MIT Study Outlines a 'Perfect' Solar Cell 110
Daniel_Stuckey writes A new MIT study offers a way out of one of solar power's most vexing problems: the matter of efficiency, and the bare fact that much of the available sunlight in solar power schemes is wasted. The researchers appear to have found the key to perfect solar energy conversion efficiency—or at least something approaching it. It's a new material that can accept light from an very large number of angles and can withstand the very high temperatures needed for a maximally efficient scheme. Conventional solar cells, the silicon-based sheets used in most consumer-level applications, are far from perfect. Light from the sun arrives here on Earth's surface in a wide variety of forms. These forms—wavelengths, properly—include the visible light that makes up our everyday reality, but also significant chunks of invisible (to us) ultraviolet and infrared light. The current standard for solar cells targets mostly just a set range of visible light.
Least helpful summary ever? (Score:5, Insightful)
Re: Least helpful summary ever? (Score:1)
When Cell absorbs the androids, he will become Perfect Cell!
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I doubt it's the least helpful summary only because it does contain one informative sentence: "It's a new material that can accept light from an very large number of angles and can withstand the very high temperatures needed for a maximally efficient scheme."
Re:Least helpful summary ever? (Score:4, Informative)
Is this the least helpful summary ever on /.? It could be. I read it, and found it really didn't tell me anything I didn't already know, and gave very little clue as to how this study's results might even be helpful. I have a strong suspicion it's clickbait and so am moving along.
Hmmm .. you know .. that could just as easily describe a Bennett Haselton story
Re:Least helpful summary ever? (Score:5, Informative)
Well, going to the abstract of the actual paper, What they have is silicon milled with dielectric cavities (waveguides) that are tuned to the frequency of your solar cell. Hot black bodies can emit any wavelength, but the tuned cavities can only efficiently emit one. Other wavelengths destructively interfere. In that respect they work just like antennas at radio wavelengths.
The tuned light is efficiently absorbed by the solar cell. Natural sunlight isn't because some of the photons are too high in energy, and the excess gets wasted as heat, and some are too low and don't kick out an electron at all. Thus you get around 25% efficiency in a good cell these days.
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So it is just like putting too much air in a ballon!
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At least they avoided offending any butterflies and Predators.
Might be viable (Score:2)
Hard to tell, would depend on how it ramps up in large scale industrial application.
Interesting 85 percent absorption rate, though. Most of the PV growth in solar has been using cheaper materials, not efficiency of absorption.
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Interesting 85 percent absorption rate, though.
And highly suspect, considering the theoretical upper limit is 86%. The number of real machines that achieve that high a percentage of their theoretical limit is vanishingly small. Unless Josef Drexler has managed to perfect a nanoassembler that builds solar panels, that 85% isn't happening.
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Did you mean this guy?
Sorry, yes, Eric. I have no idea why my brain found Josef in that slot in my memory and didn't even question it.
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You can cheat and get more (Score:2)
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I can see two ways PV can grow.
The first is when space is precious and every single watt is needed. This can be urban areas, applications in space, even things like a weather monitor in an extremely remote area. Here, it matters less of currency per watt than watts obtained.
The second is where currency per watt matters, and there are large surfaces that can be covered, be it a rooftop solar array, a tent, windows, and other surfaces where a couple watts here and there lost isn't critical. There are a lot
perfect? (Score:3)
i think the most important feature for this technology would be cost/kwh. does it deliver that ?
(surface area we have enough of)
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Most important is cost/kwh? How about comparing it to the total cost, over time, of other sources of energy. (for instance, factor in the loss of fossil fuel and pollution or warming of the Earth, or the handling of radioactive waste from nuclear...those typically are not included in the cost/kwh, but should be. Of course, if you're a shiphead and are only interested in money and don't give a ship about anyone else, then yes, cost/kwh is the most important thing.
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How about comparing it to the total cost, over time, of other sources of energy
solar and wind already have won that race. they already are cheaper than any of the other technologies, even without factoring the externalities. so the question is : is this new solar tech cheaper than the currently-on-the-market panels
Re:perfect? (Score:4, Informative)
solar and wind already have won that race
The US Dept of Energy [wikipedia.org] does not agree with you. Look at the "Total Levelized System Cost", Solar is the highest cost by far, although Wind does pretty well in good locations.
Re:perfect? (Score:5, Informative)
Those figures are completely wrong and very out of date. Power Purchase Agreements have recently bought wind energy for $0.0365 per kwh - that is half the figure on the table linked. That cost includes subsidies, the actual agreement was $0.025 per kwh. For solar the PPA is for $0.05 per kWh (0.08 inc subsidy), with the price of solar falling rapidly I'd expect cheaper PPA's to be struck going forward.
http://cleantechnica.com/2014/... [cleantechnica.com]
http://cleantechnica.com/2014/... [cleantechnica.com]
Re:perfect? (Score:4, Insightful)
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I gave figures including subsidies. PPAs are a good way to look at price because that is what the utility is paying for the energy.
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Eh?
0.23% in 2013 (EIA), There are many GW's of solar capacity being added, that figure will double and treble etc. Solar PV is perfect for areas that use a lot of air-conditioning which accounts for a sizable chunk of electricity usage in the US.
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I corrected by error in a followup post, meant to type 0.5%.
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Which is a bit backwards IMHO since solar thermal is a damn good way to drive a big heat pump. Little ones not so much, but it would be perfect for large office buildings and shopping malls.
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About fracking:
http://geology.com/royalty/pro... [geology.com]
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I don't think the fracking boom will last long, the cheapest wells are typically done first, and if the price of gas rises much then renewables are a lot cheaper.
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The US Dept of Energy is irrelevant.
Relevant is the price you pay if you buy solar panels or wind mills on the market. And your parent is right. Solar is even cheaper than wind right now, and both are significantly cheaper than coal.
Go figure!
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yeah! and lets pump all the byproducts from all unregulated coal plants and mines into your house.
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Re: perfect? (Score:1)
Large solar collectors are required and the material needs to withstand 1500K so I don't think it will be useful for those applications.
Re:perfect? (Score:5, Interesting)
With solar panel prices now at $500 per KW, most of the system cost is now the installation cost. So improving efficiency lowers installation cost (less panels). Current panels being sold are about 15-18% efficient, best lab panels are over 40% efficient and the theoretical peak is about 65% efficient. Improvements in installation systems and in panel efficiency could easily lead to solar generated electricity being sold for less than $0.04 per kWh from the current $0.08 per kWh (including subsidies).
Panel technology improvements:
http://bxhorn.com/wp-content/u... [bxhorn.com]
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One producer expect $400/kW in a few years: http://www.pv-tech.org/news/su... [pv-tech.org]
Panel prices are already well into very affordable ranges. As you say, the real work now is getting all the other parts of the cost down (wiring, mounting racks, inverters, labor, land, and paperwork - permits, planning, etc.)
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There is room for improvement, especially with charge controllers. Charge controllers are more for off-grid, but there is still room for improvement. Cheaper MPPT [1] charge controllers would be useful, as well as ones that are better equipped for higher voltages (so thinner gauge wires can be used or more panels stacked up in series.) Controllers able to handle higher amperages don't hurt either, since we are getting to the point where it doesn't take many solar panels to hit amp limits on a lot of cont
Re:perfect? (Score:5, Interesting)
There's a bunch of research going into reducing the costs. There are huge areas where the installation cost can be reduced. Integrated and standardized framing, cheaper roof mount systems or even integral mounting systems that become the roofing material, flush roof mount with tracking, integrated, cheaper and more efficient micro-inverters, etc. In fact solar city just dumped about 50 million bucks into some heavy research on just that and the beauty is that because they are an installer and directly involved in the research they can test each idea directly and have first hand knowledge on where the expensive parts of the process are and what works and what doesn't. The quickest way to drive down install costs is to get the inspectors, the engineers, the installers and the panel designers all in the same room which they can do. If they can drive down the install cost they'll be greatly simplifying the install process which will in turn drive down the inspection costs and a bunch of similar follow on costs. And of course they aren't the only one pouring money into installation cost reduction.
There's a ton of waste in residential installs right now because they are using 100 year old methods. With real research going into this I expect they'll be able to at least halve the installation costs. If they succeed at that they'll drive solar power prices below the cost of coal almost immediately. This doesn't include the other things that are being researched like technology that will heat the panel just enough to dump snow in the winter, better heat tolerance and things like automatic tracking without having to move the panel (tilting the cell in the frame or focusing lens/prisims).
There's so much money being poured into research it's pretty darn cool IMO. Solar PV is getting more research than almost any other industry out there because of it's potential. Companies like Solar City have been turning down investment money because so much is pouring in that they can't invest it all.
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Even with current advances, there are still a bunch of links with the solar chain. For example, micro-inverters are one innovation which minimize the effect of shade on a panel (where just shading one cell causes the whole panel's incoming energy to drop by half or more.)
Once solar roof shingles become inexpensive and standardized to the point where replacing those is as easy as conventional shingles, this will dramatically increase energy gain. Similar with solar window tint on south (or north depending
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Storage cost is expensive. Or is it merely meant to be a daytime use to cut utility consumption?
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You mean large/grid scale storage? I think that could become cost competitive when matched with renewables going forward, more R&D is required. Pumped Hydro is of course already highly economical but it is not feasible everywhere.
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No, home scale.
I've been looking at very basic power systems for a small boat to provide nominal battery based power on the water and between inverters and batteries the solar side of it is trivial. It's the storage side that gets expensive.
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AFAIK home battery storage solutions are just starting to come out, I read an article recently where one of the home solar PV installation companies will start to include batteries as part of the system as standard. Battery prices will likely go below $200 per kWh of storage in the next 2-3 years. The battery and solar markets are crazy with innovation right now, Tesla's battery 'Giga-factory' is rumored to want to produce more batteries than just for cars.
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Roughly 5 kilowatt-hours of usable deep cycle agm battery is like $2,300 and by "usable"I mean draining it to 50% -- I would suspect that's on the optimistic side if you want long life.
I have no idea what my non-full-sun needs would be, but maybe 30kw-h if you exclude central air conditioning.
Obviously a home system designed around 48v would be more efficient than a 12v based system but it's still close to $18k for 30kwh of 48v battery.
To make it at all realistic you would have to get super compulsive abou
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Car batteries are far cheaper, see:
http://green.autoblog.com/2014... [autoblog.com]
$5500 for a 24kWh battery, hopefully prices like this will make it to home systems soon. Tesla's battery $20,000 for 85kWh, about the same per kwh.
30kWh is a lot of electricity, maybe you could shave a big chunk off of that with more efficient appliances, lights and standby settings. UK households average around 12kWh/day.
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30kWh is just a guess based on a minimum of 12 hours without maximum solar output.
You're right, I could shave some of it off but then the lifestyles start changing. DVRs get shut off, computers (which I access remotely in a professional basis) need to get moved to paid hosting (which amounts to paying someone else for electricity).
I've done some of it -- lights are already 90% CFL or LED. Fridge is 3 years old and likely reasonable in terms of power consumption. Clothes dryer, furnace and stove are natur
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Actually thermophotovoltaics, like stirling engine collectors, have the advantage that you can use them as a an electricity generator from natural gas at night instead of using a dedicated natural gas plant. Not sure if TFA is a technology that enables that use case, but it has been looked at as a way to combine the installation costs of solar arrays and natgas plants. Also there's been speculation as to whether they can be made into a more efficient way for hybrid cars to burn gas than an ICE.
TFA, though
Uses blackbody emission (Score:5, Interesting)
This system uses blackbody emission to re-radiate absorbed photons within a specific bandwidth, which can be selectively optimized for.
However, since it uses blackbody emission, it does not explicitly NEED light as the energy source. Any kind of heating will suffice. This is really just a very fancy means of converting entropic energy into something useful. Could be very useful when coupled with radio-isotope decay systems, for instance. (This, coupled with existing RTG tech, could produce more efficient RTGs)
Sadly, it requires that large numbers of useful photons be produced from the emitting blackbody source, which means it needs some pretty non-trivial temperatures. This isn't going to be something that is used in normal residential settings.
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Some larger trucks already do something like this (via the Peltier effect IIRC). 0.1 MPG is an important improvement for a big rig.
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Sadly, it requires that large numbers of useful photons be produced from the emitting blackbody source, which means it needs some pretty non-trivial temperatures. This isn't going to be something that is used in normal residential settings.
Could it be an alternative for solar concentration?
But then I have to ask why not just melt salts and store them so you get energy storage as well.
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But then I have to ask why not just melt salts and store them so you get energy storage as well.
Because crushed stone is even cheaper than salts or oil for thermal storage. Not much is cheaper than that. You circulate air through a heat exchanger and the rock bed to store heat, and reverse the flow to extract heat. The heat exchanger in turn gets hot fluid from the focus of a solar concentrator. Melty stuff like oil or salts need liquid-tight tanks. A hot rock bed can be a concrete lined ditch filled with rock, but doesn't need to be perfectly air tight, just about as tight as most ventilation sy
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That's a problem already well taken care of. On the Cresent Dunes project the hot and cold storage (cold being a figurative word given the salt in that tank is still upwards of 180degC) were only a tiny fraction of the cost of the plant. The word salt is figurative too as typically what they pump around is more like fertiliser than actual salt.
Anyway you're missing a very VERY big gotchya with your idea. Air is a horrendous medium to transfer energy. In any plant design cooling towers or fin fans are the ab
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Wait, what? Blackbody radiation is broad spectrum, with a peak defined by the body temperature. There is no bandwidth selectivity, it's a continuous curve. (One which peaks at visible wavelengths for the solar bb temp which,not surprisingly, most earth creatures have evolved to see.)
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True, however the steepness of the peak is relevant.
Compare the spectral footprint of sunlight at sea level:
Clicky [advancedaquarist.com]
With the typical power curve of pure blackbody emissions:
Clicky [fsu.edu]
The latter one has a single peak. The former has a much "flatter", but also noisier distribution. One can optimize at the near infra-red band, where the blackbody emission peaks consistently, and harvest the vast majority of the emitted photons. Especially since this band is also very close to the innate emission/capture band of pu
Optimal rather than perfect (Score:5, Interesting)
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> I didn't see anything about how much more efficient this is than generating electricity directly,
> but presumably it's better since the solar cell responds best to a specific wavelength
Single-junction cells have a single band-gap energy that defines the minimum energy of a photon that will cause photoemission. In the case of silicon that's about 1.1 eV, which corresponds to light in the near infrared (really near, basically red).
When white light shines on a cell, every that's red-or-higher can caus
Carnot efficiency (Score:2)
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Not a heat engine.
This is a black body emission system.
http://en.wikipedia.org/wiki/B... [wikipedia.org]
Basically, it is the result of the conservation of energy being employed. As an object heats up in a vacuum, it sheds the heat energy as increasingly more energetic photon emissions. Any substance that is not at absolute zero will emit blackbody photons. These are usually in the far infra-red spectral band, though under very high temperatures more energetic photons will be emitted. This is how your typical tungsten fila
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Not sure it applies (Score:2)
In the article the intermediate body is simply absorbing heat energy but then re-radiating it at a specific frequency. Would the Carnot effiency rules apply?
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Which makes it not black body, right? Blackbody radiation is a curve (Plank's spectral distribution of emissive power, 2piC1/(lambda^5(e^C2/lambdaT) -1)
I don't think Carnot necessarily applies here as it's the limit for thermodynamic cycles. This appears to be similar to a radiative laser, in that you put any radiation in, but what comes out is single wavelength or very narrow bandpass. The challenge, from a logical position, is that this material appears to violate the laws of entropy. Normally, you would
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Blackbody radiation is emitted from all sides of the emitter; it cannot be made directional. This means that the design that MIT has created, with the collector sandwiched against the emitter, will be at most 50% effective (When used with a light-source derived heat source). This is because some non-trivial portion of the re-emitted light will be beamed off the back of the device, where there is no collector to catch it!
Couldn't you put the intermediate radiator behind a layer of glass with a coating that is tuned to be highly reflective at the exact frequency that it is re-radiating at? That would reduce the amount of wasted energy.
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> 1) Blackbody radiation is emitted from all sides of the emitter; it cannot be made directional.
Emitter is a cylinder heated from the center. Electricity making cells are a larger cylinder around it. Photons emitted from the inside of the hot cylinder will mostly hit another part of the cylinder.
>2)... This means the emitter has to be bitching hot.
Make the ratio of cylinder sizes large enough, and your electricity making cells won't melt. They will get pretty warm, and you can extract secondary h
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Thermodynamics has nothing to do with photovoltaic.
There is no physical (as in laws of physic) limit that prevents a photovoltaic cell to be 100% efficient.
Why are americans so obsessed with 'laws of thermodynamic' and have no clue about them?
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Thermodynamics has nothing to do with photovoltaic. There is no physical (as in laws of physic) limit that prevents a photovoltaic cell to be 100% efficient.
Why are americans so obsessed with 'laws of thermodynamic' and have no clue about them?
Read the article. It's not for photovoltaics, it's for thermophotovoltaics.
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Does not change a thing. :) ;)
It is still based on photons, only in the IR band
Thermodynamics is about heat exchanges, consider a heat reservoir and a heat sink. Does not matter if it is a fluid or a gas. It is 'mechanic' in the sense of real materials involved, not a spooky photon radiation
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Ho hum... (Score:2)
Behind a paywall (Score:1)
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Hints for paywall circumnavigation:
Google $FirstAuthorsName + $SomeUniquePartOfArticleTitle
Example: Jeffrey Chou Selective Solar Absorption
Scan the results and avoid all that steer back to the paywall.
Find anything? No? That's usual.
Next try adding the $MagicWord = pdf
Example: Jeffrey Chou Selective Solar Absorption pdf
Look carefully at results. Maybe you will find a prepublication copy somewhere?
This will at least give you a flavour of the research work and might tempt you to support the $BILLION science
The "perfect" solar cell... (Score:3)
... from whose perspective? At least one perspective holds that the perfect solar cell is one that doesn't even work, a thin strip of plastic made to look like a solar cell that costs a helluva lot less than the real thing:
Today I was walking home from an errand to a store.I saw the remains of a “Dual Power Calculator” in the gutter; it had an intact solar cell in the top.“Cool!”, I thought; “I’m going to rescue that solar cell for some DIY thing.”I grabbed the top part and tossed it in my bag.
When I got home, I dismantled it to remove the “solar cell”.I discovered that it was a fake, a thin strip of plastic separate from the body made to look like a solar cell.
WTF....
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When I got home, I dismantled it to remove the âoesolar cellâ.I discovered that it was a fake, a thin strip of plastic separate from the body made to look like a solar cell.
Thin film solar [wikipedia.org], perhaps?
The only real way to tell would be to remove the batteries from the calculator, put it in the sun, and see if it works. (and of course if it didn't work, it might just be that it was broken, which might explain why it was left in the gutter)
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Nope, not thin film. There were no wires, no leads, no solder pads nor terminals. Unless there's wireless solar cells now in that form factor, it was a fake.
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Reminds me ...
Many years ago there was an ad for a device that you plugged inline with the distributor (old car technology) that would amplify the voltage to the spark plugs and give the engine more power.
It was billed as, "With transistor."
That was back when transistors were the big buzz word. I was a noob electronics technician and I knew transistors had three leads. How could a transistor possibly amplify when only two leads were being used?
I found one on the side of the road and I tore it apart and, sur
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Nowadays they just sell mysterious liquid engine/fuel system "treatments" that cost nothing to make but they can sell at a huge markup.
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Now that I have that silliness out of the way there are a few engine/oil treatments that do solve a specific problem (sticky val
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I was thinking that the "perfect" solar cell already existed.... [larouchepac.com]
The problem isn't energy effiencey but cost. (Score:2)
Work on getting the $/power down. If you can get energy efficiency gains cheap enough fine otherwise work on making them cheap enough to replace shingles on every house.
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Walmart already puts solar panels on many of their stores: http://cdn2.tekgoblinmedia.com... [tekgoblinmedia.com]
Besides generating electricity, the panels protect the underlying roof from sun exposure, thus extending their useful life. When they run out of rooftops, they can start on the parking lots. This not only generates more electricity, it provides covered parking. In sunny states this is very desirable. Once electric cars become more popular, charging stations powered by panels above the parking lot will be another
Perfect Cell, eh? (Score:2)
What a horrible article (Score:2)
Holy smokes Motherboard's posts suck. They don't even bother to try to understand the BS they're spewing.
"Light from the sun arrives here on Earth's surface in a wide variety of forms"
Light from the sun arrives here on Earth in exactly one form, photons. The only difference between a red photon and a blue photon is its kinetic energy. If a Honda Civic is driving down the road at 20 mph, and then speeds up to 30 mph, would you say those were two different forms of car?
"The band gap is a feature of photovolta
I discovered this a long time ago (Score:2)
The article seems to give no information about proof that any of this could be done, just "hey, wouldn't this be really cool if we could do this?".