Shading and electric performance of a prototype greenhouse blind system based on semi-transparent photovoltaic technology

Abstract

Photovoltaic (PV) energy is emerging in the greenhouse industry to compensate energy demands for cultivation. Because both crops and PVs need sunlight, their compatibility on the same land unit often conflicts. To overcome this difficulty, we prototyped a venetian-blind-type shading system comprising semi-transparent bifacial PV modules that concurrently function for greenhouse shading control and electricity production. The PV blind installed in a test greenhouse was operated automatically according to the external solar irradiance. When the solar irradiance was higher than a predetermined threshold level, the PV modules were oriented parallel to the roof with sunlight shading of 42%. The PV modules were oriented to be perpendicular to the roof when the irradiance level was low, prioritizing the sunlight intake into the greenhouse. The blind system operations were managed completely by the electrical energy generated by the PV modules. Actually, the PV-produced electricity was surplus to the blind system operations, suggesting that additional greenhouse appliances can be operated by the PV-produced electricity. This system might be applicable to greenhouses in high-insolation regions as an energetically stand-alone dynamic shading system to produce a better light environment for crops.