Avalanche Effect Demonstrated In Solar Cells 234
esocid writes "Researchers at TU Delft (Netherlands) and the FOM (Foundation for Fundamental Research on Matter) have found irrefutable proof that the so-called avalanche effect by electrons occurs in specific semiconducting crystals of nanometer dimensions. This physical effect could pave the way for cheap, high-output solar cells. Solar cells currently have relatively low output, typically 15%, and high manufacturing costs. One possible improvement could derive from a new type of solar cell made of semiconducting nanocrystals and could theoretically lead to a maximum output of 44%, with the added benefit of reducing manufacturing costs. In conventional solar cells, one photon can release precisely one electron. However, in some semiconducting nanocrystals, one photon can release two or three electrons, hence the term 'avalanche effect.' This effect was first measured by researchers at the Los Alamos National Laboratories in 2004, and since then the scientific world had raised doubts about the value of these measurements. This current research does in fact demonstrate that the avalanche effect can occur."
Wait and see (Score:5, Insightful)
However, I'll bet the keys on my keyboard that solar is going to be a lucrative market in the near future. Heck, it already is for solar cell manufacturers.
Isn't price the key? (Score:3, Insightful)
To me, the big issue is not efficiency but cost per watt. Many regions of the world have plenty of the land, particularly energy guzzlers like the US. What we really need is a super-cheap way to use that land for solar generation.
Re:Isn't price the key? (Score:5, Informative)
Re:Isn't price the key? (Score:5, Interesting)
Efficiency matters, for a few reasons, including:
1. Indirect costs (installation labor, racks, mounts, etc.) scale with the area of the array. The area of array required for a given power output goes with the inverse of efficiency. These costs are pretty significant, so efficiency has a direct impact on installed costs.
2. There's lots of area available for solar panels, but solar energy is pretty diffuse, so you need a lot of area anyway. If a 1% efficient system cost a dime per watt installed, great, but you'd have to cover huge areas to generate significant amounts of electricity. There are practical limits. Even at 10-20% efficiency, you're still looking at large areas to generate a meaningful amount of juice.
Re:Isn't price the key? (Score:4, Interesting)
Re:Isn't price the key? (Score:4, Insightful)
Tidal/geothermal power are much more constant and predictable sources than solar or wind. However, I think all of these renewable technologies are each a piece of the overall energy puzzle. Solar, Wind, Tidal, Geothermal...they've all got strengths and individual industries working for them. The current model of a dominant source is fading away into a more diversified energy market. "Never put all your eggs in one basket", as they say.
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Tidal/geothermal power are much more constant and predictable sources than solar or wind. However, I think all of these renewable technologies are each a piece of the overall energy puzzle. Solar, Wind, Tidal, Geothermal...they've all got strengths and individual industries working for them. The current model of a dominant source is fading away into a more diversified energy market. "Never put all your eggs in one basket", as they say.
Just to expand on that a little, we have to accept that there is no silver bullet that is going to give us a single source of renewable energy (yes, I know that it is ultimately all solar). The sun only shines during the day. The wind doesn't blow consistently. Every renewable source has strengths and weaknesses
But, if you can come up with enough ten-percent solutions, you can get there eventually, with the added benefit of distributed generation.
Heck, Germany is already up to 14.5 percent renewable
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Whoops, I just realized that tidal isn't solar, my bad, it's lunar. Nuclear is solar, just not from our current star, so in that sense I guess tidal could be construed as solar, but that's a bit of a stretch.
Like Dr. Sagan said, "We are star stuff"...
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Wasn't trying to slag off solar power btw, just pointing out how 1kW per square metre is pretty diffuse at least by tidal standards, and probably by wind standards too. I think all forms of renewable energy are worth considering though, and things like solar and wind power tend to complement each other quite well, as when it's dark and stormy, it will probably also be quite windy.
Do you get many tornadoes or s
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Manufacturing Energy Costs? (Score:5, Insightful)
How many joules are consumed from raw materials to a deliverable PV cell of a given output wattage? Of the old "about 15%" (really about 20-25% these days), and of these new proposed "avalance" PV material ones?
I want to compare that energy cost to the cells' projected energy contribution over their lifetime, which is about 30+ years for today's PV cells. How long would the new ones last in typical service?
Re:Manufacturing Energy Costs? (Score:5, Informative)
The head of Applied Materials' solar division said in a 2007 talk at Stanford that their current production process costs about 2 years of output for a solar panel. He thinks they can get that down to 6 months of output; he said some things about improvements to the sputtering process. which is derived from IC manufacturing technology where the wafers are smaller.
They'll probably do it. What Applied Materials does is improve semiconductor process technology. They're the world's largest maker of semiconductor fab equipment. This led them into making LCD displays, and then solar panels.
Re:Manufacturing Energy Costs? (Score:4, Interesting)
The numbers [energybulletin.net] are all over the place and constantly coming down with new technologies, but you're looking at breakeven after 1-5 years or so.
This is pretty good (EROEI is >> 1), and will continue to get better.
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A domestic rooftop grid can receive something like 400W:m^2 (averaged across weather/seasons/night) here in NYC, generating 72W:m^2 (at the more likely 18% efficient PV). My building is 7.6x21.3m, 162m^2, or 11.655KW. We have 4 apartments, which consume (as the average household in NYC) about 2KW each. So we've got
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APDs (Score:5, Informative)
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During a photodiode's avalanche breakdown, for example, the act of a photon hitting a reverse-biased photodiode diode excites an electron into the conduction band. The excited electron gains energy from the strong reverse bias potential and "smashes" into other electrons on its way down-potent
Re:APDs (Score:4, Interesting)
A high energy electron hole pair is created by a photon, which then relaxes down to a lower energy state. But, instead of emitting a phonon (heat), it creates another electron hole pair, and you end up with two. I suppose this process could repeat itself, so that many different wavelengths would all produce energy with reasonable efficiency.
This is in all likelihood facilitated by the complex energy band structure of the (essentially) polycrystalline semiconductor.
I'm not so sure how directly applicable all of this is. I suspect that some theorist postulated that this could happen, but it was difficult to prove experimentally. It seems to me that the hard work of actually producing an workable device hasn't been done yet.
From what I can tell, this work is done in PbSe, which I don't think is a suitible for huge volume production.
But I could be wrong in all this.
Los Alamos (Score:5, Informative)
http://science.slashdot.org/article.pl?sid=04/05/20/1436213 [slashdot.org]
Solar Cells Get Boost
Posted by michael on Thursday May 20 2004, @02:15PM
from the juiced-up dept.
Science Technology
An anonymous reader writes "Researchers from Los Alamos National Laboratory have tapped the efficiencies of nanotechnology [trnmag.com] to double solar cells' potential energy production. The key to the method is the use of lead selenium nanocrystals which can produce 2 electrons where 1 was produced before. Other optical applications can also benefit."
Someone said it before, I will now. (Score:4, Insightful)
SOMEBODY PLEASE BRING SOME ACTUAL "IMPROVEMENTS" TO MARKET!!!
If all the "improvements" to solar cell manufacturing I have read about in recent decades became actuality, we would all have homes and cars powered solely by a 1-meter-square panel on the roof and the panels would cost $1 apiece.
Please, either DO SOMETHING with this, or stop making predictions!
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The subsidies are a temporary measure that serve to kick-start the build-out of the infrastructure to support a new market in the face of opposing forces, such as cheap coal or subsidized nuclear.
IMHO, "free" markets are not always the most efficient way to achieve change, especially when there is a large capital barrier to entry.
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3 GW (peak), isn't much in the grand scheme of things, but I t
MOD UP (Score:2)
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What is holding up your flying car is not the car itself, it is infrastructure. Letting everybody who could afford to fly go wherever they wanted to, uncontrolled, would be pure mayhem. Death, destruction, and injury on a massive scale. Until they get absolutely reliable tracking and automated control, there will be no commonly available "flying cars". And the technology to do that, i.e., a distribu
Flying Car? (Score:4, Insightful)
Anti-grav units? Powerful downward facing thrusters? Wings? Rotors?
Truth be told, there's nothing holding up your flying car except the name. It's not a flying car. It's a personal aircraft, and they come in many different sizes and shapes, from ultralights, LongEZs, and autogyros, to Beavers, Cesnas and Learjets.
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I'm pretty sure if it was beyond revolutionary and economically feasible then it would be along faster than you can spit "I want it, and I don't know how it works, but I want it now!"
Or would you rather they make something that can't turn a profit, and just have the government subsidize it?
Re:Someone said it before, I will now. (Score:5, Insightful)
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When JFK pledged to put a man on the moon in 10 years, we did it -- even though the Cold War arguments re: national security were a bit hysterical.
Why can't we have a leader pledge to reduce America's dependence on oil by 50% in 10 years? Sounds just as possible to me as Apollo XI would have in 1960. And it's obviously more practical.
Re:Someone said it before, I will now. (Score:4, Insightful)
If the Apollo program were at the scale required for reducing oil consumption, we'd have colonized most of the moon by now.
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All you have to do is make more economical energy generally available. It's still a project with participation in the thousands or tens of thousands. Once a way to save money is readily available, the millions will do so.
The hard part is when the way to save money is available, but not readily. In other words, when it's available, but you have to make substantial changes or investments in order to realize it. For instance, imagine photovoltaic panels
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Get out of the lab, get onto my roof!
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But in order to install that solar, I need the cost to come down such that break even falls within the five year range (or less)....assuming constant / current energy prices and usage.
La
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That must be a really, really large house. How many m^2 floor space does it have ?
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An example of a currently available solar panel [affordable-solar.com] intended for roofing application is 136 watts, and about 30 would fit on that sample roof, for a total possible 4,080 watts at any given point. Where I am, I can expect an average of 4.5 hours of full production per day, or 18 kwh/day, or 540 kwh/month. That's possible, but would require avoiding high load items like
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Don't forget _solar_ heating. That way, you can squeeze a bit more efficiency out of the space on your roof, plus it can be used to cool the solar cells, which improves their efficiency also.
This is far from insightful (Score:5, Insightful)
If you actually read up on solar cells instead of sounding off like an idiot, you would know that the cost per watt is dropping quite fast, durability has doubled in the last 5 years, that Sharp are making cells which are nearly twice as efficient as much of the competition and they are being sold as roof panels, that the recently opened German factory can sell everything it makes for many months ahead.
Nobody has ever pretended that a 1 sq M panel would power anything large. There is only so much sunlight, and nobody has ever pretended the second law of thermodynamics would be broken. No-one has ever pretended that 1 sq M panels would cost $1 apiece; you could not make a structure to withstand wind loading that cheaply. There is a huge difference between actual forecasts of an eventual $1 per peak watt, and $1 per sq M. $1 per watt works out at about $140 per sq M for a 14% efficient panel.
To the people who modded this insightful: if you can't tell an obvious troll from engineering reality, plase hand in your geek cards now and go play with Facebook.
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Hmmm. We'd need other advances as well. Forgetting the fact that there are clouds some of the time and the sun is below the horizion about half of the time, and assuming that the roof of your house/car is pointed squarely at the sun at all times (slightly possible if you have po
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The problem isn't research. This is exactly how research goes. You investigate 1000 things for 10-20 years, and ONE comes out the door to use in widespread industry.
So - 1000 slashdot stories, times 10 dupes and repeats over the 10 years, times 10 because it's re-reported on all the other bloggies/forumish
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Thermaldynamics? (Score:5, Interesting)
I just hope all these advances, especially ones that make solar cells cheaper to manufacture go into production. There are huge chunks of the world that are lifeless desert, and would be perfect for large solar and wind arrays, assuming one could find a way to transport the generated electricity to cities without too much current loss. Perhaps some chemical reaction that pulls carbon from the air directly to make ethane, then another reaction that converts the ethane to ethanol to be piped to places that can burn the ethanol for electricity. Yes, the chemical reactions to pull carbon from the air, and get it into ethanol are wasteful, but for very long distance transfer of energy (100-200+ miles), it would be less wasteful to do that, than to use standard power transmission lines. Even though the ethanol electricity generating plants would be adding carbon into the air, it would be carbon neutral due to the carbon being extracted at the solar/wind site.
Re:Thermaldynamics? (Score:5, Funny)
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Re:Thermaldynamics? (Score:5, Interesting)
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Are you now using a brail keyboard? Or are you the lucky one who drank the ethanol and typing while drunk.
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Why turn perfectly good ethane into ethanol ? That doesn't
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You can get a 95% efficient PV cell without violating those "thermaldynamic laws".
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Citation needed.
Sunlight isn't just visible light. If you want to get that high efficiency and use sunlight, you would need solar cells that are sensitive far into the far infrared range, which means that you'd essentially have to convert heat directly into electricity. Second law of thermodynamics says that that's a no-no.
Of course, if you can somehow shine monochromatic light on a solar cell which is sensitive to exac
Developing nations (Score:3, Interesting)
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Actually, the weather has been really nice here for a couple of weeks now
Let's be realistic (Score:5, Insightful)
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Re:Let's be realistic (Score:5, Funny)
Re:Let's be realistic (Score:5, Insightful)
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I agree. Give it some time though. These large social changes take time. Hell, people still use Snail mail for bills and communication. And where the hell is that "paperless environment" while we are at it? Late in 2007 the futures for Oil were predicting $200/barrel by the close of 2008. Then the fun will begin.
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I know a couple people who made/make their money in private equity and managing investment funds, people who hard-nosed financial types, who are convinced it's more like 5 years away.
There's been a huge run on Si that's kept Si prices high and solar prices slightly up; once a ton of in-process Si capacity turns on, it should get interesting (hint: don't go long on Si right now).
BTW the qualifier to your prediction isn't that valid these days...
Sunlight is better used for heating (Score:3, Interesting)
Re:Sunlight is better used for heating (Score:5, Insightful)
I get free heating all summer long, but in the winter it's too cloudy to make a difference. Yeah, skylights sound good and all, but give me a solar panel over that any day.
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Re:Sunlight is better used for heating (Score:4, Interesting)
I look forward to a future with solar powered desalination plants.
It's a much brighter outlook than continent wide water wars forcefully giving everyone a skylight.
Not just africa. How about the middle east? (Score:2)
When I was last in Australia, I was quite impressed at the various little things they did to use solar power (vs here in Canada where snow cover makes it rather less useful for a good part of the year).
I'd imagine that a middle-eastern country could set up major solar-electric centers, followed by climate-control (air conditioning) powere
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You do realize, though, that if the solar generated electricity is consumed inside the building, the laws of thermodynamics dictate that the electrical power consumed eventually dissipates as heat inside the building. I have nothing against skylights, per se, but this is the same heat you're worried about letting in through the skylight. And besides, what are you proposing here? steam powered laptops?
--
[FaunOS [faunos.com]]
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However, photovoltaics is excellent for powering something else - air conditioning. If you stick photovoltaics on your roof, you get a double whammy: Less heating from the sun because the photons are either deflected or converted into energy, and electricity to power the air conditioning at daytime. I imagine this is parti
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Erm. Some of my colleagues heat their (superinsulated) houses with solar, with a small electric auxiliary heater. This year, they didn't have to use the auxiliary heater from late January on.
So, sure, you may not be able to heat your house with solar all the time, and in all latitudes, but you can use it to significan
Penny wise, pound foolish (Score:5, Insightful)
We seem to cavil about a few million dollars, or even a few hundred million, being spent to jump start emerging energy technology, but we have no problem spending billions on oil industry subsidies.
We need to acknowledge that any new tech investment involves high risk. Success brings high rewards. We accept exactly this reasoning when oil executives tell us that oil exploration is expensive and risky, and therefore requires continuing subsidies even when record profits are rolling in. A few million spent on alt energy research that tanks, however, is usually reported as a "this is what happens when you listen to the tree huggers" story.
An attitude adjustment as 'way overdue, and a rediscovery of our spirit of adventure and innovation. Perhaps putting some money into finding out whether this kind of solar cell works and can be mass produced would be a place to start.
Re:Penny wise, pound foolish (Score:5, Informative)
Maybe because most alternative energy sources are big money losers? Take a look at page 16 of this report [doe.gov] for the actual numbers about subsidies...
I predict once you can start to get alternative energy sources like solar and wind down an order of magnitude or so in terms of cost you'll see things turn around. However, for now they're getting somewhere around 100X the subsidy per Megawatt-hour that "Big Oil" gets.
An improvement from 15% to 40% simply isn't enough - natural gas and oil get around $0.25 per MWhr, while solar and wind get 100 times that amount per MWhr. And remember, those nasty "Big Oil" companies also pay over $3 in direct federal taxes for every $1 in profit. Over $200 billion flows into the Federal government every year in terms of direct taxes and fees (that's not including the taxes you're paying on consumption of their products).
Right now, and for the last 20 years, wind and solar have been huge money-losers, and only exists BECAUSE of the massive subsidies. If we subsidized wind or solar at a level to get useful output levels, we'd spend literally trillions more per year.
And then there's that whole baseload thing...
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The problem isn't oil - it's the abuse of it. Like an adict we've allowed oil to change the entire structure of our nation and our society. When the oil is gone this structure will not be sustainable.
It won't be armageddon. People will simply move back into the cities. The suburbs will become ghettos just as the inner cities are now and then they will die out. By the end of the century New York, Chicago and the other large cities of the US will contract back into the boundaries they had in the year 1900
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The other piece of work that needs to be done behind all of this is to make the suburbs more foot-friendly. Once you don't need to drive to work, the next thing is
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New oil is getting more expensive, but that's because of extraction, not supply. The actual cost of pumping isn't that high, accounting for a few dol
Wind Energy works, just ask Denmark (Score:3, Interesting)
Right now, and for the last 20 years, wind and solar have been huge money-losers, and only exists BECAUSE of the massive subsidies. If we subsidized wind or solar at a level to get useful output levels, we'd spend literally trillions more per year.
Nice try, troll. Countries like Denmark have had tremendous success [foxnews.com] with alternative energy sources such as wind power. Currently about 20% of the energy used in Denmark comes from wind power, and there is about a $5 billion market in exporting turbines. Currently over a third of the wind turbines used worldwide [wikipedia.org] are built by Danish manufacturers such as Vestas.
On windy days, Denmark actually generates "too much" power from wind (about 40%) so they are working on an electric car system [theregister.co.uk] to act as
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Then again, quoting someone named Rune Moesgaard would have made it hard to take you seriously. So I understand.
Re:Penny wise, pound foolish (Score:4, Informative)
Your overlook many of the less obvious subsidies. For example, the Army Corps of Engineers routinely dredges canals used by the oil industry at taxpayer expense. The explanation is that they're staying in training. Canals that don't serve oil tankers, regardless of need, do not receive such treatment.
There are many, many examples of such hidden subsidies, none of which are accounted for in your numbers. I invite you to seek them out for yourself rather than take my word for them.
An article in Nature 445, 147 (11 January 2007) published online 10 January 2007, and "Money Down the Pipeline: Uncovering the Hidden Subsidies to the Oil Industry" by the Union of Concerned Scientists are good places to start your investigation.
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3 trillion = 3,000,000,000,000
divided by 60,000 equals 50,000,000
Fifty million dollars per home for a photo-voltaic system ? I think you're a few orders of magnitude off. Make that "You could build photo-voltaic systems for 60,000,000 homes", and you're at least in the same ballpark (if these systems are large _and_ use fairly expensive solar cells).
Oh, ho ho ho... (Score:5, Funny)
Irrefutable? Then it's NOT science! (Score:5, Insightful)
OTOH, I rather doubt that the scientists themselves claimed irrefutability here. The journalists are probably to blame.
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but snowballs... (Score:2)
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I am surprised nobody asked that before, but the answer is surprisingly simple. The photons obviously have enough energy do move several electrons, but the photovoltaic cell (junction) is a tiny laywer over some opaque substrate (normaly silicon). So you only have one chance of absorbing those photons.
There are some manufacturing processes that could create one junction over another, but those processes are very expensive and the material isn't completely transparent. Probably because of this (I don't know
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Decentralize - Decentralize - Decentralize. (Score:5, Insightful)
Imagine for a moment if we geeks hadn't come up with DNS but instead tried to use a small handful of machines to handle domain name resolution. The Internet would collapse rather quickly no?
Funny then that to date our power grid is based on a centralized model. Sadly, as much as 20-30% of all power generated is lost during transmission over the grid.
Now effective solar panels and batteries to go with them would allow us to move to a more decentralized model. Imagine whole neighborhoods creating most - though not all - of their power needs. If the panels can get to around 80% of the needs of the house then the current power plants we have can be the only ones we need for awhile.
Or even better, instead of having massive plants with a huge footprint make use of smaller pup nuclear reactors - about the size used in a naval ship. One of those could be placed where the power substations are now and pick up the slack that the solar panels can't fulfill. They wouldn't present any real contamination danger as once their fuel was spent after 30 years or so you truck out the entire unit and refurbish (i.e. refuel) it under controlled conditions in a remote area - while in service the internals of the thing aren't opened up.
These things also wouldn't have to make as much power as the current power stations because, by virtue of being closer to the customers they serve, they wouldn't lose as much power in the lines.
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40% is already a reality. (Score:2)
So if this is an improvement up to 40%, then it is FAIL. If it can be applied to the existing 40% cells to make them even more efficient then Solar power is about to take off in a big way.
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I'd rather have 40% efficiency solar cells at half the cost than 50% efficiency solar cells at the same cost.
Solar power is going to take off in a big way once the price of the panels drops enough. Let's hope this discovery helps with that.
Re:Or great! (Score:5, Funny)
You'd have to use a thick black raincoat, a wide brimmed hat and sunglasses to protect yourself from the ultraviolent radiation though. And cover up any exposed spots with SPF 10000 suncream.
Even then I'd scuttle back into the basement once the batteries had recharged.
why come out? (Score:3, Funny)
Re:Or great! (Score:4, Funny)
You know it also comes in a new convenient spray can [rustoleum.com]!
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PhysOrg says I'm right, too. [physorg.com]
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Oh yeah. There will be a hydrogen economy if/when we manage to get useful energy out of nuclear fusion. Until then, hydrogen is just a fuel with one advantage on paper and a long list of disadvantages in practice.
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My house + 50% = 30kwh / day
= 6 square meter
30% efficiency
Only about 20 square meters required.