Hydrogen from the sun
A company from the UK announced in June 2002 that they want to introduce a new cost-effective system for phovoltaic H2
production to the market soon. The system combines the generation of electricity from sunlight with the electrolysis of
water to separate hydrogen and oxygen in a single process.
According to the Hydrogen Solar Production Company (H2SPC), the new technology is simpler and less expensive than
conventional silicon solar cells. With this, it was possible to produce hydrogen onsite on a sufficient scale to meet the
needs of an individual car, thereby avoiding the costs and challenges relating to the transportation of the gas.
The process relied on nanocrystalline semiconductor materials whose molecular structure gave them an enormous internal
surface area. Oxides of titanium, zinc, tin or niobium were used which formed crystalline arrays. The minute pores between
the crystals were then filled with a semiconducting or conducting medium. As a result an extremely fine network was formed,
providing for the substances' conductivity. Dye could then be absorbed into the structure to enhance the range of light
wavelengths which can be "harvested".
H2SPC says they are working with a "tandem cell" approach, using two thin layers of different metal oxides for the two
electrodes of the cell. This helped to further enhance the range of wavelengths absorbed. The front cell intercepted at the
blue end of the spectrum, setting up the voltage. The green and read part of the spectrum were intercepted by a second cell
which is placed behind the first one, making the electrones for H2 generation available.
H2SPC believes to be able to
demonstrate the process on a commercial scale within the next six months. The company holds the rights to this technology
which was developed by Prof. Michael Graetzel from EPFL in Lausanne.
Source: H2Report, June 2002
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