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.
I would rather the damn politicians stop destroying American's access to energy and get a tremendous reduction in my energy bills and a tremendous increase in energy availability from real sources of power.
Which is to say you will still need a grid with a very similar capacity regardless of your solar cell investment.
Now where shall that capacity come from? Solar cells ? Wind (same lousy energy density as Solar).
A HUGH chunk of the cost of building the plants in the 70's was the legal costs from the suits brought by the nuke wackos. Seabrook actually had TWO plants under contruction, but ended up only finishing one and bringing it online because it took 10 years of legal wrangling and all those costs involved just to get that ONE up and running. It would have taken them another 10 to get the second one going, and they just didn't want to spend that money that was essentially down the drain.
I don't believe that. These plants cost several billion each to build. The legal costs couldn't have been but a small fraction of the overall costs of building the plant. That sounds like a bogus excuse to me.
I'd rather have a compact reactor to defend than a monstrous LNG terminal (which is where we are heading).
I feel like my family is safer living far away from any nuclear power plants.
Contrary to your feelings nukes are far safer in terms of human life than coal mining or propane.
Remind me how many people were hurt in Three Mile Island?
ZERO. That's what you get when you design for the worst possible case, a core melt, which is a tractable problem.
When a plant is being built, or has been completed, but cannot open for years because of legal wrangling, they are not making any money, thus it is a hugh cost to them. Why do you think that utility companies stopped building them? It wasn't worth it to them from an economic standpoint. It's the same reason there hasn't been a new refinery built in almost 30 years.
Yup.Fortunately, we already have one.
Now where shall that capacity come from? Solar cells ? Wind (same lousy energy density as Solar).
Where it's cost-effective, yes. Most of our energy for the foreseeable future will continue to come from the same sources as today; my point is that there isn't, and won't be soon, a single replacement.
You're free to live next door to one.
What better way to destroy it?
Also, the government would cover cost overruns due to regulatory delays, up to $500 million each(!!!!!)
Delays in construction due to vastly increased regulations were of the high costs of some earlier plants.
The Act also funds a Next Generation Nuclear Plant project at INEEL to produce both electricity and hydrogen.
Oh God, make it stop.
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