Economic Potential of Solar Thermal Power Plants With Direct Steam Generation Compared to HTF Plants

Abstract

The direct steam generation (DSG) in parabolic trough collectors is a promising option to improve the mature parabolic trough solar thermal power plant technology of the Solar Energy Generating Systems (SEGS) in California. According to previous studies [1–3], the cost reduction of the DSG process compared to the SEGS technology is expected to be 8 to 25%. All these 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 MWel) 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 investigated. To assess the different cases, detailed yield analyses 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 compared to a reference system using synthetic oil as heat transfer fluid (HTF). This paper focuses on two main project findings. First, the 50 MWel DSG system parameter comparisons are presented. Second, the detailed comparison between a DSG and a SEGS-like 100 MWel system is given. The main result of the investigation is that the benefit of the DSG process depends on the project site and can reach an 11% reduction of the levelized electricity cost (LEC).

Concentrating Solar Power

“…239,240 The results from these projects point towards a 8-14% reduction in LCOE compared to SEGS-like plants using synthetic oils as the HTF. 241 Despite the promise of direct steam generation, several engineering challenges, arising due to the twophase flow, need be addressed. These include the higher operating cost due to high pressure required to pump the two-phase mixture.…”

Analysis of an innovative direct steam generation-based parabolic trough collector plant hybridized with a biomass boiler

“…This allows the fluid to fully evaporate before exiting the solar field. In a previous analysis, a live steam temperature of 500°C was identified as a viable option within DSG plants . To match the pressure of the indirect steam generation plant considered, the same pressure of 100 bar is considered for the DSG plant.…”

“…Analyses available in the literature have shown that live steam at the exit of DSG fields can reach a temperature of 500°C and a pressure of 120 bar, which leads to a direct increment in the system's overall efficiency, ultimately leading to low cost of energy . The economic potential of DSG‐based PTC plants compared with indirect steam generation PTC plants, which mainly uses synthetic oil as HTF, has been reported in the literature . These studies have concluded that DSG‐based PTC has the potential to reduce the levelized cost of energy up to 11%.…”

Techno-economic heat transfer optimization of large scale latent heat energy storage systems in solar thermal power plants

“…This limits the maximum operation temperature to 400°C and, thus, the overall plant efficiency. Instead, solar thermal power plants based on direct steam generation (DSG) with steam temperatures up to 550°C offer higher efficiencies [1,2]. For further cost reduction cost efficient thermal energy storage (TES) system is required.…”