A Water-Chilled Coolbox Gets Vaccines on Tap to the World’s Poorest
It was a walk past a frozen lake 10 years ago that got Ian Tansley thinking differently about global health. The Welsh inventor had spent decades travelling and developing solar technologies throughout Africa and Asia. Yet one puzzle he was keen to crack – how to deliver vaccines on a wide-scale basis to the poorest, most remote communities – had so far eluded him.
Vaccines are notoriously hard to deliver safely, requiring refrigeration at certain temperatures, which means having access to a constant power supply. Yet hot climates, intermittent availability of electricity, supply shortages and unreliable storage facilities mean that one in five children – more than 19m worldwide – do not get even the most basic immunisations to keep them healthy.
Using the frozen lake as his inspiration, with its frozen top but liquid bottom, Tansley developed a refrigeration system, Sure Chill, that harnesses water’s unique properties to keep vaccines cool at 4C – yet doesn’t require a constant power supply. The refrigeration compartment is surrounded by water, and relies on the fact that the liquid is at its heaviest at 4C, when it sinks. When the device has power, the water cools and forms ice above the compartment, leaving only water at 4C cooling the contents. When the power is switched off, the water warms and rises while the ice begins to melt, and water at 4C remains below to keep the vaccines chilled.
Sure Chill – which was awarded a $1.5m (£1.2m) Grand Challenges grant from the Bill and Melinda Gates Foundation and is now used to deliver vaccines in 38 countries – has proved a major breakthrough in global health. Tansley’s immunisations cold-box can keep vaccines cool for up to 35 days in even 43C weather. And the technology is entirely scaleable, from a cool box up to a warehouse.