Dynamic Modeling and Sensitivity Analysis of a Stratified Heat Storage Coupled with a Heat Pump and an Organic Rankine Cycle

The storage of electrical energy is becoming increasingly important to satisfy the demand through renewable energy sources. In this paper, a continuous and discrete simulation of a pumped thermal energy storage system are compared with respect to their computational time and accuracy. The stratified heat storage is modelled using spatial one-dimensional considerations and abstractions. Results show, that the discrete simulation with fixed time step is about 60 times faster and has neglectable deviation in the resolution of heat loss computations and accuracy, compared to the continuous System Dynamics model. The conducted sensitivity analysis shows, that parameters of the storage fluid have little influence on the overall result. The determining factor regarding losses in the storage and possible savings for users, is the insulation of the thermal storage. Increasing the number of temperature layers considered in the simulation shows so called deadlayers, which block the storage if not removed during operation.