Own Transcript of the Interview with Dr. Gerhard Knies, BBC Radio 4, "The World Tonight".

BBC: Forget oil, forget gas, forget nuclear. The energy source of the future is solar. We are not talking a couple of panels on the roof to heat the bath water - we are talking a desert full of mirrors. Its part of a plan, put to the German government today in a report on alternative energy sources for Europe. The report suggests a big expansion of the type of solar power that is already being set up in Spain, Australia and Nevada. But this would be based in North Africa and for general European consumption. It is called Concentrating Solar Power - and one of the scientists who wrote the report, Dr. Gerhard Knies, told me how it works.

DR. GERHARD KNIES: Well, when you concentrate light - either with a lens or with a mirror - then you get a hot spot and there you can generate, with sunlight, very high temperatures: 200, 300, 400 degrees Centigrade. And that is enough to boil water. So, if you boil water, you get steam and with the steam you drive a steam turbine and that is connected to an electric generator and then you get electricity out.


BBC: What would that look like? Fields of mirrors?

KNIES: Yes, this would be fields of mirrors. If you could think of long troughs and they are like mirrors with a width of about 10 meters and the light which gets into that trough is then concentrated by reflection on to a pipe and so all the sunlight will be absorbed and then the water begins to boil.


BBC: How much space would this take up?

KNIES: Well, a typical size is may be 300 by a 1000 meters. So if you want to, say, power all Germany with such kinds of mirrors, you would need an area with the size of the two cities, Berlin and Hamburg.


BBC: Now, you are talking about doing this in the desert in North Africa for example. You will then have to get the energy from there to Europe - because you are talking about Europe's energy needs.

KNIES: Yes. Actually, North Africa is already connected with electric power cables to Europe. So this has to be expanded. So they go through the sea (through the Mediterranean or through the Straits of Gibraltar) and we make use of the high-voltage trick. So if some energy is transmitted with a power line, if you raise the voltage by a factor of ten, then you have only one tenth of the losses.


BBC: Is this commercially viable?

KNIES: Yes. Such cables are already in existence: they are used from Norway to Germany, they are used in dozens of places on the earth already. If you want to transmit power either through the sea or when you want to transport power over distances of more than 500 to 1000 kilometres - then it pays off. Then such high tension cables are economically the better choice.


BBC: Presumably, building great fields full of mirrors and the technology that goes with them is very expensive, though?

KNIES: Of course, it's expensive but fossil fuels are also getting expensive. So the point is to see whether heat from the sun is more competitive than heat from fossil fuels. And right now, it costs 50 to 60 dollars to obtain solar heat equivalent to the heat that one would get from burning a barrel of oil. So this technology could compete with oil at that price. Now everybody feels that fossil fuel prices are not only higher, but may also keep going up to unknown heights. And so it is much safer to go with solar energy.

Source:
TREC 2006