Container Energy Storage Systems : Structural & Door Design Essentials

Overall Structural Design

The overall structural design of the module must comply with current national standards and design specifications. It should integrate practical engineering considerations with the judicious selection of materials, structural schemes, and construction measures. This approach ensures that the structure meets requirements for strength, stability, and rigidity during transportation and installation, as well as for waterproofing, fire resistance, corrosion resistance, and durability.

The container’s framework is built upon metal structural components that must provide sufficient rigidity and load-bearing capacity. These components are designed to support the installation of electrical elements and withstand mechanical, thermal, and electromechanical stresses (such as those generated during operation or short-circuit conditions). Moreover, the framework must not be compromised by the hoisting, transportation, or installation of the complete equipment set. The exterior shell of the equipment should be smooth, tightly sealed, aesthetically pleasing, and corrosion-resistant, capable of withstanding harsh climatic conditions including humidity, salt spray, severe cold, and sandstorms.

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I. Cabin Frame – Design Requirements

Base Plate Dimensions

• The size of the base plate section steel must be determined through load calculations.
• It is essential to ensure that the deflection of the base plate beam meets structural design standards and that strict anti-corrosion measures are applied.

1. Structural Strength and Rigidity Requirements

• Load-bearing Capacity:
  The frame must support the weight of the battery system, auxiliary equipment, and other loads, while also accommodating dynamic loads (such as vibrations and impacts during transportation and hoisting).
• Deformation Resistance:
  During transportation, hoisting, and operation, the frame should maintain sufficient rigidity to prevent deformation that could damage equipment or battery packs.
• Wind and Snow Resistance:
  For outdoor applications, the design must account for resistance to wind pressure and snow loads.

2. Material Selection

• High-Strength Steel or Aluminum Alloy:
  These materials are commonly used for energy storage container frames due to their excellent strength, durability, and corrosion resistance.
• Weather-Resistant Coatings:
  The frame’s surface should be treated with anti-corrosion and anti-rust coatings to extend its service life.

3. Standards and Regulations

• Dimensional Standards:
  Designs should comply with ISO container standards (such as 20-foot or 40-foot containers) or custom specifications to ensure ease of transportation and storage.
• Safety Standards:
  The design must meet local or international energy storage system standards (e.g., UL 9540, IEC 62933).
• Fire Protection Requirements:
  Fire isolation and high-temperature protection must be incorporated into the design.

4. Welding and Integrity

• The entire cabin frame should be welded as a single unit to ensure sufficient strength and rigidity. The structure must not deform or suffer damage during hoisting, transportation, or installation.

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II. Cabin Doors and Box – Design Requirements

Cabin Doors:

• The door design must facilitate the transportation and inspection of internal equipment.
• Fire-rated doors are required, and the burning performance and fire resistance of other structural components must comply with relevant local legal requirements.

Exterior Shell Construction:

• The cabin’s exterior shell is typically constructed from cold-rolled steel sheets that have undergone anti-corrosion treatment or from stainless steel sheets.
• The sides, roof, and floor of the box should be filled with insulation material to ensure excellent thermal insulation and heat preservation. This insulation must also meet fire protection requirements, preventing cold bridging and condensation.

Roof Panel and Insulation Materials:

• Roof Panel:
  Use lightweight, high-strength, corrosion-resistant, and waterproof materials.
• Intermediate Layer:
  Should be made of non-combustible material.
• Insulation Materials:
  These should have low water absorption, low density, a low thermal conductivity, and sufficient strength.

Minimizing Exposed Fasteners:

• The prefabricated cabin shell should be designed to minimize the accumulation of dust and water.
• Exposed fasteners should be minimized to prevent screws from penetrating the shell and causing water ingress. Any penetrations must be properly sealed.
• If exposed fasteners are unavoidable, they must be made of stainless steel to prevent rusting.

Foundation Connection:

• The cabin must be securely connected to its foundation, preferably welded to pre-embedded foundation components.
• The junction between the cabin and foundation should be sealed with weather-resistant silicone to prevent moisture intrusion.

Ventilation and Heat Dissipation:

• Cabin doors may incorporate louvered vents or designated spaces for cooling equipment, ensuring both waterproof and dustproof performance.
• Pressure Equalization:
  The door design should include pressure equalization vents to manage pressure differences between the interior and exterior.

Thermal Management:

• The cabin should offer excellent thermal insulation and be equipped with appropriate heating, cooling, and ventilation systems.
• These measures ensure that all electrical equipment operates within its designated temperature range under typical ambient conditions, while preventing condensation inside the cabin.

Door Specifications:

• The door must open to an angle of at least 90° and be equipped with a limiting device to secure it in the open position.
• It should possess sufficient strength so that its operation and sealing remain uncompromised after hoisting and transportation.
• The dimensions of the door must be designed to accommodate the equipment inside, ensuring ease of handling and maintenance.