Dreaming of Saharan Solar Power

It sounds like a pipe dream, but it is technically feasible. Solar thermal power plants in the Sahara could provide electricity for all of Europe. So where's the catch? Steffen Leidel reports

Tuareg in the Sahara (photo: dpa) — The Sahara is barren and low in natural resources. But it does have plenty of sunshine. Researchers and developers are trying to turn the desert rays into electericity

As long as the sun shines, the world has no energy problems, at least in theory. Six hours of sunshine in the desert regions of the world are enough to cover the world's energy needs for an entire year.

And for over 20 years scientists have been dreaming of harnessing the constant blaze of the desert sun as a source of power.Finished concepts are already available. In 2003 the Club of Rome introduced its Desertec concept.

In its vision, Middle Eastern and North African states would produce power with the help of alternative energy sources such as solar thermal power plants and wind parks, initially for the producer states themselves. Beginning in 2020, this power would be exported to Europe as well.

Negligible line loss

According to the calculation of the Deutsches Zentrum für Luft- und Raumfahrt (DLR), it would require an investment of around 400 billion dollars by 2050 for solar thermal power plants to cover 15 percent of Europe's electricity needs.

Parabolic mirror (photo: DW/Leidel) — The parabolic mirror concentrates the sun's rays on the absorber tube, which heats up

"That sounds like a lot. But by that time, the investment and operation costs for the solar thermal power plants would be lower per kilowatt hour than for power plants using fossil fuels", says Hans Müller-Steinhagen from the DLR's affiliate, the Institut für Technische Thermodynamik in Stuttgart.

According to the experts, there are no technical problems associated with transmitting the power to Europe. The solar power would be transmitted across the Mediterranean as direct current rather than alternating current. This would mean that losses en route would be much lower than with classic high voltage cables.

Solar energy at night

In contrast to photovoltaic systems, solar thermal power plants do not transform solar energy directly into electricity; first, it is stored as heat. This is done using the so-called parabolic trough technology.

Enormous parabolic mirrors concentrate the sun's rays on a so-called absorber tube in which special thermal oil is heated to a temperature of up to 400 degrees.

The hot oil is then used to create steam which drives the turbines producing electricity.The advantage over photovoltaic technology is that solar thermal facilities can use special heat reservoirs to provide electricity at night as well, when the sun is no longer shining.

The output of these facilities is considerable. A power plant with an area of 40 by 40 kilometers would be enough to cover all of Germany's electricity needs.

Spain is number 1

Solar thermal energy is currently experiencing a boom. At this time there are 80 projects worldwide for the construction of such solar power plants, says Lars Waldmann, spokesman for Schott Solar.

Based in Alzenau, Lower Franconia, the company is the global market leader for absorber tubes. The most important markets are the USA and above all Spain, where there are currently around 30 projects for solar thermal facilities.

Schott provided absorber tubes for the world's largest project as well. In Granada in the South of Spain three solar thermal power plants are currently under construction.

The first is expected to go into operation this year, providing 200,000 people with electricity. "Spain has an outstanding infrastructure for solar thermal energy", says Waldmann.The boom was triggered by the law guaranteeing feed-in compensation of around 20 cents per kilowatt hour.

The first projects in North Africa

Conditions like these do not yet exist in North Africa. However, Waldmann sees a great potential for solar thermal power plants in the region. Feelers have been put out to Morocco.

Solar tower (photo: DW/Leidel) — Solar tower at the DLR testing grounds near Almeria. The sun's rays are concentrated at the uppermost point, creating an updraft which powers the turbines

"There are discussions and relatively concrete plans, even if no ground has yet been broken", says Waldmann.Alongside Morocco, Algeria, Libya and Egypt have also expressed interest in solar energy. The first power plants have already been built, according to DLR expert Müller-Steinhagen.

"For these countries, it is a market of the future. They can cover their own electricity needs, and at some point they can export as well. Besides, solar thermal facilities can also be coupled with the desalination of sea water", says Müller-Steinhagen.

But one great obstacle remains. Enormous initial investments are required to construct solar power plants: "It's as if you were to build a coal power plant today and at the same time you had to buy the coal for the next 25 years," says Müller-Steinhagen.

These countries cannot finance these investments by themselves. In this respect there is still a need for political and economic clarification, agrees Winfried Speitkamp, Africa expert from the University of Gießen and co-organizer of an interdisciplinary working group on solar energy partnerships with Africa.

Above all, he feels that the planned Mediterranean Union has the obligation to work out a joint approach on the issue, one that must take social and cultural aspects into account as well.

"As soon as people get the message that solar energy is a money-making opportunity, the threat of conflicts emerges." In this respect there is no difference between sun and oil.

Steffen Leidel

Translated from the German by Katy Derbyshire

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