Featured Application: Concentrated solar power (CSP) plant with open volumetric receiver.Abstract: By using metallurgical slag from an electric arc furnace that is otherwise not recycled but deposited as an inventory material in thermal energy storage for concentrated solar power plants, it is possible to make a significant step forward in two transformation processes: energy and raw materials. As this type of slag has not been considered as an inventory material for this purpose, it is important to clarify fundamental questions about this low-cost material and its storage design. In this paper, design studies of slag-based thermal energy storage are carried out. Different slag-specific design concepts are developed, calculated and evaluated by a method based on established management tools. Finally, concepts for further investigations are defined. The highest aptitude value and the lowest risk value are achieved by the vertical storage design with axial flow direction. Therefore, it is taken as the lead concept and will be considered in complete detail in further research. Also, a closer look, but not as detailed as the lead concept, is taken at the horizontal storage with axial flow and the vertical storage with radial flow direction.In CSP plants, molten salt technologies have been extensively deployed in CSP applications for the storage of thermal energy prior to steam or electricity generation. An example among many is the Solana power plant with 280 MWe and a storage system able to supply full power for six hours. [2] The technology of regenerator-type storage is less developed, but has the potential for higher efficiency and lower costs. In particular, the application of regenerators in CSP power plants with an open volumetric receiver seems to be a promising approach, as shown in Figure 1.
Thermal energy storage (TES) systems are central elements for various types of new power plant concepts and industrial processes. Depending on the specific application, energy storage systems based on sensible heat transfer with packed beds as storage inventory are a promising storage technology. Due to thermal expansion and shrinking of the packed bed’s particles during cyclic thermal charging and discharging, high technical risks arise and possibly lead to material failure. In order to accurately design the TES, suitable tools for calculating thermo-mechanical induced forces and stresses are mandatory. For this purpose, different model approaches and tools are available. Continuum models offer time-efficient simulation results but need proper parametrization, which usually requires extensive experimental effort. This paper focuses on laying the groundwork on how to facilitate the effort for the parametrization of a continuum model by deploying a discrete particle model in order to simulate soil mechanical experiments. In this context, a specifically designed test rig is introduced, which is applied for the validation of the discrete particle model.
For conventional power plants, the integration of thermal energy storage opens up a promising opportunity to meet future technical requirements in terms of flexibility while at the same time improving cost-effectiveness. In the FLEXI- TES joint project, the flexibilization of coal-fired steam power plants by integrating thermal energy storage (TES) into the power plant process is being investigated. In the concept phase at the beginning of the research project, various storage integration concepts were developed and evaluated. Finally, three lead concepts with different storage technologies and integration points in the power plant were identified. By means of stationary system simulations, the changes of net power output during charging and discharging as well as different storage efficiencies were calculated. Depending on the concept and the operating strategy, a reduction of the minimum load by up to 4% of the net capacity during charging and a load increase by up to 5% of the net capacity during discharging are possible. Storage efficiencies of up to 80% can be achieved.
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