Development and field-test of a two axes Fresnel solar concentrator for Combined Heat and Power generation

The technical and economic sustainability of current photovoltaic (PV) systems is heavily affected by the costs and performances of the adopted PV cells. Solar concentrator systems represent an effective solution to reduce the solar cell surface and, at the same time, to increase the global conversion efficiency. The adoption of high performance multi-junction PV cells, e.g. Triple-Junction Photovoltaic (TJPV) cells, leads to this purpose. This paper presents full details about the design, development and field-test of a Fresnel lens solar concentrator for the micro-cogeneration of electrical power and thermal energy. Proposed plant can operate both stand-alone, to supply remote users non-connected to the national power grid, or as a node of the power grid for a distributed and sustainable energy production, i.e. Smart Grid network concept. A two axes solar conversion prototype is designed and built integrating several modules to guarantee the required plant functions. Basically, TJPV cells allow power production while Water Heat Exchangers (WHEs) are installed for both thermal recovery and cell cooling. Tested TJPV cells are InGa/GaAs/Ge on Ge substrate while the possible operative concentration factors are up to 1000x. A two axes solar tracker is integrated for sun collimation during the whole day. Motion control, together with monitoring of the environmental conditions and conversion performances, is provided thanks to a real-time interface developed adopting LabView© Integrated Development Environment (IDE). A preliminary experimental campaign to field-test the developed prototype is conducted analysing both the prototype performances and the parameters that heavily affect the plant conversion efficiency, e.g. solar irradiance, concentration factor, cooling water and air temperatures. The obtained results are presented and discussed.