Energy storage container is an integrated energy storage system developed for the needs of the mobile energy storage market. It integrates battery cabinets, lithium battery management systems (BMS), container dynamic environment monitoring systems, and can integrate energy storage converters and energy management systems according to customer needs.
Energy storage container has the characteristics of simplified infrastructure construction cost, short construction period, high degree of modularization, and easy transportation and installation. Energy storage container can be applied to thermal power, wind power, solar power stations or islands, communities, schools, scientific research institutions, factories, large load centers and other applications.
1. Classification of energy storage container
Classified by materials used, energy storage containers can be divided into three types:
- Aluminum alloy energy storage container: the advantages are light weight, beautiful appearance, corrosion resistance, good elasticity, convenient processing, low processing and repair costs, and long service life; the disadvantages are high cost and poor welding performance;
- Steel energy storage container: the advantages are high strength, firm structure, high weldability, good water tightness, and low price; the disadvantages are heavy weight and poor corrosion resistance;
- FRP energy storage container: the advantages are high strength, good rigidity, large internal volume, good heat insulation, anti-corrosion, chemical resistance, easy to clean, and easy repair; the disadvantage is that it is heavy, easy to age, and the strength of the bolts is reduced.
2. Design of energy storage container
● Battery compartment: The battery compartment mainly includes batteries, battery racks, BMS control cabinets, heptafluoropropane fire extinguishing cabinets, cooling air conditioners, smoke detector lighting, surveillance cameras, etc. The battery needs to be equipped with a corresponding BMS.
The types of battery are lifepo4 batteries, ternary lithium battery, lead-carbon battery and lead-acid battery. The cooling air conditioner is adjusted in real time according to the temperature in the warehouse. The monitoring camera can remotely monitor the operating status of the equipment in the warehouse. A remote client can be formed to monitor and manage the running status and battery status of the equipment in the warehouse through the client or app.
● Equipment warehouse: The equipment warehouse mainly includes PCS and EMS control cabinets. PCS can control the charging and discharging process, convert AC to DC, and can directly supply power to AC loads without a grid.
In the application of energy storage system, the functions and functions of EMS are more important. In terms of distribution network, EMS mainly collects the real-time power status of the power grid through communication with smart meters, and monitors changes in load power in real time. It can control automatic power generation and assess the state of the power system. In a 1MWh system, the ratio of PCS to battery can be 1:1 or 1:4 (energy storage PCS 250kWh, battery 1MWh).
3. Composition of energy storage container system
Take the 1MW/1MWh energy storage container system as an example. The system generally consists of an energy storage battery system, a monitoring system, a battery management unit, a dedicated fire protection system, a dedicated air conditioner, an energy storage converter, and an isolation transformer, and is finally integrated in a 40-foot container.
● Battery system: Mainly composed of batteries connected in series and parallel. First, more than a dozen groups of batteries are connected in series and parallel to form a battery box, and then the battery boxes are connected in series to form a battery string and increase the system voltage. Finally, the battery strings are connected in parallel to increase the system capacity, and are integrated and installed in the battery cabinet.
● Monitoring system: It mainly realizes the functions of external communication, network data monitoring and data collection, analysis and processing. Ensure accurate data monitoring, high voltage and current sampling accuracy, data synchronization rate and fast execution speed of remote control commands. The battery management unit has high-precision monomer voltage detection and current detection functions to ensure the voltage balance of the battery module and avoid the circulation between the battery modules, which affects the operating efficiency of the system.
● Fire-fighting system: In order to ensure the safety of the system, a dedicated fire-fighting and air-conditioning system is installed in the energy storage container. Fire alarms are sensed through safety devices such as smoke sensors, temperature sensors, humidity sensors, and emergency lights, and fires are automatically extinguished. The dedicated air-conditioning system controls the cooling and heating system of the air-conditioning system through a thermal management strategy according to the external ambient temperature to ensure that the temperature inside the energy storage container is in an appropriate range and prolong the service life of the battery.
● Energy storage converter: It is an energy conversion unit that converts battery direct current into three-phase alternating current, which can operate in grid-connected and off-grid modes. In the grid-connected mode, the converter performs energy interaction with the grid according to the power command issued by the upper-level dispatcher.
In the off-grid mode, the energy storage converter can provide voltage and frequency support for the load in the factory area, and provide black start power for some renewable energy. The outlet of the energy storage converter is connected to the isolation transformer, so that the primary side and the secondary side are completely electrically insulated, and the safety of the energy storage container system is guaranteed to the greatest extent.
4. Advantages of energy storage container system
● Energy storage container has good anti-corrosion, fire-proof, waterproof, dust-proof (wind and sand), shock-proof, anti-ultraviolet, anti-theft and other functions.
● The shell structure, thermal insulation materials, interior and exterior decoration materials of the energy storage container are all made of flame retardant materials.
● The installation of the air inlet and outlet of the container and the air inlet of the equipment can facilitate the replacement of the standard ventilation filter. At the same time, it can effectively prevent dust from entering the energy storage container when encountering strong wind and sand blowing electricity.
● The anti-shock function must ensure that the mechanical strength of the container and its internal equipment meets the requirements under transportation and earthquake conditions, and there will be no failures such as deformation, abnormal function, and non-operation after vibration.
● The anti-ultraviolet function must ensure that the properties of the materials inside and outside the container will not be deteriorated due to ultraviolet radiation, and will not absorb the heat of ultraviolet rays, etc.
● The anti-theft function must ensure that the container will not be opened by the thief in the open air outdoors. It must ensure that a threatening alarm signal is generated when the thief tries to open the container. At the same time, the alarm is sent to the background through remote communication. This alarm function can be shielded by the user.
● The energy storage container standard unit has its own independent power supply system, temperature control system, heat insulation system, flame retardant system, fire alarm system, mechanical interlock system, escape system, emergency system, fire protection system and other automatic control and security systems.
Customers purchasing lithium ion battery storage systems will intensify their demand for energy and electricity as energy storage systems move to longer durations. Lithium battery container energy storage system is based on advanced lithium battery technology, equipped with standardized converter equipment and monitoring management system, which can better meet the growing demand for energy storage. With the continuous breakthrough of lithium battery technology in the future, the cost of energy storage containers is expected to be greatly reduced, and the prospect is worth looking forward to.