State-of-the-art of Concentrating Photovoltaic Thermal Technology

Concentrating Photovoltaic Thermal (CPVT) Technology is still a niche application of the global photovoltaics market. This is despite the fact that CPVT has the potential to provide at the same time electrical and thermal energy to industrial customers and can significantly increase the overall efficiency of conversion of solar radiation. In this paper we present an overview of the state-of-the-art of Concentrating Photovoltaic Thermal (CPVT) Technology, give an outlook into potential improvements and efficiency in the near future and present our own performance simulations of CPVT systems.
CPVT systems can use parabolic trough or Fresnel mirrors or lenses, but they have to face the challenge that the electrical and the thermal part of the receiver have contrary temperature requirements. The PV cells should be kept at low temperature to achieve high conversion efficiency, but the thermal part should generate high output temperatures to supply industrial heat loads. In the spectral splitting approach, the solar spectrum is divided into a part used by the PV cells and another part used to heat a thermal fluid. Spectral splitting can significantly improve the performance of compact CPVT receivers.
We present simulations of electrical and thermal performance of spectral splitting concepts to quantify the potential gain in electrical conversion efficiency and the additional thermal power output. Three different PV
technologies were analysed, and the impacts of cell temperature and concentration factor were calculated. The optimised spectral splitting filter configuration yields an increase of the theoretical efficiency of 64 % for crystalline Silicon cells, compared to the full spectrum operation. The waste heat dissipation within the cells is reduced by 91 %. The loss of absolute electrical output is over-compensated by the additional thermal gain.