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Vaccine fridge keeps its cool during 10-day power cut

作者:喻啾    发布时间:2017-10-08 06:00:06    

By Duncan Graham-Rowe A TYPE of fridge that can stay cool for up to 10 days without any power has been developed. Besides keeping food and medicines fresh for longer during outages, in future it could cope well with the deliberate power cuts imposed on domestic white goods by renewable-energy-powered smart grids. Originally developed to help store vaccines in developing countries, the low-power cooler is partly the result of good insulation. But it also incorporates 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 batteries to store power for use during outages, or an energy storage medium, such as ice, to cope with intermittent power. But batteries tend to have limited life-spans and ice will behave differently depending on the ambient temperature – either providing too much or too little cooling, and so leading to unwanted temperature fluctuations inside the fridge. This is where phase-change materials come in. They behave normally while in solid form: as they absorb heat the material’s temperature rises. But when they begin to melt – 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,

 

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