The Potential of direct steam Generation in Parabolic Troughs - Results of the German Project DIVA

The direct steam generation (DSG) in parabolic trough collectors is a promising option to improve the mature SEGS type parabolic trough solar thermal power plant technology. According to previous studies the cost reduction of the DSG process compared to the SEGS technology is expected to be 8 to 25 %. All theses studies were more or less preliminary since they lacked detailed information on the design of collector fields, absorber tubes required for steam temperatures higher than 400°C and power blocks adapted to the specific needs of the direct steam generation. To bridge this gap, a detailed system analysis was performed within the German R+D project DIVA. Power blocks and collector fields were designed for four different capacities (5, 10, 50 and 100 MW) and different live steam parameters. The live steam temperature was varied between saturation temperature and 500°C and live steam pressures of 40, 64 and 100 bar were analyzed. The thermal efficiency of the collector operated at temperatures higher than 400°C was calculated based on latest results of SCHOTT’s high temperature selective coating development. To assess the different cases, detailed yield analysis of the overall system were performed using hourly data for the direct normal irradiation and the ambient temperature for typical years. Based on these results the levelized costs of electricity were determined for all cases and the most promising parameters were identified