Development of Steelmaking Slag Based Solid Media Heat Storage for Solar Power Tower Using Air as Heat Transfer Fluid: The Results of the Project REslag

Solar power towers with thermal energy storage based on direct-flow regenerators have the potential to generate cost-effective base-load electricity. An inventory option that opens up further cost-saving potential but has not yet been extensively investigated for this application is slag from electric arc furnace. This use has not only economic advantages, but also serves environmental protection, since a large proportion of this type of slag is currently not used any further, but is disposed of in landfills. In the completed EU project REslag, various subsequent uses of the slag were investigated, including the possibility presented here of using sintered slag pebbles as an inventory for regenerators in solar power towers with air as the heat transfer fluid. The main results from the different phases of the project are presented, with a focus on the investigations not yet published. In addition to results from thermal simulations on different designs and on the partial load and off-design behavior of the storage lead concept “Axial flow—standing”, these are mainly results from fluid mechanical calculations on the distributor design of the storage and from material investigations on the slag. In summary, it can be stated that the sintered slag pebbles are thermally, mechanically and chemically competitive with conventional inventory materials and the principle feasibility of a slag-based storage was confirmed by the results of these investigations. The defined storage lead concept was elaborated in detail and the performance of the design was confirmed by simulations and experiments.