Roland Piquepaille writes: "Many people predict that one day we'll drive cars powered by hydrogen. These 'green' cars would only release water after combustion of the hydrogen, which would be good for our planet. But there is a big hurdle: we really don't know how to store safely this hydrogen. Now, researchers in the U.K. and Canada say they've discovered — almost by accident — a new material which could be used to safely store hydrogen at room temperature. This new material, a rhodium-hydrogen compound, can store and release hydrogen with a simple switch. And the researchers hope to have an hydrogen tank prototype ready within two to three years. Read more for additional references and a diagram showing the molecular structure of this new material."