MIT researchers have published details of a new open-source forced-air evaporative cooling chamber. Described as being less expensive than refrigerated cold rooms, the chamber is intended to offer accessible cold storage for smallholder farmers, as well as significantly reduce post-harvest waste in hot and dry climates.

The chamber, which can be housed in a used shipping container and powered by either grid electricity or solar panels, has a capacity of 168 produce crates. The design uses industrial fans to draw in hot, dry air, which is passed through a porous wet pad. This creates cool, humid air that is directed through crates of produce, allowing rapid cooling. The air is then directed through the raised floor and to a channel between the insulation and the exterior container wall, where it flows to the exhaust holes near the top of the side walls.

The project was led by MIT Professor Leon Glicksman of the Building Technology Program within the Department of Architecture and Research Engineer Eric Verploegen of MIT D-Lab. Verploegen has been exploring the potential of evaporative cooling since 2016, focusing initially on small-scale “Zeer” pots and larger zero-energy cooling chambers or ZECCs. The new design distinguishes itself from these earlier models through its active airflow system and substantially larger capacity.

“Delicate fruits and vegetables are most vulnerable to spoilage if they are picked during the day,” Verploegen explained. “And if refrigerated cold rooms aren’t feasible or affordable, evaporative cooling can make a big difference for farmers and the communities they feed.”

The team claims that the system uses only a quarter of the power compared to refrigerated cold rooms, whether connected to the grid or solar panels. The incorporation of used shipping containers as the structure of the chamber is also described by the team as a “great example of up-cycling.”

Pilot projects have been conducted in Kenya and India, where smallholder farms and insufficient cold storage facilities have led to significant post-harvest losses. These pilots, one on-grid and one off-grid, have yielded promising results, demonstrating the potential for reducing waste and sustaining the freshness of fruits and vegetables.

“We're continuing to test and optimize the system, both in Kenya and India, as well as our test chambers here at MIT,” Verploegen explained. “We will continue piloting with users and deploying with farmers and vendors, gathering data on the thermal performance, the shelf life of fruits and vegetables in the chamber, and how using the technology impacts the users. And, we're also looking to engage with cold storage providers who might want to build this or others in the horticulture value chain such as farmer cooperatives, individual farmers, and local governments.”