Transporting vaccines usually requires careful heat management – the container holding the drugs can’t get too cold or too hot. The temperature range is normally between 36 and 46 degrees Fahrenheit (2 and 8 Celsius), which doesn’t leave a lot of room for error considering the payload can prevent serious outbreaks of disease. Besides getting the vaccines to their destination, the container must be kept close to freezing while everyone in the area comes in to get vaccinated, which can range from days to weeks. While a well-insulated container packed with ice can be sufficient for the travel time required, it’s not effective in the long term.
Bruce McCormick of SAVSU Technologies (Santa Fe, New Mexico) developed the NanoQ thermal shipping containers that keep their contents at nearly constant temperature for long distance journeys. He wanted to extend the capabilities of the NanoQ and discovered that in the 1980’s scientists at Sandia National Lab developed an interesting refrigeration technology based on adsorption. It was in the form of a solar powered ice maker that was dusted off and brought out of storage by Sandia engineer Brian Iverson. He took the device apart, studied the original notes from the team that developed it, and used technology not available thirty years ago to improve its design so that vaccines can be kept cool as long as there’s access to water and sunlight.
Here are some details from Sandia:
The icemaker has a 1-meter-square solar collection area, a condenser and evaporator. Thermal energy is collected and the heat drives a fluid, in this case methanol, out of a porous carbon material.
The fluid moves by gravity to the condenser where it liquefies. At night, when heat is no longer driving fluid off the carbon, the condensed liquid evaporates and the gas is absorbed back into the carbon, drawing heat from the environment. That reaction has a cooling effect that freezes water in a trough, creating from 2 to 12 pounds of ice a day. “It needs no electricity or photovoltaic cells. It’s a refrigeration cycle,” Iverson said.
McCormick said the icemaker is key to SAVSU’s ability to offer the NanoQ to international agencies as a permanent replacement for costly, impractical refrigeration systems. “They go together,” he said.
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