Power-to-Heat integration in a two-stage Brayton Battery configuration: Increasing system Cost Efficiency and Flexibility

Kurzfassung

Utility-scale Electrical Energy Storage (EES) supports the expanding integration of intermittent renewable energy sources allowing a reliable and flexible supply of low-carbon or even zero-carbon electricity. The Joule-Brayton Battery is an emerging EES technology that has been extensively investigated in the last decade. The focus of the previous research work has been on one-stage concepts with respectively one middle pressure and one low pressure thermal energy storage (TES). On the one hand, such one-stage concepts have the advantage of low equipment costs; on the other hand, these concepts require high mass flow rates which results in significant exergy losses due to the pressure loss in TES and heat exchanger (HX). The present contribution proposes a two-stage concept (see Fig. 1, left) comprising one high pressure two-tank TES, one low pressure TES and two middle pressure TES. In contrast to one-stage concepts, this configuration enables with its thermodynamic cycles from Fig. 1 (right) reduced mass flow rates by up to 40% accompanied with round-trip efficiencies higher than 60%. In addition, the integration of Power-to-Heat (PtH) further decreases the mass flow rate improving the cost efficiency of this Brayton Battery configuration in analogy to the investigation from. Results from thermodynamic analysis of this advanced plant configuration quantify these improvements and illustrate the trade-off between round-trip efficiency and cost efficiency.