ABSTRACT
The planet earth traveling through space is richly endowed with raw materials and energy resources. Planet earth can be seen as a spaceship where the inhabitants have to contend with the same problems of survival as present-day astronauts. Direct solar energy is particularly interesting, since it is picked up continuously as the earth travels through space. The solar power reaching the earth's surface is 10000 times greater than the average power currently generated by man. In overall terms, therefore, the world's consumption of energy is still comparatively moderate. All industrialized countries are channeling considerable effort into energy research and into the development and demonstration of the necessary technologies. The production of synthetic fuels from coal and from oil shale rose in the seventies to much publicized pilot projects supported by some of the major oil companies. Geothermal heat is another interesting energy source, since, in principle, it can be tapped nearly everywhere on earth.
