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.
At this latitude, and with the way my house faces, that would work best.
Then I'd dedicate output to producing heat in winter and cooling in summer.
Not in the budget yet, though.
It has long been recognized that there is nothing about photo-electric power generation that could not be miniaturized; one possible alternative early on was the simple thermocouple [piezo-like] technology, which could be miniaturized to a 'chip' containing multiple photo-generators.
I have wondered what has happened to this type of research. I think the gentleman is correct: essentially it is a market-driven technology; with increasing costs of fossil fuels, and the stubborn cost of silicon cells, an alternate technology appears more attractive -- especially if it is CHEAPER.
Thanks for the ping. FReegards... IR
Fine, but what's wrong with using solar power too if we can figure out a way to do it cheaply?
Who says you can't do both?
Well, we definitely are going to do the feel good stuff, I'm not so sure about the later.
Seems to me like there are pushes for all kinds of alternative energies, including nuclear, which I think is the best solution for electricity generation.
When is the last time we built a reactor in this country?
Now when is the last time the government subsidized solar and wind in this country?
Why should the government SUBSIDIZE any of these technologies? If they are shown to be cost effective and marketable, they will attract investors on their own. Regarding the nuke plants, the government doesn't need to subsidize them, but it could sure help by reducing the chances of the plants being held up in frivilous lawsuits like they were in the late 70's and 80's.
Answer: Because the company that owns patents on the lion's share of the technology to produce the cells is...
(certainly not the glaring deficiencies of the technology)
I would be happy to replace my roof with these cells and get SOME reduction in my energy bills, if they ever become cost effective. It isn't an all or nothing proposition.
Chernobyl was nothing like anything in this country in its style of contruction, so there are no concerns about that type of accident. Seabrook was phenomenal in the level of construction for security purposes. The reinforcing steel within the concrete walls and dome are 4" thick! There's no way a plane crashed into it would do any damage to the structure; the plane would simply disentegrate. Even with the accidents that have happened, there hasn't been any danger to the general public. Three Mile Island didn't release any real levels of radiation outside the plant, regardless of breathless reporting to the contrary. As a bumper sticker reads: "More people have died in Teddy Kenndey's car than in any nuclear power plant accident in the US."
The biggest reason nuclear hasn't gone further than it has is because folks just don't understand the process, and were easily manipulated and frightened by the rhetoric of the anti-nuke crowd.
From what I've read there is space to store the spent nuke fuels safely, again it's just an education process.
If nuclear energy were more readily available, some companies might consider switching from coal because of the emissions and the effect on the environment. It's also possible that the cost of natural gas could go up, also being an influence on switching to nuke generated electricity.
Another effect of having nuke plants is the availability of electricity at a reasonable cost to power hybrid or electric cars, and that would affect how much oil needs to be imported to refine into gasoline.
Ping.
Ping.
There is no single viable alternative. Twenty years from now, I believe our power generation will be more scattered and diverse, with more and smaller plants using a variety of sources; still fossil fuels, mostly, but with solar, wind, tidal, biomass, and stuff we haven't thought of yet or I'm not thinking of just now.
Photovoltaics are useless on cloudy days or at night, and even under ideal circumstances they're not efficient and don't do much. But make them cheap and durable enough to use as roof shingles, and you've got something.
Fire up Google Earth, skim over any city or town, and check out all that rooftop space with sunlight beaming down on it. That's free energy that's either reflected back or absorbed as heat, which the A/C has to combat. Solar doesn't have to be very efficient to be useful on a scale that huge.
All roofing materials will eventually have to be replaced. The next time I have to replace the roof, if I could spend $800 for new asphalt shingles or $1200 for solar shingles, it's worth the extra money even if it only knocks 10% off my energy usage. Much more so in desert climates where they get a lot of sun and use a lot of power in daylight hours, and even more near the poles, where they get sunlight for most of the day half of the year.
The one and only problem with solar energy, under current conditions, is price. The energy itself is free. Make the cells cheap enough and durable enough, and it will become cost-effective, because there's enough available surface area to reap a lot of energy even with poor efficiency.
My house has hundreds of square meters of roof with the sun beating down on it in the daytime. You know what that does? It makes my attic real damn hot. Make solar cells cheaper, with the input energy free, and that changes the math.
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.
Battery banks? You only need that if you're trying to go completely off the grid. If you can get electricity for free 12 hours a day and pay for it the other 12, isn't that better than paying all 24?
You're right that energy storage is a legitimate issue with solar, but there are plenty of ways to store energy other than electrical batteries.
If your solar panels are generating more power than you need in the daytime, which is an unlikely occurrence, apply the excess power to pump water uphill; after the sun goes down, it can flow back downhill and drive a turbine.
Someone more clever than I could probably come up with something using coiled springs, pendulums and counterweights -- in a word, clockwork -- to capture mechanical energy and release it over time. Excess energy winds it up when the sun is out, and the clock releases it when it's dark.
Or the excess electricity could be used for electrolysis, and the H2 and O2 recombined later to run a generator, create heat or drive a vehicle.
The biggest mental shift in thinking about energy is going to have to be that we stop looking for one silver bullet. Until and unless we can build cheap and safe fusion reactors all over the place, it just ain't out there.
We've got to think more flexibly, be more nimble, and be able to take what's available where it is -- whether it's sunlight, wind, tides, coal, petroleum, methane, biomass, fission or fast-moving rivers -- and ramp one up and the others down as the economics shift.
That's not waste, that's fuel for a breeder.
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