Caltech Makes Flexible, 86% Efficient Solar Arrays 439
Posted
by
kdawson
from the bend-me-shape-me dept.
from the bend-me-shape-me dept.
strredwolf writes "Caltech has released a flexible solar array that converts 95% of single-wavelength incandescent light and 86% of all sunlight into electricity. Instead of being flat-panel, they stand thin silicon wires in a plastic substrate that scatters the light onto them. The total composition is 98% plastic, 2% wire — the amount of silicon used is 1/50th that of ordinary panels. So as soon as they can get these to market, solar could be very viable and cheap to produce." Update: 03/01 21:02 GMT by KD : Reader axelrosen points out evidence that the 80%+ efficiency figure is wrong. MIT's Tech Review, in covering the Caltech announcement, says that the new panel's efficiency is in the 15%-20% range — which is competitive with the current state of the art. And the Caltech panel should be far cheaper to manufacture.
In requires polymer to make... (Score:4, Interesting)
Re:I think its entirely reasonable to say... (Score:5, Interesting)
It sounds like the summary here is overstating the efficiency a bit. The numbers are for the absorption efficiency, not the overall conversion efficiency.
'The light-trapping limit of a material refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight. "We've surpassed previous optical microstructures developed to trap light,"
.
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The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons--in technical terms, the wires have a near-perfect internal quantum efficiency. "High absorption plus good conversion makes for a high-quality solar cell," says Atwater. "It's an important advance."'
It looks like the overall efficiency is still very very high while using minimal resources. This is exactly the kind of innovation the U.S. needs for carbon-friendly jobs.
It's plastic ! (Score:2, Interesting)
How durable can this device be? It's made up of 98% plastic.
Re:I think its entirely reasonable to say... (Score:5, Interesting)
I saw this posted by grobbo at engadget: http://www.engadget.com/2010/02/28/caltech-gurus-whip-up-highly-efficient-low-cost-flexible-solar/#comments [engadget.com]
Turns out the only benefits to this are the flexibility and low cost (which are good, sure, but not that exciting).
According to their letter to nature.com this "also may offer increased photovoltaic efficiency", _may_ suggests to me there probably isn't any significant improvement.
For anyone wondering why high absorption and a high QE don't necessarily result in high energy conversion (like I was a few hours ago) it's because 30% of the photons have insufficient energy to free an electron in silicon, and most of the rest of the photons have more energy than needed to free an electron, so any excess energy beyond that required to free a single electron is wasted as heat.
Re:Absorbed not necessarily equal to electricity (Score:5, Interesting)
Because I don't pay for the nuclear plant or the hydro dam
Yes you do (if you use power from one).
However, getting the money together to buy and install the solar panels is all on me, the homeowner
No it's not. I see/hear ads from solar power rental places all the time (on local media no less, but then again it is Los Angeles). They will do the full install at no upfront, then charge you amortized payments--if the payments are less than what you save on electricity (which their ads claim will usually be the case, for what that's worth, I have no idea if that part's true) then they pay for themselves on day one.
Re:Plastic? 10 years under the sun? (Score:5, Interesting)
Saturn vehicles. Body panels are solid plastic, and I know Saturn has been around since the 90s.
Re:Plastic? 10 years under the sun? (Score:4, Interesting)
Seconded. I sold a '94 Saturn last year that had been parked in the Arizona sun for many years. (Got rid of it due to multiple electronics failures and an engine oil leak that'd not be worth it to fix). Survived the sunlight just fine.
And the plastic body panels were GREAT. Lightweight and dent-proof.
red light (Score:4, Interesting)
i'd love cheap energy from the sun, but this won't be it.
Re:Plastic? 10 years under the sun? (Score:2, Interesting)
You mean like vinyl siding? We also clad window and skylight frames with it. And then there's acrylic and lexan, visible at any general aviation airport, sitting in the sun.
The problem with plastic is perception. It can be designed to do a whole lot of things really well. Problem is, part of what that means is it can be used to make really cheap shit well, and people start to think plastic means cheap shit.
Re:I think its entirely reasonable to say... (Score:1, Interesting)
Sadly, they haven't. All they have published is that they can absorb light, and convert most of said photons into electricity. The bandgap for silicon is about 1.1ev (1100nm, in the infared), with means you don't absorb any sunlight below 1100nm, and a photon at 1100nm generates the same amount of energy as does a photon at 500nm (which has twice the energy). All of this adds up to a '100% efficient' cell that only converts about 20% of sunlight into usable energy. The paper also notes that they are working on getting the voltage up, due to the 1.1ev bandgap of silicon, a 100% efficiency cell would output 1.1v, and anything less than that you are loosing more efficiency.
What they did to was find that by building a silicon solar cell upright, and filling in the gaps between the pieces of silicon with a light scattering polymer, they could get away with less silicon. Which is quite an achievement, but hardly worthy of the outrageous claims made by the article.
Re:I think its entirely reasonable to say... (Score:3, Interesting)
Re:It's plastic ! (Score:4, Interesting)
Ever heard of polycarbonate? They use it to produce composite bulletproof window panes, safety shields for industrial machinery, impact-resistant safety glasses, underwater portholes, etc. It does degrade somewhat under UV light, but then, you can just put an UV filter on top of it, it's not going to be a problem for the panel itself. And there are other transparent plastics with very good properities for this application.
Re:I think its entirely reasonable to say... (Score:1, Interesting)
The important bit is the tiny amount of semiconductor being used and the sparse matrix. That opens the door to using rarer materials to capture the photons silicon misses and there's so much space in the array mixtures of different nanowires seem very possible. Right now it may indeed just be cheaper but there's plenty of scope for massive efficiency improvements as well.
Re:Absorbed not necessarily equal to electricity (Score:3, Interesting)
Hmmm.
So if financing a nuclear power plant is economically attractive, then so should financing consumer solar panels. In fact if they are lightweight an easy to install, it'd be a lot more feasible to repossess and resell them, although that means you'll probably need to insure them against theft.
That said, I'd bet the problem is with consumers rather than banks. Most houses wouldn't be able to generate enough power to go off the grid, and the payback time doesn't justify the aggravation of having another household system to manage and the changes to the appearance of the house. I'll bet farmers who use photovoltaics (e.g. vineyards) get loans for their systems like any other kind of equipment.
Re:I think its entirely reasonable to say... (Score:3, Interesting)
Disclaimer: University of Michigan Solar Car Team alum
Cool, someone who knows this stuff (I don't). So given the following numbers from TFA:
The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight.
and
The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons
and
High absorption plus good conversion makes for a high-quality solar cell
And if the current efficiency is around 40%, my two questions are:
In essence, I'm asking:
I am an idealist at heart, so the idea of breakthrough efficiency levels in solar energy has my mind running a million "what if"s! I just can't imagine all that would be possible with that type of enery available to us.
from the ignore-kdawson-the-idiot dept. (Score:4, Interesting)
solar payback period (Score:3, Interesting)
Right now, solar cells are so expensive, they take something like 15 or 20 years to pay for themselves, so most property owners don't see a big incentive. Lower that price to 10 years or 8 years, or even lower, and suddenly the demand for these things will skyrocket.
The payback period for solar is already under 10 years. New Jersey [calfinder.com] has a payback period of 1.5 years, "New York and Delaware are next in line with payback in 3-6 years, and California, Maryland, Massachusetts and Wisconsin all tied for fourth at seven years." Of course, if because of this everybody went out and started buying solar energy systems, the cost could go up, higher demand drive prices up. Then again because of economy of scale and competition prices could go down even more.
Falcon