A simple tool for a rough estimate of the economic viability of a thermal energy storage for a specific application has been developed within an international working group (IEA SHC Task 42 / ECES Annex 29). The costs per installed storage capacity of thermal energy storages have been evaluated via a Top-down and a Bottom-up approach. The Top-down approach follows the assumption that the costs of energy supplied by the storage should not exceed the costs of energy from the market. The Bottom-up approach focuses on the realised storage capacity costs of existing storages. An important finding is that the annual number of storage cycles has a large influence on the cost effectiveness. At present and with respect to the investigated storages, seasonal heat storage is only economical via relatively large hot water storages. However, if the annual number of storage cycles is sufficiently high, other thermal energy storage technologies become cost-competitive.
Christoph Rathgeber studied Physics at the Technical University Munich, Germany. He has been working in the Thermal Energy Storage group at the Bavarian Institute for Applied Energy Research (ZAE Bayern) since 2010. His main research area is phase change material development and characterization. Since 2015, he has been working as a PhD student on the prediction of solid-liquid phase diagrams of multi-component salt-water systems. In the framework of IEA ECES, he has investigated the economics of thermal energy storages.