Energy storage systems are mainly divided into five categories: physical energy storage, electrochemical energy storage, thermal energy storage, hydrogen energy storage, and electromagnetic energy storage. Among them, physical energy storage and electrochemical energy storage are the most widely used.
Physical Energy Storage
Storing energy through physical media. Common technologies include:
Pumped hydro storage: Utilizing off-peak electricity hours, water is pumped to an upper reservoir to store potential energy, and released to generate electricity during peak hours. Mature technology, large capacity, and long lifespan, but dependent on geographical conditions.
Compressed air energy storage: Storing compressed air in underground salt caverns or tanks during off-peak electricity hours, and releasing it to drive turbines to generate electricity during peak hours. Suitable for large-scale energy storage, economical, but site selection is limited.
Flywheel energy storage: Converting electrical energy into the kinetic energy of a high-speed rotating flywheel for storage. Fast response time (milliseconds), suitable for short-term, high-frequency scenarios such as grid frequency regulation.
Gravity Energy Storage: Utilizes the potential energy changes during the lifting and lowering of heavy objects to store energy. It boasts long cycle life and no self-discharge, but is currently in its early stages of development.
Electrochemical Energy Storage: Achieves energy storage and release through internal chemical reactions within the battery. This is currently the fastest-growing technology:
Lithium-ion Batteries: Dominate the market, accounting for over 90%, especially lithium iron phosphate batteries. They offer high energy density and long cycle life, and are widely used in power systems, residential, and commercial energy storage.
Sodium-ion Batteries: Rich in sodium resources and low in cost, with good low-temperature performance (capacity retention exceeding 90% at -40℃), they are considered an important supplement to lithium batteries and are accelerating their commercialization.
Flow Batteries (e.g., vanadium redox flow batteries): Energy is stored in an external electrolyte tank. Power and capacity can be independently designed. They offer high intrinsic safety and long lifespan, making them suitable for long-term energy storage scenarios.
Lead-acid/lead-carbon Batteries: Low cost and mature technology, but with low energy density and short lifespan. They are mostly used in small off-grid systems or as backup power.
