DW-TV: Professor Volker Quaschning from the University of Applied Sciences in Berlin is an expert on renewable energies. Will the plastic solar cells be a major breakthrough for solar energy?

Volker Quaschning: There could be a breakthrough in the future, but today, the crystalline silicon solar cells - they are the major technology, they cover more than 90 percent of the market. And 10 years ago, we said other technologies such as thin-film silicon solar cells or other thin-film technologies, or even the organic PV will do the race. But today the race is still open, and we have a large cost-reduction in the past, so the crystalline silicon solar cells, they came down for $60 per watt in the 1970s to less than $1 today, and so the race is still open, I would say.

Wow, and can that drop of prices really be kept up?

Yes, we have to, because we would do the energy revolution, so we would like to come to 30 percent of solar technology within the next 20 or 30 years, and this is only possible if the costs go down by the factor of two or three, then it would be possible. Which technology can do this - it's open.

Right now we have about 3 percent that solar energy accounts for the electrical power in Germany. Where do all the roofs come from to put up all these solar cells?

We're looking in the cities such as Berlin. You have to look for the solar systems - you do not see so many solar systems. In southern Germany, it's a little bit different. But we room for it to double, or even to tenfold, the installation of solar systems, so it's no problem to install them here.

The goal is to actually change our energy production by 2050 completely to renewables. Are you optimistic that we can reach that goal?

Yes, we have to reach it, because we have the change of climate - if you want to avoid different damages, we have to achieve the goal 2050. If we do not do that, we have a big problem, so we have to do it, and I think we can do it.

You say we can do it, we have to do it, but what's happening at the moment is that we import nuclear power from abroad and that we also are about to build new coal-fired power plants here in Germany.

But we also have a high increase in solar installations. Ten years ago, solar technology was not really important for Germany. Today we have 3 percent, and we expect 30 percent in 20 to 30 years. It's possible. And the old technology, they will not survive.

Clean driving is also an important topic. One way to do that is by using hydrogen. Carbicol seems to be a nice solution, but after all, hydrogen is not that explosive. Do we really need a solution like that?

The answer is very difficult because we have no good solution for the transportation sector at the moment. So for electricity production, we know the main technologies - solar and wind energy - but in the transportation today, we are developing battery systems. The problem is that the range of a battery car is limited, so we need other technologies for long distances. That could be the hydrogen solution. But today, hydrogen is very expensive, and we have to produce the hydrogen from carbon dioxide-free fuel, electricity or sun or wind energy.

As you said, there are quite a few different solutions. There's also lots of different developments. They're also putting much energy into developing better batteries. So are we not wasting resources on too many different technologies?

Today we do not know what would be the solution. If we know the solution, we only have to do the development in one solution. But today, the race is open, and we have to look on the battery systems - the possibility or advantages of battery systems are very good - but they have the problems, and if you cannot solve the problems, hydrogen has potential. And perhaps both technologies will be important for the future.

So we don't really know what the future of energy supply will look like, do we?

We do not know, but we have solutions today, and we can solve the problems.

(Interview: Ingolf Baur)