BESS's installation platform provides physical protection and a fixed space for various indoor BESS equipment, meeting the requirements of the site's environmental standards. It also possesses its own independent power supply system, temperature control system, heat insulation system, flame retardant system, fire alarm system, electrical interlocking system, mechanical interlocking system, safety escape system, emergency system, and fire protection system, among other dynamic control and safety assurance systems.
Based on their construction and installation methods, they are generally divided into fixed buildings (including prefabricated buildings) and prefabricated modules, with the latter mainly referring to containerized and outdoor cabinet types, as shown in the figure.
In recent years, with the increasing demand for energy storage applications and the continuous expansion of intelligent functions such as electrical and control systems, higher and higher requirements have been placed on the life-cycle cost and convenience of installation platforms. The disadvantages of fixed buildings, such as large footprint, long construction period, inability to move, and inconvenience in later expansion, have become increasingly prominent, while prefabricated container installation platforms, represented by containerized structures, are being used more and more widely.
Containerized prefabricated cabins
Containerized prefabricated modules have transformed the electrical system layout, architectural design, and construction mode of BESS (Building Safety System), enabling the rapid construction of large or medium-sized BESS projects through two main stages: factory prefabrication and on-site installation. Their standardized design, modular combination, industrialized production, and intensive construction not only shorten project construction cycles and reduce environmental pollution but also greatly facilitate commissioning, subsequent maintenance, and expansion.
outdoor container
Besides containerized containers, another major form of prefabricated storage is the outdoor container. Strictly speaking, outdoor containers are theoretically more flexible and specialized, allowing for customized design in terms of structural strength, corrosion resistance, and appearance, based entirely on the capacity, electrical connection methods, application site, and functions of BESS (Body Storage System).
However, after adapting to changes in strength, corrosion resistance, and dimensions, containers have transformed from simple cargo containers into integrated platforms for electrical equipment that comply with relevant regulations and standards. Furthermore, due to their availability and global logistics compatibility, they still occupy a significant proportion in energy storage projects, especially large-scale ones. From the perspective of key design aspects such as structural corrosion resistance, temperature control, and fire safety, containerized and outdoor containerized prefabricated storage systems share a high degree of similarity and can learn from each other. Their internal equipment installation processes are also largely consistent.
Prefabricated modular installation platforms also have certain drawbacks, such as:
1) Poor long-term durability: If the design process does not adequately consider climatic conditions and environmental factors, especially wind, sandstorms, salt spray, extreme cold, and high pollution levels, the materials used in the prefabricated modules, while meeting the quality inspection requirements of the enterprise or integrator, may still experience corrosion and insufficient durability under extreme conditions;
2) Certain safety hazards: Due to the compact installation of equipment within the prefabricated modules, they are generally arranged according to the shortest electrical safety distances specified in standards and specifications. Improper handling may lead to safety hazards such as electrical leakage and short circuits.
Therefore, it is even more necessary to continuously strengthen the research and application of new materials, manufacturing methods and processes, fire protection and monitoring technologies for prefabricated containers. For containerized prefabricated containers, while drawing on rich experience in the manufacturing, transportation and use of standard containers, efforts should be made to continuously achieve flexibility, speed, efficiency, safety and intelligence.
The prefabricated containerized modules used in BESS (which can be called BESS containers or containerized energy storage boxes) can be selected according to different standard specifications depending on the capacity of the BESS. However, in order to pursue system compactness and prefabrication, other design dimensions are often not excluded, provided that transportation convenience and the lowest overall cost are ensured.
Here is the extracted table in English (standard shipping container dimensions):
| Specification | Length (m) | Width (m) | Height (m) | Volume (m³) | Max Payload / Tare Weight (kg) |
|---|---|---|---|---|---|
| 20'GP | 5.890 | 2.350 | 2.390 | 33.1 | 21780 / 2220 |
| 40'GP | 12.029 | 2.350 | 2.390 | 67.6 | - |
| 40'HC | 12.029 | 2.350 | 2.698 | 76.3 | 28700 / 3800 |
| 45'HC | 13.546 | 2.350 | 2.693 | 85.7 | - |
Containers are generally made of three materials: aluminum alloy, steel, and fiberglass. Steel containers are strong, structurally robust, have good weldability and watertightness, and are relatively inexpensive; however, they require high-weather-resistant steel and surface anti-corrosion treatment to improve their long-term environmental adaptability, and are also quite heavy. Fiberglass containers are also common. Their advantages include high strength, light weight, ease of molding, heat insulation, flame retardancy, corrosion resistance, and chemical resistance. They also have a long service life and low overall cost, making them a relatively ideal container material. However, their strength may decrease at some bolt tightening points or structural joints.
A standard steel shipping container is a six-sided cuboid, consisting of a roof, gable walls, side walls, doors, floor, frame, corner fittings, and other accessories, as shown in the diagram.
BESS containers primarily use steel, with channel steel for the bottom beams and high-quality corrugated steel sheets for the body and roof, with an effective thickness of no less than 2.0mm.
BESS containers are designed for a 25-year lifespan and employ "high weather resistance and corrosion protection technology." This process follows the relevant standards: CECS343-2013 "Technical Specification for Corrosion Protection Coating of Steel Structures" and GB/T30790.2-2014 "Corrosion Protection of Steel Structures by Paint and Varnish Protective Coating Systems Part 2: Environmental Classification." The container body surface and related metal parts should first undergo rust and oil removal, localized grinding, and overall sandblasting to enhance the adhesion of the powder coating.
The coating employs a three-layer anti-corrosion paint application:
The first layer is an epoxy zinc-rich primer with a dry film thickness of at least 40µm. This primer offers superior anti-corrosion performance, strong adhesion, and a high zinc powder content, providing cathodic protection and excellent water resistance.
The second layer is an epoxy micaceous iron oxide intermediate coat with a dry film thickness of at least 50µm. Rich in zinc powder, the electrochemical protection provided by the zinc powder gives the coating outstanding rust prevention, high film hardness, strong adhesion, and good mechanical properties.
The third layer is an aliphatic polyurethane anti-corrosion topcoat with a dry film thickness of at least 50µm, exhibiting excellent weather resistance and durability. The paint film is full, aesthetically pleasing, and glossy, offering good decorative properties. The coating is tough, has strong adhesion, and provides good impact and abrasion resistance, as well as excellent chemical, water, and oil resistance.
The bottom of the BESS energy storage container undergoes sandblasting and zinc spraying, followed by heavy-duty asphalt paint anti-corrosion treatment. It should meet the Class [level] standard specified in GB1720-1979 "Test Method for Coating Adhesion" or the Method A test standard in GB 1726-1979 "Test Method for Coating Hiding Power".
The container should be watertight on all sides, with no water accumulation on the top and no water seepage at the bottom. The container's internal and external air inlets and outlets should be equipped with easily replaceable standard ventilation filters to prevent dust from entering the container during strong winds and sandstorms. The container should possess sufficient mechanical strength to ensure that it and its internal equipment do not deform or malfunction under transportation and earthquake conditions. It must have UV protection to ensure that the properties of the container's internal and external materials do not deteriorate or overheat due to UV exposure. The container's protection rating should be no less than IP54.
The BESS container should be equipped with relevant warning signs and escape routes according to GB 2894-2008 "Safety Signs and Their Use Guidelines", as shown in the figure.
In addition to a door of sufficient size reserved for the access of electrical equipment, BESS containers should also have two single-leaf passenger doors at the long side end to separate passengers and cargo. These passenger doors also serve as emergency escape doors, with a width of no less than 900mm. They employ push-rod type safety escape locks, and are equipped with door closers and limit rods, ensuring the doors can be opened from the inside in any emergency and remain open during construction. Sealing rubber strips are installed around the door frame and door body to ensure the container's airtightness; a water guide channel is installed above the door panel to prevent rainwater ingress. Rock wool insulation material can be filled in the middle of the door body, providing fireproof and thermal insulation properties.