No matter how abundant or renewable, solar power has a thorn in its side. There is still no cheap and efficient long-term storage for the energy that it generates.

The solar industry has been snagged on this branch for a while, but in the past year alone, a series of four papers has ushered in an intriguing new solution.

Scientists in Sweden have developed a specialised fluid, called a solar thermal fuel, that can store energy from the sun for well over a decade.

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