Liquid CO₂ Energy Storage
The process is simple:
Liquid CO₂ Energy Storage (LCES) stores energy by compressing carbon dioxide (CO₂), cooling it into liquid form and storing it at ambient temperature. Liquid CO₂ has a significantly higher energy density than compressed air systems. When power is needed, the liquid CO₂ is pumped, reheated and expanded through a turbine. The carbon dioxide remains within the system under normal operating conditions and returns to the gas holder and is reused in the next cycle.
Main configurations:
- Stand-alone LCES: the storage plant operates as an independent, closed thermodynamic cycle as previously described.
- LCES integrated with a gas turbine: LCES can be integrated with a gas turbine plant so that waste heat from power generation is used during the discharge process. Instead of relying only on heat recovered and stored during CO₂ compression, the system uses the gas turbine’s exhaust heat to warm the pressurised CO₂ before it enters the expansion turbine. A higher turbine inlet temperature increases the energy available during expansion and can raise the plant’s electricity output. This configuration can therefore combine long-duration energy storage with flexible power generation and more effective use of heat that would otherwise be lost.
- LCES integrated with industrial waste heat: The same principle can be applied at industrial sites with suitable and sufficiently continuous waste-heat streams. During discharge, industrial heat can be transferred to the CO₂ before expansion, increasing the mechanical energy recovered by the turbine. Such integration could be relevant for industrial clusters where storage, electricity demand and thermal processes are located close together.
As an emerging technology, LCES is not yet as mature or widely deployed as pumped storage hydropower or conventional compressed-air storage. Nevertheless, R&I projects demonstrate its potential to complement other storage technologies and provide multi-hour flexibility to a renewable-based power system.
Why is LCES important to support the Energy Transition?
Long-duration energy storage technology that stores electricity by using CO₂ as the working fluid in a closed thermodynamic cycle. During operation, the CO₂ remains within the system and is continuously reused, meaning it is not released into the atmosphere under normal operating conditions.
Like other thermodynamic energy storage technologies, LCES can provide medium- to long-duration electricity storage, helping to balance renewable electricity generation and demand over periods ranging from several hours to multiple days. By relying on established turbomachinery technologies, LCES has the potential to provide utility-scale flexibility while complementing other long-duration energy storage solutions.
LCES offers:
- Storage durations ranging from several hours to approximately one day.
- Flexible siting without the need for specific topographical or geological formations.
- A closed cycle in which CO₂ is retained and reused as the working fluid.
- Potential applications in renewable energy shifting, balancing and congestion management.
- Opportunities for integration with gas turbines or industrial waste-heat sources