• Bookstore

The beer bottles lie on a board in rows, all connected by hoses which allow cold water to flow through them and be heated by the sun's radiation.  The more conventional solar heaters have an anti-freeze liquid that heats at a very low temperature, which in turn heats water in a cistern.

"I invented this for my mother. I wanted her to shower at any time more comfortably," says Ma Yanjun, of Qiqiao village, Shaanxi Province, "a real solar water heater is too expensive to me, so I came up with the idea of making one on my own."

A "real" solar heater in the UK will cost anything from £3,200-£6,000 to install.

"I hope this invention can be promoted nationwide, and allow mothers in undeveloped rural areas to have a hot shower," he added.

Ma has now helped more than 20 families in the village to make and install their own beer bottle solar water-heaters.

He says he will build a public bathroom for the village using his invention when he has the money to buy enough beers.

This invention reminded us of the Plastic Bottle Greenhouse, which seems to be popular with schools.  Perhaps schools could also create solar hot water from old beer bottles too!