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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; fresnellens; photovoltaics; solar; solarcells
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To: longtermmemmory
"The Islamic world would be pushed back into a dessert tribe mentality."

Does this mean that they will soon have an overweight problem too?

21 posted on 11/10/2006 11:59:52 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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" The goal is to engineer a concentrating system that focuses sunlight, that tracks the movement of the sun"

I can tell you right now that as long as they think that way, they will never succeed. (Unless of course they are Muslims, and believe that:

Tabari I:236 “‘When the sun rises upon its chariot from one of those springs it is accompanied by 360 angels with outspread wings…. When Allah wishes to test the sun and the moon, showing His servants a sign and thereby getting them to obey, the sun tumbles from the chariot and falls into the deep end of that ocean. When Allah wants to increase the significance of the sign and frighten His servants severely, all of the sun falls and nothing of it remains in the chariot. That is a total eclipse of the sun. It is a misfortune for the sun.’”

But it will be very difficult to make the system work with Allah screwing around scaring people whenever he feels like it..

22 posted on 11/10/2006 11:59:53 AM PST by Nathan Zachary
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To: Rockpile
"I don't think Christopher Reeve (RIP) will be walking anytime soon."

Thats because the Democraps already have him raised from teh dead and flying


23 posted on 11/10/2006 12:02:42 PM PST by Bommer (If people evolved from apes, why are there still apes?)
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To: Nathan Zachary
"But it will be very difficult to make the system work with Allah screwing around scaring people whenever he feels like it.."

No problem. Just pass Allah a note that Mohammed wants things a certain way. He'll cooperate.

Allah lets Mohammed have anything he wants.

24 posted on 11/10/2006 12:04:27 PM 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: kinoxi

I don't know if this is real or not, but a lot of buzz has been happening in the marine message boards about it.
On a boat, it's not about $ per square foot, it's all about power per square foot.

http://dbksolar.com/JIL-3000.htm


25 posted on 11/10/2006 12:06:36 PM PST by Senormechanico
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To: aculeus

What kind of working fuild will be used to carry away the heat?

Be fun to see how these turn out for residentail use.


26 posted on 11/10/2006 12:07:03 PM PST by ASOC (The phrase "What if" or "If only" are for children.)
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To: longtermmemmory

That is why, even if a (over)unity device is invented,(and near unity, very efficient ones probably have been) it will never be allowed exist. It would change the world completely.

The devistation would be unimaginable.


27 posted on 11/10/2006 12:07:58 PM PST by Nathan Zachary
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To: Senormechanico
I didn't see a price on that interesting link.
;)
28 posted on 11/10/2006 12:09:10 PM PST by kinoxi
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To: aculeus
"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."

That is, 1 gigawatt of power at the zenith of the sun each day, and less at other times including zero power during the coldest times of the year for as much as 18 hours a day.

These people know what they are doing by giving junk calculations without the basis for their calculations. Like someone once said, there is a fool born every minute (and today, that would be every millisecond).

Oh, by the way, if you want to see the actual costs, include the battery storage necessary for 24 hours plus at least 6 times the area of cells stated above, not to mention the capacity for spurious peak loads. Having looked at this before, I think the what you pay for electricity increases between 100 and 1000 times what you are paying now!

Thinking like that stated in this article is dangerous and stupid. Your family can face extinction, mine won't. Have a hunch, bet a bunch!
29 posted on 11/10/2006 12:12:20 PM PST by Herakles (Diversity is code word for anti-white racism)
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To: ASOC
"What kind of working fuild will be used to carry away the heat?"

In most parts of the country, water with a non-toxic antifreeze could be used. You would need a closed loop system with heat transfer as shown in this diagram. There should be no contact with the domestic water. (If toxic antifreeze is used, a double buffer system is recommended.)

http://www.west-norfolk.gov.uk/images/Solar%20Hot%20Water%20Heating%20Diagram.gif

You could also use a number of oils as a transfer medium.

30 posted on 11/10/2006 12:16:47 PM 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: Nathan Zachary

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

I don't think anyone is going to be giving away free energy. The trick is to find something cheaper than fossil fuels.

While it may change the economy as we know it, I don't see it crippling the economy. It might slow down or you might even see a boost while everyone scrambles to build a new infrastructure to support the technology.


31 posted on 11/10/2006 12:20:51 PM PST by tfecw (It's for the children)
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To: aculeus

Boeing? Cool. It would be great to have a solar house. Hopefully similar breakthroughs will come soon, for battery technology--to date the weak link.

Honda will bring Hydrogen cars out, soon. And they won't wait for the massive "infrastructure" delivery system problems.

Honda, long maker of small portable generators, will introduce household size hydrogen converters. Buy a car and converter as a system.

Apparently hydrogen can be made from natural gas.Thinking broadly on such developments, both seem to encourage property and home ownership.

A personal solar generating system is unlikely to be so portable, as to allow a renter to carry it from apartment to apartment.

And I doubt an apartment owner could easily set up for multiple converters to hook up to natural gas lines.

In both cases, property owners are favored. One more set of reasons for investing in real estate.


32 posted on 11/10/2006 12:21:57 PM PST by truth_seeker
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To: aculeus

Just what we need.

Hire the illegals to polish the lenses everyday.

Maybe they can make a machine like a lawn mower and they can ride on it and do the four acres.


33 posted on 11/10/2006 12:22:13 PM PST by Dan(9698)
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To: paulcissa

Yeah, we'd have to put Kerry in the Oval Office for that to happen.

Sorry, Mr. Reeve.


34 posted on 11/10/2006 12:30:45 PM PST by HKMk23 (PRO-LIFE: Because a Person's a Person, no matter how small.)
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To: spinestein

They'll have to raise Reeve from the dead first. Tall order.


35 posted on 11/10/2006 12:31:13 PM PST by dc-zoo
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To: Ben Mugged

We don't burn oil to make electricity anymore.


36 posted on 11/10/2006 12:32:54 PM PST by dangerdoc (dangerdoc (not actually dangerous any more))
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To: kinoxi

http://dbksolar.com/Purchaser.htm

I have no affiliation with this company.


37 posted on 11/10/2006 12:34:00 PM PST by Senormechanico
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To: aculeus
"Now Spectrolab on their production floor does better than we do in the lab. So it basically blew that myth out of the water."

Nice job in manufacturing.

38 posted on 11/10/2006 12:41:28 PM PST by TheDon (Are you a cut and run conservative?)
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To: aculeus

In the future, for driving, the feds are going to need a sun tax. And for taking a break, a shade tax.


39 posted on 11/10/2006 12:43:38 PM PST by samtheman
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To: Herakles
Thinking like that stated in this article is dangerous and stupid.

How is ongoing development of alternative energy technology dangerous and stupid?

Your family can face extinction, mine won't.

So the solar panels on my boat are going to kill my family?

40 posted on 11/10/2006 12:56:34 PM PST by atlaw
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