Most COVID vaccines require cold chain infrastructure to maintain required storage temperatures in the -30° C to -80° C range. The last stage of distribution can be challenging for rural or suburban areas where such infrastructure is not available. Researchers from Carrier and U.S. Oak Ridge National Laboratory (ORNL) collaborated on the design of an effective/solution to mitigate the challenges posed by vaccine distribution logistics.

The engineers retrofitted a commercial refrigeration container designed to ensure that vaccines remain at ultra-low temperatures during long transport and while locally stored. A testbed was configured with a lightweight aluminum container equipped with a refrigeration system, vaccine packages and optimal cargo layout and storage rack design that kept temperatures consistent and uniform throughout the container.

The tested refrigeration container units and vaccine packages were fully instrumented to monitor the operational performance. The measurement includes temperature distribution inside the refrigeration container unit, temperature inside vaccine packages, supply and return air temperature of refrigeration system, pressure difference between inside and outside of refrigeration container unit, and carbon dioxide and oxygen concentration level inside refrigeration container unit.

Compared with regular storage, the refrigerated storage container can create -30° C surrounding temperatures of the vaccine packages and slow the dry-ice sublimation process to extend the useful lifetime of maintaining the vaccines in dry-ice packages. Polyurethane rigid foam panels played a critical role in keeping the temperature in the container low even on a summer day. Simulation studies also demonstrated that this method can hold required temperatures for extended time periods.

The research is published in the International Journal of Refrigeration.

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