Overview Hydrogen has over the last century enjoyed repeated bouts of interest as a fuel source. Though these have repeatedly fallen flat, hydrogen-based production has recently enjoyed a renaissance, due to a trifecta of improving political, economic, and technological conditions. Importantly, hydrogen presents an answer to a major problem in the energy transition debate: decarbonizing fuel sources while maintaining energy security and reliability. While electrification has a first-mover advantage in certain areas (e.g., light-duty vehicles), hydrogen is seen as particularly viable in “hard-to-decarbonize” sectors such as heavy-duty transportation, which requires fuel supply for substantial distance and payloads. These trends are still nascent. There has long been a small hydrogen market, primarily for industrial applications;