Reducing the cost of electricity storage with a novel solar thermal support scenario in pumped thermal energy storage (PTES)

Abstract

Pumped Thermal Electricity Storage (PTES) is a system that allows the conversion of electrical energy into thermal energy and its more cost-effective storage. Thermal integration is one of the methods applied to increase the round-trip efficiency (ηrt) of PTES. The disadvantage of TI-PTES systems that use solar energy as a heat source is the need to store hot water with an additional heat storage system due to fluctuations in solar energy. Additional heat storage system significantly increases the cost of energy storage. In this study, a novel solar thermal integration scenario was presented. The novelty in the study has been utilizing the same water tanks for both the thermal storage of electricity and thermal support. Thermal support for PTES was provided by a concentration photovoltaic thermal (CPVT) system. Thus, it was aimed to reduce additional heat storage costs. With the proposed design (STI(CPVT)-PTES), the power supplied to the compressor (ẆCOMP) and round-trip efficiency varied in the range of 0.52–2.6 MW and 41.1–128.3 %, respectively. The overall exergy efficiency of the system varied between 19 % and 42 % depending on solar energy, sunshine duration, and parameter values. The parameter that most economically affected the system was the mass flow rate of the heat source (ṁhs), and the lowest levelized cost of storage (LCOS) was obtained as 0.227 $kWh−1 at a ṁhs of 250 kg/s. With STI(CPVT)-PTES, a reduction in LCOS ranging from 1.3 % to 33.2 % was achieved compared to other thermal integration scenarios. Analysis results revealed that the proposed system has a high potential to be an alternative to other thermally integrated PTES systems.