Articles
USE OF A GAS ABSORPTION HEAT PUMP IN COMBINATION WITH BOREHOLE THERMAL ENERGY STORAGE IN ORGANIC PROTECTED HORTICULTURE
Article number
915_6
Pages
55 – 59
Language
English
Abstract
Both conventional and organic protected horticulture have to face problems of high energy costs.
Companies growing organic vegetables are smaller than conventional producers, where electricity and heat cogeneration is a possible solution because of the larger, more suitable scale for introducing cogeneration.
In addition to economic reasons, organic growers should implement extra efforts to reduce the use of non-renewable energy.
Carbon dioxide is an important factor to enhance horticultural production and food quality.
In a working group of growers and an energy specialist, all these parameters were put together.
The best solution for small companies using carbon dioxide could be the use of a gas absorption heat pump (GAHP) in combination with Borehole Thermal Energy Storage (BTES) in an extra isolated greenhouse.
As a result, this concept was installed at the organic research centre in Kruishoutem, Belgium.
A new 1280 m² greenhouse divided into 6 compartments was installed.
By using a double upper screen and polycarbonate in the outer walls, an U-value of 2.75 W m-2 K-1 was obtained.
Three GAHP were installed with 41.6 kW thermal power delivered (delta T brine inlet – hot water outlet 35°C) in combination with both short-term and long-term cold and heat buffer storage (45 m3 each, short-term), BTES (28 holes of 100 m depth, long term) and an air handling unit to cool and dry the air (4750 m3 h-1).
During the summer, pump operation is dictated by the need for CO2. The heat is collected short term in the heat buffer storage or long term in the BTES. The cold generated is used to dehumidify and cool the air so the ventilation requirement is reduced, and the emissions from the GAHP can be used for CO2 fertilisation.
During the winter, pump operation is dictated by the need for heat, in combination with the need for CO2. This is achieved through preferred heat production at times of high radiation, when absorbed heat is shunted to short term storage.
Cold that is produced can be used to dehumidify the air but is mainly used for exchange with the relatively high temperature (loaded in summer) in the BTES, so the temperature of the BTES (and soil) is back in balance at the end of the winter.
The heat delivered from the BTES improves the efficiency of the GAHP.
Companies growing organic vegetables are smaller than conventional producers, where electricity and heat cogeneration is a possible solution because of the larger, more suitable scale for introducing cogeneration.
In addition to economic reasons, organic growers should implement extra efforts to reduce the use of non-renewable energy.
Carbon dioxide is an important factor to enhance horticultural production and food quality.
In a working group of growers and an energy specialist, all these parameters were put together.
The best solution for small companies using carbon dioxide could be the use of a gas absorption heat pump (GAHP) in combination with Borehole Thermal Energy Storage (BTES) in an extra isolated greenhouse.
As a result, this concept was installed at the organic research centre in Kruishoutem, Belgium.
A new 1280 m² greenhouse divided into 6 compartments was installed.
By using a double upper screen and polycarbonate in the outer walls, an U-value of 2.75 W m-2 K-1 was obtained.
Three GAHP were installed with 41.6 kW thermal power delivered (delta T brine inlet – hot water outlet 35°C) in combination with both short-term and long-term cold and heat buffer storage (45 m3 each, short-term), BTES (28 holes of 100 m depth, long term) and an air handling unit to cool and dry the air (4750 m3 h-1).
During the summer, pump operation is dictated by the need for CO2. The heat is collected short term in the heat buffer storage or long term in the BTES. The cold generated is used to dehumidify and cool the air so the ventilation requirement is reduced, and the emissions from the GAHP can be used for CO2 fertilisation.
During the winter, pump operation is dictated by the need for heat, in combination with the need for CO2. This is achieved through preferred heat production at times of high radiation, when absorbed heat is shunted to short term storage.
Cold that is produced can be used to dehumidify the air but is mainly used for exchange with the relatively high temperature (loaded in summer) in the BTES, so the temperature of the BTES (and soil) is back in balance at the end of the winter.
The heat delivered from the BTES improves the efficiency of the GAHP.
Authors
N. Vergote, H. Marien
Keywords
technology, BTES
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