Photovoltaic Power Options for Mars GEOFFREY A. LANDIS1 AND JOSEPH APPELBAUM" SUMMARY Mars exploration will require power systems to operate on the Martian surface. One power system is a photovoltaic array. The properties of Mars relevant to photovoltaic array performance are surveyed. Several types of solar cells usable in a photovoltaic array are detailed and analyzed, and possible applications on Mars discussed. The applicability of photovoltaic technology to manufacturing methane propellant from Mars carbon dioxide is analyzed. Introduction Mars is a challenging environment for the use of solar power. In addition to the lower sunlight intensity compared to Earth orbital applications, the twelve-hour night (although not as severe as the moon's 14 day darkness) requires that any solar power system include a large storage system. Wind, low temperature, sand, dust, and corrosive peroxide-rich soil, make the Martian surface an environment one could hardly call benign. For any manned mission, a significant priority for a power system will be reliability and absence of dangerous failure modes. Due to the high price of transporting materials to Mars, an additional priority for a surface power system will be low weight. Photovoltaics provide low-cost power with high reliability and no moving parts. They have powered the space program since Vanguard, and there is every reason to believe they will play a major role in the coming exploration of Mars. Sunlight on Mars Ilie solar intensity on the surface of Mars is considerably lower than that available in Earth orbit. This is primarily due to the greater distance of Mars from the Sun. The average solar intensity at the orbit of Mars is 590 W/m2 compared with 1370 W/m2 in Earth orbit. The eccentricity of Mars' orbit results in a variation in intensity of about ± 19% over the course of a year. Scattering and absorption of light by dust in the Martian atmosphere also decreases the sunlight available. The availability of sunlight on Mars has been reviewed elsewhere [1,2,3] and will be only briefly discussed here. Sverdrup Technology, Inc. Work supported under NASA contract NAS-33-25266. National Research Council Resident Research Associate at NASA Lewis. Permanent address: Tel-Aviv University, Faculty of Engineering, Ramat-Aviv 69978, Israel. Work supported under NASA grant NAGW-2022.
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