Sustainability means using resources in such a way that future generations are not put at a disadvantage 1 . But mankind has gone, especially since the Industrial Revolution, from a sustainable towards an exhausting way of consumption. In particular to satisfy the increasing need for energy, resources that have been built up in millions of years are abused in a comparatively short period of time. If we keep on going without searching for alternatives, we leave our descendants with the problem of keeping up the standard of living we introduced without these resources. Moreover might the intense use of fossils and the inherent emission of greenhouse gases have a detrimental influence upon our environment.
Nuclear energy is no acceptable alternative.
Apart from problems with the storage of nuclear waste, reactor catastrophes have shown that the inevitable residual risk is far too big to be answered for. The only energy source that can cope with the increasing demand of mankind in the long run is the sun. Apart from geothermal and tidal energy, which cannot satisfy our demand, it is the only source being fully regenerative. It is nearly inexhaustible, the energy impinging on the earths surface during one hour being enough to satisfy the current annual world energy consumption 2 . Since the major drawback of solar energy is its intermittent availability, means to store it have to be found.