Improving the thermo-economic performance of a pumped thermal electricity storage (PTES) with a hybrid thermal integration scenario consisting of solar energy and waste heat

The pumped thermal electricity storage system stores electrical energy in the form of thermal energy and, when needed, converts the thermal energy back into electrical energy. The lack of geographical constraints and its comparatively lower cost than other electrical energy storage systems make this technology worthy of further investigation. Applying thermal integration to pumped thermal electricity storage systems to improve power-topower efficiency and reduce costs is a widely discussed topic. Various thermal integration methods, such as waste heat, district heating, ocean thermal energy, geothermal, and solar energy, are included in many studies in the literature. The novelty in this study lies in the thermo-economic investigation of a hybrid thermal integration scenario, which combines different heat sources. Thermo-economic analyses were carried out for different thermal support ratios and solar (concentrated photovoltaic thermal) system parameters. Waste heat, solar energy, and hybrid scenarios were compared in terms of round-trip efficiency and energy storage cost. Hybrid thermal integration increased the round-trip efficiency of pumped thermal electricity storage from 45.7 % to 96.1 %. Moreover, thanks to hybrid thermal integration, the system's levelized cost of energy storage decreased by 10.9 % compared to the solar energy scenario and by 12.69 % compared to the waste heat scenario. The system's overall exergy efficiency was observed to elevate in tandem with an increase in the thermal support ratio. The effect of the thermal integration method on energy storage density was low level and the energy storage density varied between 0.81 kWh/m3 and 0.83 kWh/m3 for all scenarios. The thermo-economic findings in the presented study revealed that possible hybrid thermal integration scenarios for pumped thermal electricity storage should be evaluated.