Solar Power Efficiency Increased With New Coating

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LONDON, England (CNN)-- Researchers have developed a new anti-reflective coating that booststhe efficiency of solar panels and allows sunlight to be absorbed fromalmost any angle.

Scientists from the Future Chips Constellation (FCC) at the RensselaerPolytechnic Institute in New York have created the coating usingnanotechnology -- engineering devices on a molecular scale.

They are hopeful that it can transform the solar energy market in the coming years.

A typical untreated silicon solar cell absorbs just over two thirds ofthe sunlight it receives. But with the FCC's nanoengineered coating,that figure rises to 96.21 percent.

In their paper: "Realizationof a near perfect antireflection coating for silicon solar energyutilization," published in the scientific journal Optics Letters,researchers report that gains in absorption were consistent across theentire spectrum of sunlight -- ultraviolet, visible light, and infrared.

"To get maximum efficiency when converting solar power intoelectricity, you want a solar panel that can absorb nearly every singlephoton of light, regardless of the sun's position in the sky," saidRensselaer physics professor Shawn-Yu Lin, and head of the FCC researchteam. "Our new anti-reflective coating makes this possible."

Comprising of seven tiny layers, each 50 to 100 nanometers in height,the coating is made of silicon dioxide and titanium dioxide nanorodspositioned at an oblique angle.

The FCC team found thatstacking the coatings one on top of another enhanced theanti-reflective properties of each layer. Having a series of layersalso helps to "bend" the flow of sunlight which assists in capturinglight that would otherwise be reflected off.

Lin, an expert innanostructure photonics and a pioneer in the field of photoniccrystals, says that the new coating could be applied to just about anyphotovoltaic material.

Conventional solar technology has thusfar dictated that solar panels be mounted on south-facing roofs, or inlocations where the sun source is unrestricted and strong. But this newcoating could change all this.

It would also mean that largescale solar farms, like the giant array in Alentejo, Portugal, couldincrease their output while saving on energy used to track the sun.

"The anti-reflective coating requires multi-layer coatings which areslightly more complex than the typical single-layer ones," Lin toldCNN. "However, the thickness of each individual layer does not need tobe precise. This makes manufacturing easier."

Lin is currentlyexploring partnerships and licensing arrangements, and estimates theproduct could be on the market as soon as the next two to three years.

"The economics of modern day solar cells depends largely on thethickness of the substrate (500 - 1000 micrometers) and the processingcost for making the junctions. Our coating has a thickness of 0.7 to 1micrometer. The additional cost for incorporating our antireflectivecoating should not exceed two to four percent of that for existingsolar cells," Lin said.

The only downside that Lin and his teamhave found so far is that the nanorods can be fragile. Future researchwill focus on protecting them better and investigating the use of athin porous film to make them more robust.

In response to thepaper's publication, Professor Darren Bagnall from the NanoscaleSystems Integration Group at the UK's University of Southampton toldCNN, "It's a really impressive surface, and to get down to reflectivityfrom all angles of 3.5 percent is pretty impressive. But it's reallyonly going to deliver maybe four or five percent more power from thesolar cell."

Bagnall is himself trying to nanoengineersurfaces for solar cells by mimicking the surface of moth eyes, whichpossess excellent antireflective surfaces.

He says that theFCC paper is only talking about the amount of light that's transmittedto the device, not the efficiency of the device itself. "Reflection isa relatively small part of the problem," he said.

Jeremy Leggett, founder of Solar Century, a leading UK solar-energy company, also gave a cautious welcome to the new research.

"I've seen this before from other university research groups and thereis a world of difference between nice results in the lab andcommercially viable products," Leggett said. "But at some point one ofthem is going to work."

Leggett believes that the future is already very bright for the solar indust... more...

Tags: Solar Power, Solar Energy, Alternative Energy, Solar Photovoltaics

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