"Solar Power will become much
cheaper"

Mr. Pitz-Paal, you predict a bright future for "Concentrating Solar Power Technology". What does that mean exactly?

What technologies already exist for this purpose? How do they differ from each other?

In the case of parabolic trough collectors, the concentrator is a trough in the shape of a parabola, along the focus line of which a pipe is heated. The new linear Fresnel systems are closely related to these. They represent a simplified approach - the parabolic trough is divided into slices, so to speak, and arranged on one plane. Then we also have the socalled tower power plants with central receivers. In this case, mirrors are moved to follow the sun and concentrate the radiation at the top of a tower equipped with a heat exchanger. There is also a system with parabolic dishes fitted with a radiation receiver at the focal point which passes the solar energy directly to an interfaced engine. Collectors of this type, however, can only generate a few tens of kilowatts.

That is not very much. Which technologies are suitable for large-scale power plants?

Parabolic trough collectors are already relatively well established. They have been used commercially in the USA since the mid-80s. Early this year, the first commercial tower power plant went into operation, a 10 megawatt plant in Seville. All the other technologies are still in the pilot phase - we cannot really speak of commercial use yet.

What does the economic viability of solarthermal power plants depend on?

One essential factor is the location - the incident solar radiation which occurs there. The more radiation, the better. The differences are great. In Germany, solar radiation is not even half as high as in southern Spain. In the Californian desert it is another thirty or forty per cent higher - three times as high as in Germany in other words. That makes power generation much cheaper. Another important factor is the size of the solar power plant. The larger the plant, the more viable. And then, of course, the technology is also crucial - it has to be as inexpensive as possible while nevertheless being efficient. If higher temperatures can be achieved at lower cost, the viability can be increased. That is exactly the aim of Fresnel technology.

How realistic are solar power plants in Africa? The sunshine is very reliable there.

There have already been invitations to tender in various African states. In Algeria, construction of the first power plant is just starting. Morocco and Egypt will probably conclude contracts this year. The potential in North Africa is enormous. There are really large open spaces there, with very high radiation combined with a rapidly growing demand for energy. Particularly in the case of Africa, it is important that solar technology be developed quickly and for it to become competitive. This is due to the fact that in Africa, unlike here, there are very few subsidies for regenerative energy.

If we bundle solar power generation for Europe in that region, are we not making ourselves as dependent in future on the sunny countries of Africa as we now are on the oil states?

But renewable resources are still relatively expensive to produce, so there is littel demand. According to DLR forecasts, production costs for solarthermal power plants will be halved by the year 2020. How will this be achieved?

By the mass production of components, by the construction of very large plants and by the achievement of better efficiency by means of higher temperatures -for example by direct steam generation using Fresnel technology - and by the integration of large thermal energy storage units. All of these factors are already feasible. But until we have reached that stage, we will be dependent on subsidised markets.

Do firms who invest now have to accept that they will make losses in the initial phase?

I think not because, fortunately, there are feed-in tariffs and other incentives. The market introduction of solar technology has political support, the additional costs for renewable energies in Spain and Germany, for example, are borne by all power consumers - an essential mechanism which costs the individual citizen very little but which will benefit national economies in the long term, as prices for fossil fuels are rising.