Engineers unveil high-efficiency liquid CO₂ energy storage system to stabilize renewable power grids

A novel two-stage cold and heat storage design achieves a round-trip efficiency of 56.12%, offering a scalable and high-density solution for long-duration energy storage.

As the global transition to renewable energy accelerates, the intermittency of wind and solar power remains a significant challenge for grid stability. To address this, a research team from the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, has developed a novel Liquid CO₂ Energy Storage (LCES) system. This system, featuring a breakthrough two-stage cold and heat storage design, significantly enhances heat transfer efficiency and storage density.

The findings, published in the journal ENGINEERING Energy (formerly Frontiers in Energy), provide a roadmap for more efficient, large-scale energy storage infrastructure.

Optimizing the CO₂ Cycle

Liquid Carbon Dioxide Energy Storage (LCES) is gained attention due to its high energy density, safety, and long operational lifespan. However, energy losses during the phase change of carbon dioxide have historically limited the overall efficiency of these systems.

The research team proposed a system based on the Linde-Hampson (L-H) liquefaction cycle, integrated with a graded (two-stage) thermal management strategy. By using methanol as a cold storage medium and a combination of thermal oil and pressurized water for heat storage, the system achieves a more precise thermal match during the compression and expansion processes.

Record-Breaking Performance

The study involved rigorous thermodynamic modeling and exergy analysis to evaluate the system’s heat transfer characteristics. Under design conditions, the novel system achieved:

• Round-Trip Efficiency (RTE): 56.12%
• Energy Storage Density (ESD): 29.46 kWh/m³
• Exergy Efficiency: 93.73%

"Energy storage technology is becoming increasingly crucial to balance power demand and supply," says Yunkai Yue, the corresponding author of the study. "Our two-stage storage design minimizes energy destruction near the CO₂ critical point, making the system both more compact and more efficient than traditional compressed air storage."

Future Outlook

The analysis revealed that while liquefaction pressure has a minor impact on the liquefaction ratio, the system’s efficiency is highly sensitive to the temperature and pressure of the storage cycle. By identifying the optimal liquefaction pressure, the researchers have laid the groundwork for the commercial industrialization of LCES.

This high-density, high-efficiency technology offers a promising alternative for future carbon-neutral power systems, potentially reducing the land footprint and cost of energy storage facilities worldwide.

JOURNAL: ENGINEERING Energy (formerly Frontiers in Energy)

DOI: https://doi.org/10.1007/s11708-024-0963-3

Article Link: https://link.springer.com/article/10.1007/s11708-024-0963-3

Cite this article: Zheng, P., Hao, J., Zhang, Z. et al. Analysis of heat transfer characteristics of a novel liquid CO₂ energy storage system based on two-stage cold and heat storage. Front. Energy, 2025, 19(2): 193-204. https://doi.org/10.1007/s11708-024-0963-3