Carnot battery with thermochemical energy storage and supercritical CO2 power cycle: Thermodynamic and techno-economic characteristics
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PUBLIC SUMMARY
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A Ca(OH)2/CaO-based Carnot battery with S-CO2 cycles and waste heat recovery is proposed.
Multi-objective optimization achieves 67.95% round-trip efficiency and 1.200 RMB/kWh LCOE.
Scaling from 10 MW to 50 MW reduces LCOE by 46.3% and doubles IRR to 13.64%.
Materials influence system economics mainly via the unit price–design cycle life ratio.
Profitability mainly depends on discharge pricing; high TPC remains the main challenge.
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ABSTRACT
The global transition toward decarbonized energy systems necessitates efficient long-duration energy storage solutions to address renewable intermittency. Conventional technologies face limitations in scalability, safety and geography, highlighting the promise of Carnot batteries. This study proposes a novel Carnot battery system integrating calcium hydroxide/calcium oxide thermochemical energy storage, supercritical CO2 Brayton heat pump and power cycles, and industrial waste heat recovery. Through multi-objective optimization using the NSGA-II algorithm and HEATSEP framework, the system achieved a round-trip efficiency of 67.95% and a LCOE of 1.200 RMB/kWh at 50 MW scale—placing it at a high level among current Carnot battery systems. Sensitivity analyses confirm robust scalability: when scaling from 10 MW to 50 MW, the LCOE decreases by 46.3% and the IRR increases from 6.79% to 13.64%. Furthermore, increasing the annual operating hours to2560 h significantly reduces the LCOE while substantially raising the IRR. For high-cost materials, extending cycle life can yield 21.47% reduction in LCOE. Critically, system profitability is governed by discharge revenue. In markets with modest price differentials, economic feasibility therefore depends on additional reductions in capital cost, such as implementing deep integration with existing coal-fired assets. This integrated system and optimization directions provide a practical, generalizable blueprint for near-term, cost-competitive Carnot batteries. -
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Liu H., Zhang Y., Xu Q., et al. (2026). Carnot battery with thermochemical energy storage and supercritical CO2 power cycle: Thermodynamic and techno-economic characteristics. The Innovation Energy 3:100163. https://doi.org/10.59717/j.xinn-energy.2026.100163
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Liu H., Zhang Y., Xu Q., et al. (2026). Carnot battery with thermochemical energy storage and supercritical CO2 power cycle: Thermodynamic and techno-economic characteristics. The Innovation Energy 3:100163. https://doi.org/10.59717/j.xinn-energy.2026.100163
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Figure 1.
Conceptual schemes of the proposed Ca(OH)2/CaO Carnot battery system powered by excess electricity.
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Figure 2.
Multi-objective optimization results and techno-economic performance of the Carnot battery system
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Figure 3.
Multi-objective optimization results of Carnot battery system
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Figure 4.
mpact of energy storage material cost and cycle life on the economic performance of the Carnot battery system
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Figure 5.
Impact of annual operating hours on techno-economic indicators
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Figure 6.
Evolution of key techno-economic indicators for the Carnot battery system across scaling capacities from 10 MW to 50 MW
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Figure 7.
Sensitivity of economic indicators to electricity price dynamics
