Design and optimisation of non-imaging concentrator for low concentrating photovoltaic thermal co-generation system

A Concentrating Photovoltaic-Thermal (CPVT) system is an integration of solar photovoltaic (PV) and solar thermal technologies along with a concentrator, which can simultaneously generate electrical and thermal output. Use of concentrators such as Compound Parabolic Concentrators (CPC), Linear Fresnel Reflector, Parabolic trough etc. helps in collecting more solar radiation which in-turn results in higher grade of thermal energy and more electrical output per unit area. CPC is a non-imaging solar concentrator where exact image of the source is not formed instead, there is a transfer of energy in the form of radiation from the source to the absorber. The non-tracking nature of this concentrator makes it unique from the other concentrators mentioned above thus reducing the cost and complexity of the system. The major drawback of the compound parabolic concentrator is the formation of nonuniform flux distribution on the absorber which can be minimized by the use of optimised homogenizer. In this work, optimised homogenizer design has been carried out for 2X, 2.5X and 3X CPC each truncated to 1.7X. The simulation results show that the optimised homogenizer significantly reduces the non-uniform illumination on the PVT absorber. In addition, simulations show that considering material requirement and acceptance angle, 2.5X CPC truncated to 1.7X is optimum design.