What if a low-cost solar thermal ice production system could be used to refrigerate vaccines without electricity? Adam Gage, Peter Shoaf, Jeromie Webster, and Logan Olsen think it would be pretty cool. The team developed a method to harness naturally occurring adsorption/desorption cycles to help developing countries increase vaccine availability.
Their system uses solar rather than mechanical energy, which decreases maintenance. It requires no chemical additives and relies on materials that can be locally sourced in developing countries. For example, it uses methanol (wood alcohol) and biochar, both sourced from biomass, for the adsorption cycle. The team’s vision was to develop a low-cost set of materials and accompanying instructions that someone with a modern education could readily use to create a refrigeration unit from scratch.
“We are employing the adsorption cycle of methanol and biochar to freeze water and produce ice,” says Gage. “We have our biochar saturated with methanol during the day, and the sun’s radiation will vaporize the methanol and condense in the air-cooled copper condenser and collect.” At night, the collector cools, creating a pressure difference that causes the methanol to evaporate and draw heat from the water to create ice. The evaporated methanol will then re-adsorb to be used the next day. The unit will produce two kilograms of ice per day within a refrigeration space of two liters. It keeps vaccines between 2 and 8 degrees Celsius.