Articles
NOVEL METHODS OF HEATING AND COOLING GREENHOUSES: A FEASIBILITY STUDY
Article number
719_24
Pages
223 – 230
Language
English
Abstract
This study was carried out to explore the feasibility of ways of cooling, and heating, greenhouses that would permit significantly higher CO2 concentrations than are currently used in order to increase grower income.
A simulation model was used to estimate the energy required for heating and cooling a greenhouse to maintain temperatures suitable for tomato production and to provide CO2 for aerial enrichment.
Crop value was estimated from a total crop photosynthesis model and tomato price.
The simulations were conducted for a tomato crop grown from December until October with average UK weather.
The heating and cooling systems considered were an endothermic energy system, a combined heat and power system (CHP), water chillers, heat pumps, two evaporative cooling systems, and the selective rejection of solar infrared radiation.
Separate models were developed to estimate the performance of each heating/cooling method and were integrated with a greenhouse model to estimate the performance of each heating/cooling method.
The reference system used for comparison was a greenhouse cooled using conventional roof ventilation, heated with hot water from a natural gas fired boiler with a heat store, and with CO2 obtained from the boiler flue gases.
When compared on the basis of the annual margin between crop value and energy cost, the systems that gave larger margins than the reference system were ranked as CHP, selective absorption of solar infra red radiation, endothermic energy system, heat pump driven by a natural gas fired engine using ground/ground water as the heat sink and heat source, and the evaporative cooling of ventilation air.
The endothermic and the CHP system using a heat driven chiller produced 2.5 times less emission of CO2 than the reference system.
A simulation model was used to estimate the energy required for heating and cooling a greenhouse to maintain temperatures suitable for tomato production and to provide CO2 for aerial enrichment.
Crop value was estimated from a total crop photosynthesis model and tomato price.
The simulations were conducted for a tomato crop grown from December until October with average UK weather.
The heating and cooling systems considered were an endothermic energy system, a combined heat and power system (CHP), water chillers, heat pumps, two evaporative cooling systems, and the selective rejection of solar infrared radiation.
Separate models were developed to estimate the performance of each heating/cooling method and were integrated with a greenhouse model to estimate the performance of each heating/cooling method.
The reference system used for comparison was a greenhouse cooled using conventional roof ventilation, heated with hot water from a natural gas fired boiler with a heat store, and with CO2 obtained from the boiler flue gases.
When compared on the basis of the annual margin between crop value and energy cost, the systems that gave larger margins than the reference system were ranked as CHP, selective absorption of solar infra red radiation, endothermic energy system, heat pump driven by a natural gas fired engine using ground/ground water as the heat sink and heat source, and the evaporative cooling of ventilation air.
The endothermic and the CHP system using a heat driven chiller produced 2.5 times less emission of CO2 than the reference system.
Publication
Authors
P.J.C. Hamer, B.J. Bailey, M.G. Ford, G.S. Virk
Keywords
Simulation, crop models, heat pumps, CHP, CO2 emissions, tomato
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