What is Battery Energy Storage?

A battery energy storage system (BESS) is a system that uses batteries as an energy storage carrier to store and release electrical energy. It can store electrical energy for a certain period of time and supply electrical energy at appropriate times according to demand. It has functions such as smooth transition, peak shaving and valley filling, frequency regulation and voltage regulation.

The stored power can come from renewable sources such as solar and wind, or from conventional power generation. When needed, the system releases this energy to support grid stability, meet peak demand, or provide backup power. A typical BESS is made up of battery modules, a Battery Management System (BMS), and power conversion equipment such as inverters.

 

A battery energy storage system consists of: batteries, electrical components, mechanical support, heating and cooling systems (thermal management systems), a bidirectional power conversion system, an energy management system, and a battery management system.

 

As one of the key technologies for new energy storage, energy storage batteries play a crucial role in increasing the proportion of renewable energy consumption and ensuring the safe and stable operation of the power system. Lithium-ion batteries, as key components of energy storage, are the "central hub" determining the progress of electrochemical energy storage. Lithium-ion batteries are classified into lithium iron phosphate batteries and ternary lithium-ion batteries according to their cathode materials. The energy storage market is mainly dominated by lithium iron phosphate batteries. Eliminating the day-night peak-valley difference is the main application scenario for energy storage systems, and the product's usage time directly affects project profitability. An energy storage unit, usually referring to a battery, is the basic device in an energy storage system used to store and release electrical energy.

Battery Structure:

Positive Electrode Material: The part of the battery where the oxidation reaction occurs. Common positive electrode materials include lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), and lithium nickel manganese cobalt oxide (NMC).

Negative Electrode Material: The part of the battery where the reduction reaction occurs. Common negative electrode materials include graphite, silicon, and tin.

• Electrolyte: The medium for ion transport in the battery. It can be liquid or solid (solid electrolyte). The electrolyte allows ions to move between the positive and negative electrodes, completing the charging and discharging process.
• Separator: Located between the positive and negative electrodes, its function is to prevent direct contact between the positive and negative electrodes, which could lead to a short circuit, while allowing ions to pass through.
• Current Collector: Usually made of metal (such as copper and aluminum), used to transfer the current from the cell to the external circuitry.
• Battery Casing: The external structure of the battery, used to protect the internal components and provide mechanical support.
• Battery Management System (BMS): Responsible for monitoring and managing the battery's charging and discharging process, ensuring safe battery operation and optimizing its performance and lifespan.

Working principle of energy storage batteries

Thermal Management Components

• Sensors: Temperature sensors, pressure sensors, etc., used to monitor parameters such as temperature and pressure of the battery and the environment in real time.
• Control Unit: Typically a microcontroller or computer system, controlling the operation of thermal management equipment based on sensor data and preset algorithms.
• Cooling Equipment:
• Air Cooling System: Includes fans, air channels, heat exchangers, etc., dissipating heat through airflow.
• Liquid Cooling System: Includes pumps, coolant, radiators, cooling plates, etc., removing heat through coolant circulation.
• Heating Equipment: Such as electric heaters, phase change material heaters, etc., used to heat the battery in low-temperature environments.
• Insulation Materials: Used to reduce the impact of the external environment on the battery temperature and maintain internal temperature stability.
• Actuators: Such as valves, pumps, etc., used to control the flow of coolant or air.
• Connectors: Includes pipes, cables, etc., connecting various components to ensure normal system operation.

Thermal Management Working Principle

1. Temperature Monitoring: Sensors continuously monitor the temperature of the battery and the environment, transmitting the data to the control unit.
2. Data Analysis: The control unit analyzes the data to determine whether cooling or heating equipment needs to be activated.
3. Cooling Process:-Air Cooling: When the temperature exceeds a set threshold, the fan starts, pushing air across the battery surface to remove heat.-Liquid Cooling: A pump pushes coolant through a cooling plate or directly into contact with the battery, absorbing heat before flowing back to the radiator for heat exchange.
4. Heating Process: In low-temperature environments, the heating equipment activates, releasing heat through electrical energy or phase change materials to raise the battery temperature.
5. Temperature Regulation: The control unit adjusts the intensity of cooling or heating based on real-time data to ensure the battery temperature remains within its optimal operating range.
6. Heat Distribution Uniformity: A well-designed airflow path or coolant flow path ensures uniform temperature distribution within the battery pack.
7. Safety Protection: The system also includes overheat protection, leak detection, and other safety functions to prevent potential safety hazards.
8. Intelligent Optimization: Modern thermal management systems may integrate artificial intelligence algorithms to optimize control strategies, improve energy efficiency, and increase response speed.
9. Remote Monitoring: The system may support remote monitoring and control functions, allowing maintenance personnel to understand the system status in real time and make adjustments.

Battery Management System (BMS)

The Battery Management System (BMS) is a core component of an energy storage system, responsible for managing and monitoring the operating status of the battery pack to ensure its safety, reliability, and efficient operation. The following are the basic components, working principles, and key functions of a BMS:

Battery Management System (BMS): Basic Components

Hardware Components:

• Sensors: Used to monitor physical parameters of the battery such as voltage, current, and temperature.
• Circuit Boards: Includes the main control circuit board and communication circuit boards, responsible for data processing and communication.
• Processor: The core control unit, which analyzes and calculates the battery status and executes corresponding control strategies.
• Relays and Protection Circuits: Used to disconnect the battery's charging and discharging circuits in abnormal situations, protecting the battery from damage.
• Communication Interface: Used for data communication with external systems (such as vehicle control systems, servers, etc.).

Battery Management System (BMS) Working Principle:

1. Data Acquisition: The BMS collects battery parameters such as voltage, current, and temperature in real time through sensors.
2. Data Processing: The processor processes the acquired data, calculating key information such as the battery's charge/discharge state, remaining capacity, and internal resistance.
3. Control Strategy Execution: Based on the data processing results, the BMS executes corresponding control strategies, such as adjusting the charge/discharge current and performing battery balancing.
4. Communication and Feedback: The BMS exchanges data with external systems through a communication interface, receives external commands, and feeds back battery status information to the external systems.

 

An energy storage converter (PCS) can be likened to an "oversized charger," a key component in an energy storage system. It possesses bidirectional conversion capabilities and plays a crucial role in the system. It enables energy conversion and bidirectional flow between the energy storage battery and the grid. It can convert direct current (DC) to alternating current (AC) or vice versa to meet the grid's charging and discharging needs of the energy storage system. The PCS acts as a "bridge" in the energy storage system, connecting the energy storage battery and the grid, ensuring the efficient and stable operation of the system.

 

An Energy Management System (EMS) is a key component of an energy storage system. It is responsible for monitoring, controlling, and optimizing the energy flow and operational efficiency of the entire system.

"A good solution originates from top-level design, and a good system stems from the EMS," highlighting the importance of the EMS in energy storage systems.

The EMS exists to aggregate information from all subsystems within the energy storage system, comprehensively monitor the overall system operation, and make relevant decisions to ensure safe system operation. The EMS uploads data to the cloud, providing operational tools for the operator's back-end management personnel. Simultaneously, the EMS is responsible for direct interaction with users. User maintenance personnel can use the EMS to view the real-time operation of the energy storage system and implement monitoring.