ENVIRONMENTAL CONCERNS Availability of clean, safe and affordable energy to all citizens in sufficient quantities is a prerequisite for a sustainable society. In addition, the world energy supply should be sustainable in itself, meaning that the use of finite fossil resources has to be gradually replaced by the application of renewable energy technologies and that greenhouse gas emissions have to be decreased substantially. To ensure the security and sustainability of future energy supply in Europe, we need diversified and renewable energy sources. The increasing share of renewable energy is a necessary ingredient of greenhouse gas mitigation policies, along with a strong requirement to improve energy efficiency. Changing living standards and patterns to sustainable ones and ensuring the protection of the environment are now recognized as major policy goals. Presently almost one-third of the world population does not have access to commercial energy (in particular, to an electricity grid), which seriously hinders development, is linked to poverty and causes a variety of health problems. In spite of the recent success of renewable energies in some areas, the growing global energy consumption still causes an increase in the consumption of fossil fuels and associated CO2 emissions. This highlights the urgency to develop and implement renewable energy technologies that can be made available to all people in urban and rural areas and that can make a substantial contribution to the increasing energy demand.