germany too. During the GEO T Expo at Messe Essen on November 13, specialists will show what potential geothermics has in horticulture and landscaping.

The greenhouse of the Dutch firm Wijnen Square Crops close to the German border near Venlo is being extended to an area of 32 hectares. Tonnes of capsica which need heat above all ripen in it from March to November. In greenhouses, this heat is often generated by burning expensive natural gas. Until the end of 2012, Square Crops also utilised for the gigantic glass plantation a block-type thermal power station which had a handsome nominal power of 20.6 megawatts and was operated with natural gas. Because the margins for capsica fluctuate and the energy costs are rising at the same time, a geothermal district heating station has been supplying the energy since the start of 2013. "In this way, we want to reduce the consumption of natural gas by at least 80 percent and the carbon dioxide emissions by 90 percent. A complete supply would be ideal because the plants need heat throughout the year and an average temperature of 22 degrees Celsius under glass," says Pieter Wijnen, co-founder of Square Crops.

Grower Pieter Wijnen

Wijnen will be amongst the users who will report on their positive experiences at the Expert Forum during the GEO T Expo at Messe Essen on November 13. "Previously, the average consumption was 35 cubic metres of natural gas per square metre. We are now replacing this using geothermics. Around eight cubic metres of hot thermal water per hectare and hour is needed for this purpose," he explains. The calculations show that the vegetable cultivation business wants to save 17 million cubic metres of natural gas and 30,000 tonnes of CO2 in this way. The necessary thermal water comes from a depth of nearly 2,000 metres through two boreholes and enters a heat exchanger at 80 degrees Celsius. In turn, this heat exchanger contains a medium which already reaches its boiling point at very low temperatures and thus provides the required thermal energy. Thereafter, the cooled water is guided through a third borehole into the underground thermal water source once again. During this process, the pumps convey nearly 250 cubic metres of hot water per hour. Wijnen has invested nearly ten million Euros in the circuit and this should pay off in 15 years at the latest. Although so-called energy shields are automatically placed over the glass roofs on cold days and in the winter, the heat requirement is, in a word, enormous because capsica prosper best of all under single glazing. "In the summer, this may sometimes be 4.8 megawatt-hours of heat because the plants need a lot of heat at night as well. In the winter, this amounts to over 30 megawatt-hours in 24 hours," he says.

Because the underglass sector in Holland is one of the significant branches of the economy, glasshouse operators such as Square Crops receive subsidies for energy-saving innovations and the utilisation of renewable energies. The Dutch state wants to lower the greenhouse gas emissions in the sector in this way. Around Venlo, seven horticultural businesses are already placing their faith in geothermics and various applications have been submitted for additional boreholes. German horticultural businesses can only dream of these figures. "Germany does not have any of these gigantic greenhouse clusters located close to each other or any major state funding. Of course, that cannot be compared. Nevertheless, there is a great need for cost efficiency in greenhouses. Research projects in which geothermics is also playing an important role are being carried out on this subject," says Gabriele Harring from the Management Board of Bundesverband Zierpflanzen ("Federal Association for Ornamental Plants"). Such a project is the energy-autarkic greenhouse which Prof. Dr. Horst Rüter from Harbour Dom GmbH will introduce at the Expert Forum. Although the pilot plant of EnBW AG on a Demeter farm near Lörrach has only 78 square metres, it should do without any fossil fuels whatsoever. To this end, the scientists are using geothermal heat probes, an underground heat accumulator and special plastic lenses on the roof which guide the rays of sunshine on to pipes and heat the water flowing in them. "The plastic lenses are readjusted to the movement of the sun using motors. In principle, everything functions and it is possible to cultivate plants in a sustainable way in an autarkic greenhouse," says Rüter.

In contrast, Gemüsebau Steiner GmbH wants to start in great style straight away in 2014 with its "Chiemgau tomatoes". In Kirchweidach in Bavaria, the Austrian company has already begun to construct a greenhouse with an area of 11.2 hectares for the cultivation of tomatoes. The thermal water for the heating has a temperature of 127 degrees Celsius and comes from a borehole with a depth of over 5,000 metres. "Apart from the community, the vegetable-growing business is the main customer for Geoenergie Bayern GmbH. The company predominantly generates heat for this business's needs and uses the remaining potential for electricity production with steam turbines. At the same time, it is the as yet largest German greenhouse project using geothermics. Similar to Square Crops in Holland, Gemüsebau Steiner can also use the fact that the tomatoes are produced without any CO2 for advertising purposes. Moreover, the crop of the nightshades should replace imported goods on the regional markets and make long transport routes superfluous. For Waldemar Müller-Ruhe from Bundesverband Geothermie ("Federal Geothermal Association"), this form of heat utilisation is an absolutely logical concept. "I hope that the investors in Kirchweidach and Holland will be able to make use of their competitive advantages and thus to raise the interest."

Further information about the fair can be found at

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