Using solar energy to heat, cool and dehumidify tomato greenhouses in France: a feasibility study

A. Grisey, C. Levaillant, D. Martin, V. Stauffer
In the current context of predicted shortages of fossil fuels, carbon taxations and increased awareness of environmental impacts, using renewable energy to heat greenhouse vegetable crops has become a priority. In France, most heated greenhouses use natural gas-fired combined heat and power systems for heating (50% of the total area). The objective of this study was to determine the feasibility of using solar thermal energy to heat, cool and dehumidify vegetable greenhouses when using hot air (up to 250°C) generated by Fresnel concentrating mirrors combined with heat storage in an insulated rock bed with a storage capacity of several days. Several scenarios were studied, evaluating energy demand under different climate conditions. A solar collector with a surface area of 30% of the greenhouse area provided an energy mix that paid for itself rapidly in regions where heating was used throughout the year. The return on investment was less than 10 years. The combination of hot air produced by the solar collector and air conditioning using absorption chillers was particularly effective to dehumidify and cool the greenhouse with high thermal COP (coefficient of performance) values when double effect absorption was available. This system with internal greenhouse dehumidification reduced energy consumption in comparison with opening and venting greenhouses. In regions with both hot and sunny conditions where greenhouse cooling is necessary, the combination of solar hot air and absorption chilling also resulted in a favourable return on investment, because the system can be used throughout the year for heating, dehumidification and cooling. Our study also determined the energy storage capacity needed to manage the solar power fluctuations. The next step is to set up a trial on a significant scale (a few thousand m2) to confirm the merits of solar energy converted into hot air for controlling greenhouses.
Grisey, A., Levaillant, C., Martin, D. and Stauffer, V. (2020). Using solar energy to heat, cool and dehumidify tomato greenhouses in France: a feasibility study. Acta Hortic. 1296, 731-738
DOI: 10.17660/ActaHortic.2020.1296.92
solar collectors, climate control, energy storage, return on investment

Acta Horticulturae