Developing a method to safely store, dispense and refuel a vehicle using hydrogen continues to challenge researchers searching for alternative fuels. At the Pacific Northwest National Laboratory (PNNL), scientists are focusing efforts on a storage medium the size of a small pellet.
The medium is solid ammonia borane, or AB, compressed into small tablets. Each milliliter of AB weighs about three-quarters of a gram and harbors up to 1.8 liters of hydrogen. A fuel system using the AB pellets will occupy less space and weigh less than systems using pressurized hydrogen gas, scientists say. That should lead to fuel cell-powered vehicles with the room, range and performance of today's vehicles.
Research continues. PNNL scientists are learning to manipulate the release of hydrogen from AB at predictable rates, aiming to control the production of hydrogen much like a gas pedal feeds fuel to a vehicle's combustion engine.
"The refueling method requires chemically digesting or breaking down the solid spent fuel into chemicals that can be recycled back to AB with hydrogen," explains PNNL scientist Don Camaioni.