Storing energy in magic beans

From the article on solar power, but this probably deserves its own post. Article is from September, but I missed it when it first came out.

When a type of salt is added, vermiculite, which is normally used to pot cactus and similar plants, takes on an extraordinary property. Blow warm air over it — breathing will do — and it dries out. But if you then expose it to cold, damp air, it absorbs the water and releases heat. Dubbed “magic beans” by researchers at Swansea University, the material can be used to store heat energy for months in this way.

A fridge-freezer-sized box of it could be used to provide effective heating for a domestic house for potentially months during the winter.

Professor David Worsley, an engineer at the university, said: “In the summer, we’ve got this massive amount of hot air collected by solar thermal collectors. We wanted to make a material you could put heat into and save it for the winter. You drive hot air over it, it drives all the water off and in the winter all you do is introduce cold damp air. It absorbs the water and releases energy... It will keep the heat until you put some damp air on it — so you can time-shift solar energy from the summer into the winter. We are really excited by this.”
http://www.independent.co.uk/news/science/heating-vermiculite-potting-plants-heat-storage-summer-sun-winter-swansea-a7234406.html