Micro-Cogeneration with a Fresnel Solar Concentrator

The technical and economic sustainability of photovoltaic (PV) systems is heavily affected by the cost and performances of the adopted PV cells. Solar concentrators represent an effective alternative to reduce the solar cell surface and, at the same time, to increase the global conversion efficiency. Such systems include optic elements to concentrate the solar radiation to a small area where high-efficiency PV cells are located. Particularly, the adoption of multi-junction cells, e.g. TripleJunction Photovoltaic (TJPV) cells, is encouraged to increase the power conversion performance. This paper presents full details about the design and operating features of a Fresnel lens solar concentrator for the micro-cogeneration of electrical power and thermal energy. The two axis controlled prototype integrates five different functional modules to guarantee the required features. Basically, the TJPV cells allow power production, while eight Water Heat Exchangers (WHEs) are installed for both the cell cooling and the recovery of thermal energy. The operative concentration factor is up to 800x through eight non-imaging Fresnel lenses integrated to the solar collector. Furthermore, a two axes solar tracker assures sun collimation during day-time. The prototype control, together with the monitoring of the environmental conditions and the energy conversion performances, is provided thanks to a semi-automatic real-time interface developed adopting LabView© Integrated Development Environment (IDE). A set of preliminary field-tests is assessed to study both the solar collimation accuracy and the prototype overall energy performances. The obtained evidences are presented and fully discussed in this paper.