Organic Rankine Cycle and Carnot Battery Systems for Thermal Energy Storage and Energy Flexibility

Power-to-power energy storage is emerging as a foundational component for future energy systems with high shares of variable renewable electricity. In these systems, long-duration storage, flexibility, and reliability play crucial roles in maintaining stability and enabling deeper renewable integration. Among the available storage options, Carnot batteries, including Pumped Thermal Energy Storage (PTES), transform electrical energy into heat and back into power, providing large-scale storage capacity, competitive costs, and minimal geographical constraints. Their overall performance depends strongly on the power-conversion stage, where Organic Rankine Cycle (ORC) technology enables efficient power generation from low- and medium-temperature heat sources such as stored thermal energy, industrial waste heat, and renewable thermal resources. With recent advances in thermodynamic design, working fluids, thermal storage materials, system optimization, and control, ORC-based Carnot batteries are gaining momentum. Nevertheless, important challenges remain in achieving higher round-trip efficiency, improving economic viability, ensuring scalability, and facilitating integration into low-carbon energy networks.This Research Topic aims to bring together researchers and practitioners working on ORC-based Carnot batteries, PTES, and integrated heat pump and thermal storage systems that complete the power-to-power loop. The objective is to advance the thermodynamic performance, configuration, and material selection of these systems, as well as to refine control and optimization strategies for dynamic operating conditions. Central questions include identifying the most effective working fluids and thermal storage media for superior round-trip performance, determining how charge and discharge units can be co-optimized at the system level, and exploring control approaches that enable flexible, grid-supportive operation. The ultimate goal is to highlight pathways toward efficient, cost-effective, and scalable power-to-power storage solutions that support renewable energy deployment and industrial decarbonization.To gather further insights into the design, integration, and operation of power-to-power thermal storage systems, we welcome contributions addressing, but not limited to, the following themes:• Thermodynamic and exergy analysis of ORC, PTES, and Carnot battery systems• Evaluation and improvement of round-trip, power-to-power efficiency• Selection of working fluids and development of thermal storage materials• Co-optimized integration of ORC systems, heat pumps, and thermal storage• Modeling, simulation, and optimization of charge and discharge cycles• Control, monitoring, and operation strategies for energy flexibility• Techno-economic assessment, scalability, and lifecycle evaluation• Demonstration and pilot-scale applications and real-world case studies• Power-to-power storage for renewable integration and industrial decarbonization Topic editors: Ricardo Mendes, Helder Santos, Márcio Santos Source: https://www.frontiersin.org/research-topics/82828/organic-rankine-cycle-and-carnot-battery-systems-for-thermal-energy-storage-and-energy-flexibility