Seismic design of high temperature tanks supported on thermal isolation
The main advantage of solar thermal power stations in comparison to other power stations like wind power or photovoltaic systems is the simple and cost-effective integration of the energy storage system. The integration of a thermal energy storage systems in this specific kind of power station leads to a reduction of the electricity generation costs and allows to provide base load power despite the volatile solar radiation. Consequently, a simple, efficient, and cost-effective high temperature heat reservoir constitutes an essential element of a solar thermal power station. Furthermore, these heat reservoirs provide the power station with a certain flexibility and in that way make a contribution to the stability and the service security of the energy supply system based on a high proportion of renewable energies.
A very good possibility for the high temperature heat storage are molten salts, which are stored in steel tanks at a temperature of 600°C. Because of the high temperatures a heat isolation layer has to be embedded between the tank bottom and the reinforced concrete foundation to keep the upper foundation surface under 80°C. Conventionally foamglas and calcium silicate are used for isolation. This kind of thermal isolation is cost-intensive and provides no protective function for tanks in seismic active regions, because the ground motions are transferred directly onto the tank structure.
This leads to stability problems at moderate earthquake loads and therefore constitutes a risk for the supply security. An economic alternative with low material costs and an easy implementation is the thermal isolation through a bulk of lightweight materials like igneous rocks or expanded clay. The bulk originating an isolation effect improves the seismic stability of the storage tank. The objective of the project is to prove with experimental and computational research the suitability of the bulk as a sustainable foundation material for static and dynamic influences and to develop a corresponding construction principle.