Cold fusion

Cold fusion is a hypothesized type of nuclear reaction that would occur at, or near, room temperature. This is compared with the "hot" fusion which takes place naturally within stars, under immense pressure and at temperatures of millions of degrees, and distinguished from muon-catalyzed fusion. There is currently no accepted theoretical model which would allow cold fusion to occur.

In 1989 Martin Fleischmann (then one of the world's leading electrochemists) and Stanley Pons reported that their apparatus had produced anomalous heat ("excess heat") of a magnitude they asserted would defy explanation except in terms of nuclear processes. They further reported measuring small amounts of nuclear reaction byproducts, including neutrons and tritium. The small tabletop experiment involved electrolysis of heavy water on the surface of a palladium (Pd) electrode. The reported results received wide media attention, and raised hopes of a cheap and abundant source of energy.