The performance of a solar thermal parabolic trough plant with thermal storage is dependent upon the arrangement of the heat exchangers that ultimately transfer energy from the sun into steam. The steam is utilized in a traditional Rankine cycle power plant. The most commercially accepted thermal storage design is an indirect two-tank molten salt storage system where molten salt interacts with the solar field heat transfer fluid (HTF) through a heat exchanger. The molten salt remains in a closed loop with the HTF and the HTF is the heat source for steam generation. An alternate indirect two tank molten salt storage system was proposed where the molten salt was utilized as the heat source for steam generation. A quasi-steady state simulation code was written to analyze the key environmental inputs and operational parameters: solar radiation, solar field size, thermal storage system, heat exchangers, and power block. A base case with no thermal storage was modeled using design parameters from the SEGS VI plant and the effects of solar field size were analyzed. The two differing indirect two-tank molten salt storage designs were modeled and their solar field size and thermal storage capacity were treated as parameters. Results present three days of distinct weather conditions for Las Vegas, Nevada. Annual and monthly electricity generation was analyzed and the results favor the thermal storage case with the solar field HTF interacting with steam. Additionally, the economic trade offs for the three arrangements and speculation of operating strategies that may favor the alternate storage design is discussed.
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