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."
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.
Developing nations (Score:3, Interesting)
Sunlight is better used for heating (Score:3, Interesting)
Re:Someone said it before, I will now. (Score:3, Interesting)
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: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.
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.
Re:Isn't price the key? (Score:4, Interesting)
Re:Thermaldynamics? (Score:5, Interesting)
Re:Someone said it before, I will now. (Score:2, Interesting)
Re:Thermaldynamics? (Score:3, Interesting)
Re:Someone said it before, I will now. (Score:3, Interesting)
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:Max Power (Score:2, Interesting)
My house + 50% = 30kwh / day
= 6 square meter
30% efficiency
Only about 20 square meters required.
Wind Energy works, just ask Denmark (Score:3, Interesting)
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 a "sink" to dump the excess energy. (currently the hydroelectric generating facilities in Norway and Sweden are used to smooth out the changes in energy production from wind)
The wind power project has been such a success that Denmark is currently planning to double its offshore wind farms, after studies showed that it would not harm the environment. The current goal is to increase wind power to 30% of total output by 2025.
Re:Someone said it before, I will now. (Score:3, Interesting)
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.
Re:Decentralize - Decentralize - Decentralize. (Score:3, Interesting)
Why don't we just use our homes to munch up our waste products and convert them to gas to run fuel cells that make electricity or process the at an urban level for gasses and pass that waste product further - for example why can't we use sewage water with a lot of nutrients to soak up carbon from our underground freeways or power stations with algae and produce bio-diesel. Given that the process would have inefficiencies, but who cares - they were waste products anyway, and after the inefficiencies you rightly point out in the grid anyway how much energy do we throw away after we have used it?
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.
Re:Manufacturing Energy Costs? (Score:3, Interesting)
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 3.65KW extra, or 31.4% surplus to sell back to the grid.
NYC has an average 25850 people per Km^2, with an average household of 2 people. A square KM of PV could generate 72MW for those people's requirement of 26MW. Even if only 1/3 of the City's area were PV, we'd power ourselves completely. [demographia.com]
If PV averaged 40% instead of the 18% I used in these figures, that's only 1/6 the area needed. If the City and state offered tax incentives per grid watt self-generated for 5 years (while those PVs paid back their manufacturing energy investment), most roofs would have them. Consider the extra savings from offloading from our blackout-prone Con Edison grid, and replacing blacktop roofs with something insulating, and NYC would probably show a net energy profit after less than 10 years. Which, like everything else in NYC, would be readily converted to actual monetary profit.
Re:Someone said it before, I will now. (Score:3, Interesting)
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 with a 10 year payback vs either a 1 or 2 year payback, or some sort of "encouragement legislation" in place that turned the 10 year payback into a 1 or 2 year payback.
Re:Isn't price the key? (Score:3, Interesting)
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 sandstorms or anything like that in Arizona (guessing that's what AZ is