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."
APDs (Score:5, Informative)
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."
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:Isn't price the key? (Score:5, Informative)
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...
Re:Move along (Score:3, Informative)
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.
Re:but snowballs... (Score:3, Informative)
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 about all the problems) people are unable to stack more than 2 junctions.
So, making a photon displace several electrons at a time seems to be the best alternative. People are doing that with quantum dots for a time now, but quantum dots are very unstable. Now those researches were able to create the same effect using a well designed crystal. That is a big step foward.
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.
Re:Someone said it before, I will now. (Score:3, Informative)
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 electric cooking, dryers, heating, and cooling. Oh, and the total cost would be $775*30 or $23k, plus installation, charge controller, inverter and storage (batteries).
A much more efficient solar panel [affordable-solar.com], not designed to be applied directly to the roof but which would require a frame mounted on the roof and fit in a 7x7 grid, or 49 panels, could generate 9,800 watts max, or 44kwh/day, or 1,323kwh/month. That's a much more useful number, and might even handle an electric dryer, cooktop, and cooling. Still doubt it could handle heating (excepting heat pump or geothermal). And it would cost $53,900, plus installation, charge controller, inverter, and storage. Amortized over 20 years of service, that's $225/month, which is probably cheaper than your electric bill. Though if you had to take a loan, it would cost $414/month for those 20 years, which is probably more than today's electric bill for that amount of power.
And none of that includes the cost of storage and storage maintenance, which is currently usually battery power.
Both the cost of the panels and the cost of the storage need to come down for the solution to be viable for the average person.
Re:Someone said it before, I will now. (Score:2, Informative)
That right there should be enough to show that you know next to nothing to what you're talking about. Here's a non-exhaustive list of just the USA's commercial solar panel manufacturers:
Suniva, GreenBrilliance, Signet Solar, Advent Solar, Innovalight, SunPower, Miasolé, DayStar Technologies, ASE Americas, Inc., Kyocera Solar, Atlantis Energy Inc., EPV Solar, Crystal Systems Energy Conversion Devices, Evergreen Solar, Powerlight, PowerFilm, Silicon Valley Solar (SV Solar), SunWize, TerraSolar, Inc., United Solar Systems Corp. (UniSolar), Solaicx, Alps Technology, OptiSolar, ICP Solar, Day4Energy.
Some of the larger ones worldwide include Shell Solar, BP Solar, Sharp Solar, and Sunpower. The US based Sunpower Corporation had an annual revenue of over 3/4 of a billion dollars in 2007, and profits of 147 million dollars. Not exactly chump change.
Re:Penny wise, pound foolish (Score:3, Informative)
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 dollars per barrel; the cost is driven by exploration, royalties, transport, and refining. There's plenty of reserves AND pumping capacity - both are actually on the upswing. Peak oil isn't even close in terms of reserves OR pumping.
Aside: there's one thing the US Congress could do TODAY to eliminate $1 per gallon of gas: simply eliminate Federal taxation of gasoline and the oil companies. That accounts for about $1 per gallon. ""Evil Big Oil" is lucky to make $0.10 per gallon of gas, and they have to pay $3 in taxes for every $1 in profit they make. In the mean time, the Federal government not only gets that $3, but a direct $0.182 per gallon - about double what "Evil Big Oil" makes, per gallon.
Re:Wind Energy works, just ask Denmark (Score:3, Informative)
Then again, quoting someone named Rune Moesgaard would have made it hard to take you seriously. So I understand.