Battelle completing multi-year safety testing program for compressed hydrogen storage systems for vehicles
16 July 2012
Battelle is wrapping up a multi-year safety testing program—including the development of test methods and then conducting the safety tests—for 350 bar and 700 bar hydrogen storage systems for use in vehicles. Battelle won a competitive bid contract in 2008 for the program from the US Department of Transportation’s National Highway Traffic Safety Administration (NHTSA).
Battelle has for decades served as an integral resource for developing safety test methods for new vehicle technology; the institute provides NHTSA data and information that the agency can use to establish the federal motor vehicle safety standards for new vehicles, said Dr. Denny Stephens, Research Leader for Integrated Vehicle and Transportation Systems at Battelle, who led and managed the team on the hydrogen testing project.
Results from Battelle safety testing on hydrogen vehicle fuel systems are expected to confirm that hydrogen fuel containers are rugged and robust, capable of maintaining structural integrity even in severe crashes and capable of remaining leak tight. The results will be handed over to NHTSA for their consideration, said Stephens, and will flow into the agency’s regulatory development process for upcoming hydrogen-fueled vehicles.
Testing was performed at Battelle’s High Energy Research Laboratory in West Jefferson, Ohio, as well as at vehicle crash facilities in Texas and Ohio.
In the tests that we’ve performed—and this is crash tests of some mockup hydrogen vehicles as well as crash tests of actual hydrogen fuel cell vehicles—in all cases the container, the tank and the fuel system remained leak tight. This was despite impacts to the tank itself, in crashes rear and side up to 40 mph. So this was impacts to the fuel tank region. The tanks were well protected—the vehicle provides substantial protection. Then, the tanks, being high pressure tanks, are extremely robust in a crash scenario. In addition, there is plumbing and the fittings that convey the gas. Those were deformed substantially. They are very ductile and can accommodate the deformation that occurs in a crash without leakage.—Dr. Denny Stephens
Stephens said that the Battelle team also found that some common assumptions concerning small hydrogen leaks were not correct. Tests suggest that hydrogen from very small leaks does not disperse evenly, thereby allowing flammable concentrations to form when conventional wisdom suggests it is safe.
An additional significant finding was the indication that hydrogen permeation appears to increase flammability of interior vehicle fabrics, increasing propensity for secondary fire after hydrogen ignition.
We did show in some tests that measures needs to be taken to ensure that hydrogen does not accumulate in the passenger compartment. That it should not be allowed to accumulate by either not allowing a leak, or by providing an external means to ensure that it would be rapidly evacuated from the passenger compartment.—Dr. Denny Stephens
Battelle test results suggest that, with appropriate safety testing, hydrogen vehicles can be as safe as conventional vehicles on the road today.
Other hydrogen systems. It can take two to five years to establish test methods for a new technology, depending upon who is involved, and their particular schedule, Stephens said. Although the Battelle team has not investigated solid-state hydrogen storage systems yet, Stephens made a few observations on the prospect.
Usually when you look at a new technology, you look at existing standards and verify the performance-based elements of them in terms of safety. At a high level, maybe 25-50% [of the work done on compressed hydrogen storage] might be applicable [for solid state systems], but then you have to get into specifics for the particular element. We looked at the failure mode and effects of high pressure hydrogen, we would look at what would be the failure modes for solid state systems.
One of the important elements in any of these systems is the vehicle duty cycle—the service environment for the vehicle. That’s basically how many refueling cycles it will go through, and what are the extremes of service—very hot days in Arizona, versus very cold days in Alaska—and looking at that range of conditions and then defining the engineering duty cycles which basically sets the operating range for the performance of the system. That’s one element that definitely can be carried over: the service environment and duty cycle.
Part of where we’ve supported industries through the years is understanding the challenges of automotive service, heavy vehicles, trucks, transit buses, motor coaches, the rigors, and then establishing the fuel system safety requirements to ensure that these system can operate safely throughout their design service life through real world environments.—Dr. Denny Stephens
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