Thin-film photovoltaic solar array parametric assessment

This paper summarizes a study that had the objective to develop a model and parametrically determine the circumstances for which lightweight thin-film photovoltaic solar arrays would be more beneficial, in terms of mass and cost, than arrays using highefficiency crystalline solar cells. Previous studies considering arrays with near-term thin-film technology for Earth orbiting applications are briefly reviewed. The present study uses a parametric approach that evaluated the performance of lightweight thin-film arrays with cell efficiencies ranging from 5% to 20%. The model developed for this study is described in some detail. Similar mass and cost trends for each array option were found across eight missions of various power levels in locations ranging from Venus to Jupiter. The results for one specific mission, a main belt asteroid tour, indicate that only moderate thin-film cell efficiency (-12%) is necessary to match the mass of arrays using crystalline cells with much greater efficiency (35% multi-junction GaAs based and 20% thin-silicon). Regarding cost, a 12% efficient thin-film array is projected to cost about half as much as a 4junction GaAs array. While efficiency improvements beyond 12% did not significantly further improve the mass and cost benefits for thin-film arrays, higher efficiency will be needed to mitigate the spacecraftlevel impacts associated with large deployed array areas. A low-temperatur e approach to depositing thinfilm cells on lightweight, flexible plastic substrates is briefly described. The paper concludes with the observation that with the characteristics assumed for this study, ultra-lightweight arrays using efficient, thinfilm cells on flexible substrates may become a leading alternative for a wide variety of space missions.