Hydrogen for road transportation: achievements and developments.

At the beginning of this millenium, hydrogen appears as a potential energy carrier for the future. Thus, it could serve as a storage medium for renewa ble energy forms, which should play an increasing part in the world energy supply. In a closer future, hydrogen could also become a fuel for prospecti ve fuel-cell and internal-combustion vehicles. We present here an inventory of the various technologies related to the use of hydrogen in road transpo rtation : propulsion type (fuel cell and electric motor, or internal combus tion engine), hydrogen production, on-board storage, infrastructure. Safety , standardization and regulation aspects will also be addressed. Presently, the majority of hydrogen buses are equipped with polymer membrane fuel cel ls (PEMFC), directly supplied with hydrogen from pressurized vessels (300 b ars). On the other hand, car manufacturers are developing various types of experimental vehicles : internal-combustion engine cars with liquid hydroge n storage, fuel cell (PEMFC) cars with storage of hydrogen (liquid, gaseous , hydride) or of methanol. The type of required infrastructured will depend on the type of fuel chosen by the car makers and on the requirements of th e oil companies. Several hydrogen supply stations, of different technologie s, have already been set up. They deliver gaseous or liquid hydrogen produc ed by reforming of natural gas or by electrolysis. The building of a hydrog en-based fueling system requires the development of specific means of produ ction, transportation, storage and delivery. Public acceptance will have to be won by guaranteeing safety, reliability, performance and competitivity. Presently, research and development work is mainly carried out on: on-boar d storage of hydrogen; on-board systems for the production of hydrogen from methanol and petrol; standardization and regulation.