Compressed Air Energy Storage (CAES) efficiency variations stem from thermodynamic processes, heat management strategies, and system design choices. Below are the primary contributing factors:
Thermodynamic Processes and Heat Management
- Adiabatic vs. diabatic operation: Adiabatic CAES retains heat from compression (e.g., using thermal storage) and reuses it during expansion, achieving 70–75% efficiency in advanced systems. Diabatic systems discard this heat, lowering efficiency to 25–45% due to irreversibilities and reliance on external heat sources (e.g., natural gas).
- Near-isothermal compression: Low-pressure systems (≤10 bar) minimize temperature changes during compression/expansion, reducing energy losses and approaching ~100% theoretical efficiency in idealized conditions. However, practical designs face mechanical limitations, limiting real-world performance.
Component and System Efficiency
- Cumulative component losses: For systems requiring separate compression and expansion stages, efficiency is multiplicative (e.g., 80% compressor and 80% turbine efficiency yield ≤64% system efficiency).
- Heat source reliance: Traditional diabatic CAES uses natural gas combustion during expansion, lowering electric-to-electric efficiency to 40–52%. Advanced systems leveraging renewable energy or stored thermal energy avoid this penalty.
Operational Parameters
- Pressure levels: High-pressure systems (e.g., 70+ bar) require multistage compression/expansion with intercooling, introducing additional losses. Low-pressure designs simplify heat management but increase storage volume requirements.
- Exergy losses: Cooling air post-compression in diabatic systems destroys exergy, while adiabatic systems preserve it, directly impacting round-trip efficiency.
| Factor | High Efficiency | Low Efficiency |
|---|---|---|
| Thermal Management | Adiabatic + heat recovery | Diabatic (waste heat) |
| System Type | Advanced A-CAES (70–75%) | Traditional D-CAES (25–45%) |
| Component Efficiency | High-efficiency compressors/turbines | Suboptimal component design |
| Pressure Strategy | Low-pressure, near-isothermal | High-pressure, non-isothermal |
The interplay of these factors determines whether a CAES system operates closer to its thermodynamic limits or exhibits significant energy penalties.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-are-the-main-factors-contributing-to-the-efficiency-differences-in-caes-systems/
