Conceptual Design of a 2X Trough for Use Within Salt and Oil-Based Parabolic Trough Power Plants

Recent studies in the United States suggest that parabolic trough levelized energy costs (LECs) can be reduced 10-15% through integration of a large salt energy storage system coupled with the direct heating of molten salt in the solar field. While noteworthy, this relatively small predicted improvement may not justify the increased technical risks. Examples of potential issues include increased design complexity, higher maintenance costs, and salt freezing in the solar field. To make a compelling argument for development of this new system, we believe that additional technical advances beyond that previously reported will be required to achieve significant LEC reduction, greater than 25%. The new technical advances described include the development of a high-concentration trough that has double aperture and optical concentration of current technology. This trough is predicted to be more cost-effective than current technology because its cost ($/m2) and thermal losses (W/m2) are significantly lower. Recent trough optical performance improvements, such as more accurate facets and better alignment techniques, suggest a 2X trough is possible. Combining this new trough with a new low-melting point salt now under development suggests that a LEC cost reduction of ~25% is possible for a 50 MW, 2X salt plant relative to a conventional (1X) 50 MW oil plant. However, the 2X trough will also benefit plants that use synthetic oil in the field. A LEC comparison of 2X plants at sizes 200 MW shows only a 6% advantage of salt over oil.