Nonisothermal Receivers

Abstract

The reradiation losses, inherent to every thermal receiver, can be significantly reduced by exposing the working fluid to monotonously increasing irradiance and preventing energy exchange between parts of the receiver that are at different temperatures. In this way the highest temperatures are reached only near the end of the working fluid’s path. The improvement is much more pronounced for nonuniform as compared to uniform irradiance. For a Gaussian distribution of irradiance we calculate improvements exceeding a factor of two for the efficiency at a given temperature (0.8 of the peak stagnation temperature), and for the temperature at a given efficiency of 0.8. These results are independent of the peak irradiance and of the width of the distribution. Even a coarse partitioning into two mutually isothermal parts can already produce a significant improvement over the totally isothermal receiver.