A Direct-Heating Energy-Storage Receiver for Dish-Stirling Solar Energy Systems

Dish-Stirling solar receiver designs are investigated and evaluated for possible use with sensible energy storage in single-phase materials. The designs differ from previous receivers in utilizing axial conduction in the storage material for attenuation of the solar flux transients due to intermittent cloud cover, and in having convective heat removal at the base of the receiver. One-dimensional, time-dependent heat transfer equations are formulated for the storage material temperature field, including losses to the environment, and a general heat exchange effectiveness boundary condition at the base. The solar source flux is represented as the sum of steady and periodic cloud-transient components, with the steady component solved subject to specified receiver thermal efficiency. For the transient cloud-cover component the Fast Fourier Transform algorithm (FFT) is applied, and the complex transfer function of the receiver is obtained as a filter for the input flux spectrum. Inverse transformation results in the amplitudes and mode shapes of the transient temperature component. By adjustment of design parameters, the cloud-cover amplitude variations of the outlet gas temperature can be limited to acceptable magnitudes, thus simplifying control systems.