Off-design characterisation of a hybrid energy storage based on pumped thermal energy storage and low-concentration solar thermal collectors

Long duration storages (i.e. 6+h) could foster the power sector transitions towards renewable energy sources. Among the many technologies proposed for such a task, pumped thermal electricity storage (PTES) recently gained much attention from researchers. A PTES plant based on low-concentration solar collectors, a vapour compression heat pump, and an organic Rankine cycle (ORC) is studied. In the proposed configuration, the solar collectors produce the thermal energy required by the heat pump during the charging phase. The heat pump operates with a reduced temperature lift and upgrades the solar thermal energy to store it at a higher temperature in sensible heat storage. The electric roundtrip efficiency is very high when the thermal energy is discharged through the ORC, thanks to solar thermal energy contribution. In the paper, the system performance in and off-design are analysed. An off-design model is used to map both heat pump and ORC for a set of representative operating conditions. Such performance maps were then used to characterise the system performance when coupled with a solar thermal energy production profile. In this way, the whole system operation was simulated for some representative days of the year. Results show that the average round trip efficiency is between 0.85 and 0.87, and the system can operate in various radiation conditions.     «

Long duration storages (i.e. 6+h) could foster the power sector transitions towards renewable energy sources. Among the many technologies proposed for such a task, pumped thermal electricity storage (PTES) recently gained much attention from researchers. A PTES plant based on low-concentration solar collectors, a vapour compression heat pump, and an organic Rankine cycle (ORC) is studied. In the proposed configuration, the solar collectors produce the thermal energy required by the heat pump dur...     »