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The new solar coating, made from a special nanomaterial may not look like much, but it helps solar cells to be 42 percent more efficient, making them close to being cost competitive. Best of all it can be easily produced with existing infrastructure.  (Source: Rensselaer/Shawn Lin)
New coated cell 43 percent more efficient, can be easily produced with current production lines

Solar breakthroughs are relatively commonplace.  However, typically they are iterative -- small increases by a percent or two in efficiency.  Researchers at the Rensselaer Polytechnic Institute have invented a new solar cell that is anything but iterative as it blows away past offerings by a large margin; something RPI calls a "game-changer" for the solar business.

Against relatively cheap coal power, solar -- like nuclear and wind -- has struggled to compete from a purely economic standpoint.  Worse yet, it trails wind and nuclear in terms of how close it is to being cost competitive.  The light at the end of the tunnel is that solar have shown the highest gains in efficiency of any alternative energy source, making its future look very bright.

The new RPI solar cell is a normal cell covered in a special anti-reflective coating which traps sunlight from nearly every angle and part of the spectrum.  The new cell is near perfect; it absorbs 96.21 percent of the sunlight shined on it, while a normal cell could only absorb 67.4 percent.  That 43 percent efficiency boost, coupled with mass production, if properly implemented could place solar on the verge of competing unsubsidized with coal power, at last.

Shawn-Yu Lin, professor of physics at Rensselaer and a member of the university’s Future Chips Constellation describes the breakthrough, stating, "To get maximum efficiency when converting solar power into electricity, you want a solar panel that can absorb nearly every single photon of light, regardless of the sun’s position in the sky.  Our new antireflective coating makes this possible."

Most materials have a mixture of light absorbing (anti-reflective) and light reflecting properties, depending on the angle and wavelength of light.  For example, eyeglasses allow light to pass through on direct angles, but begin to reflect light at sharper angles.  Solar panels in their current form operate with similar mixed character.  In order to improve efficiency, mechanical components must be added to turn to panel to face the sun.  This system entails significant cost and loss of energy efficiency, as well as a great maintenance burden.

With Professor Lin's discovery, the world's first cost-efficient static solar arrays could be produced.  No matter what angle the sun was at, nearly all sunlight would be absorbed and converted to power.  Professor Lin describes, "At the beginning of the project, we asked ‘would it be possible to create a single antireflective structure that can work from all angles?’ Then we attacked the problem from a fundamental perspective, tested and fine-tuned our theory, and created a working device."

Rensselaer physics graduate student Mei-Ling Kuo helped Professor Lin investigate various antireflective coatings.  Their eventual choice was a nanomaterial, consisting of several fine anti-reflective sheets.  Normal antireflective coatings consist of one sheet, which absorbs light at a specific wavelength.  By stacking seven separate layers into a composite coat, they were able to absorb nearly the entire spectrum.  Furthermore, the staggered nature of the layers "bent" the flow of sunlight to a favorable angle, trapping it in the coating.  This means that if light manages to reflect off a lower layer, it will be sent back down by the upper layers.

Each layer was made from a special nanomaterial consisting of silicon dioxide and titanium dioxide nanorods positioned at an oblique angle.  The material was grown through standard chemical vapor deposition techniques, and could be applied to the manufacturing of most standard solar cells, including III-V multi-junction and cadmium telluride cells.

On a microscopic level the nanomaterial looks like a forest of tiny, densely packed trees.  Each layer is 50 nm to 100 nm thick.

The team hopes to bring their technology quickly to market, as it will require little in the way of manufacturing line changes. The research is detailed in the paper "Realization of a Near Perfect Antireflection Coating for Silicon Solar Energy", published in the journal Optics Letters.

Besides Lin and Kuo, the other researchers listed as co-authors on the paper were E. Fred Schubert, Wellfleet Senior Constellation Professor of Future Chips at Rensselaer; Research Assistant Professor Jong Kyu Kim; physics graduate student David Poxson; and electrical engineering graduate student Frank Mont.

The research was funded with the help of funding from the U.S. Department of Energy’s Office of Basic Energy Sciences, as well as the U.S. Air Force Office of Scientific Research.

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RE: so how about actual efficiency?
By Amiga500 on 11/5/2008 11:28:53 AM , Rating: 5
Rome wasn't built in a day.

Its an improvement, a big improvement. Add it to other improvements (like bacterial hydrogen production from water) and it will become viable some day.

Just because it isn't there yet is no reason to abandon the lot.

RE: so how about actual efficiency?
By FITCamaro on 11/5/08, Rating: 0
RE: so how about actual efficiency?
By chrnochime on 11/5/2008 12:59:38 PM , Rating: 1
I haven't read up on the latest nuclear power plant technology in a long time but last time I checked, there is still that little problem of safely disposing radioactive waste which contain uranium, plutonium, amongst other radioactive elements. Limitless power from reprocessing? Not like you can infinitely reprocess the waste anyway. I never do understand how nuclear proponents can just downplay the waste disposal issue when it's still impossible to make them not substantially radioactive within even 300 years, let alone 100 years.

RE: so how about actual efficiency?
By Cuddlez on 11/5/2008 2:04:52 PM , Rating: 5
Well then start reading:

1. As a matter of fact you're right we can't reprocess it infinitely, but given the amount of Uranium we have now, using a breeder type reactor the fuel would last "several BILLION years". Not quite forever, but I'd say it's close enough. Mind you, within the next billion or so years, I'm pretty sure we'll have a working fusion reactor. Which, of course, runs off of hydrogen. And since hydrogen is the most common element in the Universe we wouldn't run out of fuel until the universe is gone. Bu by then I'm pretty sure energy production won't really matter...

2. As for reprocessing, we can (again in a breeder type reactor) reuse as much as 97% of the spent fuel. This is according to British Nuclear Fuel.

3. As for the waste, well if most of it gets re-used then there won't be as much left to worry about. And the great thing about radioactive waste... it goes away eventually! It doesn't seem like people think about it much but substances like lead, arsenic and mercury are always poisonous. They always have been, and always will be. But spent nuclear fuel, after so many years becomes relatively harmless (I wouldn't go eating it or anything).

For good info check out this website:

And here are my references for points 1 and 2. Point 3 is basically my own deduction based on points 1 and 2.


RE: so how about actual efficiency?
By Starcub on 11/7/2008 10:53:46 PM , Rating: 2
I hope the 3% of the waste that they just dump into the sea isn't radioactive. If it is, I can't see how they can claim it is ok. Security and waste disposal have traditionally been a big part of the cost of nuclear power, and it sounds like they are cutting corners to make it economically viable.

By FITCamaro on 11/5/2008 3:43:26 PM , Rating: 2
For storing what little waste is left and unused after reprocessing, we've got lots of these big, giant rock things called mountains that are useless and can be made to have plenty of space inside to store it in. Preferably glassified then stored.

RE: so how about actual efficiency?
By werepossum on 11/5/2008 6:46:31 PM , Rating: 3
by chrnochime on November 5, 2008 at 12:59 PM
I never do understand how nuclear proponents can just downplay the waste disposal issue when it's still impossible to make them not substantially radioactive within even 300 years, let alone 100 years.

My college chemistry professor said if we really want to dispose of nuclear waste, dilute it, put in large barrels with tiny holes, and dump it in the oceans. We don't create radioactivity, we simply concentrate it, so to safely dispose of it we simply need to un-concentrate it. He also said that would be stupid, because concentrated energy will always be valuable once we have the technology to use it.

Regarding the solar efficiency invention, I think that's a really good thing. Solar, being point-of-use, has the capability to reduce generation and transmission requirements. But it needs to get a lot cheaper to be practical even for grid peak-shaving. Right now solar is nowhere near ever paying back its cost unless you get a hefty tax break - which just means using the confiscatory power of government to subsidize your toy.

RE: so how about actual efficiency?
By Starcub on 11/7/2008 11:08:09 PM , Rating: 2
Right now solar is nowhere near ever paying back its cost unless you get a hefty tax break - which just means using the confiscatory power of government to subsidize your toy.

Depends on where you live and what you can afford. Solar typically has a payback period of 10-20 years (and I'm not talking about just PV panels); however the up-front costs are expensive. That's only going to improve with subsized research. But the biggest payoffs will come from better energy storage technology.

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