Sunday, December 14, 2008

The Schulten method and Photocatalytic method




The Shulten method is based on decomposition of water composed of four steps of closed cycle. The highest temperature needed to perform this method is 927 degC which can be obtained without any trouble. During this method a cycle of reactions between methane (CH4), water (H2O), carbon monoxide (CO) and some others substances occurs. The efficiency of whole cycle is 40-45per cent which is quite satisfying.


Photocatalytic method
Transforming solar energy in the solar cells into electricity, which flew through the cover made of rhodium, molybdenum, wolfram and presently porphyrynium compounds (nearing in structure to chlorophyll) decompose water not electrolytic but catalytic.
The photocatalytic process uses semiconducting catalysts or electrodes in a photoreactor to convert optical energy into chemical energy. A semiconductor surface is used to both absorb solar energy and to act as an electrode for splitting water. This technology is still at an early stage of development. The most stable photoelectrode is TiO2; however, this material has a conversion efficiency of less than 1%. New materials, which require no external electricity should be studied. In order to reduce corrosion, ultra thin layers of protective material on the semiconducting surface could be coated. Investigations also can be directed toward in the areas of low cost systems, multiple layers of organic dyes and thin film semiconductors.
The Hydrogen produced is very pure and can feed electronic fuel cells.In a single step, solar energy is collected and transformed into electric charges, which split water at two separate points (the anode and the cathode) releasing two separate gas streams of oxygen and hydrogen respectively. Thus the need for gas separation is avoided.The front cell intercepts at the blue end of the spectrum, using a partially transparent crystalline thin film. The remaining part of the spectrum of white light is intercepted by a second cell (placed behind the first one), thus increasing the efficiency of the device beyond that of a single cell unit.

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