Compressed air energy storage

Compressed Air Energy Storage

Longtime storage - thermal mechanical storage solutions

Thermal mechanical long-term storage is an innovative energy storage technology that utilizes thermodynamics to store electrical energy as thermal energy for extended periods. 

Siemens Energy Compressed air energy storage (CAES) is a comprehensive, proven, grid-scale energy storage solution. We support projects from conceptual design through commercial operation and beyond. Our CAES solution includes all the associated above ground systems, plant engineering, procurement, construction, installation, start-up services and long term service support.

Long-duration power storage: cost-effective and at grid-scale

As renewable power generation from wind and solar grows in its contribution to the world’s energy mix, utilities will need to balance the generation variability of these sustainable resources with demandfluctuations. Power-generation operators can use compressed air energy storage (CAES) technology for a reliable, cost-effective, and long-duration energy storage solution at grid scale. 

Siemens Energy CAES improves utilization of renewable energy resources by absorbing GW-hours of energy that would otherwise be curtailed and provides grid balancing and reserve services with lower fuel usage and carbon footprint than other controllable resources.

Diabatic CAES Cycle Schematic: D-CAES

Diabatic storage units dissipate part of the compression heat into the atmosphere with intercoolers. The air must be reheated to be returned to the CAES cycle. Energy and ancillary services with low fuel consumption provide best efficiency.


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Adiabatic CAES Cycle Schematic: A-CAES

The adiabetic CAES cycle stores energy in form of pressure in a cavern, while compression heat is stored in a thermal storage. For re-electrification both forms of energy are being utilized. No additional fuel is needed to heat up the released air. 


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Proven components packaged for a new market


Responds quickly

Responds quickly - Designed to be started and brought to full load in less than 10 minutes, eliminating the need for intermediate-load plants and providing a cost-effective way to meet spinning reserve requirements. 

Excellent load-following capability and exceptional part-load efficiency

CAES generation also has excellent load-following capability and exceptional part-load efficiency

Full compression in less than five minutes

Full compression can be available in less than five minutes to quickly absorb load rather than reducing your base load generation.

Flexible cycling options

Flexible cycling options - The CAES plant allows for independent operation of the compression and expansion systems, allowing for simultaneous load absorption and balancing.

Generation efficiency

Generation efficiency - Relatively flat heat rate across all operating ranges, thus overall generation efficiency is near the same at 10 percent as it is at 100 percent.

Days of storage

Days of storage - The intermittency of renewables coupled with unpredictable weather patterns means the reality of long periods where balancing is paramount to absorbing renewables. 


CAES is the ideal solution for energy and ancillary services including:

  • Load leveling / balancing
  • Ramping regulation
  • Frequency oscillation
  • Transmission optimization
  • VAR support

Performance Summary

Power OutputSystem FlowLHV Heat RateLHV Fuel Usage
MWlbm / sBTU / kWhlbm / s