Latitude- and Temperature-Based Optimization of Beam-Down Solar Central Receiver Systems

The geometrical configuration of the beam-down SCR system is optimized for the maximum solar-to-thermal conversion efficiency, taking into account the effects of latitude and receiver temperature. System characterization and optimization are undertaken with a numerical model combining an in-house developed Monte-Carlo ray tracing optical model and a simplified receiver heat transfer model. Differential evolution (DE) algorithm together with parallel computing using OpenMP are employed. Under the assumptions made in this study, it is found that the acquired radiative power at the receiver aperture from the optimized systems ranges from about 35 MW to 45 MW, and the eccentricity of the hyperboloidal tower reflector are between 1.6 and 1.7. The maximum achievable solar-to-thermal conversion efficiency decreases from 0.43 to 0.36 when an SCR system operated at 1,800 K is moved from latitude 0° to 50°, which is mainly due to the increased cosine and shading losses with higher latitudes. In addition to reduced efficiencies, the heliostat field gets larger for higher latitudes, worsening its techno-economic performance when considering the cost per unit useful energy output. A clear trend of efficiency decrease with the higher receiver temperature is demonstrated, resulting from the significant increase of receiver radiative emission losses with the temperature.