Bill Gates has donated $1.4 million (£836,000) to a Welsh inventor who has designed a new fridge that can keep vaccines cool without electricity.

The technology is designed for use in the developing world and can keep vaccines cool for 35 days.

Ian Tansley of The Sure Chill Company, based in Snowdonia, north Wales, developed the unique technology which uses water to keep supplies of vaccines and blood cool in remote medical centres, where electricity may be in short supply.

"The devices will allow vaccines to be stored safely in challenging environments with no power and ambient temperatures as high as 43°C," he told the Daily Mail.

"Conventional refrigeration technologies can put vaccines at risk of either freezing or getting too warm. Our technology ensures that vaccines reach children in the best condition possible and has the potential to save the lives of countless children across the world."

At four degrees, water is at its heaviest and sinks. As explained on the company's website, the technology adapts its temperature naturally so it "automatically cools to the optimum temperature: a constant four degrees even without power".

"Water surrounds a Sure Chill refrigeration compartment," it reads. "When it has power, the water cools and forms ice above the compartment leaving only water at four degrees cooling the contents.

"When the power is switched off, the water warms and rises while the ice begins to melt, keeping only four-degree water cooling the contents of the compartment. So it has its own internal and entirely natural energy store that maintains a completely steady temperature. The system can operate like this, without power, for days and weeks."

The equipment has received funding from the Bill and Melinda Gates Foundation, which aims to enhance healthcare and reduce extreme poverty across the globe, and in America, to expand educational opportunities and access to information technology.

The most recent donation from Gates will enable the company to begin field trials in East and West Africa in the next year.

Sure Chill operate 10-day coolers in over 30 countries and the firm is recognised by the World Health Organisation.