Simulation of a Pumped Thermal Energy Storage Based on a Reversible HP-ORC-system

orc2019 Tracking Number 74

The use of renewable energy sources such as solar and wind power leads to variations in the electricity supply especially during the night phase. This entails the need for storage facilities to balance the electrical load profile and a storage that does not degrade during the loading and unloading cycles. One solution consists of a pressurized hot water storage tank which is loaded with a heat pump (HP) and unloaded with an ORC (Organic Rankine Cycle). In order to minimise the electrical energy required to charge the storage tank, a waste heat flow at an elevated temperature level (<100°C) is used. By upgrading the waste heat flow through the heat pump and storing the upgraded heat, it is possible to convert it back into electricity via an ORC when it is required and thus to recapture a large proportion of the exergy of the supplied electrical power. In order to minimise the material costs of the system, double use of the components for the heat pump and ORC modes is also considered. The results of our simulations show the influence of the heat source used, the storage temperature, the storage type (sensible or latent) as well as the selection of fluid and the working machine on the overall process. In particular, the choice of fluid and working machine is decisive for the efficiency of the plant.