intended to generate a given amount of power -from sunlight. This is because every PU system includes components whose cost is proportional to the area ATTACHMENT : covered by the system and this area is inversely proportional to the conversion efficiency of the cells. For single solar cells, the limit theoretical efficiency lies between 25 and 30Z. Cascade or tandem cell systems, which consist of a number of solar cells made from photovoltaical 1y active semiconductors (PUAS) having appropriately selected bandgaps in the range 1.0 eU to 2.2 eU have substantially higher theoretical limit efficiencies. For an "infinite" number of cells made from an "infinite" number of PUAS and maintained at 300 K, this flat plate limit efficiency is 687. while the high concentration ratio (10A4) limit efficiency is around 867. For a cascade of twelve cells made from twelve properly selected PUAS, the flat plate limit efficiency i“ around 50Z for 300 K. This paper presents an out1 ine of a research program which would result in cascade solar cells capable of such high efficiencies. It shows how to select PUAS alloy systems having the required range of bandgaps. It describes the optimized "unit cell" of such a cascade stack and discusses requirements other than bandgap which must be satisfied by the PUAS intended for cascade cells. A brief review of the current status of research in this area is included. Title: Thermophotovoltaic power sources for space applications Source: Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Uirginia, USA, Feb. 22-25, 1982. (Paper No. UI-3) Authors: Loferski, J. J.; Uera, E.; (Brown University, Providence, Rhode Island) Severns, J. G.; (U.S. Naval Research Laboratory, Washington, D.C.) Keywords: space energy conversion, solar cells, Abstract: This paper explores some aspects of solar thermophotovoltaic (TPU) power sources for space applications. Such a TPU power supply consists of a mirror for concentrating sunlight onto an absorber whose temperature is raised into the 1500 C to 2000 C range. The absorber then becomes a radiator whose ATTACHMENT : energy output is directed onto solar cells lining a chamber surrounding the radiator. The optimum semiconductor for TPU systems depends on the temperature of the absorber but since the radiator temperature is much lower than the effective black body temperature of the sun, the band gap of the preferred photovotaic material is closer to that of germanium (0.7 eU) than that of silicon (1.1 eU). The paper discusses optimum design Ge cells; cascade solar cell combinations which lead to higher efficiencies than those obtainable from Ge alone; the use of rare earth oxide coatings on the radiator to shift the output to match the peak response of a Ge cell, etc. Calculations show that for radiator temperatures in the 1500 C to 2000 C range and power densities on the PU cells of about 25 W/cm(cm), solar energy conversion efficiencies in excess of 207 are possible. A preliminary design of a 10 kW module is discussed; larger power levels are achieved by combining the appropriate number of such modules to reach the desired power level . Among the advantages of TPU systems are radiation hardness because the PU cells are mounted inside a sturdy container and the possibility of thermal energy storage so that the system can continue to function even after solar energy input is cut off. Title: Solar energy conversion for space power systems Source: Proceedings of the AFOSR Special Conference on Prime-Power for High Energy Space Systems, Norfolk, Uirginia, USA, Feb. 22-25, 1982. (Paper No. UI-4) Authors: Holt, James F.; (Air Force Wright Aeronautical Laboratories) Keywords: space energy conversion, solar cells, Abstract: The Space Transportation System makes possible operating in space various satellite systems using 50kW and above, of electrical power. These systems will be launched and boosted into orbit by the Orbiter and such boosters as the Inertial Upper Stage... ATTACHMENT : Solar power is especially suited for space based radar and space communications systems. Higher power is more urgently needed in the high al t i tude orbits. Recent concepts in solar cells, batteries, and power conditioning will enable the development and operation of up to 30kW continuous electrical power in higher orbits well before year 2000. Before 1990 continuous power of 10 to 15kW levels are possible operating in the higher orbits. This forecast is based upon thin (2-mil) silicon solar cells, thin (2-mil) gallium arsenide solar cells, nieke 1-hydrogen and liquid metal-sulfur high energy density batteries, and 3-mil multi-band gap advanced solar cells, in that time sequence. The present power per unit weight would be increased from the present 1-2 watts/lb to 12 W/lb for the total power system. However, in order to appreciably increase the power capability of systems
RkJQdWJsaXNoZXIy MTU5NjU0Mg==