A device for storing and releasing hydrogen gas. The hydrogen gas can be used to drive pneumatic mechanical mechanisms. The hydrogen gas is stored in a metal hydride material. The metal hydride is in thermal contact with a thermoelectric module (10) (TEM). When acted upon by an electrical current through the TEM one volume of metal hydride (12) is heated and releases hydrogen gas while a second volume of metal hydride (28) is cooled and absorbs hydrogen gas. There is a pressure difference generated between the heated volume and the cooled volume. This difference in pressure is used to drive a pneumatic-mechanical mechanism to perform work.
