Greenhouse with a CPV system based on NIR reflecting lamellae

In previous research a new type of greenhouse with an integrated concentrated photovoltaic system (CPV) was developed based on a circular covering geometry and an integrated filter for reflecting the near infrared radiation (NIR) of the greenhouse and exploiting this radiation in a solar energy system. The performance of the system was promising. In this study further optimalisation of the CPV system is made to avoid the large construction for solar tracing and the high investment. Hereto all parts for the solar concentrating system will be integrated into the greenhouse. The NIR-reflector material is carried out as a NIR-reflective lamellae 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 the 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 economic analysis.