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August 14, 2008

NREL Solar Cell Sets Efficiency Record of 40.8%

Colorado, United States [RenewableEnergyWorld.com]

Scientists at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) have set a world record in solar cell efficiency with a photovoltaic device that converts 40.8 percent of the light that hits it into electricity. This is the highest confirmed efficiency of any photovoltaic device to date.

The 40.8 percent efficiency was measured under concentrated light of 326 suns. One sun is about the amount of light that typically hits Earth on a sunny day.

The inverted metamorphic triple-junction solar cell was designed, fabricated and independently measured at NREL. The 40.8 percent efficiency was measured under concentrated light of 326 suns. One sun is about the amount of light that typically hits Earth on a sunny day. The new cell is a natural candidate for the space satellite market and for terrestrial concentrated photovoltaic arrays, which use lenses or mirrors to focus sunlight onto the solar cells.

The new solar cell differs significantly from the previous record holder – also based on a NREL design. Instead of using a germanium wafer as the bottom junction of the device, the new design uses compositions of gallium indium phosphide and gallium indium arsenide to split the solar spectrum into three equal parts that are absorbed by each of the cell's three junctions for higher potential efficiencies.

This is accomplished by growing the solar cell on a gallium arsenide wafer, flipping it over, then removing the wafer. The resulting device is extremely thin and light and represents a new class of solar cells with advantages in performance, design, operation and cost.

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Reader Comments (13)
 
No image available
August 14, 2008
I wonder why this is being presented as the record when University of Delaware researchers have already achieved 42.8%?

http://www.udel.edu/PR/UDaily/2008/jul/solar072307.html

Stephen
Comment 1 of 13
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August 14, 2008
I would be happy buying the ones over 40% from over a year ago, where are they! you have done it, now start building and distributing them.
Comment 2 of 13
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August 14, 2008
I used to be interested in the triple junction cells until I discovered that the cost per watt was high. Yes, these cells are more efficient than regular cells but need a light concentrating system, a cooling system and a tracking system to make the cells functional.

This method has good potential but seems to need more development.

adrianakau2aol.com
Comment 3 of 13
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August 15, 2008
I find it interesting that NREL is spending our tax dollars on a solar power system that can only be used by NASA. It's a break though for sure, but how about trying to solve the problem at hand on earth and not above it.
Comment 4 of 13
August 15, 2008
While it's easy to defend taxpayers and the monies that go into R&D for NASA and other, it's also important to note the trickle down effect of such practices. Without solar research done for NASA there are several solar technologies that simply wouldn't exist today. As a commercial and residential solar consultant, I am aware of the costs and accounting that take place with solar installations on homes and businesses.

I would rather defend a feed-in tariff from our legislators that would do much more in terms of completed projects, lowering costs through economy of scale, and result in quicker development of a green manufacturing sector and related jobs and economic benefits. These feed-in's are what has created such impactful renewable benefits in Europe. Most notably, Germany and Spain.

I wouldn't be too upset on the monies going into the NREL. They are working on so many benefiting projects that all lead to better and more affordable choices for us and the world, going forward. They are also an incubator of talents and technologies that lends itself to new ventures, major breakthroughs, and ultimately, the solutions we so desperately need.

In ten years when you're standing back looking at your plug-in hybrid with the three kilowatt absorption body... plugged into your 100 square foot, six kilowatt solar array that's also supplying the energy to your home and hobby shop... you'll probably complain that all this stuff costs a lot of money and ought to do more. But that's what people said about their '70's solar thermal systems, and there's plenty of them still doing work today.

As for me and mine, we'll see you out there, on our bikes of course... JD Howell, Eugene, OR.
Comment 5 of 13
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August 15, 2008
I agree with you Brad , They should suspend funding for all nasa projects until they release some technology to the private sector to ease energy costs here.
Comment 6 of 13
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August 15, 2008
It should be noted that the 42.8% efficiency claim has not been independently confirmed and to my knowledge has not been published in any peer reviewed paper. As such it should be viewed with skepticism. The PV R&D community has been very careful to have world record claims independently verified with a few notable exceptions.

Concentrator PV is a viable option for many terrestrial commercial and utility scale applications with many systems already deployed with a rapid growth in new concentrator systems.
Comment 7 of 13
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August 20, 2008
The University of Delaware work appears to be a system, which splits the incoming light up into 3 bands directed on to 3 different types of solar cell. Whereas the NREL is a single, integrated device.
I agree with Adrian that for terrestial applications the key parameter is cost per watt. For space applications (and yes, guys we do use satellites) the key parameter will be watts per kg (or lb if you are American), so the NREL device would probably win.
Comment 8 of 13
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August 20, 2008
Michael Miller - triple junction cell technology was originally developed by NREL and has be licensed and a few companies are making high efficiency triple junctions cells - namely Spectrolabs and Emcore, as well as Cyrium Technologies. NREL is continuing research in an effort to reduce the cost of these TJ cells. These cells are used in high concentration photo voltaic systems, currently being developed by many companies (a few of the ones further along in development include Sol Focus, Solar Systems, Amonix, Concentrix, Soliant, Green Volts). I think this is money well spent. If you are really concerned about where your tax dollars are going, there are a lot bigger targets. NREL funding is barely a drop in the bucket.
Comment 9 of 13
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August 20, 2008
This is a clarification for my previous entry. My group at NREL did independently measure the 42.8% solar cell reported by Delaware and others. This number is the sum of the solar cell efficiencies as reported assuming they were in a module with ideal optics. This result is nonstandard only in that the cell were tested at different times and not as a group and the reference conditions was the standard global instead of the usual direct spectrum used for concentrators. The 40.7 and 40.8% results were also measured by the PV Cell and Module performance group at NREL and are for a monolithic 3-junction cell under standard concentrator reporting conditions.
Comment 10 of 13
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August 21, 2008
Have you ever noticed that Solar PV has several "world record breaking" developments a year for the past decades, but we still are installing the same money loosing panels on the roof?
Comment 11 of 13
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August 22, 2008
Sloppy definitions of well-known physical concepts do not improve readability for the layman, and suggest to those who see the error that there may be other, less obvious, errors in the publication. To wit: one sun is not "about the amount of light that typically hits Earth on a sunny day." One sun is about the light power that typically hits Earth per square meter, when the sun is directly overhead, on a sunny day. It has a value of 1 kWatt per square meter. Thus, "326 suns" requires that this 1 kWatt be concentrated, without losses, into a circle with a diameter of a little less than 2.5 inches. That enormous concentration factor is what necessitates the cooling, etc., mentioned by other commentators, which generally takes energy as well. It should also be expected that conversion efficiency would be lower at other concentration factors, since one would typically quote the best possible result when trying to set a record.
Comment 12 of 13
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July 20, 2009
Such high concentration breaks down in hazy or cloudy weather becoming very inefficient.
Comment 13 of 13
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