Today’s studio guest is Professor Bernd Rech from the Helmholtz Center Berlin.  DW: Professor Rech, southern Spain has lots of sun, but it can get pretty dusty when the wind is blowing. Can all that sand and dust destroy a solar power plant? Bernd Rech: It can destroy a solar power plant, but in general I would say the engineers have taken care and it will work. And also you have to look where you will place your power plant. Now as solar energy generation becomes more cost-effective, the higher its yield. How high can we go? In principle, we can go up to 80 percent in conversion efficiency. In the lab we have shown up to 40 percent. But in typical applications today, they are in the range of 10 to 20 percent. So there is still a lot to do, but it’s already much better than nature. And is that a purely technological problem? It’s a technological problem, it’s a fundamental problem, from some side, but it’s also an economic problem. So the most efficient solutions are not the most cost-effective solutions today. All right – it’s a problem in a good deal of fields, actually. So if my electricity comes from a solar power plant, can I watch TV even when the sun isn't shining? If it’s photovoltaics, you can only watch TV when the sun is shining. If it’s a solar terminal plant, then there’s some storage included. So it will depend on the system that you use or if you have storage at home. What would you say is the best strategy for this type of energy generation? Using these huge central power plants, or small decentralized facilities? I think it will be a combination. So you should use as much as possible decentralized. But certainly an international or a big grid would help a lot. Why isn't solar power more prevalent here in Germany, and what can we do to make it more popular? In Germany it’s quite popular now, and it’s increasing. But I think the great future is in countries which have much more sun than in Germany. And I think the oil pric...