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Saturday, 15 October 2011

Produce Hydrogen Using Solar Energy

The most abundant renewable energy source is undoubtedly solar energy. The sun sends to earth a power of 90,000 terawatt (TW) compared to 14 TW consumed by the world's population, and will continue to do so for several billion years. However, because of its intermittent nature and low density, it is essential to be able to store and concentrate the solar energy as fuel.
One of the most attractive possibilities of doing this is to turn it into hydrogen, a clean fuel (its combustion produces water only) with a high energy density (2.7 times more than oil), although its gaseous state at an ambient temperature and pressure makes its storage and transport difficult. This hydrogen is then used to power fuel cells to generate electricity. There are several ways to obtain hydrogen from the sun. The first is to perform the water electrolysis from the electrical energy supplied by photovoltaic panels. But another method, inspired by biological processes, could change it in a more or less near future, our energy supply.

The conversion of solar energy into fuel is indeed beautifully performed by the living world, including plants, through photosynthesis. Green plants use the sun continuously to convert water and carbon dioxide (CO2) into high-energy molecules such as sugars or fats. Well, they are not the only ones. Some microorganisms such as unicellular algae or cyanobacteria have the ability to make a simple water photolysis.

Clearly, they use solar energy to "break" the water molecule into oxygen and hydrogen. The water does not absorb photons (or "grain" of light) from the Sun, this veritable “force tour" is by means a molecular systems that’s incredibly sophisticated and effective to collect and convert solar photons into energy efficient Chemical photosystem. The produced energy can be used for the oxidation of water into oxygen and hydrogenises for the reduction of water into hydrogen. 

What is remarkable here is that these two enzyme systems are used as catalysts abundant metals such as manganese, nickel or iron, while the electrolysers and fuel cells today rely on noble metals such as platinum, which is very expensive and scarce in the earth's crust. We often forget to say that there is no future for a hydrogen economy if it does not solve the problems of catalysts.

With more knowledge about these natural and spectacular developments of chemistry, many "bio-inspired" chemists believe that artificial photosynthesis say that the implementation of the direct conversion of solar energy into fuel systems, synthetic unnatural, is within reach and should be developed. This particular fact was evidenced by some major research programs in the United States, involving the Department of Energy (DoE) or prestigious universities (CalTech, MIT), Europe (projectSolarH2) and in many European countries(EPFL, Switzerland).

Basma - Green Energy International Correspondent - 15th Oct 11

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