Analysis of Renewable Energy Integrated Pumped Thermal Energy Storage Systems

In this paper, a novel configuration of a pumped thermal electricity storage system is proposed which can integrate excess thermal energy from different renewable thermal energy sources, e.g. concentrated solar power, waste heat and deep geothermal energy plants, as well as excess electricity from direct electricity generating renewable energy sources, e.g. solar photovoltaic and wind energy plants. The proposed configuration can also be used as a retrofit option to existing conventional fossil fuel-based power plants. A conventional two-tank sensible heat storage is used as a thermal energy storage system that can be charged using direct renewable thermal energy and using a heat pump utilizing excess electricity. Different discharging cycles, including a Joule–Brayton system and a conventional steam Rankine cycle system, can be used. The proposed system can achieve a higher capacity factor compared to those of stand-alone plants.

As a case study, a conventional two-tank molten salt-based thermal energy storage system integrating concentrated solar power, considering a heliostat system, and a solar photovoltaic plant is investigated. The overall operational strategy of the plant was developed and based on that annual simulations were performed for a selected configuration. The results of the case study suggest that for a given requirement of capacity factor, the final selection of the capacities of the solar photovoltaic plant, heat pump and heliostat field should be done based on the minimum levelized cost of energy. Moreover, for high capacity factor requirements, the proposed configuration is promising.