State-of-the-art concentrating solar power (CSP) systems uses a liquid salt that serves as the heat transfer fluid and is directly stored in large tanks as thermal energy storage (TES) medium. Currently, there are two commercial molten-salt power towers that use sodium/potassium nitrate, known as “solar salt,” as both the HTF and TES medium: Gemasolar (Spain, 19 MWe, 15 hours TES) and Crescent Dunes (USA, 110 MWe, 10 hours TES). The limit of solar salt thermal stability is around 600°C. New power cycles are being developed that operate at higher temperature (e.g. the s-CO2 Brayton Cycle, at 650°C to 750°C) and thus TES systems will require alternative salts, such chloride salt blends that are stable at these higher temperatures.
Although the cost of chloride salts is relatively low, temperatures above 700°C necessitate the use of expensive alloys due to the decline in metal tensile strength with temperature. The cost of the hot storage tank can become a key barrier to the introduction of high-temperature salt storage. One way of possibly overcoming this problem is by lining the inside of the tank with some kind of insulating system, such that the tank wall is at a lower temperature than the salt, and hence a conventional lower-cost steel can be used.
The objective of this project is to investigate different options for internal tank lining, including a review of past work and generation of possible new concepts. There is the opportunity to carry out small scale laboratory tests of different insulating options, if novel concepts are identified. Otherwise, the project could focus on technoeconomic evaluation of different tank lining options.