The development of autonomous solar cold rooms faces several challenges, particularly in regions with abundant solar resources but limited or no electrical grid infrastructure. Key issues for agricultural goods storage include the need for reliable energy storage, efficient refrigeration systems, and the ability to transport these systems to meet distribution needs. Previous studies have primarily focused on technical and economic indicators during the design phase, often overlooking the dynamic temperature evolution of stored goods, which is crucial for food preservation.

The study involved the collaboration between CEA and AIRWELL to design and test a prototype of an Autonomous Solar Powered Cold Room (CFSA) system. The CFSA system includes a lead-acid battery, a 3.1 kWth refrigeration unit using refrigerant, a configurable PV field with 20x 500Wc PV modules, 8000 VA DC/AC inverter and DC MPPT chargers, and a cold room, connected to a backup electrical network. The system was tested under dynamic conditions representative of maintaining food temperatures. To simulate realistic energy behavior, heating resistors controlled by a dynamic thermal simulation were used to emulate the internal thermal load. This approach accounts for the quantity of goods stored and their dynamic changes over time, considering variable efficiencies of the PV field, refrigeration unit, and battery.

The CFSA was tested on the CEA platform from August to November 2024. Instrumentation included thermocouples, hygrometers, anemometers, pyranometers, temperature/humidity sensors, rain gauges, and controllable dimmers for heating resistors.

The simulation used Scilab to model thermal and mass transfers, considering door openings, convective exchanges, and matter transfers. The simulation calculated outputs like air temperature and virtual mass of matter in the CFSA, providing insights into the system's performance under various scenarios.

The battery demonstrated a nocturnal discharge regime, maintaining continuous operation of the refrigeration unit. It showed an autonomy of 30 hours of refrigeration without solar input during the temperature drop phase and 150 to 200 hours in the stabilized temperature phase.

The PV field's performance was verified under different weather conditions. In periods of strong sunshine, the battery reached maximum charge by midday, clipping half of the achievable PV production. With reduced sunshine, the PV field ensured operational autonomy with 3kWh/kWc/day. Under low sunshine and temperature difference conditions, recourse to a backup source was observed approximately every 3 days.