Pumped thermal energy storage (PTES) as smart sector-coupling technology for heat and electricity

Thermal energy storage combined with thermal cycles is an alternative option for storage in electrical power grids. Intermediate storage of electric energy as heat offers advantages such as free choice of site, small environmental footprint, life expectancies of 20–30 years and optional low-cost backup capacity. The key element in pumped thermal energy storage (PTES) concepts is the application of a left running thermal cycle to transform low temperature heat into high temperature heat, which is stored in the thermal storage during charging. PTES allows higher storage efficiencies than a direct electric heating of the thermal storage unit. The optional combination of electricity and heat during charging and discharging makes PTES a promising tool for the management of various types of energy in systems with high shares of renewable energy. CHEST (Compressed Heat Energy STorage) is a specific PTES variant based on Rankine cycles using either water or organic media as the working fluid in combination with latent heat storage units. This paper focuses on the application of CHEST for the management of heat and electricity. Different options for the implementation of CHEST will be presented, for these variants, characteristic values such as operating parameters and power ratio are given and the required components described. The focus is on the technological possibility of using pumped thermal energy storage as a sector-coupling technology for heat and electricity through low temperature heat integration. In addition, new findings of an in-depth numerical simulation of a fully heat-integrated, subcritical PTES using butene as the working fluid are presented.