A Theoretical Comparison of Optically Concentrating, Solar Water-Splitting Devices

The use of optically concentrating lenses provides a mechanism to reduce the cost and energy input required to manufacture solar fuels-producing devices. The direct production of hydrogen via water splitting could thereby be realized in a cost-competitive, low carbon fashion. In this work, a modeling approach is used to assess which concentrator architectures are appropriate for integration with wireless photoelectrochemical cells. The model captures optical, heat transfer, photoelectrochemical and climactic phenomena. The variation of design parameters such as lens type, optical concentration ratio, deployment location, cell dimensions and tracking schemes are explored.

It is found that the devices that perform most efficiently employ modest concentration ratios, continuous tracking of the sun, and maintain sufficiently small photovoltaic cell size in order to reduce potential losses in the electrolyte. However, designs that exhibit the lowest cost and energy input per unit of produced fuel have somewhat higher concentration ratios and simpler tracking mechanisms. Employing passive cooling to maintain sufficiently low cell temperature during extreme ambient conditions becomes difficult as the photovoltaic cell size and optical concentration ratio increase.