Potentials of thermal energy storages integrated into steam power plants

Facing volatile power markets utilities require improved load flexibility of conventional power plants. One promising option to fulfill future demands of electricity systems and enable additional business opportunities is based on the integration of thermal energy storages (TES). With high thermal charging and discharging power as well as reasonable thermal storage capacities, these technologies open up the potential for increased dynamics in short-term and long-term applications. Therefore a consortium of power generation companies, power plant suppliers as well as universities and research institutes has been working on the integration of TES concepts into steam power plants since 2017. The project is supported by the German Federal Ministry for Economic Affairs and Energy and is named FLEXI-TES (Flexibility by Thermal Energy Storages). The selection of a suitable storage technology, its integration and sizing milestones the conceptual phase of FLEXI-TES. Thereby technoeconomic variation studies regarding storage technology and dimension supervised by heat flow calculations result in suitable options and integration topologies. Preliminary results show that the optimization of storages regarding to specific costs alone do not suffice. A suitable thermal storage concept needs high energy density to minimize capacity costs and requires integration in the steam power plant with a remarkable contribution on plant output minimizing power related costs. The paper introduces different storage concepts presenting their flexibility and economical potential. Thereby the capability of increasing and reducing the power plant output by charging and discharging the storages will be presented and co-benefits will be pointed out.