4E (energy, exergy, economic, environmental) analysis of a medium-high temperature heat pump energy storage system for data center waste heat recovery

Data centers generate abundant low-grade waste heat at 35-45°C, but its recovery is hindered by limited application scenarios and poor economic feasibility. To address this, a combined cooling, heating and power (CCHP) system integrating data center waste heat utilization with medium-high temperature (100-200°C) thermal storage is proposed. Focusing on the heat pump thermal storage subsystem, three typical 200°C sensible heat storage configurations are investigated: an R245fa reverse Rankine cycle coupled with steam mechanical vapor recompression (MVR) in a staged compression arrangement, an argon reverse Brayton multi-cycle, and a CO2 transcritical cycle.

Steady-state thermodynamic models are developed for a 10 MW thermal storage target, and a 4E (energy, exergy, economic, and environmental) analysis is performed. The results indicate that the CO2 system delivers the best overall performance, achieving a coefficient of performance (COP) of 2.36, an exergy efficiency of 63.7%, an annualized investment cost of 5.536 million USD, a levelized cost of heat (LCOH) as low as 0.0692 USD/kWh, annual pollutant emission reductions of 6978.8 tonnes, and a comprehensive environmental revenue of 0.281 million USD. Among the other two systems, the R245fa-based configuration with staged MVR ranks second, while the argon system exhibits the lowest performance.

When CO2 is adopted as the working fluid for the CCHP system, the round-trip efficiency (RTE) reaches 74.41% and the specific electricity consumption for steam generation (SEC) is 192.7 kWh per tonne. This study highlights the merits of CO2 in medium-high temperature thermal storage and CCHP driven by data center waste heat, offering a promising technical pathway for data center waste heat recovery, industrial heating decarbonization, the development of zero-carbon parks, and power peak shaving.