The field of solar energy conversion has become an important discipline with a recognized potential to significantly contribute to the world supply of energy. It is diversified and encompasses a wide variety of disciplines - from mechanical engineering to physics, from biology to architecture, from ocean science to agriculture, from chemistry to atmospheric science, to name some of the major fields. It involves fields which have matured to the engineering aspects, such as the conversion of solar energy into heat or of wind into shaft work. It includes other fields in which more basic science research is necessary to unravel the micro-structures of nature, as, for example, for photovoltaic conversion or for certain bioengineering tasks. Several of these fields have elements which have been common knowledge for centuries but sometimes forgotten at times of cheap energy supplies, while others have barely started with first studies. Most of the fields have seen during the last decade a substantial advance in sophistication, in theoretical understanding, in demonstrated feasibility, in developing hardware, in field testing, with some moving into a phase of initial commercialization.