A typical bay inside HRL's class 10 "clean room."
I visited Energy Conversion Devices (ECD) in Michigan, which champions hydride storage and was once partnered with GM. ECD says its metal hydrides "work like a sponge by bonding hydrogen atoms to a metal alloy, forming a safe, compact, low-pressure storage medium. A tank with a metal hydride inside can hold three times more hydrogen than can be stored as a compressed gas in the same space." The company claims its systems "could provide enough fuel to power a laptop for a month or a vehicle for hundreds of miles on a single charge."
The basic aim of the work at Sandia and HRL is the same, and it"s daunting. As James Spearot, director of GM"s chemical and environmental sciences laboratory, points out, something has to give before fuel-cell cars can have the range of today"s vehicles. Carmakers can either change the vehicle architecture to allow more room for fuel storage (basically, having tanks everywhere) or improve the capacity of the storage system. GM is currently investigating five different storage options, involving 15 separate material systems. So it remains a long haul, but it"s a step that has to be taken before hydrogen storage can be standardized and a nationwide system of filling stations established.
Hydrogen is the most abundant element in the universe, and it"s all around us, but it"s difficult to isolate and it"s a devil of a material to work with, because it is so light and slippery. The goal of the research is to create a storage system built around a complex metal alloy that can hold five to six percent of its weight (doesn"t sound like a lot, does it?) in hydrogen. That means that the "gas tank" equivalent, if it weighed 100 pounds, would carry five to six pounds of hydrogen. The greater efficiencies of hydrogen mean that such a car would have acceptable range, and metal hydride storage (with lithium boro-hydride as the material) promises systems holding 13 percent of their weight in hydrogen.
Hydrides store hydrogen and release it when exposed to heat. So you not only have to get the hydrogen to bond to the metal, you have to find an energy-efficient way to release it, too. They"re working on that, using what are known as "destabilizing agents." My favorite presentation over two days of talks was one by Leslie Momoda, director of the sensors and materials lab at HRL. She also compared hydrides to a sponge taking up water. The problem, she said, is that the sponge doesn"t want to be squeezed; the hydrogen is tightly bound to it.
Momoda"s analogy was to a child holding a balloon. If you try to take the balloon away, the child resists and it takes a "high energy investment" in the form of heat to get her to let go. But if you hand her an ice-cream cone she"ll be distracted and will release the balloon with minor effort. So the ice cream is the destabilizing agent, and the agent (the cone) can be used over and over with successful results. GM"s work with magnesium hydride as a destabilizer shows promise in allowing the system to work with lower temperatures (435 degrees Fahrenheit instead of 750 degrees).
Another challenge is getting this all to happen quickly, so the hydride can be recharged with hydrogen in three to five minutes, approximately the same time it takes to fill your gas tank now.
We finished our HRL tour with a visit to the lab"s 10,000-square-foot "clean room," where people in white Gore-Tex lab suits worked on the next generation of 150-gigahertz extreme microchips (10 times faster than today"s silicon-based chips). We looked in through little windows at people working on such tools as the electron beam pattern generator, etching semiconductors and other high-tech work. The work was right out of a movie; I half expected Dustin Hoffman to rip off his face mask and start yelling about a virus that had gotten loose. Did it have anything to do with cars? Probably not, but you may see those chips in a future car that will do everything but drive itself.
Outside the labs was one of GM"s HydroGen3 fuel-cell vans, not the latest technology but close to it. HydroGen3 carries 3.1 kilograms of hydrogen at 10,000 pounds of pressure, enough to give it a range
of up to 180 miles. The current GM fuel-cell vehicle, the Sequel, will reportedly be able to carry eight kilograms of hydrogen and go 300 miles. Hydride storage offers the possibility of doubling that range, but it"s not there yet. In 2005, it remains a head-scratcher for those people in the Gore-Tex suits.
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