Developing A Control Strategy For Carnot Batteries: Analysis Of Temperature Glide Effects In Organic Rankine Cycle And Heat Pump Modes

Energy storage is a critical technology to integrate renewable energy into the power grids successfully and has been widely recognised as essential for the energy transition. Carnot Batteries (CBs) offer a promising solution for long-duration energy storage by integrating thermal energy storage and power cycles. This study investigates the impact of temperature glide on the evaporator and condenser of a CB system designed to produce 50 kWe and 500 kWth. A physics-based model is developed, incorporating manufacturer data to accurately reflect real performance. The analysis evaluates system efficiency in both organic Rankine cycle (ORC) and heat pump (HP) modes, considering the component limitations.
The results indicate that no single temperature glide pair optimises performance in both operational
modes. Instead, the optimal glide values vary depending on the operating conditions. This highlights
the importance of conducting detailed analyses, particularly when secondary fluid circuits are shared
between modes, as significantly different operating conditions can arise. Consequently, implementing
a mode- and condition-dependent control strategy is essential for maintaining high efficiency in CBs.
Additionally, this study identifies the optimal temperature glides for the analysed system, demonstrating
their dependence on piping, fittings, and component selection.