BMW announced yesterday that it will introduce hydrogen fuel technology in its 7-Series car in April 2007. Since hydrogen fueling stations are not yet readily available, the car will actually have two separate fuel tanks to enable it switch between regular gasoline and hydrogen. More is available from this Reuters article, including:
“A spokesman said the car would be leased to selected customers rather than sold because of its high price. Leasing rates would be similar to those for a top-end BMW 760LI with a full-service package.”
The Green Car Congress has also picked up on this story. They provide more interesting information about the car, and there’s a lively debate with a healthy dose of skepticism going on there about the car and the technology. From the GCC:
“BMW Group has given preference to the use of liquid hydrogen as the appropriate source of energy for the automobile…
The cruising range in the hydrogen mode is more than 125 miles (200 km), with another 300 miles (500 km) available in the gasoline mode.”
GCC also explains some of the challenges to using liquid hydrogen (as opposed to gas) as a fuel source. I hope I summarize this correctly, but go over there for the details. For one, hydrogen exists in a liquid state at extremely cold temperatures (around -250°C–you won’t want to be dripping any of that stuff at the fuelling station!). Therefore, the car’s fuel tank must be able to keep the liquid hydrogen very well insulated or else it will boil off. When it boils the vapor pressure in the fuel tank increases, and as the pressure increases some vapor must be let off. So essentially as the fuel sits unused over time you’ll eventually start losing it. In fact, GCC writes,
“The period in which a half-full hydrogen tank will be emptied completely in a controlled process is about 9 days, and even then the car is still able to cover approximately 12 miles (20 kilometers) in the hydrogen mode with the fuel remaining in the tank.”
So beyond the obvious lack of availability of liquid hydrogen fueling stations, another drawback is the loss of fuel. Also, while the hydrogen engine won’t emit carbon mono-/dioxide, it will still emit nitrogen oxides.
Before launching into any further analysis or criticism, I think it’s worth applauding BMW for taking the first step to realize an environmental goal. The Bush administration and the environmental community have largely hailed a hydrogen economy as THE long-term energy solution, and while much thought has gone into that decision some healthy debate and reality checks won’t hurt.
First of all, the advantages of using hydrogen as an alternative to greenhouse gas emitting fuels would be nullified if our source of hydrogen is fossil fuels. Other lingering issues, some of which may be insignificant or easily overcome: pressure release of hydrogen gas from fuel tanks (loss of purchased fuel), hydrogen flammability, problems with water vapor tail pipe emissions (for example, deposition of water vapor onto roads in the winter could create nightmare driving; water vapor as a greenhouse gas/effects of pumping water vapor into the atmosphere on a large scale)?
All this aside, we still have several good years (decades?) to wait until we really start seeing a robust hydrogen economy. Aside from proving that a hydrogen-fueled car can be a reality, the BMW push does little to make it available on a large scale. The price of the car is prohibitively high, and the car will clearly be marketed to high-end customers. In this sense, the BMW initiative probably won’t do for hydrogen what the Prius did for hybrids.