Slashdot Mirror
Gas Powered Fuel Cell Could Help EV Range Anxiety
thecarchik writes "While electric-car advocates may avoid the issue, some buyers simply won't choose a plug-in car that can't travel unlimited distances. That's where the Chevy Volt-style range extender comes in, though the Volt adds unlimited range by burning gasoline in a conventional engine to generate electric power. Now, a new type of fuel cell offers the potential for a different kind of range extender, one that removes the enormous practical problem facing hydrogen fuel cells: the lack of a distribution infrastructure to fuel vehicles that require pure hydrogen to feed their fuel cells. Researchers at the University of Maryland have managed to shrink the size and lower the operating temperature of a solid-oxide fuel cell by a factor of 10, meaning it could conceivably produce as much power as a car engine but occupy less space. The advances come from new materials for the solid electrolyte, as well as design changes, and the researchers feel they have further avenues for improvement left to explore."
This is (generally) true - at highway speeds, the vast majority of the sound is either aerodynamic or from the tires impacting the road. Even at 25mph/50kmph, you'll get more than enough sound from that to warn pedestrians.
The problem is at parking lot speeds. You don't get much noise at all just moving at 5mph/10kmph. Even with a gas engine, it's mostly the acceleration that provides the noise, the engine revving up, not the engine just running.
Since the main time pedestrians and cars are maneuvering near each other and have significant risk of collision is in precisely those situations, I think the "electric engines don't make enough noise" problem could actually be a legitimate problem. By no means a showstopper or a product-killer - after all, a car is usually a pretty large object, and I for one tend to notice large objects in motion. The solution could be just a simple "noise generator used when moving below X speed" - that would handle the pedestrian problem, without increasing noise in areas where noise is an issue and pedestrians are not.
Temperature is actually more important than the energy density in this case. At 650C never mind 900C, you'll still have a lot of trouble with heat--material have an unfortunate tendency to expand and warp (or, worse, snap) at that kind of temperature. Thus, you may be able to turn your car on and off only dozens of times before the SOFC breaks down. This is the real reason why SOFC has never been seriously considered for cars--SOFC has always been relatively compact for the amount of energy they produce (except for the apparatus you'd need to get rid of the huge amounts of heat).
Now, 650C is easy, at least if you are using natural gas as feedstock. (Gasoline may be somewhat more difficult, but not impossible.) Other solid oxide fuel cells that are trying to enter the market operate at or near that temperature range. 350C, though--wow. That will be remarkable, and may indeed be able to brings in an era of fuel cell vehicles, but it'll involve whole new set of chemistry, and I won't believe it until I see it.