A small pellet
of solid ammonia borane (240 mg), as shown, is capable of storing
relatively large quantities of hydrogen (0.5 liter) in a very small
volume.
— Hydrogen may prove to be the fuel of the future in powering the
efficient, eco-friendly fuel cell vehicles of tomorrow. Developing a
method to safely store, dispense and easily "refuel" the vehicle's
storage material with hydrogen has baffled researchers for years.
However, a new and attractive storage medium being developed by Pacific
Northwest National Laboratory scientists may provide the "power of
pellets" to fuel future transportation needs.
The Department of Energy's Chemical Hydrogen Storage Center of
Excellence is investigating a hydrogen storage medium that holds promise
in meeting long-term targets for transportation use. As part of the
center, PNNL scientists are using solid ammonia borane, or AB,
compressed into small pellets to serve as a hydrogen storage material.
Each milliliter of AB weighs about three-quarters of a gram and harbors
up to 1.8 liters of hydrogen.
Researchers expect that a fuel system using small AB pellets will
occupy less space and be lighter in weight than systems using
pressurized hydrogen gas, thus enabling fuel cell vehicles to have room,
range and performance comparable to today's automobiles.
"With this new understanding and our improved methods in working with
ammonia borane," said PNNL scientist Dave Heldebrant, "we're making
positive strides in developing a viable storage medium to provide
reliable, environmentally friendly hydrogen power generation for future
transportation needs."
A small pellet of solid ammonia borane (240 mg), as shown, is capable
of storing relatively large quantities of hydrogen (0.5 liter) in a
very small volume.
PNNL scientists are learning to manipulate the release of hydrogen
from AB at predictable rates. By varying temperature and manipulating AB
feed rates to a reactor, researchers envision controlling the
production of hydrogen and thus fuel cell power, much like a gas pedal
regulates fuel to a car's combustion engine. "Once hydrogen from the
storage material is depleted, the AB pellets must be safely and
efficiently regenerated by way of chemical processing," said PNNL
scientist Don Camaioni. "This 'refueling' method requires chemically
digesting or breaking down the solid spent fuel into chemicals that can
be recycled back to AB with hydrogen."
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