Material Optimization for Concentrated Solar Photovoltaic and Thermal Co-Generation

We conducted an analytic study of concentrated solar photovoltaic and hot water co-generation based on various solar cell technologies and micro channel heat sinks. By co-optimizing the electricity generation and heat transport in the system, one can minimize the cost of the key materials and compare different tradeoffs as a function of concentration ratio or other parameters. Concentrated solar Photovoltaic (PV) based on multi junction cells can yield around 35–40% efficiency. They are suitable for high photon energy flux and they are already available in the market. However, due to high heat fluxes at large concentrations, such as 100–1000 Suns, heat sinks could be costly in terms of material mass, space, energy for pumping fluid, and system complexity. In addition, since the efficiency of solar cells decreases as the ambient temperature increases, there is a tradeoff between electricity and hot water cogeneration. Similar to our previous analysis of thermoelectric (TE) and hot water co-generation, PV/solar thermal system is also optimized. The results are compared with thermoelectric systems as a function of the concentration ratio. The solar concentrated co-generation system using either PV or TE for direct electricity generation collects more than 80% of solar energy when it is optimized. We calculate the overall cost minima as a function of concentration ratio. Although there are some differences between PV and TE, the optimum concentration ratio for the system is in the range of 100–300 Suns for both.