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Posted on 09/12/2006 9:29:36 AM PDT by aculeus
Not everyone gets a solar cell named after them: but Michael Gratzel did. He says his novel technology, which promises electricity-generating windows and low manufacturing costs, is ready for the market.
Michael Grätzel, chemistry professor at the Ecoles Polytechniques Fédérales de Lausanne in Switzerland, is most famous for inventing a new type of solar cell that could cost much less than conventional photovoltaics. Now, 15 years after the first prototypes, what he calls the dye-sensitized cell (and everyone else calls the Grätzel cell) is in limited production by Konarka, a company based in Lowell, MA, and will soon be more widely available.
Grätzel is now working on taking advantage of the ability of nanocrystals to dramatically increase the efficiency of solar cells.
Technology Review asked him about the challenges to making cheap solar cells, and why new technologies like his, which take much less energy to manufacture than conventional solar cells, are so important.
Technology Review: Why has it been so difficult to make efficient, yet inexpensive solar cells that could compete with fossil fuels as sources of electricity?
Michael Grätzel: It's perhaps just the way things evolved. Silicon cells were first made for [outer] space, and there was a lot of money available so the technology that was first developed was an expensive technology. The cell we have been developing on the other hand is closer to photosynthesis.
TR: What is its similarity to photosynthesis?
MG: That has to do with the absorption of light. Light generates electrons and positive carriers and they have to be transported. In a semiconductor silicon cell, silicon material absorbs light, but it also conducts the negative and positive charge carriers. An electric field has to be there to separate those charges. All of this has to be done by one material--silicon has to perform at least three functions. To do that, you need very pure materials, and that brings the price up.
On the other hand, the dye cell uses a molecule to absorb light. It's like chlorophyll in photosynthesis, a molecule that absorbs light. But the chlorophyll's not involved in charge transport. It just absorbs light and generates a charge, and then those charges are conducted by some well-established mechanisms. That's exactly what our system does.
The real breakthrough came with the nanoscopic particles. You have hundreds of particles stacked on top of each other in our light harvesting system.
TR: So we have a stack of nanosized particles...
MG: ...covered with dye.
TR: The dye absorbs the light, and the electron is transferred to the nanoparticles?
MG: Yes.
TR: The image of solar cells is changing. They used to be ugly boxes added to roofs as an afterthought. But now we are starting to see more attractive packaging, and even solar shingles (see "Beyond the Solar Panel"). Will dye-sensitized cells contribute to this evolution?
MG: Actually, that's one of our main advantages. It's a commonly accepted fact that the photovoltaic community thinks that the "building integrated" photovoltaics, that's where we have to go. Putting, as you say, those "ugly" scaffolds on the roof--this is not going to be appealing, and it's also expensive. That support structure costs a lot of money in addition to the cells, and so it's absolutely essential to make cells that are an integral part.
[With our cells] the normal configuration has glass on both sides, and can be made to look like a colored glass. This could be used as a power-producing window or skylights or building facades. The wall or window itself is photovoltaicly active.
TR: The cells can also be made on a flexible foil. Could we see them on tents, or built into clothing to charge iPods?
MG: Absolutely. Konarka has a program with the military to have cells built into uniforms. You can imagine why. The soldier has so much electrical gear and so they want to boost their batteries. Batteries are a huge problem--the weight--and batteries cost a huge amount of money.
Konarka has just announced a 20-megawatt facility for a foil-backed, dye-sensitized solar cell. This would still be for roofs. But there is a military application for tents, and Konarka is participating in that program.
TR: When are we going to be able to buy your cells?
MG: I expect in the next couple of years. The production equipment is already there. Konarka has a production line that can make up to one megawatt [of photovoltaic capacity per year].
TR: How does the efficiency of these production cells compare with conventional silicon?
MG: With regard to the dye-cells, silicon has a much higher efficiency; it's about twice [as much]. But when it comes to real pickup of solar power, our cell has two advantages: it picks up [light] earlier in the morning and later in the evening. And also the temperature effect isn't there--our cell is as efficient at 65 degrees [Celsius] as it is at 25 degrees, and silicon loses about 20 percent, at least.
If you put all of this together, silicon still has an advantage, but maybe a 20 or 30 percent advantage, not a factor of two.
TR: The main advantage of your cells is cost?
MG: A factor of 4 or 5 [lower cost than silicon] is realistic. If it's building integrated, you get additional advantages because, say you have glass, and replace it [with our cells], you would have had the glass cost anyway.
TR: How close is that to being competitive with electricity from fossil fuels?
MG: People say you should be down to 50 cents per peak watt. Our cost could be a little bit less than one dollar manufactured in China. But it depends on where you put your solar cells. If you put them in regions where you have a lot of sunshine, then the equation becomes different: you get faster payback.
TR: Silicon cells have a head-start ramping up production levels. This continues to raise the bar for new technologies, which don't yet have economies of scale. Can a brand-new type of cell catch up to silicon?
MG: A very reputable journal [Photon Consulting] just published predictions for module prices for silicon for the next 10 years, and they go up the first few years. In 10 years, they still will be above three dollars, and that's not competitive.
Yes, people are trying to make silicon in a different way, but there's another issue: energy payback. It takes a lot of energy to make silicon out of sand, because sand is very stable. If you want to sustain growth at 40-50 percent, and it takes four or five years to pay all of the energy back [from the solar cells], then all of the energy the silicon cells produce, and more, will be used to fuel the growth.
And mankind doesn't gain anything. Actually, there's a negative balance. If the technology needs a long payback, then it will deplete the world of energy resources. Unless you can bring that payback time down to where it is with dye-cells and thin-film cells, then you cannot sustain that big growth. And if you cannot sustain that growth, then the whole technology cannot make a contribution.
TR: Why does producing your technology require less energy?
MG: The silicon people need to make silicon out of silicon oxide. We use an oxide that is already existing: titanium oxide. We don't need to make titanium out of titanium oxide.
TR: An exciting area of basic research now is using nanocrystals, also called quantum dots, to help get past theoretical limits to solar-cell efficiency. Can dye-sensitized cells play a role in the development of this approach?
MG: When you go to quantum dots, you get a chance to actually harvest several electrons with one photon. So how do you collect those? The quantum dots could be used instead of a [dye] sensitizer in solar cells. When you put those on the titanium dioxide support, the quantum dot transfers an electron very rapidly. And we have shown that to happen.
TR: You are campaigning for increased solar-cell research funding, and not just for Grätzel cells.
MG: There's room for everybody.
I am excited that the United States is taking a genuine interest in solar right now, after the complete neglect for 20 years. The Carter administration supported solar, but then during the Reagan administration, it all dropped down by a factor of 10. And labs like NREL [National Renewable Energy Laboratory in Golden, CO] had a hard time surviving. But I think there is going to be more funding.
Copyright Technology Review 2006.
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I'm all for the products you mentioned, and the sentiment of getting off oil, but fyi oil is hardly used to generate electricity in this country: It's mostly coal and nat gas with some nukes & hydro. Oil is used for transportation, industrial purposes and heating in the NE.
Both.
I thought the energy cost was the issue.
I am thinking for mundane things like outside lighting and secondary lighting like signage.
Energy density is a large part of ultimate cost. 60 square meters to run a hair dryer is huge!! The average household would need hundreds of square meters of cells to say nothing of industrial energy needs. Even if the cell were free you still have energy storage costs, you still need people to come and shovel snow off the cells or wipe dust off of them, you still need real power generation capacity for when its cloudy, and you would need to cover several States with solar cells.
I live in the mountains and have modest power needs. I've run the numbers on solar and quickly concluded that even the battery banks required for modest power were cost prohibitive. Of course, one of my neighbors claims to be 100% solar with 20 square meters of cells....But late at night...there is this mysterious humming sound.
I believe the big ConEd generating plant on the East Side of Manhattan runs on bunker fuel ... heavy oil similar to that burned in ships. Not sure about other NYC plants but doubt they burn coal and know they're not nuke.
Great article! Thanks for posting it. Good investment possibilities with it.................FRegards
Not 60 m^2. Where is the error?
You compared it to hair dryers (1200W each) which by their nature use a lot of power for a short period of time. Why didn't you say that 2.3kW could power 35 60W light bulbs? I only have three 60W light bulbs on in my house at night. My TV only uses 300W. 2.3kW would power seven of them. My computer runs about 160W and my refrigerator about 700. 2.3kW would go a long way towards satisfying my electrical demands.
ping
"I wonder .... if it is affected by the temperature that it operates at."
Not as much as silicon, according to the inventor. It's in the story.
I have read several reports of people who either used their own money entirely or counted on subsidies and converted their homes to near-total solar. This costs from $20,000 to $50,000
and results in usually roof-mounted photovoltaic panels delivering from 4 to 6 kw.Large battery banks and inverters are also part of the package as is buying the most energy effiecient appliances.
Frost free refrigerators and freezers use lots more electric than the earlier models of our parents. There are a couple of companies that make rather high priced units which use a small portion of the usual ones.
Anyone who thinks oil isn't subsidized should check his reality meter. The military cost alone to keep it flowing are enormous.Not to mention the political deals with less than stellar personages.
You really can't convince me it is good for the U.S. to be dependent on others for food,fuel,fiber, or anything else.
You left out the 10% efficiency of the Si cells and so you need to scale the area of the cells by nearly 10X.
You need to throw your washer,dryer,over AC and heat into the mix as these are your primary power needs (which are small compared to those needed to operate our industry and infrastructure) Also that is 2.3 KW is peak production. I shot the photo around 1 pm. Take a 50% hit for the 12 hours of darkness. Take another 25% hit for nonideal angles of the sun. Take another hit for storage.
You can't live in the modern world on <1 KW average power draw with a footprint the size of a house.
$5 a watt is still the price. What is the price for this new tech?
ping for later.
Which is to say you would have added power (a very small intermittent and expensive amount) but not capacity to the grid. You still require that real power plants capable of on demand generation be built.
The problem with solar power is not that the energy density sucks, it's that the panels cost way too much.
Uh, if the energy density was higher you could get by with a single small panel.
I'd have a system that produces more than enough electricity for my needs in the winter (gas heat)
So again, when it comes to important matters, like not freezing to death, you choose an energy source with a much, much higher energy density.
Take a few other steps to reduce your energy consumption and you could have several hundred dollars a month more in disposable income. Wouldn't that be a good thing?
An advancing civilization requires increased energy consumption, energy supplies should be getting denser and cheaper not more diffuse. The only time US energy consumption declined was during the Great Depression. Solar is a cute feel good trick but is primarily a diversion from the main issue of securing our nation's access to energy.
One could also argue that a system driven by the background radiation of the universe would provide power far longer than solar energy but like solar the stuff is rather diffuse and difficult to harness.
Folks start looking at the energy content of a kilo of uranium vs. a train full of coal. We have centuries worth of uranium if not hydrocarbons. If we could find a way to store fission energy conveniently such as nuke powered coal gassification or a nuke driven ethanol production process we could break free of the ay-rabs.
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