Guidelines For Use Of Hydrogen Fuel In Commercial Vehicles: Greencell Technologies Part 2

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GreenCell Technologies, Canada Part 2: In some ways, a gaseous hydrogen fuel leak is less dangerous than a leak of diesel fuel or gasoline. Leaking diesel fuel and gasoline can puddle and spread over a large area, and the puddles will persist because they evaporate slowly. Gaseous hydrogen leaks tend to be vertical, with only a relatively narrow area/volume in which a flammable mixture exists—the hydrogen quickly rises and dissipates in open air to nonhazardous levels.
If designed properly, the most likely location of a major hydrogen leak from a vehicle will be through the pressure relief device (PRD) on the hydrogen fuel storage cylinders, which should vent away from the occupied area of the vehicle. PRDs are designed to vent the entire contents of a hydrogen tank in only a few minutes—after which there is no lingering risk of hydrogen fire or explosion if the release was in the open air. Large hydrogen leaks inside buildings are more dangerous unless the facility has been designed to evacuate the leaked gas and to minimize ignition sources at ceiling level.
GreenCell Technologies, Canada - Leaking ...
... liquid hydrogen can pool and spread, but will quickly evaporate as it is heated by the surrounding air. The distance it will spread and the rate of evaporation will depend on the size of the leak and on ambient conditions. As it evaporates, the cloud of gaseous hydrogen formed over the spill may move horizontally as it rises and dissipates. This hydrogen cloud may be cold enough to cause frostbite to exposed skin and should be avoided.
While diesel fuel and gasoline leaks are easily visible and accompanied by a strong characteristic smell, gaseous hydrogen leaks are invisible and odorless. The only indication of a gaseous hydrogen leak may be a whistling noise similar to escape of other high-pressure gases. A liquid hydrogen leak may be accompanied by an area of fog surrounding the leaking hydrogen and/or the formation of frost on the tank or lines in the vicinity of the leak, because the super cold hydrogen cools the surrounding air and causes water vapor to condense.
Based on hydrogen's chemical and physical properties, there are a number of general principles that govern safe design and use of hydrogen fuel. These are essentially the same principles that apply to the use of any gaseous fuel (e.g., natural gas), but their application may be slightly different based on the properties of hydrogen. The most important safety principle in any situation is education—making anyone who will come into contact with a vehicle aware of a potential hazard. For hydrogen and other alternative-fueled vehicles, this is done with appropriate labeling to let users, emergency responders, and the public know that hydrogen is present.
GreenCell Technologies, Canada - As with other motor fuels, fire and explosions are the most significant everyday hazards associated with hydrogen. Also as with other fuels, a hydrogen leak from a vehicle's fuel or engine system, or from a fueling station, provides the starting point for all fire and explosion hazards. Safe design for using hydrogen, both for vehicles and for fuel stations and buildings, therefore, requires attention to these safety principles: Properly label all vehicles that use hydrogen fuel. Avoid fire and explosion by: Avoiding leaks through proper design and maintenance, Providing leak detection systems to detect leaks and, if a leak is detected, shut off the fuel system as soon as possible, Removing ignition sources from areas where leaked hydrogen might be present, and GreenCell Technologies, Canada - Properly ventilating all enclosed spaces where leaked hydrogen might accumulate. These general principles translate into specific design and operating requirements for hydrogen-fueled vehicles, the facilities that will house or maintain them, and hydrogen fuel stations. In most aspects, commercial vehicles powered by hydrogen will be identical to those powered by diesel fuel, but some hydrogen-specific design elements are required. Likewise, operation of these vehicles will be similar to operation of diesel-fueled vehicles, with a few exceptions. Each vehicle manufacturer will develop their own designs, which are likely to vary significantly in the details, while adhering to the same general design principles noted above.