Performance bounds and perspective for hybrid solar photovoltaic/thermal electricity-generation strategies

Hybrid solar photovoltaic (PV)/thermal power systems offer the possibility of dispatchable, affordable and efficient solar electricity production – the type of transformative innovation needed for solar cell devices to realize high grid penetration. The PV sub-system enjoys high efficiency, and the thermal sub-system can ensure uninterrupted power delivery via backup gas heating and/or multi-hour thermal storage. However, elucidation of the basic performance bounds, and the quantitative perspective required for judging the leading hybrid strategies relative to one another, as well as relative to the existing alternative of autonomous photovoltaic and solar thermal power systems, have remained incomplete. A more thorough and basic evaluation of the performance of the assorted combinations of PV and solar thermal sub-systems over a wider range of possible operating conditions than regarded previously is presented here. This involves analysis of the most fundamental processes limiting system efficiency, tempered by the realities of current and foreseeable PV and thermal technologies. The 3 leading hybrid strategies are: (1) concentrated solar beam radiation irradiating an integrated PV–thermal receiver, with the unique advantage of recuperating PV thermalization losses as heat delivered to the thermal receiver, thereby contributing to driving the turbine, (2) the spectral splitting of concentrated solar beam radiation, with sub-bandgap photons directed to a thermal receiver and the rest to concentrator PV cells, and (3) nominally 1 sun PV cells performing double duty as both a direct converter and as a spectrum-splitting reflector that concentrates sub-bandgap photons onto a thermal receiver. The two figures of merit appraised are: (a) the solar-to-electricity conversion efficiency, and (b) the share between thermal and PV electricity production.