In a public relations move to improve the image of hydrogen power, BMW loans a hydrogen-powered car to the Petersen Museum.

When I read the press release from the Petersen Museum, my heart sank. People just don’t get it, especially people who are bad at math. BMW has loaned two hydrogen-powered cars to the Petersen Museum--one to show, and one to loan out to politicians and VIPs for photo ops. Groan! The press release says, “BMW raises awareness of this alternative fuel by loaning these vehicles to celebrities, government officials, and other high-profile individuals as a way to get the word out about this endless supply of clean fuel.”

“Endless supply?” Oh really? For starters, hydrogen is not a fuel, it is an energy carrier. Liberating hydrogen from its most common naturally occurring compound (water) requires energy, and lots of it. (The other common hydrogen carrier is petroleum, and the irony is just too rich for me to bear.) Most hydrogen, in fact, is created by consuming petroleum or natural gas. In short, hydrogen power means you’re only moving the greenhouse gas emissions away from the point of energy use, which makes another statement in the press release completely irrelevant: “While hydrogen is combustible, it is not a carbon-based fuel, so the only thing that comes out of the tailpipe while running on hydrogen is water vapor.”

In case you’re bad at math, here are some numbers that ought to make you squirm in your chair. Liquid hydrogen has an energy density of 2,600 Watt-hours per liter, which compares very unfavorably to gasoline’s 9,700 Watt-hours per liter, and diesel’s 10,942 Watt-hours per liter (all figures by volume, not mass). In short, you need to burn almost four times as much hydrogen by volume to go the same distance as gasoline. When you compare the energy density of liquid hydrogen to gasoline on the basis of mass (and not volume), the gulf between the two “fuels” is even greater, meaning hydrogen cars (if we can’t prevent them from building them) will be heavier, not lighter. Moreover, hydrogen is stored under high pressure, making it a whole order of magnitude more dangerous than gasoline. Remember the Hindenburg, and why we don’t make those kind of aircraft any more?

And let's not forget the whole point of alternative fuels: to reduce greenhouse gases. From an atmospheric standpoint, water vapor--the only emission from hydrogen combustion--contributes far more to global warming than carbon dioxide. The greenhouse effect of water vapor is so great, in fact, that meteorologists must account for it in making weather predictions, where they currently don't for carbon dioxide. Water vapor is the earth's most significant source of greenhouse gas, and accounts for about 95 percent of the earth's greenhouse effect. Currently, the water vapor in the atmosphere is mostly naturally occuring (about 99.9 percent), but when we start pumping out water vapor from automobiles in the millions of metric tons daily, we could have a problem that pales by today's standards.  

Hydrogen energy can, of course, be stored much more easily when it is linked to carbon atoms in a chain. When hydrogen's energy is stored in the form of bonds with carbon atoms, the fuel does not have to be stored under pressure, and has a very high energy density. The resulting long-chain hydrogen-carbon polymer … oh, never mind. I forgot. That long-chained hydrogen-carbon polymer is called gasoline.

Feel free to disagree with me. Write your assemblyman or congressman, Maybe they can pass a bill that changes the laws of physics.