How Does Compressed Air Energy Storage Work?

The Growth of Renewable Power Generation and the Role of Compressed Air Energy Storage (CAES)

The growth of renewable power generation is experiencing a remarkable surge worldwide. According to the U.S. Energy Information Administration (EIA), it is projected that by 2050, the share of wind and solar in the U.S. power-generation mix will reach 38 percent, which is twice the proportion recorded in 2019. The incorporation of Compressed Air Energy Storage (CAES) into renewable energy systems offers various economic, technical, and environmental advantages.

What is Compressed Air Energy Storage?

By 2030, it is anticipated that renewable energy sources will account for 36 percent of global energy production. Energy storage systems will be instrumental in attaining this objective. Mechanical storage systems stand out among the available energy storage methods due to their reduced investment expenses, prolonged lifetimes, and increased power/energy ratings. Notably, commercialized large-scale Compressed Air Energy Storage (CAES) facilities have arisen as a prominent energy storage solution.

Incorporating CAES technology into renewable energy systems can help achieve the Sustainable Development Goals (SDGs) outlined by the United Nations. These goals include affordable and clean energy (SDG 7), industry, innovation, and infrastructure (SDG 9), and climate action (SDG 13).

How Does Compressed Air Energy Storage Work?

The CAES system follows a conventional three-phase model of a gas turbine, encompassing charging, storing, and discharging. During the charging phase, CAES uses off-peak and cost-effective electricity to compress ambient air, which is then stored in a dedicated pressurized reservoir. When energy demand is high, the stored compressed air is released, expanded, and passed through a turbine to generate electricity.

Traditional Compressed Air Energy Storage System Configurations

CAES technology encompasses different types, including adiabatic systems and diabatic systems. The key distinction between these configurations lies in how they handle the heat generated during the compression process.

• Diabatic CAES systems: These are the first-generation technology where ambient air is compressed using a compressor train. The compression process generates waste heat, which is dissipated to the surrounding environment through intercoolers. During the discharge phase, fuel is combusted to heat the air before its expansion in the turbines, enabling electricity generation during peak demand periods.
• Adiabatic CAES systems: Developed to address the limitations of diabatic CAES, these systems focus on effectively capturing and storing the waste heat generated during compression. The stored heat is then recycled to elevate the turbine inlet temperature of the compressed air during the discharge phase. Adiabatic CAES aims to reduce or eliminate reliance on fossil fuels, offering a more sustainable energy storage solution.

Recent Developments in Novel Configurations of CAES

In addition to adiabatic and diabatic configurations, two other types of CAES systems have been proposed: isothermal CAES (I-CAES) and supercritical CAES. I-CAES aims to maintain stable compression and expansion temperatures of the compressed air during the charging and discharging processes, respectively. Supercritical CAES involves compressing the air to a supercritical thermodynamic state, recovering and storing the waste heat generated during compression, and utilizing liquefied air for electricity generation.

Components and Operational Necessities

1. Motor/generator with pulleys on both ends
2. Multistage air compressors with intercoolers and aftercoolers
3. Control system for an expander train
4. Accessories (fuel storage and management, refrigeration systems, mechanical systems, power systems, and heat exchangers)
5. Storage of pressurized air underground or aboveground

Advantages of Compressed Air Energy Storage

• Improves high-demand preservation and decreases the electrical grid’s burden
• Reduces reliance on the electrical infrastructure, decreasing energy costs and maintenance costs
• Stores energy for several hours to days, assuring a consistent power supply during periods of high demand or when intermittent resources are not producing
• Enhances power grid stability during periods of excessive electrical demand
• Requires relatively little upkeep compared to other methods

Limitations and Challenges

Despite its advantages, compressed air energy storage faces challenges and limitations. The scarcity of appropriate geological formations for underground caverns may hinder its extensive application. Additionally, energy losses due to thermal dispersion during the compression and expansion processes reduce overall efficiency.

Market Assessment

The future market potential for compressed air energy storage (CAES) systems is substantial. The global compressed air energy storage market was worth $4 billion in 2021 and is expected to reach $31.8 billion by 2031, expanding at a compound annual growth rate (CAGR) of 23.6% from 2022 to 2031. This growth is primarily driven by the increasing influence of renewable energies.

Cost and Performance Assessment of CAES

According to calculations done by Pacific Northwest National Laboratory, a 1000MW CAES plant incurs various costs, including cavern storage, CAES capital, total installed cost, fixed O&M, and calendar life years.