No matter how well they're engineered, hydrogen cars offer no real answer to the imminent threats posed by global warming.
David Talbot - Technology Review - March/April 2007
BMW’s Hydrogen 7 sedan burns hydrogen or gas in an internal combustion engine; liquid hydrogen is stored in a heavy trunk-mounted tank.
By the time Klaus Draeger, BMW's manager of research and development, took the microphone at a Berlin hotel last fall, the assembled journalists' bellies were full of mint juleps--and it all started to make sense. Maybe the world's oil crisis and the threat of climate change could be sensibly addressed by using hydrogen as a transportation fuel. Draeger sketched the alluring vision of a future in which high-performance luxury cars burn hydrogen and emit mostly water vapor. The hydrogen could someday be provided by renewable sources of energy, he said, and nobody would have to make any sacrifices. And we journalists would get to drive the first such cars the following day.
"You'll be pioneers! You will be sitting at the wheel of the Hydrogen 7, driving through Berlin and the countryside. And for the first time, you will drive this hydrogen-powered luxury saloon," Draeger exclaimed, using the Britishism for "sedan." BMW will lend 100 of these cars to yet-unnamed public figures as part of its global clean-energy promotional campaign. In some ways, the campaign resembles GM's effort to tout its own hydrogen-car program. GM's focus is on a futuristic fuel-cell car. The BMW version uses internal combustion: it burns hydrogen rather than skimming off its electrons. Same message, though: hydrogen is the answer.
"Experts will tell you that hydrogen has the biggest possibility to replace fossil fuels," Draeger explained, as the wine flowed. "Please see the Hydrogen 7 as an offer. We can only make this car a reality with our partners in political science, the world of business, the energy industry." He concluded with an appeal to "politicians the world over" to make the production, delivery, and storage of clean hydrogen affordable.
The next day, I got a look at the Hydrogen 7. From the outside it looked like a normal BMW four-door luxury sedan. I opened the trunk and marveled at the heavy steel tank that held liquid hydrogen at -253 ΊC. While driving, I touched a button on the steering wheel to switch from gasoline to hydrogen; I noted no hiccup, just a higher-pitched engine noise. The car is very nice. But does it make environmental sense?
The simple answer is no. In the context of the overall energy economy, a car like the Hydrogen 7 would probably produce far more carbon dioxide emissions than gasoline-powered cars available today. And changing this calculation would take multiple breakthroughs--which study after study has predicted will take decades, if they arrive at all. In fact, the Hydrogen 7 and its hydrogen-fuel-cell cousins are, in many ways, simply flashy distractions produced by automakers who should be taking stronger immediate action to reduce the greenhouse-gas emissions of their cars. As of 2003, transportation emissions accounted for one-third of all U.S. carbon dioxide emissions.
Nobody has made this point more clearly than Joseph Romm does in Hell and High Water. Romm is an MIT-trained physicist who managed energy-efficiency programs in the U.S. Department of Energy during President Clinton's administration and now runs a consultancy called the Center for Energy and Climate Solutions. His book provides an accurate summary of what is known about global warming and climate change, a sensible agenda for technology and policy, and a primer on how political disinformation has undermined climate science. In his view, the rhetoric of "technology breakthroughs"--including the emphasis by President Bush and some in the auto industry on a future hydrogen economy--provides little more than official cover for near-term inaction.
Romm reminds us of the growing scientific consensus: we must quickly reduce greenhouse-gas emissions to avoid the worst effects of global warming. Therefore, Romm argues, the job of political leaders is clear. Among other things, they must rapidly adopt tighter efficiency standards for homes, offices, and industry; mandate strict increases in automobile fuel economy, which means widespread adoption of ultra-efficient cars, including hybrids; and build as many wind and solar plants as possible, while cautiously expanding nuclear power. Romm even argues that we could cut nationwide carbon dioxide emissions by two-thirds without increasing anyone's annual electric bill. He cites California's three-decade record of aggressive investment in cleaner energy technologies and energy-efficiency programs. When these investments are amortized, costs stay flat while power consumption and carbon dioxide emissions plunge. Today, Romm writes, a Californian has an electric bill no larger than the average American's but generates just one-third the carbon dioxide.
The reason hydrogen-powered cars would produce more carbon dioxide emissions than regular cars starts with the fact that it takes energy to create hydrogen. One way to produce hydrogen is to extract it directly from fossil fuels; indeed, a 2004 National Academy of Sciences study predicted that fossil fuels would be the main source of hydrogen for "several decades." The other way is to split water molecules using electricity. Naturally, BMW talks up this approach, envisioning electricity that would ultimately be supplied by renewable sources. BMW brochures feature the Hydrogen 7 parked in front of wind turbines and shiny photovoltaic arrays. But renewable sources furnish only 2 percent of the world's electricity (not counting hydropower's 16 percent). Coal, by contrast, supplies 39 percent--and is the worst emitter of carbon dioxide, watt for watt. Clearly, a great use for renewable power is to replace coal power. But is it worthwhile to divert even a small part of it to the task of manufacturing hydrogen?
According to Romm's analysis, the math for hydrogen cars simply doesn't work out. Burning coal to generate one megawatt-hour of electricity produces about 2,100 pounds of carbon dioxide. It follows that one megawatt-hour of renewable power can avert those emissions. Using that electricity to make hydrogen would yield enough fuel for a fuel-cell car to travel about 1,000 miles, Romm says. But driving those 1,000 miles in a gasoline-powered car that gets 40 miles per gallon would produce just 485 pounds of carbon dioxide. In this sense, Romm says, a vehicle powered by hydrogen fuel cells would indirectly create four times the carbon dioxide emissions of today's most efficient gasoline cars.
And the numbers for the Hydrogen 7 are worse, because it burns hydrogen. Combustion produces thrilling torque, but it's far less efficient than fuel-cell technology. Also counting against the Hydrogen 7 is the fact that it stores hydrogen as a liquid; chilling hydrogen and compressing it into liquid form consumes more energy than storing it as a compressed gas. "It's safe to say this is a pointless activity," Romm says. "BMW has managed to develop the least efficient conceivable vehicle that you could invent."
BMW's new car is a marvelous piece of engineering. But it is also a distraction from the real issues: we must burn less fossil fuel and reduce our greenhouse-gas emissions today. Innovative automakers like BMW should turn their remarkable skills to making cars that are more efficient--such as BMW's new 118d economy hatchback, which on average gets 50 miles to the gallon. But the Hydrogen 7 is hardly the "new standard of sustainable pollutant-free mobility" that BMW proclaims. Draeger's offer is one we would be wise to refuse.