Comparative system analysis of direct steam generation and synthetic oil parabolic trough power plants with integrated thermal storage

• Published in: Solar energy 2012-01, Vol.86 (1), p.520-530
• Main Authors: Feldhoff, Jan Fabian, Schmitz, Kai, Eck, Markus, Schnatbaum-Laumann, Lars, Laing, Doerte, Ortiz-Vives, Francisco, Schulte-Fischedick, Jan
• Format: Article
• Language: English
• Subjects: Applied sciences; Comparative analysis; Direct steam generation; Electric power plants; Electrical engineering. Electrical power engineering; Electrical power engineering; Electricity generation; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat transfer; Miscellaneous; Natural energy; Non classical power plants; Parabolic trough power plant; Phase change material storage; Photovoltaic power plants; Power plants; Solar energy; Solar thermal conversion; Solar thermal power plants; System comparison; Thermal energy storage; Transport and storage of energy; Yield analysis
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2011.10.026

► Including thermal energy storage considerations. ► Including annual yield analysis, investment structure and levelized electricity cost. ► DSG system about 1–7% more costly with, but 5–8% cheaper without storage system. ► Identification of DSG research needs. ► Conclusions on recommended applications of DSG. Parabolic trough power plants are currently the most commercially applied systems for CSP power generation. To improve their cost-effectiveness, one focus of industry and research is the development of processes with other heat transfer fluids than the currently used synthetic oil. One option is the utilization of water/steam in the solar field, the so-called direct steam generation (DSG). Several previous studies promoted the economic potential of DSG technology (Eck et al., 2008b; Price et al., 2002; Zarza, 2002). Analyses’ results showed that live steam parameters of up to 500°C and 120bars are most promising and could lead to a reduction of the levelized electricity cost (LEC) of about 11% (Feldhoff et al., 2010). However, all of these studies only considered plants without thermal energy storage (TES). Therefore, a system analysis including integrated TES was performed by Flagsol GmbH and DLR together with Solar Millennium AG, Schott CSP GmbH and Senior Berghöfer GmbH, all Germany. Two types of plants are analyzed and compared in detail: a power plant with synthetic oil and a DSG power plant. The design of the synthetic oil plant is very similar to the Spanish Andasol plants (Solar Millennium, 2009) and includes a molten salt two-tank storage system. The DSG plant has main steam parameters of 500°C and 112bars and uses phase change material (PCM) for the latent and molten salt for the sensible part of the TES system. To enable comparability, both plants share the same gross electric turbine capacity of 100MWel, the same TES capacity of 9h of full load equivalent and the same solar multiple of the collector field of about two. This paper describes and compares both plants’ design, performance and investment. Based on these results, the LEC are calculated and the DSG plant’s potential is evaluated. One key finding is that with currently proposed DSG storage costs, the LEC of a DSG plant could be higher than those of a synthetic oil plant. When considering a plant without TES on the other hand, the DSG system could reduce the LEC. This underlines the large influence of TES and the still needed effort in the development of a commercial storage syste