Two-faced solar cells boost yields by up to 50 percent

Two-faced solar cells boost yields by up to 50 percent
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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.

Source: bSolar, via GigaOM

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Put reflective foil on the roof to direct the rays. Even another wall of reflective foil to get all the way under.
Michael Mantion
I dont' think reflective foil would really be beneficial High gloss white will reflect enough light.. The real problem the hotter the cell gets the less efficient it is and faster it fatigues.. In cooler climates this could useful.
Foil or mylar works great and is cheap. Google search "Tonchev" and look at his data - if you don't overheat the panels and lose efficiency then it is a cheap return - especially in winter...
bi facial has been done, although production has been held up. Sliver cells as developed by the ANU, and to be commercialised by Transform Solar, a joint venture of Micron (USA) and Origin Energy (Australia).
As the name 'sliver' suggests, they are very economical with the amount of silicon they use. Given the current glut of Chinese panels, I'm not sure if the US factory will ever get going.
Gary Richardson
In the years to come, resale value and recycling incentives of older panels will be more important in panel ownership. These type of panels will have higher resale value and make it easier to trade up.
I am getting so sick and tired of the numbers game played by all these developers; they are becoming “Snake-Oil Salesmen.” Nowhere does it say what the efficiency of the panels are! If the efficiency is say 10%, then telling me that mounting it upright get 50% more efficiency still leaves me less efficient than the industry leaders that are around 21% (outside of laboratory prototypes). I’m not one for “Government intrusion” but just like the Auto Industry has MPG numbers; the Solar Industry needs to mandate efficiency numbers. This would give the average consumers the knowledge to spend their money wisely and at the same time get rid of the rift-raft developers and focus the R&D dollars on increased efficiency and lower cost.