2,000 m² Pharmaceutical Cold Storage Project in Shanghai

Cold Storage Envelope and Thermal Insulation System

The storage enclosure adopts an assembled structure of double-sided color steel polyurethane sandwich panels with a panel thickness of 150 mm. The core material is continuously foamed polyurethane (PU) featuring a density of ≥42 kg/m³, thermal conductivity ≤0.022 W/(m·K), and flame retardancy Class B1. Panel joints are fitted with eccentric locking hooks and two layers of low-temperature-resistant sealing strips. The floor is constructed with an XPS extruded polystyrene insulation layer over reinforced concrete, equipped with vapor barrier and waterproof layers to eliminate frost heave caused by underground moisture migration.

A constant-temperature vestibule (buffer room) is installed at the loading/unloading bay, equipped with two interlocking motorized sliding doors paired with flexible insulated high-speed doors, effectively mitigating temperature disturbances to the main storage zone during door-opening operations.

Refrigeration System Architecture – BITZER Parallel Compressor Units with Hot Gas Defrost

Refrigeration hosts are German BITZER semi-hermetic piston compressors configured as multi-head parallel condensing units with variable frequency capacity regulation. Detailed specifications are as follows:

Pressure sensors continuously monitor suction pressure of the parallel units to automatically load/unload compressor heads and adjust inverter frequency, stabilizing evaporating pressure between -4.5°C and -5°C and minimizing temperature fluctuations at air cooler outlets. High-precision evaporating pressure regulation serves as the core prerequisite for limiting warehouse temperature deviation within ±0.5°C.

Temperature Control Terminals and Air Distribution System

Twelve high-static ceiling-mounted air coolers are deployed inside the warehouse, featuring stainless steel casings and hydrophilic aluminum fin coils with a 4.5 mm fin spacing to extend frosting intervals. Each air cooler is oversized with a 20% air volume margin, fitted with fabric air ducts (Sox ducting) at air outlets to deliver microporous top-supply side-return air distribution throughout the storage space. Laser-drilled micro-perforations cover the duct surface to maintain an outlet air velocity of 0.8–1.2 m/s, completely eliminating direct cold air impingement on cargo stacks and stagnant air dead zones. Airflow simulation verifies temperature differences of less than 0.4°C between the top and bottom of stored goods.

Schneider Electric Control System and GMP-Compliant Data Management

The control system centers on Schneider Electric Modicon M580 redundant CPUs paired with HMIP570 HMI terminals and the EcoStruxure™ Plant Expert digital platform. The hierarchical control framework is detailed below:

The system archives timestamped online data for up to 548 days (expandable). All temperature limit violations, equipment start/stop events and user login activities generate immutable audit logs. Four tiers of access authority are established: Operator, Team Leader, Equipment Engineer and Qualified Person, fully satisfying GMP validation requirements for computerized systems.

System Redundancy and Fail-Safe Strategy

Refrigeration Units: One primary and one standby complete unit; each unit contains N+1 redundant compressor heads. Upon failure of a single compressor or an entire unit, the standby set takes over automatically within less than 30 seconds.

Power Supply: Dual municipal power feeders with a backup interface for diesel generators; the PLC control system is equipped with UPS providing a minimum 60-minute backup runtime.

Sensors: Dual PT100 sensors are installed at all critical monitoring zones. The system averages readings for control logic, triggers alarms for single-sensor faults, and automatically excludes invalid readings.

Environmental Sustainability and Energy-Saving Measures

The project prioritizes environmental protection and low-carbon operation. R449A eco-friendly refrigerant is adopted with an ozone depletion potential (ODP) of 0 and a GWP of only 1282, approximately 67% lower than R404A. EC fans on condensers adjust speed steplessly according to condensing pressure; free floating condensing is enabled in winter under low ambient temperatures to reduce compressor load, delivering an annual integrated energy efficiency ratio (EER) above 4.8. Hot gas defrost cuts power consumption for defrost cycles by roughly 35% compared to full electric heating defrost. Uniform air supply via fabric ducts eliminates extra reheating demand, resulting in an overall operating energy consumption reduction of over 25% versus conventional pharmaceutical cold storages.

Construction Implementation and Qualification Validation

Construction mobilization commenced in early March 2024, covering panel assembly, refrigeration pipeline welding and pressure testing, control system programming and commissioning, duct installation and overall system joint debugging. Empty and full-load temperature distribution mapping tests were completed in June 2024. A third-party validation body deployed 16 calibrated wireless temperature loggers for data acquisition over a continuous 72-hour period per GMP requirements. Test results show all monitoring points maintained steady temperatures between 3.2°C and 6.8°C with a maximum deviation of ±0.4°C and temperature uniformity of ±0.3°C, far exceeding the acceptance standard of 2°C to 8°C. Simulated fault scenarios including power outage, compressor breakdown and defrost interruption all triggered seamless redundant switching without exceeding temperature limits inside the warehouse.

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