Everything You Need to Know About Energy Storage

2026-02-14 | Eric

Energy storage, as the "power bank" of the energy system, is one of the core technologies that support the large-scale application of renewable energy, enhance grid flexibility, and ensure energy security. The following is an overview of the essential knowledge in the energy storage field, covering six main dimensions: basic concepts, mainstream technologies, key metrics, application scenarios, policies & market, and challenges & trends.

1. Basic Concepts: The Essence and Core Value of Energy Storage

Energy storage (Energy Storage) is the process of storing energy in a specific form using devices or media and releasing it when needed. Its core value lies in solving the problem of "time mismatch in energy supply and demand":

• Time Mismatch: For instance, solar power generation is abundant during the day but less at night, and wind power fluctuates based on wind speed.
• Spatial Mismatch: Wind and solar resources are abundant in the western regions, but the electricity demand is low, while demand is high in the eastern regions, but resources are scarce.
• System Stability: By rapidly charging and discharging, energy storage helps smooth out grid fluctuations (such as frequency regulation and voltage control), improving the reliability of power supply.

2. Mainstream Energy Storage Technologies: Classification, Principles, and Characteristics

Energy storage technologies can be classified into four major types based on energy conversion methods, each with applicable scenarios:

1. Physical Energy Storage (Mechanical Energy/Gravitational Potential Energy/Thermal Energy)

• Pumped Storage Hydropower (PSH): The most mature large-scale energy storage technology (accounting for over 80% of global installed capacity). Water is pumped to a high-level reservoir during low electricity demand and released to generate electricity during peak demand.
• Compressed Air Energy Storage (CAES): Uses a compressor to store air in underground caverns or storage tanks, which is then expanded by heating to drive turbines for power generation.
• Flywheel Energy Storage: Stores kinetic energy in a high-speed rotating flywheel, with energy conversion through a motor-generator.

2. Electrochemical Energy Storage (Electrochemical Reactions)

• Lithium-Ion Batteries (LIB): The most common electrochemical storage technology (accounting for over 90% of global new storage). Lithium ions migrate between positive and negative electrodes during charge and discharge.
• Lead-Acid Batteries: A mature technology with low cost but lower energy density, used in low-speed vehicles and backup power systems.
• Flow Batteries (VRB): Liquid electrolyte stored in external tanks circulates to the cell stack for reaction.

3. Electromagnetic Energy Storage (Electric Field/Magnetic Field)

• Supercapacitors (SC): Store charge through double electric layers or Faradaic pseudocapacitance, with high power density but low energy density, used for short-term high-power applications.
• Superconducting Magnetic Energy Storage (SMES): Uses superconducting coils to store energy in a strong magnetic field, efficient but requiring low-temperature environments and high costs.

4. Thermal Energy Storage

• Sensible Heat Storage: Stores heat through temperature changes in materials (e.g., water, molten salts), such as in solar thermal power stations.
• Latent Heat Storage: Uses phase-change materials (e.g., ice, paraffin) to absorb or release heat during phase transitions, with higher efficiency than sensible heat storage.
• Chemical Heat Storage: Stores heat through reversible chemical reactions (e.g., metal hydride decomposition/synthesis), with the highest theoretical efficiency but still under development.

3. Key Metrics: Core Parameters for Evaluating Energy Storage Systems

• Energy Density (Wh/kg or Wh/L): Energy stored per unit mass/volume, determining the system's size and weight (e.g., Li-ion > Flow Batteries > Lead-acid).
• Power Density (W/kg): Output power per unit mass/volume, determining the charging and discharging speed (e.g., Flywheel > Supercapacitors > Li-ion).
• Efficiency (%): The ratio of energy input to energy output (e.g., Li-ion > 90%, Flow > 75%, PSH > 70%).
• Cycling Life (Cycles): The number of full charge-discharge cycles before the capacity drops to 80% (e.g., Flow > 10,000 cycles, Li-ion 2000~6000 cycles, Lead-acid < 2000 cycles).
• Self-Discharge Rate (%/month): The rate at which energy is naturally lost during storage (e.g., Lead-acid > 5%, Li-ion < 2%, Flow < 1%).
• Cost (CNY/Wh): Initial investment (equipment + installation) or levelized cost of storage (LCOS), accounting for lifetime and efficiency.

4. Application Scenarios: Where Energy Storage Plays a Role

The value of energy storage depends on specific scenarios, with core applications including:

• Power Generation Side (Supporting Power Generation): Storage for smoothing fluctuations in solar and wind power, improving the integration of renewable energy.
• Grid Side (Supporting Power Systems): Peak shaving, frequency regulation, black start, and grid stability applications.
• User Side (Optimizing End-Use): Peak shaving for industrial/commercial applications and residential energy storage.

5. Policies and Market: Key Factors Driving Energy Storage Development

Energy storage policies and market dynamics are key drivers for its development:

• China: The 2021 "Guiding Opinions on Accelerating the Development of New Energy Storage" sets a target of 30GW installed capacity by 2025.
• USA: Federal ITC tax credit and state-level mandates, such as California's 11GW target for energy storage by 2030.
• Europe: REPowerEU plans and national policies accelerating storage deployment, with Germany simplifying grid connection processes.

6. Challenges and Trends: Future Key Breakthrough Directions

Energy storage faces challenges such as safety concerns, cost pressures, and technical bottlenecks. However, the future holds opportunities for breakthroughs in:

• Diversified Technological Routes: The rise of sodium-ion and solid-state batteries, with lithium-ion dominating short-term storage.
• Intelligent Management: AI algorithms for optimized charge/discharge strategies, and digital twin technologies for monitoring battery health.
• Large-Scale and Standardized Deployment: Large-scale storage stations and improving industry standards.

Conclusion

Energy storage is a "must-have" for the energy revolution. Its technological selection must be based on time and power demands, and system requirements (short-term/long-term, high/low power). In the future, with advances in technology and policy improvements, energy storage will shift from "optional" to "essential," deeply integrated into the new power system.

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