Sunday, March 30, 2008

More Photovoltaic News

Yet another set of cost-reducing gimmicks for multicrystaline solar cells:
The company's first prototype solar cells include three key innovations to improve efficiency. The first is a method for adding texture to the surface of the cells that allows the silicon to absorb more light, a trick that's been used before with single-crystalline devices but has been difficult to implement with multicrystalline silicon. The rough surface causes light to bend as it enters the cell so that when it encounters the back of the cell, it doesn't reflect right back out; rather, it bounces off at a low angle and remains inside the slab of silicon. The longer the light remains within the silicon, the greater the chance that it will be absorbed and converted into electricity.

The second innovation involves the silver wires that harvest electrical current generated by the silicon. Sachs has developed a method for making these wires as small as one-fifth the width of the wires that are typically used, while improving their conductivity. The thinner wires use less silver, which cuts down costs. Also, because the wires are thinner, they can be spaced closer together and still block less light than ordinary wires can. The closer spacing makes the wires more efficient at collecting electrical current generated in the silicon.

The final improvement has to do with a set of wide, flat wires used to collect current from the thin silver wires. These bars typically block light entering the cell, reducing efficiency. But Sachs has etched their surfaces so that they act as faceted mirrors. This achieves an effect similar to the texturing of the silicon surface. While the improvements add costs in some ways, the increases are offset by savings elsewhere, such as from using less silver, Sachs says.
Life is good at the knee in the curve. Solar clearly has its problems (not the least of which is that you've got to devote so much area to its deployment, and you have to couple if to some sort of massive-scale energy storage technology), but you have to agree that we already know how to crank out lots and lots of chips. I continue to think that this might get deployed a lot faster than we think.

Meanwhile, nuclear just can't get traction. The industry has certianly frittered away its big boost in share-of-mind. I'm becoming a lot more sanguine about photovoltaics.

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