Smallish hybrid, supposed to get such good economy by compressing air while going down the road on gasoline, and by using some form of braking compressor to further compress gas.
I’m very skeptical. I don’t think physics supports the idea.
Reported for forum change; the absence of any question makes this unsuitable for General Questions.
Link?
Big efficiency numbers aren’t unbelievable if the car is really light, or is driven solely to optimize fuel economy. A few years back there was an X Prize competition for fuel efficient cars; the 110 mpg Edison 2 won. It only weighed 750 lbs. And with an ordinary car, you can also achieve extraordinary efficiency solely with driving technique. These guys got 84 mpg out of an entirely standard car.
Still… without more details it’s impossible to judge this particular concept car. If they’re claiming that some sort of compressed air energy recovery system can triple the efficiency of an otherwise normal compact car, I call bullshit too. But I bet there’s more to this, even if it’s just an optimistic design concept.
I don’t really know anything about this car.
But, off the top of my head. If the car was turbo you could capture what would normally come out of the blow off valve and regenerative braking is proven to work for electric vehicles, I see no reason why the electricity couldn’t power a compressor.
You’d probably be able to get away with fewer batteries too. Batteries are heavy.
Besides, this is major brand(in europe). Why would they bullshit?
I don’t see the confusion. Ford demonstrated a hydraulic hybrid truck in the early 2000s, and I think UPS even tested the concept. Braking is wasted energy, and hybrids universally do something to try to recapture that wasted energy. Whether that energy is stored in a battery, air tank, or hydraulic accumulator is somewhat immaterial.
Also, is it a claim from a British model? I am to understand that the British mpg testing methodology typically gives significantly larger numbers than the American one. Not typically 118 mpg, mind you, but it’s a smaller jump.
That and imperial gallons are greater than US gallons.
The proper spelling is Peugeot, and here’s a link to a tiny Wall Street Journal article, and another one from Yahoo/ABC, with a picture.
There’s an article with some more detail here. The claims I see there seem reasonable: a compact car with this system is supposed to achieve 81 MPG (US), vs 54 MPG with a conventional engine (if I converted their figures correctly).
Basically, this compressed air storage system and some sort of hydraulic (?) pump and motor will boost efficiency by 30%-45%. Conceptually, it’s doing the same thing as an electric hybrid: capturing some of the energy lost to braking, supplementing the gas engine when more power is needed, and letting you use a smaller and more efficient gas engine. But instead of a battery, it’s using compressed air. I’m not entirely sure why that offers an improvement over electric hybrids, since (according to wiki at least) the energy density of compressed air systems and lithium ion batteries are fairly comparable. But my WAG is that you can “charge” the compressed air tank very rapidly, which lets you capture a much larger amount of energy during braking.
You don’t think physics supports what idea? A more efficient car?
I don’t think this is a ‘free energy’ claim - it’s just a way of squeezing more out of a resource.
Wouldn’t a compressed air system be cheaper to produce and maintain (once they are commodity items)? They would also require fewer resources and leave less waste than a battery-based system. It would seem to be so advantageous that I would have to question the statement that the energy densities are comparable.
My Civic Hybrid’s battery pack is pretty heavy, requires special cooling/heating arrangements and involves special procedures for emergency workers to keep them from getting electrocuted when cutting through the car. And its efficiency diminishes with age. I would expect that this compressed air system would be better in many respects, if the basic efficiency is comparable.
Also, I read somewhere, a few years ago, that there wasn’t enough lithium on the planet to make a significant portion of the rolling stock electric-hybrid or pure-electric. But air pumps and tanks and turbines can be made cheap and plentiful.
Interesting, back in college I was part of a Ford hybrid car project, and looked into this as a alternative to gas/electric hybrids. It did look very promising as pneumatic compressor-motor seemed to be a great match for a gas engine, where the high power demands would be met by the pneumatic motor and the gas engine would be optimized for efficiency and give more constant power output. This appears backwards to how gas/electric hybrids work where the gas engine is used for high power demands.
I also though that perhaps that the expanding gas may be used for a/c.
The SAE disagrees; they estimate their is enough extractable lithium to build 10 billion or so automobiles, and of course the lithium can be recycled once a car is out of use.
More about the concept vehicle. 81.1 mpg U.S. combined cycle on diesel (which is a bit more than 10% energy dense than gasoline) and that the 2015 Prius is predictedto get 90 mg EU and 60 mpg US cycles on gasoline that is a solid improvement but not crazy talk.
Since when?
I yield to the experts who have run the numbers. The thing actually works, isn’t a pipe dream. The fuel consumption numbers I saw originally were misleading, causing me to question the whole process.
My bad. Since this seems to be a viable system, cheaper to make than batteries, etc. etc., I hope it proves to be a commercial success. I particularly like the convenience of not having to use a ‘charger’, esp. when one might not be anywhere around.
Yes. I was involved in the program for the hydraulic-hybrid UPS truck. It’s the perfect application for hybrid technology that utilizes regenerative braking: city driving has relatively low speeds (= modest aerodynamic losses) and a lot of braking/accelerating. On an EPA standard city driving cycle we were able to improve fuel economy by 70% over a standard UPS truck. As a side benefit, the truck no longer needed a starter motor (UPS trucks go through a LOT of starter motors since they shut the engine off at every delivery stop).
Electric hybrids have trouble recapturing a large fraction of the energy during braking events; it’s difficult to stuff energy into the batteries that quickly, with the result that a significant fraction gets wasted. Likewise, on many hybrids the batteries and drive motor are not powerful enough to supply all of the desired acceleration on launches, and so the gasoline engine starts up and assists. And still, the Toyota Prius (for example) gets better than 50 MPG in city driving.
Now imagine a system that can recover a far greater fraction of the energy during braking, and you can see that there’s a potential for significant improvement over the MPG of the Prius and other electric hybrids. That’s what hydraulic can do.
The Green Car Congress site calls it “hybrid-air” technology, which is a bit misleading. Hydraulic fluid is the medium passing through the pumps and motors and transporting energy where it needs to go. Air (more probably nitrogen) is the compressible medium in the hydraulic accumulators. It’s typically contained inside a rubber bladder and never leaves the accumulator at all. The accumulator is where energy gets stored when you step on the brakes: the wheels drive hydraulic pumps that stuff fluid into the accumulators, increasing the air pressure (and therefore the hydraulic fluid pressure). When you get off the brakes and step on the accelerator, valves open/close to redirect fluid out of the accumulators to the other side of those pumps, turning them into hydraulic motors that drive the wheels and accelerate the vehicle.
without giving away proprietary secrets, how much pressure is built up in the nitrogen bladder?
What percent of the braking energy can you recover?
What improvements can you visualize on the hydraulic system you worked on? How can it be made better?
does it store energy from ‘going downhill’?
How many horsepower is the engine used vs. total weight?
What is fuel consumption like on highways?
Why was it said to be 117 mpg, now it is 80 something? British gallons vs. American?