In energy storage systems, batteries are the physical foundation for energy storage. Their performance directly determines the system's total capacity, energy density, and economic efficiency, making them an indispensable "energy carrier" for the entire system.
As the "heart" of the energy storage system, batteries not only undertake the core functions of energy storage and release, but also, due to their critical impact on cost, lifespan, and safety, become the primary consideration in system design and selection.
1. The Foundation of Energy Storage:
From Cell to Battery Stack Batteries are the only components capable of achieving chemical energy storage. The entire energy storage system operates on top of battery cells. A typical structural hierarchy is:
Cell → Module → Battery Cluster → Battery Stack Multiple battery stacks connected in parallel can achieve megawatt-hour (MWh) level energy storage, meeting the large-capacity demands of both the generation and grid sides.
This multi-level architecture design allows the system to meet both high-voltage, high-capacity operating requirements and flexible deployment through modular combinations.
2. The Decider of Capacity and Performance
Battery capacity (Ah) and voltage together determine the total energy (kWh) that the system can store, directly impacting the continuous power supply capability for peak shaving and valley filling.
Higher energy density (Wh/kg) means more electrical energy stored per unit volume or weight, resulting in a more compact and efficient system.
Cycle life (e.g., over 6000 cycles for lithium iron phosphate batteries) determines the system's economics; a longer cycle life results in a lower levelized cost of electricity (LCOS).
Therefore, in project planning, the choice of battery type directly affects the project's return on investment cycle and operational stability.
3. Comparison of Mainstream Battery Technologies
Currently, the mainstream energy storage battery is lithium iron phosphate (LFP) due to its high safety, long cycle life, and continuously decreasing cost advantages:
Lithium iron phosphate batteries: High safety, long lifespan, suitable for most stationary energy storage scenarios
Sodium-ion batteries: Abundant raw materials, good low-temperature performance, suitable for extreme climates, and a promising future technology
Vanadium redox flow batteries: Extremely long lifespan, deep discharge capability, suitable for long-term energy storage, but with lower energy density
