Professor Volker Quaschning is a researcher on renewables and he comes from the University of Applied Sciences in Berlin (HTW).DW-TV: Professor Volker Quaschning, when in Germany the wind blows very strongly it can already overwhelm the electrical power grid. How come the big energy suppliers didn’t invest in better grids a long time ago? Volker Quaschning: So, the grids are constructed for the distribution of the energy from central power plants, such as coal power plants or nuclear power plants to the consumers, so in the future it will be totally different. So we have distributive renewable energy systems, solar systems, on each roof and we have to change the grid. But the problem is that renewable energy system they compete with the old power plants, with the nuclear and coal power plants and the owner of these power plants they are not interested in constructing new power lines.   So, if we turn off the nuclear power plants nowadays that's actually a good thing for the renewables? Yes. And you think that is possible, to turn them off? Yes, of course. At the moment we see that we are going fast into the renewable energy technologies. So if you are looking to the 90s, we have had about three percent of renewable energy electricity in Germany. Last year we had 17 percent. And we'll see that it will be possible in 20 or 30 years to install 100 percent of renewable electricity generation in Germany. You say it will be possible within a few years, 100 percent. How is that supposed to go? We have to keep the fast growing rates of the renewable installations. So, for example, last year we have produced two percent of photovoltaic power in Germany, and more than seven percent of wind power. And we see that we can install about 20 percent photovoltaic power within the next 20 years. It's no problem; we only have to keep the installation rates we had in the last years. You seem very confident. Already today we have 20 thousand wind tu...