Jeff Bezos and Bill Gates, the world’s two richest people, have invested in a company that aims to store electricity by heating molten salt, which has been spun out of Alphabet's experimental technology company, X.

Malta, a Massachusetts-based company, has raised $26m (£21m) from Breakthrough Energy Ventures, which counts the Amazon and Microsoft founders among its investors.

The company was set up last year and hopes to be able to store electricity from solar and other renewable sources using an elaborate system that stores the energy as extreme heat and cold.

It has now been spun off from X, the experimental arm of Google’s parent company Alphabet.

Energy generated from renewable sources is often wasted, and existing storage solutions such as batteries often struggled to keep up with capacity at peak times.

Malta’s system involves electricity from solar panels being fed into a heat pump, which converts it into thermal energy. This is then stored as heat in “solar salt”, a nitrate that can store high temperatures, and as cold in an antifreeze liquid.

The heat or cold is then returned to the electricity grid when needed. Malta says the energy can be stored for days or weeks before it is needed