A CPV System Based on NIR Reflecting Lamellae Integrated into a Greenhouse: Optimizing of Optics

Abstract

In an previous research project a new type of greenhouse with an integrated concentrated photovoltaic system (CPV) was developed which has an integrated filter for reflecting the near infrared radiation (NIR) to the greenhouse and exploiting this radiation in a solar energy system. The performance of the system was promising. In this study further optimalisations of the CPV system are made to avoid the large construction for solar tracting. Hereto all parts will be integrated into the greenhouse. The NIR-reflector material is carried out as a NIR-reflective lamllea system and the CPV–module is mounted into the ridge. In this paper the results of the optimization process of the CPV system based on NIR reflecting lamellae is presented. The optimization process is based on a maximal total annual electricity production and is performed with a ray tracing model and actual radiation data. Results show that the optimization of the lamellae greenhouse can be seen from a theoretical and a practical point of view. Theoretically, the number of lamellae for the investigated concept must be high (>100) and focus with a generic focal length of 3.5 m and glazing bars must be avoided. Then the maximal annual electricity output can be over 26 kWh/m². In practice, mechanical restrictions, plant conditions and costs will determine the implementation. The proposed CPV-system has positive side-effects like reducing the heat load (and need for cooling) during summer and blocking of the direct radiation which can be harmful for some crops. With this, the feasibility of the system depends greatly on local conditions which require a tailor-made economical analysis.