2) The requirement to supply a continuous power results in a high mass penalty for long absolute eclipses and becomes unacceptable if these extremes occur rarely during the lifetime of the system. Design and Overall System Optimization The Influence of the Changed Solar Flux Figure 9 shows the solar flux distribution along the absorber walls of a cylindrical receiver resulting from a parabolic minor. Only the absolute flux depends on the orbit altitude, while the shape of the distribution stays unchanged. For the reference system the solar flux distribution results in the temperature distribution shown in Figure 10 for one complete orbit. The peak temperatures stay below 1200 K. The maximum temperature is reached at the end of the sun phase in the area with the highest solar flux. If the absorber area is decreased in order to minimize size and weight of the receiver the increased solar flux could cause unacceptable high peak temperatures. This is illustrated in Figure 11 which shows the temperature distribution for a receiver/storage unit using LiF (melting point 1120 K) as PCM operating in a 450 km orbit. The higher latent heat of LiF allows a more compact receiver design compared to the reference system. The result is a 40% weight reduction but also peak temperatures in
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