IV-B-lb. Solar Cell Blankets and Concentrators - James L. Cioni Propulsion and Power Div. Concept Derivation In deriving a reference configuration for the photovoltaic blankets and the concentrators, two basic approaches were employed. First, a series of parametric analyses were performed to determine the sensitivity of the system to configuration and basic device performance characteristics. Second, an assessment was made to determine what levels of technological achievement are necessary or probable between now and the 1990's time frame of the subject SPS. Among the set of parametric analyses first performed were analyses dealing with temperature and relative performance associated with various levels of solar concentration. From these relative performance results, a configuration was established for which sizing and performance analyses could be performed. In establishing the final reference system for the study, the driving guideline was to minimize the impact on total system cost. To arrive at such a point the system analyses had to be iterated several times since the relative contributions to cost from (a) hardware development and manufacturing cost, (b) transportation cost associated with weight and volume of the hardware, and (c) operations and maintenance costs were unknown. In arriving at the system parameters (weight, performance, and cost) an attempt was made to choose levels of achievement that are within the realm of reason, though significantly advanced in today's content. Thus, in any specific area it might be possible to predict higher potential for achievement. Parametric Performance Past experience in photovoltaics leads to the assumption that there are two potentially viable candidate photovoltaic devices to use in a concentrated solar array. The two, silicon and gallium arsenide solar cells, have potential for high efficiency and long life on an orbital station. The first step was to make relative comparisons of these two types of solar arrays. Figures IV-B-la-1, 2, 3 show the relative characteristics derived in the study to compare and contrast Si and GaAs arrays. The derivation of the figures is based on the following assumptions: 1. GaAs and Si solar cell blankets behave the same thermally; i.e., for a given concentration ratio the equilibrium temperature will be the same. 2. The basic blanket mass per unit area for each type cell would be the same and the blankets would be of the same construction type. 3. High volume production Si cells will be less efficient than GaAs cells under the same production levels. (Si = 16% GaAs = 20%).
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