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The future of solar is looking much brighter

Solar power is taking off around the world.  Europe is planning to deploy various types of solar power to the Sahara to provide for the European Union's energy needs.  Meanwhile, here in the U.S., California is expanding its solar efforts as well.

However, amid the progressing adoption of solar technology, one perpetual criticism that persists is that solar power is inefficient and expensive.  To some extents this is true.  The current generation of photovoltaic solar panels -- the type of solar power perhaps most associated with the field -- is only around 20 percent efficient and thus costs remain relatively high, like many forms of alternative energy.

A new breakthrough from U.S. Department of Energy's National Renewable Energy Laboratory (NREL) is looking to solve those problems.  It pushes solar cells to uncharted technology with a record 40.8 percent efficiency.  The new work shatters all previous records for photovoltaic device efficiencies.

The researchers first used a special type of cell, an inverted metamorphic triple-junction solar cell.  The custom cell was designed, fabricated, and independently measured at NREL.  The next step was to expose the solar cell to concentrated light of 326 suns, yielding the record-breaking efficiency.  A sun is a common measure in the solar power industry which represents the amount of light that hits the Earth on average.

The new cell targets a variety of markets.  One potential market is the satellite solar panel business.  Satellites natural absorb more intense sunlight, thanks to no atmospheric interference.  Another possible application is deployment in commercial concentrated PV cells.  Concentrated PV is a burgeoning field, with several companies currently contracted worldwide to build the first utility grade plants.

The new record was welcome news, but little surprise at NREL -- they held the previous record as well.  In order to beat their old design, one key was to replace the germanium wafer at the bottom junction with a composite of gallium indium phosphide and gallium indium arsenide.  The mixture splits the spectrum into three parts, each of which gets absorbed by one of the junctions.  Both the middle and bottom junction become metamorphic in the new design.  This means their crystal lattices are misaligned, trapping light in the junction and absorbing more of it.  This yields an optimal efficiency.

One key advantage is the new solar cell can be conveniently processed by growth on a gallium arsenide wafer.  It is also both thin and light.  The NREL believes this cell will be cheaper than current commercial models, while delivering far more power.

Some of the credit for the work goes to NREL's Mark Wanlass, who invented the cell's predecessor.  The new cell was redesigned by a team led by John Geisz.

The NREL is operated by the DOE by Midwest Research Institute and Battelle.

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RE: One thing I don't get...
By trajan on 8/18/2008 7:45:52 AM , Rating: 5
It does sound like they needed the 300+ suns of light to get it up to 40% efficiency but its still a nice feat. Aside from the usefulness in space, as pointed out, maybe these would be useful in combination with reflecting mirrors. Not necessarily one of those giant arrays they build out in deserts, but picture a satellite-dish sized reflector with a very small cell at the focal point. A 1 cm^2 cell would only need ~350 cm^2 worth reflector to hit the right efficiency. And instead of building a huge solar cell you can build a tiny one - cost savings.

Just brainstorming, I have no idea if the cell that built would actually be able to work that way, but just because you need all the extra light doesn't mean this isn't still good news. (If they got 40% efficiency using normal sunlight, with an easy to manufacture design, that would have been on the front page of most major newspapers, I'd wager).

RE: One thing I don't get...
By 67STANG on 8/18/2008 11:12:57 AM , Rating: 3
That's exactly the problem, these aren't easy to manufacture- nor are any multi-junction solar cell. (That's why they cost so much). These are typically only used in government or space appliactions as it's cheaper to run twice as many panels than it is to run twice as efficient panels.

Not really sure this is too terribly exciting news, the work that the Idaho National Laboratory did that could possibly yield 80% efficiency through a combination of light and heat absorption is much more promising...

RE: One thing I don't get...
By freaqie on 8/18/2008 2:43:24 PM , Rating: 2
A 1 cm^2 cell would only need ~350 cm^2 worth reflector to hit the right efficiency. And instead of building a huge solar cell you can build a tiny one - cost savings.

why not put a boiler down there instead and a turbine hooked up to a generator
and get 75+ percent efficiency
or a stirling engine... 80% efficient...

it is a nice idea but others are just better

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