Techno-economic assessment of a Carnot battery thermally integrated with a data center

Carnot batteries (CBs) are gaining interest as energy storage solutions, particularly when waste heat is available for thermal integration. Data centers (DCs) represent a relevant source of waste heat, as they convert most of the supplied electricity into low-grade heat, and their utilization is expected to continue increasing in the future. This study explores the feasibility of integrating an Organic Rankine Cycle (ORC)/Heat Pump (HP) CB with a DC powered by a photovoltaic power plant. First, from the thermodynamic analysis conducted in design conditions, the hydrofluoroolefin R1233zd(E) results in the most suitable working fluid, leading to 43 % roundtrip efficiency. Then, a detailed semi-empirical off-design model of a CB is employed in a rule-based control strategy to handle the ORC/HP operations. If the HP is thermally integrated with the DC waste heat, a higher coefficient of performance is achieved, and the consumption of the DC cooling system is reduced. A sensitivity analysis is conducted to explore the impact of the storage volume and the energy prices on the integrated system's technoeconomic performance. The CB implementation is economically feasible when the electricity price is high, reaching a yearly gain of 7744 <euro>, and a simple payback period of 10 years when considering a DC electric consumption of 200 kWe and a 25 kWe-sized HP/ORC. The gain increases if the electric surplus cannot be sold, obtaining a 4-year payback period. Eventually, we perform a comparison with an ORC-only configuration to assess the CB's technical and economic convenience.