Investigation Of The Wall Temperature Field Of A Molten Salt Storage Vessel

Kurzfassung

Molten salt storage tanks are widely utilized in solar thermal power plants today [1-3]. Due to their cyclic operation, the temperature inside the tank walls is fluctuating on a daily basis which induces stresses and can lead to tank failure. The hot tank of the Gemasolar power plant in Spain, for example, had to be completly reconstructed. Also, in single tank storage systems, where hot and cold molten salt is stored inside a single tank, there is a strong and dynamic temperature gradient induced. Hence, a better understanding of the actual wall temperature profile in relation to the salt temperature profile would therefore be beneficial for a precise calculation of the tank wall stresses. In previous experiments the operation of a 4 MWh single tank thermocline with filler was demonstrated, but no data of tank wall temperatures were measured. The aim of this paper is the measurement of the tank walls and molten salt temperature profiles in the DLR TESIS:store (test facility for thermal energy storage in molten salts) for stress analysis [4]. At DLR in Cologne several experiments are conducted where a thermocline is established inside a molten salt storage tank without filler. The thermocline is moved at three different speeds through the tank and also kept static to account for stand-by periods. The TESIS:store facility is operated at temperatures of 290°C and 560°C, corresponding to real system conditions. In this work the experimental findings will be presented. With the results, practical guidelines for the expected thermocline profile inside tank walls from the temperature profile in the molten salt can be derived. This allows the design of storage tanks from simplified 1D sizing-simulations of the storage tank. To our knowledge this is the first experimental analysis of wall temperature profiles of the single tank molten salt technology.