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.
Then you just aren't thinking hard enough. First, you wouldn't need "new infrastructure" for such a device. Over unity means just that. It creates more power than is required to set it in motion, whatever form of motion that may be.
You wouldn't be able to give excess away, because everyone will be able to produce their own power according to their own need once this discovery is learned by the masses. Imagine there is no longer any need for electricity. It is now freely abundant.
Energy drives our entire economy the whole world over. Industry will collapse and disappear overnight. Sure, there will still be some consumer industry, but nothing near the scale there is now, all of which is based on petroleum energy and by products, and the cost of producing energy itself.
A cheap clean, alternative renewable energy source would be devastating to our petroleum based industry we have today, and will cause quite a economic downturn and a very long period of adjustment. But it still wouldn't be free.
Completely free energy is another beast all together. We are way too overpopulated for such a thing to become available. You won't die in the cold, but good luck finding a job. They will be very hard to come by.
Sharp shows off its flat lens? Cognitive dissonance....
A free energy source would cripple our economy as we know it.
I'm afraid you are right. Attempts should still be made though.
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Energy costs are a large part of the productivity of the american (or any other) worker. Productivity drives wages.
If the cost of energy went to zero -- wages and employment would go up and not down.
Oh yes we do.
OK, here's my idea.
Manufacture 10-ft dishes that resemble the home satellite receiver dishes of the early 80s. However, the surface would be a mirror.
These dishes would be balanced so that they are able to move and track the sun with very little power required.
At the focal ppoint of the dish, you would mount solar receptor capable of receiving/converting HIGH tempratures into voltage.
This voltage is used to crack the hydrogen out of water. They hydrogen is then used to power fuel cells.
What would they be producing?
What the heck ever happened to the spray on solar stuff that got some press a while back?
I've been hearing this kind of hype about solar cells for about 45 years now, so I don't believe a word of this one. And I did some reearch on photovoltaics......
>>>I expect that any day now Michael J. Fox will be cured of Parkinson's and Christopher Reeve will walk again.
Think they'll bring Reeve back from the dead first or just make his corpse break out of the grave and walk?
There's no risk of free energy, so the argument is moot. The problem is the costs of alternate energy sources are too high, not too low. LOL!
I thought they were Stirling engines, but hey, I didn't go to MIT.
Maybe I'm missing something, they say it takes 4 square miles of sunlight using traditional cells to generate 1 power plant.. with the new refractors you only need about a backyards worth of space of actual cells... which is good.. but if the cells are only twice as effective as current cells, the refractors total input area would need to be 2 square miles, even if the actual cells only took up a backyards worth of space to get the same output?
Not very practicle for replacing the power plant entirely, or maybe I'm just not understanding.
It sounds like its cheapening the expense of them, and doubling the output which isn't bad.. but you still have the diffusion issue. What sort of load can you realistically expect from a typical solar installation today? And if it were doubled would that really make them viable in most areas (Ie Areas that aren't desert or sunny most of the year)?
Gonna need a lot more power I suspect to make that feasible.. 10' of solor energy concentrated makes a lot of heat, but it takes a LOT of energy to crack H2O into its parts... I don't think you are going to get enough H out of this sytem to power a whole lot...
Remember, every conversion costs you energy, doesn't gain you any.. better return on just using the energy the solar conversion gives you directly if you can.
Free energy would give the economy a huge productivity boost. All those resources currently devoted to producing energy would be freed up to make other stuff we want or need, some of which we can't even at the present time forsee wanting.
The only folks harmed would be those in the current energy industry who are too stupid or stubborn to work on something else. As conservatives, our role would be to thwart attempts by those folks to use the political system to stand in the way of change.
Food production. Food packaging. Transportation. Health and medical services. Retail sales. Mechanics. HVAC technician. I could go on and on. Just because insects have unlimited energy for their needs, doesn't stop bees from putting away honey. What makes you think that people will just stop working when energy costs go to near zero? They will never actually reach zero, because you still have to make the equipment, and it doesn't last forever. As long as there is entropy in the universe, work will be needed.
read later
Fresnel lenses are the death rays of the magnifying glass world. My high school A/V supervisor once gave me one off an old overhead projector. It doesn't just burn ants, it makes them explode in flames! A fresnel lens can cut through an anthill like a "laser"...
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