Two-faced solar cells boost yields by up to 50 percent
July 3, 2012
Israeli photovoltaics developer bSolar has developed a double-sided solar cell it claims can boost the energy yields of solar panels by up to 50 percent when installed vertically, or by between 10 and 30 percent in more typical installations. The "bifacial" cells rely on a back surface field (BSF) of boron rather than aluminum, which bSolar claims not only allows for an open rear face but also increases the efficiency at the front of the solar panel.
Back surface fields are effectively a barrier which reduces the electron-electron hole recombination at the surface, enhancing a solar cells overall efficiency. Unlike traditional aluminum BSFs, bSolar's is translucent, allowing more light into the cell.
It makes intuitive sense that a two-faced solar panel (if you'll pardon the expression) installed in an upright position could conceivably boost efficiency by 50 percent, provided both sides a receive the same amount of light.
More interesting is that bSolar claims up to 30 percent higher energy yields in more typical installations, by which it means ground or roof-mounted panels angled roughly perpendicular to the sun. In this scenario, the rear surface of the panel is essentially harvesting bonus light reflected from the ground or roof.
The bonus yield will inevitably be effected by the reflectivity of the surface (so, yet another reason for white rooftops) and the density of surrounding obstructions including other solar panels.
bSolar has struck deals with panel manufacturers including solar AG, asola Solarpower GmbH, Solar-Fabrik AG, SI-Modules GmbH and Solarnova Produktions-und Vertriebs GmbH. It recently announced that panels equipped with its bifacial cells would be used in a 730 kW installation by TSBM in Nasukarasuyama, Japan.