Simulation and experimental results of the CellFlux storage concept

Kurzfassung

A storage system for parabolic trough power plants which is consisting of a low cost sensible storage material and an intermediate working fluid was proposed by DLR. Heat from the primary high temperature fluid (HTF) coming from e.g. a power plant is transferred to the intermediate working fluid (air) which again transfers the energy in direct contact to the storage material. The intermediate working fluid, which is kept in a closed loop, is diverted back to the heat exchanger by a fan. The new concept allows significant cost reductions through the utilization of cost effective solid sensible storage material compared the two tank molten salt concept. The necessary heat exchanger plays an important role for the overall performance and profitability of the storage system due to its high investment costs and pressure losses. As preliminary investigations have shown, the optimization of the storage system itself contributes only partly to successful optimization. The integration into the power plant and its operation strategy allow further significant cost reductions. At DLR a pilot scale test facility with 75 kW of thermal power and a storage volume of 30 m3 is set-up to proof the feasibility of the technical concept and to validate system models developed at DLR. A dynamic model of the storage system was set-up to investigate the behavior of the system. The models have been implemented in Matlab/Simulink environment which allows studying several configurations due to its modular structure. The numeric models were validated with the experimental data of a test rig. This paper presents the results obtained from the test rig and describes the related theoretical background. Based on the findings, the expected behavior of the larger pilot scale test facility obtained from simulations is presented.