Rudolf Erren

German engineer, born in 1899, whose work focused on adapting internal combustion engines to run on hydrogen fuel. Erren developed the Erren engine and held multiple patents on hydrogen fueled propulsion, including what is described as the earliest reported use of supercharging on a hydrogen fueled engine. His hydrogen engine designs reportedly powered at least one German U-boat during the Second World War. Erren served in the German military during the First World War and later worked as a police officer before returning to his hydrogen engine research; he was interned in Canada by British forces during the Second World War and repatriated to Germany in October 1945. The International Association for Hydrogen Energy later established the Rudolf Erren Award in his honor to recognize contributions to hydrogen energy research.