Slashdot Mirror
Car Powered by Compressed Air
gripperzipper writes "CNN reports that a Korean company created a small car powered by compressed air. ENERGINE created its PHEV, or Pneumatic-Hybrid Electric Vehicle, which uses a two-stroke compressed air engine for start, acceleration, and uphill climbs. The car switches to an electric motor when its speed reaches 20-25 km/h (32-40 mi/h). Although major auto manufacturers have invested heavily in gasoline hybrids, it will be interesting to see if a market will open for this type of vehicle." Update: 04/04 17:18 GMT by T : Reader Tapsu spotted the incongruity here, writing "Interesting post, but the speed conversion has gone wrong way: "20-25 km/h
(32-40 mi/h)". ... Thus the correct speed range in miles would be
something like 12-15 mi/h."
Havn't they had something like this comercialy avalible in France for a while IIRC? Its has a ridiculously strong carbon fiber airtank that's presurised at home by a compressor using off the grid electricity. Its basically a small comuter car, but it has decent range and speed.
"Sic Semper Tyrannosaurus Rex."
On the contrary, the pressure available at a gas station might be as high as 140 psi (if you're lucky), but the diagram in TFA indicates that the high pressure tank is pressurized to around 300 bar, or ~4200 psi. This doesn't seem much of a threat to the station's business model.
The high pressure tank in that vehicle is charged to 300bar, or 4350psi.
That's higher than a SCUBA tank and it requires some heavy duty air compressor rigs to charge it.
I'd hate to be anywhere around that car in a crash or if it catches fire...
There are french cars that run completely on compressed air around for years.
http://www.gizmo.com.au/go/3523/
slashdot, wake the fsck up.
California auto stations are required to provide compressed air, water, and a gauge for measuring air pressure to any paying customers at their station. They can be fined if their pumps do not work correctly for more than 5 consecutive days.
This compressed air engine isn't directly related to a environment-friendly fuel. The fuel of the car itself isn't compressed air - it's electricity, the battery. Electric cars, or hybrid cars, have the problem that they can't obtain high torque instantly. However, compressed air does give high torque. The idea is to store compressed air in a tank, and use it as a booster when high torque is needed. The air will be compressed later on with another compressor.
Now, combine the compressed air engine with an hybrid car. You get an hybrid car with instant high torque when needed.
They are far safer in a fire, too. If there is an overpressure in the cylinder, the gas is slowly vented, where it burns. With a petrol tank, as the fuel heats up the pressure rises until the tank bursts (because they're either plastic or thin steel).
We had great news of this kind in Europe exaclty one year ago, but at the end card didn't show up in our roads. News in Italian: http://www.ecotrasporti.it/eolo.html
Site of the company in English: http://www.theaircar.com/Lucerne.html
Electric engines have the disadvantage of having little power. . .
Beg pardon? Not to mention the fact that their torque curves are the stuff that give drag racers wet dreams.
The only disadvantage electric motors have over combustion engines of any kind is, well, that they run on electricity, which has to come from somewhere.
Which turns out to be rather inconvenient.
The compressed air booster is just one way of finding some sort of dodge around the whole battery issue, and I'm not convinced it's a good one. A true hybrid seems a better solution to me, although it lacks the politically correct advantage of hiding its energy use and emissions from public view.
Bear in mind that I'm actually quite fond of compressed gas engines and have actually built a few small ones, just for my personal enjoyment and edification, but I haven't, outside of the realm of entertainment, found any problem for which they are the solution.
KFG
Okay, the compressed air tank powers the engine, which works like a hydrogen powered engine which requires compression. The electric motor is relatively small and only used in certain low power requiring situations.
(\_/)
(O.o) This is Bunny. (> <)
I live in California, and the gas station nearest my house has an air compressor and water dispenser (for radiators), and it costs $.50 to use. The air hose has a guague, but it's crappy.
I can spot posts on the net at least from year 2000 about Mexico city running taxis and public buses on compressed air.
Am I missing the point ?
Z.
When an electric car is standing still the motor does not draw power. Converting energy expended while braking into compressed air has been done on normal trucks and busses for years. Converting the batteries stored energy into compressed air is gaurenteed to loose some of the energy in the conversion and therefore will not last as long. Every time you convert energy you loose some so it makes sense to save the wasted braking energy. There is nothing really "new" about this car except they have taken a common fuel saving technology used on heavy transport fleets and applied it to an electric car. If it works for an electric car it would work for a normal car but with electric cars you can't just get a bigger fuel tank.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
[ A hole in a compressed air tank equals instant explosion. ]
Err, no. A hole of any size equals a leak and a loss of pressure. I am not sure which science friction books (pun intended) you have been reading but I have suffered many leaks in high pressure air tanks and in only one case was it dangerous. That was when a friend dropped his tank on the side of the pool and the regulator valve broke off and the tank left the scene rapidly. The type of gas was irrelevant as any high pressure tank would have taken the same trip. Do you think we would be allowed to strap these things to our backs if they were as dangerous as you say?
Petrol vapour on the other hand is very explosive so even an empty petrol tank can explode.
I love stacking my barbecues in the shed at the end of summer - you can't beat a bit of grill on grill action.
One of the real dangers with current petrol engines is that they pump petrol to the engine at high pressure to meet sudden increases in demand (acceleration) and then pump the excess back to the petrol tank. This means that there is a lot of high-pressure petrol travelling around the car and when an accident occurs the risk of fire is much higher than 20 years ago.
On the other hand petrol tank design and placement has received a lot of consideration and is no longer such a danger as it was 20 years ago. So it is no longer the large tank that presents the major danger but the system itself.
I could not find a link but several years ago on the A40 in England there was a multi car accident in which most people died in the resulting fire rather than the crash. All the petrol gets dumped on the road and all the cars burnt. People could not escape in time especially those in the rear of 2 door cars.
Pressure of a propane tank at 100 deg F is 175PSI - this is a pressure that can be easily managed.
Take note too, that any major pressure loss on a propane tank will instantly drop the temperature of the remaining liquid in the tank (as it boils), resulting in less pressure - check a Pressure-Temperature chart for propane sometime.
Compressed air at a few thousand PSI is a lot more trouble to deal with in an accident.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
It's the MDI Air Cars "The world's cleanest cars", developed by Guy Negre.
It doesn't use any fuel at all, only compressed air, and the features are good:
Weight: 750 kg
Maximum speed: 110 kmh
Mileage: 200 - 300 km
Maximum load: 500 Kg
Recharging time: 4 hours (Mains connector)
Recharging time: 3 minutes (Air station)
Someone mentioned the problems of having a (scuba) tank of compressed air sitting in the hot sun...yes, it can be a problem, obviously, if the air heats and expands above the pressure rating of the tank. I am assuming they thought of this and would make the tank adequately strong. (With scuba, the shop fills your tank to the limit, and then the hot sun gives you another 1000 psi and your burst disc goes. This is less than the five-thirds working pressure they push your tank to when they hydro it--I'm sure the tanks on the cars would have some kind of overpressure relief like a burst disc.)
The French air car article points out, "In the case of an accident with air tank breakage, there would be no explosion or shattering because the tanks are not metallic but made of glass fibre. The tanks would crack longitudinally, and the air would escape, causing a strong buzzing sound with no dangerous factor."
Well.
It's great to know that it's a carbon fiber tank so it won't turn into a screaming cloud of schrapnel, but isn't there another issue at work here?
Now, I don't know exactly where on that tiny car the tank is, but I'd assume it's under the seat someplace.
The volume of that car is what...two cubic meters? What happens when you instantly put 90 cubic meters of air inside it? (Or under it?)
Have a look at this rather larger car for an example. Look, ma! No fragmentation thanks to a steel tank, but all that air introduced to an enclosed space jiffy-pops a car like a cheap paper cup.
I'm more than willing to admit there's more to carbon-fiber tanks than I know. Maybe there's some property that prevents them from releasing all that energy in less than, say, 10 seconds, no matter how badly crushed. But I'm officially skeptical.
They say there's enough energy in a scuba tank to lift a hook-and-ladder fire truck 20 meters in the air. That's exactly the sort of energy I don't want released near me in a short timeframe. Gasoline is good in comparison because it doesn't tend to do this when the tank is ruptured.
Then again, a compressed air tank explosion might be just what I need to get ahead in today's Bay Area traffic. Up yours, Fastrak!
Depends on the pressure.
e.g.
http://zebu.uoregon.edu/2001/ph162/l10.html
The MDI aircar proposes 400 atmospheres. They don't have a production model with tanks to hold that though. Energy density is similar to recent (but not cutting edge) batteries.
The problem with compressed air is that it is basically still a heat engine whereas electric motors are not. Electric motors are 90%+ efficient and compressed air motors, well, 40% maybe.
Government of the people, by corporate executives, for corporate profits.
Efficiency is not a showstopper. Even a very inefficient 'electric' car still can beat a gasoline engine in marginal cost per mile.
Where electric cars (including those that store energy in compressed air) have problems is energy density. The compressed air car could do a bit better there if it also had a resistively heated thermal mass to heat the air before expansion. The thermal mass would be recharged from the wallplug at the same time the air tanks are refilled. Low atomic number materials can store a great deal of thermal energy; LiH heated to a vapor pressure of 1 bar, for example, stores several megajoules per kilogram.
The engines of large trucks (think 18 wheelers or similar sized cabs) start with compressed air, and have been for years. You know those air guns that service stations use to tighten/loosen lug nuts on car wheels? Same idea, just use that instead of an electric starter. Next time you're standing near a truck when the driver starts the engine, you'll hear it plain as day.
Never hit your grandmother with a shovel, for it leaves a bad impression on her mind...
No not "engine brakes", I realise they piss people off at two in the morning. The system I am talking about was implemented on busses in South Australia in the early 90's.
The "air" in a Jake brake is exhaust and, as you say, is limited by the compression ratio of the engine (not to mention choking it). The system I saw ran off the drive shaft and engaged when you hit the brake so the engines compression ratio was not a limiting factor. The inertia of the bus was used to drive an air compressor that in turn slows the bus down (ie: the compressor rather than the engine was "Jake"). When I saw the system I thought it was a good idea and assumed it had taken off, maybe it didn't, maybe it died because of cost/benifit. Popular or not the idea is nothing new, so put the "WRONG stick" down before you hurt yourself.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Petrol vapour on the other hand is very explosive so even an empty petrol tank can explode.
Actually, if you want a petrol tank to explode it pretty much has to be empty. Liquid petrol does not burn, drop a match in a completely full tank and it'll go out. Drop one in a tank of a petrol vapour/oxygen mix and you'd better be running...
25 km/h = 15.625 mi/h, not 40 mi/h
Guess someone goofed up on the metric system once again :)
If you've ever played paintball or anything else that uses gasses compressed this much, you'd have seen the tanks that will be used.
Typically, the tanks are some sort of high-tensile metal with 15-20 layers of kevlar wrapped around them. They can be shot with a bullet and not release their contents. So, safety considerations of the tank are less important than a thin metal tank full of a combustible material, such as gasoline.
wdd