Concentrating Solar Power (CSP) is the remarkably simple technique of arranging mirrors to concentrate sunlight and using the resulting heat to raise steam to drive turbines and generators, just like a conventional power station. CSP works best where there is direct sunshine and lots of it, as in deserts.Solar heat may be stored in melted salts (e.g. nitrates of sodium or potassium) so that electricity generation may continue at night or on cloudy days. And gas or biofuels may be used as a stop-gap source of heat when there is not enough sun.

With facilities for storing solar heat and hybridisation with other sources of heat, CSP can provide any combination of base load power, intermediate load or peaking power. This is a great advantage for power engineers trying to match supplies of electricity to demands for electricity which are constantly varying.

The Potential

The potential CSP plants have been supplying electricity in California since the mid 1980s, new plants came on stream recently in Spain and Nevada, and others are now being planned or built in many places around the world. The potential is enormous. Every year, each square kilometre of desert receives solar energy equivalent to 1.5 million barrels of oil. Multiplying by the area of deserts worldwide, this is several hundred times the entire current energy consumption of the world. It has been calculated that less than 1 per cent of the world’s deserts, if covered with CSP plants, would produce as much electricity as is now used by the whole world.

Given that not many people live in deserts, how could this solar bounty be used? One possibility is to move energy-intensive industries to desert areas and use the energy where it is produced. Or CSP may be used to generate hydrogen which may serve as a fuel for trains, cars, ships or even planes. But otherwise the best option is to transmit solar electricity directly to where it is needed using highly-efficient high-voltage direct-current (HVDC) transmission lines. With transmission losses at about 3 per cent per 1000 km, plus AC/DC conversion losses of 1 per cent or less at each end of an HVDC transmission line, there would, for example, be less than 10 per cent loss of power between North Africa and the UK.

Using low-loss HVDC transmission lines, it is feasible and economic to transmit electricity for 3000 km or more. It has been calculated that 90 per cent of the world's population lives within 2700 km of a desert and could be supplied with solar electricity from there. Thus CSP could become a major source of clean power for the whole world.

The DESERTEC concept

The ideas that I have sketched are part of the 'DESERTEC' concept, a set of proposals for Europe, the Middle East and North Africa (EUMENA) that has been developed by the Trans-Mediterranean Renewable Energy Cooperation (TREC), an international network of scientists and engineers. The proposals are described in detail in the 'MED-CSP', 'TRANS-CSP' and 'AQUA-CSP' reports prepared by a team of researchers at the German Aerospace Centre (DLR). Copies of these reports may be downloaded from www.trec-uk.org.uk/reports.htm.

The TREC group have given a lot of prominence to CSP, partly because it has not been very well known until recently and partly because its potential in desert regions is so large. But they recognise that there is also great potential for wind power in desert regions. And in the scenarios up to 2050 that are described in the TRANS-CSP report, imports of CSP electricity into Europe would provide up to 15 per cent of Europe's electricity and the rest would come from wind farms, wave farms, photovoltaics, tidal stream generators, and so on. In the TRANS-CSP scenarios, there would be no need for any new nuclear power stations and existing ones would be gradually phased out.