The core equipment of a solar energy storage system encompasses the entire process of power conversion, storage, monitoring, management, and safety protection. It is primarily categorized into five components: Power Conversion Systems (PCS), energy storage battery systems, Battery Management Systems (BMS), Energy Management Systems (EMS), and auxiliary equipment.
Power Conversion System (PCS)
This is the core equipment for bidirectional conversion between direct current (DC) and alternating current (AC), enabling both grid-tied and off-grid operation for solar energy storage systems:
(i) Grid-tied PCS: Connects the photovoltaic (PV) array and energy storage batteries to the public power grid. It allows surplus solar energy-generated and not consumed on-site-to be fed into the grid, or enables electricity to be stored in batteries during off-peak periods. It supports functions such as peak-shaving/valley-filling (arbitrage) and grid dispatch coordination. Mainstream power ratings range from 3 kW to 100 MW.
(ii) Off-grid PCS: Designed for independent microgrid scenarios, this system operates without reliance on the public grid. It supplies solar power directly to loads while storing excess energy, ensuring a stable power supply during "islanded" (standalone) operation.
Energy Storage Battery System
This serves as the primary medium for storing solar energy. Lithium iron phosphate (LiFePO4) batteries are currently the mainstream choice for solar energy storage applications, favored for their long cycle life and excellent thermal stability:
(i) Battery Cells and Modules: Individual battery cells are assembled in series and/or parallel configurations into standardized modules, tailored to meet specific power and capacity requirements.
(ii) Battery Clusters and Storage Cabinets: Multiple modules are assembled into battery clusters, integrated with thermal management and fire-suppression interfaces, and housed within cabinets. Large-scale utility-grade power plants typically utilize containerized storage units, while residential applications often employ smaller, wall-mounted or floor-standing cabinets.
Battery Management System (BMS)
Responsible for the full-lifecycle monitoring and safety protection of energy storage batteries:
1. Real-time collection of data-including voltage, temperature, and charge/discharge current-from individual battery cells, with this information transmitted to the Energy Management System (EMS).
2. Balancing the state of charge across battery modules to prevent overcharging or over-discharging, thereby extending the overall service life of the batteries. 3. Triggers safety protection mechanisms-such as those for over-temperature, short-circuit, or insulation faults-to rapidly disconnect the affected circuit and mitigate safety risks.
Energy Management System (EMS)
Serving as the core for scheduling and control, the EMS coordinates the operation of the entire energy storage system:
1. Collects data on photovoltaic (PV) array output, grid electricity pricing, and load consumption to generate optimal charge/discharge strategies.
2. Coordinates with the energy storage inverter and Battery Management System (BMS) to automate charging and discharging, supporting various operational modes such as self-consumption, peak-valley arbitrage, and grid frequency regulation.
3. Manages power dispatch while grid-connected, responding to power regulation commands from the grid side to ensure grid stability.
Auxiliary Equipment
1. Fire Safety and Security Equipment: Energy storage cabinets are equipped with built-in smoke detectors and temperature sensors. Large-scale power stations are outfitted with fire suppression systems-such as those using heptafluoropropane (HFC-227ea) or aerosol agents-which must be installed by qualified personnel in compliance with the national standard GB 55015, "General Code for Fire Protection in Buildings."
2. Thermal Management System: Residential systems typically utilize air-cooling, while large-scale power stations generally employ liquid-cooling systems. These maintain the battery operating temperature within an optimal range of 25°C to 35°C, thereby extending the battery's cycle life.
3. AC/DC Power Distribution and Lightning Protection: Includes low-voltage switchgear, DC distribution cabinets, step-up transformers (for large-scale power stations), and lightning protection/grounding equipment. These components ensure electrical safety and comply with the national standard GB 50054, "Code for Design of Low-Voltage Electrical Installations."
4. Remote Monitoring Terminal: Enables remote viewing of equipment status and provides fault alerts, allowing operations and maintenance (O&M) personnel to respond rapidly to any anomalies.