Energy Free Cool Storage delivers cool storage for agricultural outputs by leveraging the root cellar concept and a design which does not rely on coolants, electricity, or solar power. Root cellars are underground structures that provide low and steady temperatures as well as stable humidity. By taking advantage of subterranean geothermal soil properties, root cellars create an effective environment to ensure the stability of three key produce storage variables: humidity, temperature, and ventilation. At a depth of eight to twelve feet underground, Energy Free Cool Storage will provide a cool storage environment with 90-95% humidity and natural ventilation to keep the proper temperature, reduce excess humidity, prevent rot and mold, and remove ethylene gas.
The simple technology consists of three parts: (1) a scalable storage “tank” for agricultural output, (2) two ventilation pipes to naturally facilitate air circulation, and (3) an entryway/hatch for easy and secure access. The storage tank is where farmers, aggregators, or marketplace actors can efficiently store their produce. The pilot version of the Energy Free Cool Storage will be designed for individual farmers, while future versions will scale in size to be sufficient for aggregators and marketplaces. The Model 1 prototype will be built and tested specifically for Zambian tomato farmers and will have a 4,000 liter storage capacity. The ventilation is provided by two simple polyvinyl chloride (PVC) pipes. Although both pipes will initiate above ground, one will terminate at the top of the storage “tank” and one will terminate at the bottom of the storage “tank.” This creates a siphon in which fresh air is introduced and stale air is vented out. Wire mesh and a vent cap will prevent moisture and pests from entering through the ventilation system. A sealable hatch and small ladder will allow entry and exit from ground level. On larger models, a stairway will be introduced. Unlike many storage devices, Energy Free Cool Storage is a closed environment which facilitates the secure storage of crops. Installation method depends on size of the “tank.” The pilot version can be installed with a shovel and manual labor.
While initial models take advantage of the simplest version of a “root cellar,” future models such as the Model 2 for aggregators and markets can include solar-powered ventilation and lighting, thermometers and hygrometers, and advanced shelving and warehousing systems.