ABSTRACT
The energy spectrum of the sun has its density maximum at 0.5 μm wavelength or at 2.5 eV with a steep rise from 0.3 μm to this value. From the maximum down to longer wavelength the energy has a quasi-exponential fall-off with an extended tail into the long wavelength infrared range. Heliotechnology can be subdivided into "heliochemical", "helioelectrical", and "he-liothermal" processes. Photosynthesis is a heliochemical process and has been the basic plant process on the globe for billions of years. Passive systems in which building elements are heated by solar radiation can provide heat within living rooms. This combined with an electrical heat pump can effectively decrease the need for gas, coal, or oil heaters. The thermal system is similar to all thermal solar systems for energy generation. For example, the solar pond power plants operate with two layers of water with different salinity at different temperatures.
