Colored PV cells doesn't need direct sunlight !

One of the most common ways to turn the sun's energy into electricity is by persuading silicon to give up some of its electrons. But it's also quite expensive, so any innovation that helps reduce the cost of solar cell production is welcome. Researchers in Israel have come up with a cell that uses only 20% of the silicon in a standard cell yet yields similar amounts of electricity. It does this by diffusing any light that falls on its surface and sends it off to photovoltaic collector strips on each of its sides. And it doesn't even need bright sunlight to operate.

In a nutshell, traditional solar collectors are made of thin strips of silicon covered by transparent plates. As the sun hits the plate, electrons are knocked out of the silicon atom producing current. A team of researchers led by internationally-renowned solar guru Prof Renata Reisfeld have taken a glass plate, given it light diffusing properties and attached strips of silicon to its edges.

According to the researchers, a mixture of different flourescent dyes concentrates visible and UV light (but not heat) onto the surface of the plate. Rather than simply passing through the plate, the light is persuaded to flow to the sides by metal nanoparticles, where thin strips of photovoltaic silicon wait to surrender their electrons. The interaction of the dyes and the nanoparticles helps ensure that just the right amount of energy hits the silicon to knock out the electrons, leading to improved cell efficiency.

This effectively means that as a cell doesn't need direct sunlight to operate - it can go on producing power long after traditional full silicon cells have stopped, albeit less efficiently under cloud or partial shade conditions. As you can see in this video, no matter where the light source comes from, the colored glass disperses it to the edge where photovoltaic collectors wait to convert it into electricity.

Even if a plate is cracked or chipped, light should still get dispersed to the edges without significant loss of efficiency. It also means that panels need not track the sun as it crosses the sky or be restricted to domestic roof applications - windows and walls could also house solar collecting panels.

The researchers are currently working on a cell capable of achieving 20% conversion efficiency (traditional silicon cells tend to be about 12-17% efficient, although some have recorded much higher rates). So not only could the new colorful innovation be more efficient than existing technology but, as less silicon is needed, it can be manufactured for about a fifth of the cost.

A 200 watt panel, for instance, can currently be manufactured for USD$189 but the researchers believe that even this is too high and are aiming for the solar nirvana of grid parity.

In 2006 Professor Reisfeld formed GreenSun Energy with her team to help bring the product to the marketplace. The company established a research laboratory in Jerusalem in 2007 and has been working to improve its model ever since. Professor Reisfeld told Gizmag that project funding will determine how long it will be before the technology reaches the marketplace, but is hopeful that it will be ready within the next year or two.

Thank you to GizMag for this one