Solar energy, geothermal energy, gravitation

The following so-called renewable sources of energy will be taken into account: earth's core, earth's crust, river water, ground water, glacier ice, sea water, waves, tides, wind, ambient air, and solar radiation. Six of these eleven sources of energy will not be considered in the light of the basic conditions outlined above, as is explained in the report. The remaining five sources of energy are compared with each other in a detailed study with respect to the technical systems needed to utilize them, their economics as against competing sources of energy, availability, ecological impact, and their possible contribution in 1990 on the basis of today's energy requirement. It emerges from the study that by far the best possibilities are offered by ambient air, a source of energy simply over-looked in system studies so far. Since the direct or indirect use of solar energy is not feasible either technically or physically without the application of electricity, particular importance is attached to the further expansion of nuclear power also in this regard. (orig.)