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Published on November 14th, 2012 | by James Ayre

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Solar Energy Conversion And Storage Breakthrough, New Way To Split Water Molecules Into Hydrogen And Oxygen Created

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November 14th, 2012 by  

 
A new way to split water molecules into hydrogen and oxygen by using just the sun and ultrathin films of iron oxide (rust) has been developed by researchers from the Technion-Israel Institute of Technology. This technological breakthrough will almost undoubtedly lead to more efficient, and less expensive, ways to store solar energy.

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By using the sun to split water molecules and create hydrogen-based fuels, the energy of the sun can then be used at any time and in any place, rather than just those that are conducive to direct solar power. The researchers think that this could be a major factor in the replacing of fossil fuels.

“Our approach is the first of its kind,” says lead researcher Associate Prof. Avner Rothschild, of the Department of Materials Science and Engineering. “We have found a way to trap light in ultrathin films of iron oxide that are 5,000 times thinner than typical office paper. This is the enabling key to achieving high efficiency and low cost.”


 
Iron oxide, also known as rust, has many clear benefits as a semiconductor material; it is very common, very inexpensive to produce, stable in water, and, in contrast to other semiconductors, it “can oxidize water without itself being oxidated, corroded, or decomposed,” a news release from American Technion Society notes. There are challenges to working with it, though, the largest of which is its poor electrical transport properties. “Researchers have struggled for years with the tradeoff between light absorption and the separation and collection of photogenerated charge carriers before they die out by recombination.”

“Our light-trapping scheme overcomes this tradeoff, enabling efficient absorption in ultrathin films wherein the photogenerated charge carriers are collected efficiently,” says Prof. Rothschild. “The light is trapped in quarter-wave or even deeper sub-wavelength films on mirror-like back reflector substrates. Interference between forward- and backward-propagating waves enhances the light absorption close to the surface, and the photogenerated charge carriers are collected before they die off.”

This creates the potential of making inexpensive solar cells that can combine both ultrathin iron oxide photoelectrodes and conventional photovoltaic cells. Simultaneously producing electricity and hydrogen, these solar cells would be able to efficiently store energy for use anytime, 24 hours per day, which is a significant advantage compared to conventional photovoltaic cells. One of the primary criticisms of solar power is its inability to produce electricity when it is very cloudy, but this new technology could remedy that.

And since the new technology uses only very common materials, it could go a long way towards reducing the use of expensive rare earth elements in solar panels, most of which is imported from geopolitical competitors, reducing the use of rare elements like Tellurium and Indium by up to 90%, with no loss of performance.

The new research was just published in the journal Nature Materials.

Source: American Technion Society
Image Credits: Zonne

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.



  • solar thermal manufacturer

    I strongly believe that this technological breakthrough will definitely lead to more efficient, and less expensive, ways to store solar energy.

  • http://soltesza.wordpress.com/ sola

    This system sounds nice but it is fairly different from PV panels (and their storage batteries).

    PV panels directly generate electricity which can be used immediately (or stored in batteries for use later).

    This system cracks water and produces hydrogen. So you need fuel cells to generate electricity and a storage system for the hydrogen if you want to use the energy at a later point in time.

    Hydrogen is a dangerous material and it needs proper handling. Its storage is currently very expensive (although cheaper ways are under development).

    Hydrogen fuel cells are also very expensive today.

    All-in-all, I am not sure that this is a viable system at the moment, even if the new water-cracking panels work properly. Even a PV system with professional lithium-ion batteries would be cheaper and easier to handle/maintain than this hydrogen system.

    • http://twitter.com/WR_ Wes

      We’ve faced the same fears and reservations at every other step in the advance of progressively more potent forms of stored energy.

  • _sd_

    ‘One of the primary criticisms of solar power is its *inability* to produce electricity when it is very cloudy…’

    Nathan, I’m surprised that you reinforce this false information on solar panels, seing as you write for cleantechnica.com… Even other articles on cleantechnica state that solar panels still produce some electricity when it is cloudy. The cited source also incorrectly says they do not produce electricity when it is cloudy. I find it sloppy that both of you reinforce this false information. I hope you correct the article and don’t repeat the error.

    Sources :
    http://cleantechnica.com/2012/04/30/blackest-solar-cell-to-date-absorbs-99-7-of-light/
    http://cleantechnica.com/2012/10/12/solar-powered-electronics-more-feasible-with-new-high-voltage-solar-cells/

    • Bob_Wallace

      Some. Not much.

      The last couple days here have been heavily overcast. My panels made enough power to keep things running (refer, computer, stereo) during the daylight hours but they didn’t put anything into the batteries for the dark hours.

      I don’t have a way to measure panel output directly, but I would assume I’m getting about 1/10th the amount of sunny performance.

      • http://soltesza.wordpress.com/ sola

        That is about what I have heard for cloudy day performance. (10% of peak)

  • Hans

    The article suggests that all solar cells need rare earth metals. This is not true. The majority of the solar cells are based on silicon, which is as abundant as sand. Rare earth metals are used for thin film cells (CIS and CdTe) which serve only a small part of the market.

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