Solid-State Conversion Concepts

This paper presents a brief outline of the various solid-state energy conversion concepts currently under development by the Air Force. Much of the paper will be on the developments in solar cells and thermoelectrics with only a brief look at piezoelectrics, pyroelectrics, ferroelectrics, the Nernst effect and nuclear photon conversion. These conversion concepts are discussed from the stand-point of present capabilities to satisfy aerospace vehicle electrical power needs together with the author's estimates of possible performance if the concepts are completely developed. The energy sources considered are solar, nuclear, chemical and acoustic with emphasis on solar and nuclear. Research and development is being accomplished in the areas of solid-state energy conversion today because these materials and conversion mechanisms are most nearly ideal for unattended operation in space. That is: they are relatively static (no moving parts); are non-volatile exceptat high temperatures; are reasonably resistant to the space environment; and generally have long lifetime possibilities. The long range objective of the applied research programs in these areas is to acquire the technology for obtaining reliable, highly efficient, long lifetime, light weight, and low cost energy conversion systems for aerospace vehicles. The lifetime requirements are for essentially unattended operation for two years by 1965 and for five to ten years by 1970. Generally high watts/lb, reliability, and long lifetime are the primary objectives, and efficiency and cost are of lesser importance.