Concentrating light onto photovoltaic cells could push down solar power costs.
Donna Coveney, MIT
Posted on 07/10/2008 7:56:48 PM PDT by neverdem
Solar-power costs could be slashed by cheap collectors, claim researchers.
A simple sheet of glass coated with dye could be enough to cut the costs of solar power.
Concentrating light onto photovoltaic cells could push down solar power costs.
Donna Coveney, MIT
That's the claim from researchers who have created a 'solar concentrator' that harvests photons and funnels them into photovoltaic devices. The device allows relatively small solar cells to harness rays from a much larger area.
Mirrors that track the Sun are already used to deliver extra light onto solar panels and maximize their electricity output. But these mirrors can be costly to deploy and maintain, and the solar cell is prone to overheating.
In the 1970s, scientists tried to develop alternatives that used light-absorbing dyes. Plastic sheets impregnated with these dyes could capture photons and re-emit them at a lower energy. These photons would then bounce along inside the plastic towards a collector at the end, allowing light gathered over a large area to be concentrated at the edges.
But the research stalled because many of the dyes were unstable in sunlight, or because the photons didn’t get very far through the plastic before being reabsorbed.
Researchers led by Marc Baldo at the Massachusetts Institute of Technology in Cambridge have now come up with an alternative that uses a mixture of dye molecules in a thin film coated onto glass. Each dye absorbs light of a different wavelength to make the most of sunlight’s spectrum. By fine-tuning the dye mixture and adding an extra compound to control the re-emission process, ensuring that most of the photons get trapped inside the glass, the team thinks they can boost the power efficiency of a cadmium telluride cell from 9.6% to 11.9%, and a CIGS cell(copper-indium-gallium-selenide materials) from 13.1% to 14.5%. The research is published this week in Science1.
Baldo thinks that the efficiency can still be vastly improved. "We could ultimately double the efficiency of 90% of solar cells used today," he predicts. He also thinks that the system will be easy to commercialize. "It looks very practical to make," he says. Solar cells are very sensitive to defects in the material, but that doesn’t apply for these thin films, says Baldo. That means it could help solar cells to produce electricity at a mere US$1 per watt, which is essential if the solar industry is to be economically sustainable.
Stiff competition
Lawrence Gasman, principal analyst at the market-research company NanoMarkets of Glen Allen in Virginia, is impressed that Baldo’s system seems to be so easy to manufacture, and says that commercial interest in innovations such as these is blooming.
But dye-based systems still face stiff competition from more conventional concentrators. In May, IBM claimed to have used mirrors to concentrate 230 watts of the Sun’s power onto 1 square centimetre of solar cell. Supratik Guha, who leads IBM’s photovoltaics team, points out that this is a much higher concentration than would be possible with Baldo’s dyes.
And Eli Yablonovitch, from the University of California, Berkeley, who looked at the theory of light concentration by dyes back in the 1980s2, is unconvinced that the system will be commercially viable. Baldo’s system absorbs just 80% of photons, he points out, which isn’t good enough.
"The problem with the concept is that 20% of the photons escape back into the air. This is fatal for commercial applications, in which efficiency is king," says Yablonovitch. "Considering the competitive environment in which solar energy finds itself, giving up that much light is intolerable."
Jonathan Mapel, part of Baldo’s research team, disagrees: "That 20% off the top isn’t necessarily fatal," he says, predicting that a solar concentrator based on this technology could be available in three years.
References Currie, M. J. , Mapel, J. K. , Heidel, T. D. , Goffri, S. & Baldo, M. A. Science 321, 226–228 (2008). Yablonovitch, E. , J. Op. Soc. Am. 70, 1362–1363 (1980).
Enter Yablonovitch E into PubMed.
It didn't go back to 1980, but it looks like PubMed needs a new name.
Interesting.
Now if they can just get past the fact that the sun only shines half the time in any one location. Is there a dye for that.
I’ve tracked this for 20 years. Great that they’ve made some progress.
At least the sun shines when you need the power, unlike lots of other crackpot schemes.
I don’t know about you but I use power at nighttime too. As a matter of fact I am using power right now to use my computer at 11:45PM.
Tropical Biofuels Getting Less and Less Green
FReepmail me if you want on or off my health and science ping list.
Unless it comes from a member of NATO or an ally of equal rank, we should tax imported energy.
thanks.
This looks interesting. Right about now I am ready to try anything to get the heat bills down this winter.
What is your point?
That sounds like the same logic that we shouldn't drill for oil because it will take 10 years.
Half of the day making electricity sounds good. Air conditioners generally run while the sun shines.
I am all for solar if it is cost effective and market driven.
That’s why, at the same time that solar companies are working to improve the efficiency of their collectors, companies that make batteries to STORE that solar power are working hard to increase the efficiency of THEIR products.
They should stick their improved solar cell on a battery and go claim their $300 million from McCain.
And you can burn your coal or gas fired generators at night, or generate electricity with your hydroelectric dam at night, and not have to use these resources during the day. Solar energy is great if we can make it cheap enough. We won’t run out of solar power. If we do, we’re dead anyway. I’m always happy to see new advances in solar energy technology. It’s just getting cheaper and more efficient.
Why do you think it's a good match? It's a terrible match. 5pm on is virtually completely uncovered. Peak demand is an hour later and above average demand continues til 10 pm.
Even if you put tons of solar online, you still have to have all of the current power plants start turning on at about 2 pm and all of them are on by 5pm.
If you could turn existing power plants on and off easily, then you would save some coal and natural gas usage from 7am to 4 pm. But you still need all the existing power plants PLUS the solar generation. If you want to go to electric cars, the problem gets even worse because folks will be plugging them in at night.
As to the pumping water as battery approach. Read David MacKay's book (available for free online) about what England would have to do to make that practical. Basically, you have to pave much of england and turn it into water storage facilities.
Increasing the supply of electricity for part of the day is the only thing you accomplish with solar. But that doesn't do much at all to solve our fundamental energy problem.
It seems to me the fundamental problem is that we are funding terrorists with demand for OIL--not electricity. (forget global warming--I do modeling as a business and the AGW guys are full of crap). The only way to stop funding terrorism with demand for OIL is to reduce demand for OIL from overseas. Replacing existing electricity sources with solar does not do that because we don't use OIL to generate electricity. We use coal, nuclear and natural gas.
To reduce foreign demand for oil, we need to turn to coal-to-gas. And we need to exploit our existing oil resources. These methods are economic, they work 24/7, and they fit our existing infrastructure (coal-to-gas makes gasoline, fuel oil, jet fuel etc). That's the only way we stop funding terrorism in any near term (30 years or so) sense.
What you say is true, but you ignore the growth in China and India. Growth there alone will pump trillions of dollars into the Middle East — regardless of what we do in the US.
Actually that is nothing like saying not to drill because we will have no oil for 10 years. We know there is oil that is not being brought out of the ground and should be and should have been for the last 10 years or more, and should be in the future even it takes 10 years. The facts on solar are that regardless how efficient solar panels are they only make power when the sun shines ergo you always have to have some sort of backup plan to cover those periods when no power is being generated. In most of the US this, plus the vast amount of land area necessary to house the large numbers of panels required to produce grid level amounts of power, make solar at best a small time player in the energy generation market. I would love to believe that there is some wonderful perfectly clean, never ending utopian energy sources out there, but in reality there isn’t.
Now for the home market as a way to lower personal energy cost and reduce your strain on the grid solar may have a future. If you live in an area where there is sufficient sunlight and your property is properly oriented to take advantage of it, I think a homeowner could benefit from a solar unit. If enough homes could take advantage of this situation in any given area it could cut the requirement for building additional coal, gas or nuclear plants in that area.
Wind and solar presently produce 2% of our nation’s power. The forecast is for an average increase in energy usage of 4%/year for the foreseeable future. I don’t see how the math works out to make either a big player in the foreseeable future though I hold out much more hope for wind if it is properly placed.
What your graph shows is exactly what I am saying. Solar produces energy under ideal conditions for 12 hours/day, it meets peak need for only 6 hours per day and for most it is 12 hour production cycle it falls well short of meeting the energy needs as represented by your graph.
I am sure this graph was produced to show the effectiveness of solar generation, but in fact it graphically shows just the opposite. During 18 hours of every 24 hour day the solar doesn’t even come close to meeting demand. I am also going to assume this graph is based on maximum output, which because of variability in cloud cover and weather conditions is seldom going to be achieved outside of possibly the southern California desert. I am sure that in the temperate rain forest of northern California this graph would look much different.
As for your hydro and compressed air storage, for every watt of power you use to push that water uphill or run the compressor that is a watt not available for the grid. So effectively you are lowering your peak output to expand the time frame that the solar generated power is available for use.
“Solar energy is great if we can make it cheap enough.”
Cold fusion is great if we could just make it work too. They have been working on solar power generation for since 1893 and developed the first “highly efficient” solar cell in 1970. In the 38 years since they have managed to increase the efficiency by 8% to 30 % which means that for the 12 or so hours you actually can generate power from the sun you are wasting 70% of the energy available. That does not sound to me like cheaper or more efficient.
Again as I mentioned in an earlier post. Individual home use of solar panels to relieve strain on the grid thus reducing the need for new power plants has potential. However, as a long term, grid size power source I just don’t see it happening in my lifetime and I am only in my 50’s.
Considering the huge amount of area necessary(15,000 acres vs 15-20 acres for a comparable coal, gas, or nuclear plant) for the number of panels required for grid sized generation of power, the fact that at best they generate for 12hrs/day and in most cases do not generate at full potential each day all day, I do not see them every accounting for more than 4-5% of our Nation’s needs and I have been researching this issue for over 20 years.
Yours is a much better idea than mine. A warm floor is nice. I’ve used wood stoves all my life and the better ones are quite good. Wood supply is a problem for some folks but a pellet stove would solve that. Add a ceiling fan to move the heated air down and I think you got a system!
If you can do the install yourself more the better.
Hey, 8% to 30% is better than 0%. What's a combustion engine, like 25% or 30% efficient after many decades of improvements? Should we have never even started using combustion engines because they are so inefficient?
Per watt prices are coming down on photovoltaic cells. Other means of collecting and utilizing solar energy are becoming cheaper and more efficient as well. We're figuring out how to use other materials that are much cheaper and easier to come by than silicone in our photovoltaic cells which will have the net effect of decreasing the costs of solar energy a lot more. Someday we'll probably see a lot more large scale solar “power plants” and we'll see a lot more people with solar panels on their homes supplementing the power they get from the grid. This is a good thing.
As for competing with coal, nuclear and gas, I don't see why you have to look at it that way. This is just another resource in the mix. Electricity produced from solar energy will not account for much of our total electricity needs until it becomes cost competitive with these other resources. That's okay. I hope it does become cost effective so that it can fulfill more of our needs. That would help us stretch out some of our limited resources. I don't see why anyone would be against that. As for your 4-5% estimate, I think that is way low. If it becomes cheap enough we'll be able to use solar energy to satisfy a lot more of our electricity needs than that. The acreage it takes is inconsequential provided we do it on land not be used for anything else, or on what could be dual purpose locations, like rooftops.
MIT opens new ‘window’ on solar energy
Google search | July 10, 2008 | multiple
Posted on 07/10/2008 12:38:01 PM PDT by Kevmo
http://www.freerepublic.com/focus/f-news/2043575/posts
Thanks for ping & post, respectively.
For the renewable energy ping list — same article as the one I posted.
Correction: Thanks for ping & link to Kevmo’s thread.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.