»Hybrid power« project investigates use of photovoltaics for more efficient solar thermal power plants

A consortium led by the German Fraunhofer Institute for Solar Energy Systems ISE is developing a hybrid system for combining solar thermal power plants and photovoltaics in the »Hybridkraft« (hybrid power) project funded by the German government.
At its core, the project involves an electrically powered heater of molten salts that ensure continuous operation in large-scale solar thermal power plants, even at night. Up to now, for such operating concepts, the heat generated solarthermally (usually with parabolic troughs) for the operation of a turbine is also used to melt the salt. The molten salt then serves as a heat reservoir that can be used to drive the turbine at night. However, solar thermal plants are significantly more expensive than photovoltaic power plants, while molten salt storage is less expensive than battery storage.
In the »hybrid power« concept, solar thermal energy is also to be used to generate heat for salt melting with Frenel collectors. However, this component is of much less overall importance: The electricity comes mainly from PV during the day, and the temperature of the heat transfer fluid is also to be stabilized with PV electricity. In this way, the storage density of the molten salt and the operating temperature of the turbine can be raised, thus increasing the system efficiency.
The project will develop a 1 megawatt solar-powered heater. Moreover, the results are also relevant for another field of application, namely the conversion of electricity into high-temperature heat for industrial applications.

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