Wednesday, August 04, 2004

The prospect of a solar hydrogen economy

Hydrogen offers interesting application benefits compared to natural gas and petroleum. But it cannot be found in nature in its pure form. Instead, it must be won through complex processing of fossil fuels or by electrolysis from water. Electrolysis requires electricity, which could be produced from renewable energy sources, but also by nuclear power stations. Its production from fossil fuels causes global warming and is not sustainable. Frequently, the discussion comes back to generating electricity from solar radiation in North Africa, for example in the Sahara. Hydrogen would then be transported to Europe and used here to provide heat, generate electricity and as fuel for vehicles (’solar hydrogen economy’).

The prospects for such a solar hydrogen economy are small. In particular, it makes little sense to convert electricity - the highest quality form of energy - into hydrogen, which is then re-converted into electricity or heat at the point of use. This adds another step in the energy conversion chain with additional costs and above all additional energy losses.

Repeatedly, projects have been presented to produce electricity in the desert, and use this electricity for the production of hydrogen for Europe. They fail because of extremely high costs and technical difficulties, for example the supply of high-purity water in the desert, needed for the electrolysis, or the transport of hydrogen to Europe with reasonable losses. If one would succeed - at a high cost - to produce electricity from solar power in the Sahara, then it would make much more sense to use low loss HVDC (High-Voltage Direct Current) transmission. This would allow direct use of this electricity, rather than through the double conversion via hydrogen.

At best, the use of hydrogen as energy source could offer a meaningful alternative for mobile applications, e.g. motors or fuel cells in passenger cars, provided cheap production and storage facilities are available. The production from natural gas could be defended as a temporary solution, but is not sustainable in the longer term. The production by electrolysis using solar electricity is theoretically conceivable, but might remain limited to special cases for cost reasons (solar electricity will be much too expensive for a long time). Nuclear energy and (outside Europe) hydropower offer the best long-term prospects for the production of electricity needed for electrolysis.

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