Energy reduction measures in agricultural greenhouses heating: Envelope, systems and solar energy collection

While a great reduction of the energy demand for the environmental control of civil buildings has been reached in recent years, still a great potential of energy savings lies in other sectors like the one of agricultural production. The scope of this paper is to investigate the energy performance of some of the recent envelope and systems technologies that best can contribute to a great reduction of the energy demand for the climatic control of a greenhouse for intensive crop production. This article concentrates on three aspects: the use of polycarbonate hollow sheets to reduce the thermal transmittance of the glazing, the application of polypropylene sheets as a basal heating system and the solar energy capture by means of low cost plastic solar collectors. A tunnel greenhouse for basil production of 40 m of length and 10 m of width was considered as a case study and modelled within the EnergyPlus simulation software. The climate locations that were considered refer to the north-west of Italy. The results show that savings of the order of 30% can be achieved by using more insulated transparent materials. On the contrary, the application of the solar collectors still remains problematic because of the large land use and lower global efficiencies.