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Cheap, Superefficient Solar
Technology Review (MIT) ^ | November 9, 2006 | By Kevin Bullis

Posted on 11/10/2006 11:33:50 AM PST by aculeus

Solar-power modules that concentrate the power of the sun are becoming more viable.

A worker arranges wafers that will be fabricated into superefficient solar cells. These cells could help dramatically reduce the cost of generating electricity from solar energy. (Credit: The Boeing Company) Technologies collectively known as concentrating photovoltaics are starting to enjoy their day in the sun, thanks to advances in solar cells, which absorb light and convert it into electricity, and the mirror- or lens-based concentrator systems that focus light on them. The technology could soon make solar power as cheap as electricity from the grid.

The idea of concentrating sunlight to reduce the size of solar cells--and therefore to cut costs--has been around for decades. But interest in the technology has picked up in the past year. Last month, Japanese electronics giant Sharp Corporation showed off its new system for focusing sunlight with a fresnel lens (like the one used in lighthouses) onto superefficient solar cells, which are about twice as efficient as conventional silicon cells. Other companies, such as SolFocus, based in Palo Alto, CA, and Energy Innovations, based in Pasadena, CA, are rolling out new concentrators. And the company that supplied the long-lived photovoltaic cells for the Mars rovers, Boeing subsidiary Spectrolab, based in Sylmar, CA, is supplying more than a million cells for concentrator projects, including one in Australia that will generate enough power for 3,500 homes.

The thinking behind concentrated solar power is simple. Because energy from the sun, although abundant, is diffuse, generating one gigawatt of power (the size of a typical utility-scale plant) using traditional photovoltaics requires a four-square-mile area of silicon, says Jerry Olson, a research scientist at the National Renewable Energy Laboratory, in Golden, CO. A concentrator system, he says, would replace most of the silicon with plastic or glass lenses or metal reflectors, requiring only as much semiconductor material as it would take to cover an area the size of a typical backyard. And because decreasing the amount of semiconductor needed makes it affordable to use much more efficient types of solar cells, the total footprint of the plant, including the reflectors or lenses, would be only two to two-and-a-half square miles. (This approach is distinct from concentrated thermal solar power, which concentrates the heat from the sun to power turbines or sterling engines.)

"I'd much rather make a few square miles of plastic lenses--it would cost me less--than a few square miles of silicon solar cells," Olson says. Today solar power is still more expensive than electricity from the grid, but concentrator technology has the potential to change this. Indeed, if manufacturers can meet the challenges of ramping up production and selling, distributing, and installing the systems, their prices could easily meet prices for electricity from the grid, says solar-industry analyst Michael Rogol, managing director of Photon Consulting, in Aachen, Germany.

But the approach has been difficult to implement. "It has not delivered on the promise, mostly because of the complexity of the systems," Rogol says. The goal is to engineer a concentrating system that focuses sunlight, that tracks the movement of the sun to keep the light on the small solar cell, and that can accommodate the high heat caused by concentrating the sun's power by 500 to700 times--and to make such a system easy to manufacture.

In the face of this complexity, many have decided to focus their research efforts on cutting the cost of traditional "flat-plate" systems. This is done through making them thinner, to decrease the amount of semiconductor needed, or through turning to cheaper, though less efficient, organic materials. But now several companies claim to have developed reliable systems that can be manufactured on a large scale. For example, SolFocus is making a system that combines the concentrators and cells in one sealed package by employing manufacturing techniques similar to those used to make automobile headlamps. This way they can easily be created in large quantities, according to the company's CEO, Gary Conley.

As for the use of superefficient solar cells, critics originally said that although the cells worked well in the lab, it would be unlikely that their high efficiencies could be maintained in large-scale manufacturing. Unlike conventional solar cells, which use only one type of semiconductor (silicon), these more efficient cells, called multijunction cells, are made from layers of three types of semiconductor. This approach is meant to overcome a major limitation of silicon: although it can absorb photons from most of the spectrum in sunlight, it does so inefficiently, converting into heat, rather than into electricity, most of the energy in high-energy photons from the blue and ultraviolet parts of the spectrum. The multijunction cells use three materials designed to efficiently convert light from different parts of the spectrum, the result being that much less is converted into heat and much more into electricity.

All of the materials must be carefully engineered to work with the other materials, and they have to be assembled under very clean, well-controlled conditions. So in the 1990s, when this type of cell was still experimental, people called it "a laboratory curiosity that could never be manufactured in large volume," Olson says. "Now Spectrolab on their production floor does better than we do in the lab. So it basically blew that myth out of the water."

Other factors that have limited the use of concentrated solar, such as aesthetic objections to mounting concentrator systems on suburban rooftops, may largely restrict applications to commercial buildings or arrays in the desert.

But the advances that have come about, along with growing demand for solar and a shortage of silicon feedstock, have made concentrated solar photovoltaics attractive.

"There's a lot of uncertainty in this area, where historically there's been a lot of hype that just hasn't been delivered," Rogol says. "The biggest news for me is that serious solar people, over the course of the last year, have made notable commitments to concentrators."

Copyright Technology Review 2006.


TOPICS: Extended News
KEYWORDS: energy; photovoltaics; solar
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1 posted on 11/10/2006 11:33:51 AM PST by aculeus
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To: aculeus

This sort of news scares the heck out of radical Islam. They know their window of opportunity to defeat the west is dependent on oil profits.


2 posted on 11/10/2006 11:36:32 AM PST by Ben Mugged
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To: aculeus
Sharp Corporation showed off its new system for focusing sunlight with a fresnel lens

Sounds interesting.
3 posted on 11/10/2006 11:39:26 AM PST by kinoxi
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To: aculeus

Bump for later gettin-off-the-grid reading.


4 posted on 11/10/2006 11:39:27 AM PST by Argus (Silver Lining in the Democrat Takeover Top Ten List #6: The gay weddings will be fabulous.)
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To: aculeus

It's not that efficient if it needs a much larger sized-are of concentrator to make the small chip work. In theory, almost any solar cell would do better with large concentrator focusing more sunlight on it.


5 posted on 11/10/2006 11:40:27 AM PST by ConservativeMind
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To: aculeus
Wow. It's only been three days since the Democrats gained control of congress and already the news is reporting that environmental problems are being solved, the economy is growing and the war on terror is looking good.

I expect that any day now Michael J. Fox will be cured of Parkinson's and Christopher Reeve will walk again.
6 posted on 11/10/2006 11:41:29 AM PST by spinestein (DOING THE JOB THE OLD MEDIA USED TO DO)
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To: spinestein
I expect that any day now Michael J. Fox will be cured of Parkinson's and Christopher Reeve will walk again.

I don't think Christopher Reeve (RIP) will be walking anytime soon.

7 posted on 11/10/2006 11:44:37 AM PST by paulcissa (Only YOU can prevent liberalism.)
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To: kinoxi
new system for focusing sunlight with a fresnel lens

You should see the tiny little ants go up in flames when I do this to them... Ouch!!!

8 posted on 11/10/2006 11:45:27 AM PST by 69ConvertibleFirebird (Never argue with an idiot. They drag you down to their level, then beat you with experience.)
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To: aculeus
cost has always been the problem with solar cells, and will unfortunately, continue to be for decades to come. Until these things can be stamped out cheaply, and last a reasonable length of time, they will never be a practical answer for cheap electricity.

And don't expect that if an answer is found, that it will be made available to the regular Joe for alternative energy. There's no money to be made that way.

A free energy source would cripple our economy as we know it.

9 posted on 11/10/2006 11:46:43 AM PST by Nathan Zachary
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To: spinestein

If Christopher Reeve starts walking again, I'm getting the hell out of this country. The moon might be a good place to start.


10 posted on 11/10/2006 11:48:03 AM PST by domenad (In all things, in all ways, at all times, let honor guide me.)
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To: 69ConvertibleFirebird

11 posted on 11/10/2006 11:48:17 AM PST by 69ConvertibleFirebird (Never argue with an idiot. They drag you down to their level, then beat you with experience.)
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To: paulcissa
I don't think Christopher Reeve (RIP) will be walking anytime soon.

Do you realize how many dead people got up last Tuesday to vote? The Donks will have Mr. Reeve fixed up in no time!

12 posted on 11/10/2006 11:48:29 AM PST by gridlock (My Prognosticator Unit is busted, and stuck on "ROSY". Predictions may be unreliable.)
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To: Nathan Zachary
A free energy source would cripple our economy as we know it.

I'm afraid you are right. Attempts should still be made though.
13 posted on 11/10/2006 11:48:48 AM PST by kinoxi
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To: aculeus; RightWhale; KevinDavis

It seems to me that a system of reclined troughs which track the sun, and focus onto concentrating solar cells -- which are cooled by a liquid flowing from bottom to top, and then into a water system pre-heater, would combine enough efficiency to be of great interest to the homowner.

Especially this homeowner. Hmm, make a great camper, too.


14 posted on 11/10/2006 11:49:48 AM PST by NicknamedBob (If the Supreme Court has "Judges for Life," why is there any question about Roe vs Wade?)
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To: Ben Mugged

you comment reminds me of this comic book series called "grendel" a few years back... Similar story with a race to energy tech. First one there has all the political power.


15 posted on 11/10/2006 11:50:56 AM PST by longtermmemmory (VOTE! http://www.senate.gov and http://www.house.gov)
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To: paulcissa
I don't think Christopher Reeve (RIP) will be walking anytime soon.

Is Larry Flynt dead, yet? If he isn't, then he will be walking soon.

All thanks to the Democrats.

science be praised.

16 posted on 11/10/2006 11:51:04 AM PST by UNGN (I've been here since '98 but had nothing to say until now)
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To: paulcissa

I would bet he voted, though.


17 posted on 11/10/2006 11:52:21 AM PST by MeanWestTexan (Kol Hakavod Lezahal)
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To: domenad
"The moon might be a good place to start."

You'll need some solar cells.

Actually, solar dynamic power generation would probably work better up there. A good system was designed in the sixties.

18 posted on 11/10/2006 11:53:27 AM PST by NicknamedBob (If the Supreme Court has "Judges for Life," why is there any question about Roe vs Wade?)
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To: paulcissa
"I don't think Christopher Reeve (RIP) will be walking anytime soon."

=================================================

But he probably voted on Tuesday.

19 posted on 11/10/2006 11:54:33 AM PST by Rockpile
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To: Nathan Zachary

Imagine what happens if this tech is advanced enough just to power a single family home with normal usage.

All of a sudden, every utility company looses every residential account.

Coal demand down, prices plunge then mining goes out.

Also consider the impact on all those who live in areas where sunlight is not a given. In areas with mega condo growth.

It has to be transitioned. However once this hits it will not just be the USA it will be ALL the world.

EU would be devastated, Russia would be wiped out.

The Islamic world would be pushed back into a dessert tribe mentality. Oh wait, they would not change.


20 posted on 11/10/2006 11:57:36 AM PST by longtermmemmory (VOTE! http://www.senate.gov and http://www.house.gov)
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