Automatic screening of working fluid pairs for Rankine-based Carnot battery using an efficient cross-scale model

Rankine-based Carnot batteries represent a pivotal technology for addressing the supply-demand imbalance arising from renewable energy generation. Their appeal lies in advantages such as low cost, absence of geographical constraints, and the capacity to couple power output with energy storage. Enhancing the efficiency of Carnot batteries significantly depends on optimizing system configurations and operational parameters. Moreover, selecting appropriate working fluids is also crucial to achieving optimal performance. However, current research predominantly relies on predefined databases, with limited exploration of potential working fluid pairs designed to improve system performance. This study automatically screens working fluid pairs using computer-aided molecular design and group contribution methods to identify optimal candidates for thermal storage within the 90–130 °C range, using power-to-power efficiency as the evaluative metric. The findings highlight that the working fluid pair R1251zd-R1260zf demonstrates superior performance within the proposed system, achieving maximum power-to-power efficiency of 46 % at a thermal storage temperature of 100 °C. This work provides theoretical insights to enhance the performance of the Rankine-based Carnot battery and effectively identifies exceptional working fluid pairs suitable for this temperature spectrum, thereby presenting a new approach to optimizing working fluid pairs.