Possibilities of Using Semi-Transparent Photovoltaic Modules on Rooftops of Greenhouses for Covering Their Energy Needs

Abstract

Semi-transparent photovoltaic cells allow the transmittance of solar irradiance through them and they have been used in building’s skylights and facades. Their use on rooftops of greenhouses can result in electricity generation which can cover part or all of their energy needs without affecting the growth of the plants. This also results in the decrease of cooling requirements during the summer since less solar irradiance is entering the greenhouse and lower CO2 emissions due to energy use in it. However, their current prices are high compared with the prices of opaque PV cells. The purpose of the present work is to investigate the possible use of semi-transparent PV modules placed on the roof of energy intensive greenhouses in Crete-Greece in order to cover their energy requirements and sell the surplus electricity into the grid. Two different cases have been studied where greenhouses of 1,000 m2 each cover their high heating needs using heat pumps and solid biomass. PV modules of 42.5 KWp can be placed on their roofs covering slightly less than 50 % of their surface allowing enough solar irradiance to enter the greenhouse. In the first case the generated electricity can cover more than 80 % of total energy needs and in the second all the energy needs offering the possibility of selling the surplus electricity to the grid. However, the current high prices of semi-transparent PVs do not favour their use by farmers since their installation costs are high. Future financial support from the government could increase their attractiveness for commercial applications in greenhouses.