Air cars[1] have a unique appeal in energy and environmental discussions. I’m not sure what it is, exactly, that gives them a special place in the minds and hearts of so many of my fellow geeks. Perhaps it’s simply the notion of driving around using nothing but air as “fuel” (which is a misunderstanding, as I’ll detail in a moment), or maybe it sounds vaguely steampunk, or maybe the idea of a car making quiet, flatulence-like sounds appeals to the child in some of us more than we’d care to admit. Whatever the case, the interest in these things won’t die anytime soon, and they remain the number one oddball technology I get asked about.
The primary question with air cars, of course, is how one compresses the air in the first place. The only solution I’ve seen is to do the obvious: Run a compressor powered by electricity. This means you have all the same issues people bring up with plug-in cars regarding the emissions and other side effects of generating electricity. In addition, you have additional energy lost in compressing the air, since you get less energy out than it takes to compress it in the first place.
All of which says that while I like the basic idea of a “simple” air car, either with or without flatulence sound effects, that has none of the supply and recycling/disposal issues of batteries, I’m highly skeptical about their future as a broadly used, mainstream transportation option.
It seems I’m not the only one with doubts.
Study Says Air Cars Are Inefficient:
“It sounds ideal, like we could be free from the constraints of petroleum dependence,” said Andrew Papson, a transportation engineer and associate at the consulting firm ICF International.
But as much as the idea is attractive, Mr. Papson is skeptical about air cars. He finished graduate studies at the University of California, Berkeley, last year and was part of a team at the school that published a paper this week that was critical of air-car claims.
The “Economic and Environmental Evaluation of Compressed-Air Cars,” published in Environmental Research Letters, examined the life cycle of the compressed-air car and concluded that the air car “fared worse than the battery-electric vehicle in primary energy required, greenhouse gas emissions and life-cycle costs, even under very optimistic assumptions about performance. Compressed-air-energy storage is a relatively inefficient technology at the scale of individual cars and would add additional greenhouse gas emissions with the current electricity mix.”
Ouch.
The paper mentioned above is here [PDF].
[1] An air car is a car that uses a tank of highly compressed air as a battery, in effect. The air is fed into an engine that’s conceptually similar to an internal combustion engine. Instead of getting motive power from the rapid expansion of burning gasoline, the air car gets it from plain old air pushing against the cylinders.
