A new breed of fridge that can stay cool for up to 10 days without any power has been developed by a British company.
Besides keeping food and medicines fresh for longer during outages, in future it could cope well with the power cuts imposed on refrigeration appliances by renewable-energy-powered smart grids.
Originally developed to help store vaccines in developing countries, the low-power fridge is partly the result of good insulation. But it also uses a phase-change material to regulate the temperature, says Ian Tansley, chief technical director of the firm behind the fridge, True Energy, based in Tywyn, Gwynedd, UK.
Vaccine fridges typically use some form of battery to store power for use during power outages, or the likes of ice, to cope with intermittent power.
But batteries tend to have limited life-spans and ice will behave differently depending on the ambient temperature leading to unwanted temperature fluctuations inside the fridge which can be a problem for temperature sensitive medicine.
Phase-change materials help to solve this problem as they behave normally while in solid form as they absorb heat the material’s temperature rises. But when they begin to melt and change their phase they absorb large amounts of heat from their surroundings while maintaining a constant temperature, until the phase change is complete.
Although True Energy will not say which phase-change material it is using, the firm says it was chosen because it has a melting point that is ideal for refrigeration. “It wants to be at 5 °C,” says Tansley, and so it keeps the fridge at that temperature.
The vaccine fridge was endorsed by the World Health Organization last year. True Energy is now aiming to apply the technology to domestic and commercial fridges.