A Systematic Approach to Evaluate the Thermo-Economic Potential of Rankine-Based Carnot Batteries for Industrial Decarbonization
Authors: Benvenuto Miriam , Barberis Stefano , Traverso Alberto , Sciacovelli Adriano 
Published: August 2024

This study focusing on Pumped Thermal Energy Storage (PTES), specifically Thermally Integrated PTES (TI-PTES) as attractive and novel solution centred around combination of power-to-heat-to-power and thermal energy storage. The research and novelty of the work lies in the proposal and application systematic framework for early-stage design decisions regarding key design parameters of TI-PTES system. In particular the work specializes on TI-PTES comprising a Heat Pump (HP) with an Electric Heater (EH) for power-to-heat and an Organic Rankine Cycle (ORC) as the Heat-to-Power technology to maximize economic and environmental benefits. Both the cycles consider R1233zd(E) as working fluid with attractive future applicability and operating temperatures up to ∼210°C — hence within reach of combination of HP with EH and, on discharge, of ORC. Thus the timelines and technological relevance of the present work. However, the development and deployment of a competitive such TI-PTES solutions necessitates combined decisions regarding the technical design parameters across all key sub-systems (HTHP, EH, ORC, TES) as well as regarding the economic competitiveness of TI-PTES system as a whole. Little work has been done in this area; therefore, this paper proposes and applies a techno-economic decision-making framework to guide the TI-PTES selection toward feasible applications. The proposed framework is deliberately aimed at supporting early-stage design decision and exploration of effect of key HP, ORC, TES parameters prior to detailed thermodynamic analysis. Hence the novelty of this work compared with existing literature. The proposed framework is implemented and tested to investigate a case study of 5MW/20MWh TI-PTES system which could find application in industrial energy parks that might be in need of both energy flexibility (energy storage) and energy efficiency (waste heat upgrade/recovery) simultaneously (EES) software. The results indicate that the TI-PTES baseline case achieves a Round Trip Efficiency (RTE) of around 44%. Furthermore, the findings highlight that minimizing the temperature lift during the charge cycle while maximizing difference between hot and cold reservoirs during the discharge cycle significantly increases the RTE. Additionally, the performance of turbomachinery in the HP and ORC is crucial for overall system efficiency and economic viability. Instead, The uses of the EH permits to achieve higher temperature of the stored heat, in comparison with the only use of the HP, the latter assumed to operate up to 130°C. Ultimately the results support that the proposed TI-PTES configuration appears to be an interesting option for those applications that require electricity and thermal energy at medium temperatures. From economic stand point, The Levelized Cost of Energy results to be around 0.14 €/kWh, considering 20 years of life span of the system. In summary, the study emphasizes the importance of a multi-criteria selection of TI-PTES technological parameters to meet industrial thermal and electrical demands and achieve economic profitability. Furthermore, this study contributes to systematic decision-making in the rational design and deployment of TI-PTES, aiming to maximize decarbonization benefits in industrial sectors and enhance the potential and viability of such integrated systems.