| Popis: |
T HERMIONIC conversion of solar energy to electrical energy is a commonly proposed means of generating sec ondary power in a space vehicle. The idea hinges on the use of a reflecting collector which concentrates solar energy onto the "hot" surface of a thermionic diode or series of diodes, where the conversion takes place. The heat thus accumulated passes through the converter and is "dumped" into space by the exterior radiating surface of the con verter package. The method of energy conversion is not of interest here. Suffice it to note that the temperature on the inner surface of the diode must be very high because the efficiency of the converter is sensitive to the available tem perature difference across the two diode plates. It has been found that the most practical form of concentrator which is capable of producing the necessary diode inner plate tempera ture is a parabolic mirror. Present thermionic converters have relatively low effi ciencies, but systems of the foreseeable future are expected to convert 10% or more of the solar energy entering the con verter into usable electric energy. To provide sufficient auxiliary power without exceeding space and weight limita tions, it is apparent that energy loss in the collector system must be reduced to an absolute minimum. The purpose of this paper is to discuss what these collector losses are, and to examine means of improving the overall collector efficiency. |
