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Tests of pressurized solar radiation absorbers require suitable pressure vessels and window structures for the penetrating light in order to heat up pressurized gases or gases other than air [1]. A test setup for such investigations has been developed at the Solar-Institut Jülich and is presented below. Air and Helium are the fluids used in the experiments. Helium has more favorable heat transfer properties. Computations have shown that helium has a higher volumetric heat transfer coefficient than air. Therefore, helium is a more suitable fluid to achieve the volumetric effect. [ABSTRACT FROM AUTHOR]

The integration of high temperature thermal energy storages into existing conventional power plants can help to reduce the CO2 emissions of those plants and lead to lower capital expenditures for building energy storage systems, due to the use of synergy effects [1]. One possibility to implement that, is a molten salt storage system with a powerful power-to-heat unit. This paper presents two possible control concepts for the startup of the charging system of such a facility. The procedures are implemented in a detailed dynamic process model. The performance and safety regarding the film temperatures at heat transmitting surfaces are investigated in the process simulations. To improve the accuracy in predicting the film temperatures, CFD simulations of the electrical heater are carried out and the results are merged with the dynamic model. The results show that both investigated control concepts are safe regarding the temperature limits. The gradient controlled startup performed better than the temperature-controlled startup. Nevertheless, there are several uncertainties that need to be investigated further. [ABSTRACT FROM AUTHOR]

Volumetric absorbers are used to transfer solar radiation energy to a crossing fluid. The absorbers considered are made of parallel wire meshes. The incident radiation is modelled as a heat source with an exponential decay inside the absorber. Heat transfer depends on crossing fluid properties and flow parameters. The absorber shows a so called “volumetric effect” if the highest temperatures are found at the exit of the absorber. In case of high heat transfer coefficients and larger radiation penetration depth such a situation is found. It is interesting that the volumetric effect will not depend on the heat conductivity inside the absorber for the model considered here. [ABSTRACT FROM AUTHOR]