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40% Efficiency Solar Cells Developed
gtada writes "A story published at Physorg.com discusses recently published research into the fabrication of solar cells that surpass the 40% efficiency milestone. Such devices would be the high water-mark to date, and hint at the possibility of even more effective technology. 'In the design, multijunction cells divide the broad solar spectrum into three smaller sections by using three subcell band gaps. Each of the subcells can capture a different wavelength range of light, enabling each subcell to efficiently convert that light into electricity. With their conversion efficiency measured at 40.7%, the metamorphic multijunction concentrator cells surpass the theoretical limit of 37% of single-junction cells at 1000 suns, due to their multijunction structure.'"
It's another gallium-based technology. That's going to limit it. There's just not that much gallium available. 30%+ efficient cells using gallium have been around for a few years, but other than on spacecraft, and the Stanford Solar Car, they're too expensive to be useful. They talk about "concentrator cells", but that means mirrors and trackers, running up the system cost.
Citation: King, R. R., Law, D. C., Edmondson, K. M., Fetzer, C. M., Kinsey, G. S., Yoon, H., Sherif, R. A., and Karam, N. H. "40% efficient metamorphic GaInP/GaInAs/Ge multijunction solar cells." Applied Physics Letters 90, 183516 (2007).
when the article talks about hundreds or thousands of suns, it means they used mirrors and lenses to concentrate the light that falls on a much larger area to then fall on the solar cells. this leads to the solar cells generating a lot more electrical power and thus makes it more economical to produce power from soalr energy as compared to not using mirrors or lenses to focus light onto the panals.
Sigs are too short to say anything truly profound so read the above post instead.
So yes, this depends highly on the materials used and manufacturing process as to whether the energy payback is an issue or not. 1-20 years? Let's hope this technology is on the low end of that scale.
Also, two more issues came up that I forgot in my original post:
- Exotic Materials: The materials advertised in this article are not... common. I highly doubt this helps either the mass production price, or the long-term availability of such.
- Lifetime: How long does a panel actually last? Few manufactured items of any kind have infinite lifespans. Is the manufactured solar cell "stable" chemically/physically? This ties in slightly to my old heat/cold question, but when stressed by weather, will it hold up?
Most of my questions are challenges to be overcome, not "Death knells" to trying. But they're also things to be aware of when anything's announced with too much enthusiasm.http://hardware.slashdot.org/article.pl?sid=06/12/ 06/027228
:)
Ahh well. More publicity for Spectrolabs...
The solar cells are extremely expensive due to the Gallium in them. It's cheaper to have 1 solar cell with a thousand mirrors reflecting onto it. Hence the stellar luminosity of 1000.
Silence is golden... and duct tape is silver.
I'm sorry, but you are decidedly incorrect. The amount of sunlight that can be converted on a fully overcast day in the Seattle-Tacoma region is normally in a range of 70 to 80 percent for photovoltaic solar cells in terms of solar energy.
You might want to investigate it yourself - just pop over to Seattle City Light on the City of Seattle website and read up on it.
Now, the solar cells we use to POWER some of our public buildings, bus shelters, and schools here are not as efficient as the 40 percent that this Letter in Applied Physics speaks of, but they are about half as efficient.
Cloud cover as you understand it, depends on visible light spectra. The solar cells absorb far wider bandwidths, at least the ones in common use here.
If we were a snowbound or ice-storm city like many others - which we are not - it is possible that your statement would be less inaccurate, as the ice crystals and heavier cloud formations might refract more of the effective solar energy, but we tend to only have a mild drizzle due to the consistency of our cloud cover.
Or haven't you noticed?
Don't believe me? Go look at the bus stops with LED readouts along N 45th, some of the public schools (including two my son went two and the high school he's in now), and even Seattle Center's public meeting rooms.
See - solar cells. Perfectly happy solar cells.
Some people use solar water heaters on their rooftops here, and if you look around Phinney Ridge you'd see a few of them. There's a reason they're frequently referred to in the Seattle Times supplements on Green Houses - people USE them. Because they make sense here.
Here endeth the lesson.
-- Tigger warning: This post may contain tiggers! --
I have yet to see any scientific papers that agree with your statement in any of the online Energy journals.
Would UC Berekeley's Nuclear Engineering department be a reputable enough source for you?
They quote less than a ton of waste per GW-year. Conventional is about 35 tons per GW-year.
I'll make a note to find the reports from the Argonne Labs prototype when I get some library time in.
My God, it's Full of Source!
OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
If solar is less expensive than the available clean conventional sources then this might make sense. Otherwise, why bother? It's only in situations where you're already near existing daytime conventional capacity and the deployment of solar is much faster/cheaper in the short term than deployment of another clean conventional source that it might make sense. But if solar is expensive and/or time-consuming to deploy (relative to deploying another clean conventional source) then it simply doesn't make sense to use it even if it's only for dealing with peak load.
Forgive me, but you are completely wrong about this. Peak periods are exactly when things like solar really "shine." There are a couple thing you must understand about the interstate electricity grid:
First, is that it is over-designed on purpose. Most major utilities have operating reserves of power generation of between 12 - 18 % of the day's anticipated peak demand. On any given day, the system operator will have tens or hundreds of generation sources that it never dispatches (e.g., uses to produce power), but that are there "just in case." This means that utilities have multiple dispatch solutions in order to meet load (load being a measure of people who want to use electricity).
The second key principle is that utilities select their generation resoures based on a "least-cost dispatch" basis. While in practice, this gets incredibly complicated (and also includes environmental factors), the utility will pick the least expensive generators that can produce enough power to adequately supply the day's demand. In practical terms, this means that the utility will dispatch the dirtiest and most expensive to operate (on an incremental cost basis) generating facilities last.
The third principle is an outgrowth of the first two. On peak demand days (think middle of summer, air conditioners running at full blast, etc.), the number of dispatch options available to the utility decreases further and further as it commits an ever-increasingly greater share of its total generating capacity to meet demand. This means that your nastiest, dirtiest, foulest, most expensive generating facilities are dispatched on such days.
Imagine this scenario. You are Utility X. You have the following five generating facilities at your disposal:
1000 MW nuke.
500 MW cheaper, clean(er) coal.
500 MW slightly less cheap dirty coal.
100 MW incredibly expensive natural gas.
20 MW aging oil burner that spews out more toxics that Paris Hilton on a breathalyzer AND costs more than the GDP of small nations to operate.
Total installed capacity (a fancy term for the total amount of generation): 2110 MW.
Now imagine that hellishly hot day. Demand immediately soars to 1500 MW -- and it's not even 11 am yet. You commit your nuke and your clean coal facility. Now it's 2 pm and demand hits 2000 MW. Throw in the dirty coal. Four pm rolls around and demand hits 2040 MW. Thow in that expensive natural gas peaker! (Don't worry -- the rate payers will just end up eating the extra -- your investors are safe.)
Now it's 4:47 in the afternoon. The peak of the peak. You're at 2099 and still rising.... You are getting ready to commit the oil burner at a cost of several millions of dollars and countless hazy days. Do you need it?
Well, maybe not. If you were a smart utility executive, you invested in Demand Response and paid some of your customers to go off-grid on days like this. Additionally, you've been incouraging customers to install solar panels that are all furiously generating power right as it's needed most.
This is the moment where solar pays for itself. By reducing the peak demand by only a smidge, you reduce energy bills substantially. Solar is also one of the few alternative/clean sources of energy that peaks along with demand. Wind, for example, tends to blow off-peak. (This is even more true when you facto
The solar panels go ON the roof. You don't make a roof out of them; that would be ridiculous.
You know all of those shiny office buildings in big cities? That's all, wonder of wonders, glass. If you can have an entire 20, 30, whatever-story building with glass exterior walls, you can put some glass on your roof.
Not particularly. Because they rely on semiconductors, they only scale as well as the fabs to build them. The problem has been that the solar industry uses plants that are at the end of their semiconductor chip fabricating life; thus they do not wield great efficiency due to small wafer sizes. They also suffer from the base challenges of dealing with silicon wafers (raw cost of wafers, dicing costs, etc.) The same cost problem exists with LEDs. It's interesting to note how GE is focused on cost of production in OLEDs rather than their efficiency on GE's Global Research Blog post. Following that analogy, it's not the 40% efficiency that will launch solar cells, it's 10% efficiency at 10% of today's cost (It's about cost/kWh).
Now, if we could only figure out some way for the oil companies to reap massive profits from such a scheme, I'm sure it would happen in no time.
You mean oil companies like BP and Royal Dutch Shell? ... two of the top 6 producers of solar cells?
I'd note that most oil companies do have lots of research into alternative (non-oil) energy. It's just hard to see in their financials because oil is so lucrative. The major one that realy gets criticized for its lack of investment in areas like solar is ExxonMobil - and the reason they don't is probably the same reason that Cisco doesn't tend to develop most of its revolutionary technology inside the company. XOM and CSCO both have tons of cash, tons of cash flow and a well-priced stock giving them the ability to simply buy a producer of new equipment if it becomes a valuable market. Why bother to spend tons of money on basic research when you can let the newcomers fight it out in the market and just buy the leader when the time is appropriate? As strange as it is, that's R&D economics at many large industry-leading corporations. It's "efficient outsourced innovation".
The fact of the matter is that no matter how efficient a cell is on cloudy days, there just isn't as much energy available on cloudy days as on sunny days. A heavy overcast probably has 15-30% of the energy as a sunny day, which is certainly better than zero but is a major hit if you can't count on some sunny days to "make hay" on.
Also, efficiency matters to people with limited space in which to install solar arrays. Of course, current production crystalline technology has cells with efficiencies in the high teens, but when packaged the overall efficiency usually drops to the low teens for a number of unavoidable reasons.