Holographic spectrum-splitting photovoltaic system using bifacial cells

In this paper a photovoltaic system is proposed that achieves high energy yield by integrating bifacial silicon cells into a spectrum-splitting module. Spectrum-splitting is accomplished using volume holographic elements to spectrally divide sunlight onto an array of PV cells with different bandgap energies. Diffuse sunlight is transmitted through the holographic element and converted. Light that is reflected off the ground surface is incident upon the rear side of the module and converted by the bifacial silicon cells. A diffuse scattering surface is applied to the rear-side of the monofacial wide-bandgap cell to redirect light to the bifacial silicon and increase the light collection. The volume holographic element optimization is automated and practical system design parameters such as concentration and aspect ratio are analyzed. An example using 22.5% efficient silicon and 28.8% efficient GaAs is presented and shows that an energy conversion efficiency of 32.9% can be achieved using typical utility scale illumination parameters. An economic analysis is presented that shows the installed cost per watt can be reduced by over 30% compared to a monofacial silicon panel and can even provide benefit if the cost of the wide-bandgap cell is over 10X the cost of silicon cells.