The pitch that came with General Motors’ hydrogen-powered Chevy Equinox during a demonstration on campus Sept. 10 was not so much for the car as for the “hydrogen economy.”
The car itself is impressive, but it’s only a prototype. To put such vehicles on the market will require building a whole new infrastructure in parallel with our current system of distributing gasoline and diesel fuel. If it works it could reduce pollution, offering a way to move people and goods with home-grown renewable energy. But there are a lot of ifs and gotchas.
The Equinox is a hybrid electric vehicle in which the gasoline-driven generator is replaced by a fuel cell. Instead of exploding fuel to produce motion, fuel cells chemically combine the fuel with oxygen to produce electricity. If the fuel is a hydrocarbon like gasoline or ethanol, the exhaust is carbon dioxide and water. Along with the fact that we already have too much carbon dioxide around, we don’t yet have good fuel cells for hydrocarbons — although the Cornell Fuel Cell Institute is working on it. A fuel cell running on pure hydrogen exhausts only water.
GM has about 100 of these prototype cars on the road right now, being lent out to consumers for three-month trials and placed in a few high-profile locations like Jay Leno’s garage. According to Daniel O’Connell, GM’s director of global field service for fuel cell vehicles, GM hopes to sell the production version of the car based on performance — the electric engine is zippy — and economy. The Equinox is a small SUV that will get 45-50 miles on the hydrogen energy equivalent of a gallon of gas, at a predicted price of $3 a “gallon.” O’Connell says the SUV configuration was chosen to appeal to families. Critics have grumbled about the choice of an SUV, but if Americans are going to keep driving such vehicles they might as well come in more energy-efficient, less-polluting versions.
One catch is that the only practical fuel cells for hydrogen use platinum as a catalyst to separate the protons and electrons in hydrogen atoms. Platinum is expensive, but O’Connell says that’s not a problem, pointing out that the fuel cell uses only a little more than you find in the typical catalytic converter. Impurities in the hydrogen can gum up the works; fuel cells used in spacecraft have to be rebuilt after every mission. The fuel cell in the Equinox, O’Connell says, would have to be overhauled after about two and a half years, when the platinum would be recycled. Cornell researchers are working on ways to alloy platinum with other metals to use less of the expensive stuff, and are testing other materials to find something that would replace platinum altogether. They are also working closely with GM to improve the fuel cells they’re using now.
The next question is, Where do we get the hydrogen? O’Connell envisions a world where we make hydrogen by electrolyzing water with electricty from renewable sources like wind and solar. Of course we’re not making enough electricty from renewables now to even make a noticeable dent in what we’re getting from hydrocarbon-fired and nuclear power plants.
Some worry about a fire hazard — the “Hindenburg syndrome” — but O’Connell claims hydrogen is safer than gasoline. If a crash ruptures the tank, hydrogen dissipates rapidly into the air instead of spreading across the ground. QB is reminded of the demonstration in Chem 101 where the professor filled soap bubbles with mixtures of hydrogen and oxygen and then touched a flame to them (with a *long* stick). Pure hydrogen went “Foof!” Hydrogen with just a little oxygen went “Pop!” and an even mix of hydrogen and oxygen deafened the front row in 200 Baker. A hydrogen tank rupture in the presence of a spark would probably be a “Foof,” but a very exciting one. Ruptures would be unlikely, O’Connell claims. “We’ve shot guns at the tanks,” he says. But we note that GM has a program to train first responders to deal with hydrogen vehicles.
And finally there’s the distribution problem. O’Connell says there are now about 70 hydrogen fueling stations around the U.S., mostly in major cities, and GM is working to get more set up. In the ideal hydrogen economy of the future, O’Connell visualizes one out of three current gas stations becoming a hydrogen station. Until then travel between two hydrogen-ready cities might work, but with a range of about 150 miles on a full tank, the Equinox is not yet an SUV to take into the Colorado Rockies, or maybe even the Adirondacks. But it seems a good way for fleet users to reduce their carbon footprint. Cornell is considering using such vehicles for its own fleets, which would mean setting up our own fueling station. For commuting, it might be better to wait for the technology to arrive in smaller vehicles with even higher fuel mileage. The ideal might be a plug-in hybrid like the Chevy Volt, running all-electric around town and turning on the fuel cell a few times a year to visit Grandma.