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Friday, June 15, 2007 Ultraefficient PhotovoltaicsThe new class of materials enabling the world's best solar cell has a bright future. By Peter Fairley
A solar cell more than twice as efficient as typical rooftop solar panels has been developed by Spectrolab, a Boeing subsidiary based in Sylmar, CA. It makes use of a highly customizable and virtually unexplored class of materials that could lead to further jumps in efficiency over the next decade, making solar power less expensive than grid electricity in much of the country. The cell, which employs new "metamorphic" materials, is designed for photovoltaic systems that use lenses and mirrors to concentrate the sun's rays onto small, high-efficiency solar cells, thereby requiring far less semiconductor material than conventional solar panels. Last month Spectrolab published in the journal Applied Physics Letters the first details on its record-setting cell, initially disclosed in December, which converts 40.7 percent of incoming light into electricity at 240-fold solar concentration--a healthy 1.4 percent increase over the company's previous world-record cell. Other groups are developing promising cells based on the new type of materials, including researchers at the Department of Energy's National Renewable Energy Laboratory (NREL), in Golden, CO. The NREL researchers will soon publish results in the same journal showing that their NREL's designs are tracking Spectrolab's, improving from 37.9 percent efficiency in early 2005 to 38.9 percent efficiency today. Metamorphic semiconductors resemble the high-efficiency cells used in space. Like the cells that grace satellites and planetary landers, they employ three layers of semiconductors, each tuned to capture a slice of the solar spectrum (solar panels have only one active layer). These semiconductor layers are assembled, one upon the next, by altering elements fed to a crystal growing in a vacuum. To avoid growing crystals filled with energy-trapping defects, device designers have until recently employed only a limited repertoire of semiconductors, such as germanium and gallium arsenide, which form similar crystal structures. Metamorphic materials provide flexibility by throwing off this structural constraint, employing a wide range of materials, including those with mismatched structures. "The parameter space you can explore using mismatch opens up a whole world of possibilities," says NREL principal scientist Sarah Kurtz. What makes this possible is the addition of buffer layers between the semiconductor layers. This technique was employed in the early 1990s to make high-speed transistors combining silicon and germanium, and then introduced to photovoltaics later in the decade by Cleveland-based semiconductor developer Essential Research. Spectrolab has, however, seen the best results. Its 40.7 percent metamorphic cell improves on Spectrolab's best conventional cells by incorporating new semiconductors in the top and middle layers that excel at capturing infrared light that was all but missed by the cell's predecessors. Such high output may be just the beginning. Raed Sherif, director of concentrator products at Spectrolab, says there is every reason to believe that these metamorphic solar cells will top 45 percent and perhaps even 50 percent efficiency. Sherif says those efficiencies, combined with the vast reduction in materials made possible by 1,000-fold concentrators, could rapidly reduce the cost of producing solar power. "Concentrated photovoltaics are a relatively late entry in the field, but it will catch up very quickly in terms of cost," he predicts. (See "Solar Power at Half the Cost.") |
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Flexible, Nanowire Solar Cells
02/06/2008
Comments
cakass on 06/15/2007 at 5:23 AM
1
ranadrew on 06/15/2007 at 11:05 AM
9
www.if.uj.edu.pl/Foton/92-special%20issue/pdf/06%20kburda.pdf
However, beware statistics (numbers) can be misleading. In comparisons to nature and her processes the devil is always in the details. Cutting out a little piece of her and analyzing it in detail often leads to misinterpretations and underappreciation of her sublime design perfection.
nekote on 06/15/2007 at 11:42 AM
115
Algae are supposed to be 10 to 100+ times as efficient, per acre, per year - meaning 1% to 10% (sometimes to 200 - 20%) and there are numbers of projects active in that vein.
If those PV % are close to correct, these 240 and 1,000 to 1 *CONCENTRATING* collectors would seem to have an advantage at ~ 40%. (FWIW - sounds almost like the Solex device in the James Bond movie "The Man with a Golden Gun - 1974 :) )
The rub, as alway, is $/unit energy, delivered to the end consumers.
Which method(s) will provide the lowest delivered cost KWH or gallon of liquid fuel, as paid for by consumers?
mpalmer41 on 06/15/2007 at 5:03 PM
1
rhapsodyinglue on 06/16/2007 at 6:51 PM
55
As for the expense... I guess at this point it isn't cost competitive with the other solar concentrating technology. Recently there have been announcements of utility scale solar troughs and stirling dishes... with the largest commitment seeming to go to stirling dishes. So I'd assume they have the current cost advantage.
Given that these cells require concentrated sun there is the expense of some form of optics and a tracking mechanism. One company is developing a very novel flat panel solar concentrator that may be a good match for these ultra efficient PV cells...
http://www.solfocus.com/technology_gen2.html
nekote on 06/17/2007 at 11:23 AM
115
Care to consider Green and Gold Energy's SunCube:
http://www.greenandgoldenergy.com.au/ ?
I'm not doubting the laboratory efficiency claims.
But that % is always the very highest the efficiency can possibly be, for systems that use that style of device.
Rather, there are so many other factors (focusing, tracking, reflection, DC to AC inverter, dirt / aging, transmission distance to market, ... efficiency losses, not to mention capital and operating costs, longevity, reliability, availability ...) that weigh heavily on the final, most relevant $/KWH price to consumers. In essence the net PV %, so to speak.
So, I should have said if those PV % are close to what the end user finally gets - meaning bare minimum losses elsewhere and bare minimum additional expenses.
asdar on 07/06/2007 at 11:52 AM
62
http://www.energy.ca.gov/sitingcases/all_projects.html
They're clear down at the bottom in the section for renewables. Final construction certification is supposed to be in Aug, for stirling one, and Sept for two.
SES dish isn't as efficient as 40%, more like 20%, and has some operating expenses. I still like the tech, and think the biggest advantage is that it requires no exotic materials.
darkstar57 on 06/18/2007 at 7:41 AM
2
like melt the cell?
pfairley on 06/18/2007 at 4:40 PM
5
cscoxk on 06/19/2007 at 2:59 PM
1
OptiPes on 07/09/2007 at 8:10 PM
3
CarlHitchon on 10/16/2007 at 1:41 AM
14
I would be nice to harvest the heat left after conversion for hot-water, dryer hot air, and heating. A possible limitation is that these cells have to be kept fairly cool or efficency degrades rapidly.
sacapiloa on 06/16/2007 at 1:56 PM
9
r19578 on 06/16/2007 at 7:54 PM
1
randman420 on 06/16/2007 at 10:32 PM
6
spectator on 06/18/2007 at 4:46 PM
1
Looking generally, in the nature there is plenty of the radioactive elements, but they are almost evenly distributed all over. That makes intensity of the localized radiation to be below limit to which life has been genetically accommodated.
Problem with radioactive waste are isotopes produced by nuclear reaction, which can be more radioactive than starting material. Now, if all this waste is evenly distributed over the earth, local radiation will be really negligible. But this is not at the moment possible.
There are many other more dangerous materials, which human race is throwing around, but we do not recognize its dangers, because general public is not informed, or the facts are kept hidden by governments. Just to mention Chemical weapons (neurotoxins, neural toxic gases), like VX, which even US government has enclosed in the cement encased barrels and disposed huge amounts in the oceans. Just imagine, what can happen after several decades, when see water “eats” through these containers, and VX starts leaking under a see.
jdorgan on 07/06/2007 at 5:41 AM
1
If we do change our laws to allow reprocessing, there is a considerable (effectively infinite) energy supply. However, for each gigawatt-year of electricity generated (the size of a typical modern coal fired power plant is aroung a GW) you produce one ton of radioactive cesium and one ton of radioactive strontium - these materials have half lives of about 400 years.
Is a sustainable energy system one that each year produces two tons of radioactive material that needs 400 year stewardship? Do you think stewardship for even a couple hundred years is possible to guarantee? I remind you that the USA, at 231 years old, is the longest standing government presently on the planet.
We have a perfectly beautiful nuclear reactor, one that uses clean fusion power and which is safely located 92 million miles from earth - why not use it?
ryanweed on 08/20/2007 at 10:50 AM
1
YogaMan on 06/27/2007 at 6:41 PM
2
OptiPes on 07/09/2007 at 8:20 PM
3
valikor on 07/13/2007 at 6:41 AM
1
Valikor
jmongu on 08/01/2007 at 11:44 AM
3
Siphon on 08/27/2007 at 4:19 PM
94
Doing a lifecycle cost analysis is rather difficult if the industry cannot be accounted for all costs and responsibilities. This is also very difficult if these particular costs and responsibilities are handed over to future generations and governments.
Then there are the weapon implications, which only cause more gov't meddling.
No thanks, let's not go the France route. It's bad enough already with current government energy policy.
CarlHitchon on 10/16/2007 at 1:53 AM
14
Fire can burn, should we give that up? Nuclear wastes are minute in quantity when compared with fossil fuel wastes. Nuclear wastes are manageable. The problem with nuclear energy is political as is this anti-nuke attitude.
Macrob on 08/05/2007 at 3:31 AM
2
sbkadar on 08/16/2007 at 9:37 PM
5
I'd love to lay my hands on these cells to experiment with. But where can an individual buy such devices?