Hydrogen If you have fuel cells, you can say you're running the car on hydrogen, but unless you have a personal supply, you're really running it on electricity. (Unless you're Ford, which has an F-350 concept vehicle pickup with a 6.8-liter, V-10, internal-combustion engine that runs on pure hydrogen.) Actually, hydrogen is fundamentally an energy storage and transportation medium.
When Mark and I visited GM, it was less to observe a memorial-to the late EV-1 than to see and drive the company's newest concept car, the HydroGen3. This fuel-cell-only, electric-powered modification of the Zafira A is sold by Opel in Europe and under other GM brands around the world (Fig. 4). The only conventional battery aboard this vehicle is the one that boots up the computer. The car's 200 mini fuel cells, which fit easily in the Zafira engine compartment, produce about 200 V. A dc-dc converter delivers 320 V to the motor.
A fillup of 3.1 kg of hydrogen is stored in a pair of 10,000-psi tanks that fit under the rear seat. That's triple the pressure of a regular tank of industrial gas, so it's a little scary to think about. But most engineers don't want to think too much about sitting on top of a nearly empty tank of conventional gasoline either.
For what it's worth, 1 kg of hydrogen approximately equals the energy produced by one gallon of gasoline. But it's not easy to relate that to the real world without efficiency numbers, which are hard to obtain. In lieu of that approach, consider the HydroGen3. Its range is 150 to 180 miles—call it 50 to 60 miles per hydrogen equivalent to a gallon of gasoline. Top speed is 99 mph. With four healthy American males in the car, acceleration is sedate.
By way of comparison, the 1.6-liter conventional-engine Zafira A can go from 0 to 62 mph in a modest 13.4 seconds with a top speed of 109 mph. European-measurement efficiency standards in imperial miles/gallon are 30.1 urban, 46.3 ex-urban, and 38.7 combined. The latter figure, given the vehicle's 12.5-imperial-gallon tank, provides a range of 480 miles.
The HydroGen3 demonstrates that it's possible today to make a euro-size minivan with an electric engine that runs on electricity from a gaseous-hydrogen fuel cell. And it delivers euro-size minivan performance, except for range, which is reduced by about 60%. So far, so good. But where does the hydrogen come from?
Obtaining hydrogen the way we do today isn't a solution to petroleum dependence, since most of it comes from natural gas. In the process, some of the gas is burned to create steam, which is superheated to 700°C to 1100°C, where it reacts with the methane component of natural gas to produce carbon monoxide (yes, a greenhouse gas) and hydrogen. This process can be augmented at lower temperatures to generate even more hydrogen by reacting the carbon monoxide with more water.
Electrolyzing water is an alternative. Whether it's practical, though, depends on economics. Presently, the electricity consumed is worth more than the hydrogen produced. A process called high-temperature electrolysis (HTE), which would obtain its heat from a nuclear reactor, could be twice as efficient. But, obviously, it has yet to be commercialized (Fig. 5).
The appeal of HTE is that the same nuclear plant could produce electricity for the grid during the day and hydrogen for energy storage at night. Presently, no full-scale HTE plants are in the works. Idaho National Laboratory is still working on bits and pieces of the technology.
A greener (literally and figuratively) approach hydrogen generation would be to use algae. Normally, alga cells photosynthesize oxygen. But deprived of sulfur, they will produce hydrogen—for a while, anyway. Protein buildup then stifles the process. The path to sustainable hydrogen production from algae seems to lie along the path of bioengineering. Of course, creating franken-algae to generate hydrogen from sunshine may run into public-relations problems.
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