Stationary booster reflectors for solar thermal process heat generation

Abstract

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.The performance of a flat-plate collector with glass-foil double cover (LBM 4 GF) is compared to that of the same collector with a one-sided external CPC booster reflector (RefleC-collector) for process heat generation up to 150 °C. Efficiency curve measurements of both collector variants are reported. Reference is made to simulation results of the annual energy gain of both variants in Würzburg, Germany and Seville, Spain, at inlet temperatures of 40 °C and 120 °C. In these simulations, a novel collector simulation model accounting for the anisotropy of diffuse irradiance was used. Compared to state-of-the-art simulations the new model calculates significantly higher additional gains of the reflectors. Both collector types were installed at a pilot plant in a Laundry in Marburg, Germany. Monitoring results of one reference year for the overall system performance as well as for the additional gains by the booster reflectors are given. It is shown that the stationary booster reflectors highly increase the efficient operation temperature range and also the annual energy gain of the double covered flat-plates. Finally, a simplified economic assessment is carried out. Based on the additional gains by the boosters, the marginal costs for an investment into booster reflectors are assessed. It is estimated that the costs of installed RefleC boosters should be below ca. 30 EUR/m² in Würzburg and 55 EUR/m² in Seville for the technology to enter the solar process heat market.