How Chrysler's Battery-Less Hybrid Minivan Works 347
thecarchik writes "Chrysler announced Wednesday that it would partner with the US Environmental Protection Agency to build and test prototypes of a different kind of hybrid vehicle, one that accumulates energy not in a battery pack but by compressing a gas hydraulically. The system in question, originally developed at the EPA labs, uses engine overrun torque to capture otherwise wasted energy, as do conventional hybrid-electric vehicles. The engine is Chrysler's standard 2.4-liter four-cylinder, the base engine in its minivan line. But rather than turning a generator, that torque powers a pump that uses hydraulic fluid to increase the pressure inside a 14.4-gallon tank of nitrogen gas, known as a high-pressure accumulator."
Which is a more dangerous battery? (Score:2, Interesting)
FTFA:
That compressed gas, stored at pressure as high as 5,000 pounds per square inch, represents energy waiting to be released.
Not sure I'd want to be an a 1.0 version consumer vehicle with that much pressure without some serious discussion about the safety precautions to prevent or mitigate "unexpected pressure drops".
Can someone who's got more experience with the fluid mechanics add to this?
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More dangerous than riding around with a tank of explosive liquid?
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Not to worry (Score:2)
Any fire from the fuel will be put out instantly by the pressure releasing from the tank. It's like a really advanced fire extinguisher.
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More dangerous than riding around with a tank of explosive liquid?
You've been watching too much (or some) action fiction on tv and in the movies, and not enough mythbusters. It's basically near impossible to get a tank of gasoline to explode. I'm pretty sure it took actual explosives for the MB crew to get that to happen.
Scuba tank's burst disc ... (Score:5, Insightful)
FTFA:
That compressed gas, stored at pressure as high as 5,000 pounds per square inch, represents energy waiting to be released.
Not sure I'd want to be an a 1.0 version consumer vehicle with that much pressure without some serious discussion about the safety precautions to prevent or mitigate "unexpected pressure drops". Can someone who's got more experience with the fluid mechanics add to this?
Scuba divers drive around with aluminum cylinders containing air at 3,000 PSI. Safety "burst" discs are built into the regulator of the cylinders so that if over pressurization occurs they rupture. The results are frightening and embarrassing but its only air and not shrapnel since the cylinder remains intact. I expect there are similar technologies in the pressure vessels in these cars.
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Ask a dive instructor who is old enough, and they'll tell you about The Time I Saw a Burst Disc Retention Cage Shoot Through The Side Of Someone's Trunk And Through The Car Next To It.
Also, burst disks are not 100% reliable, nor are the correct disks always installed.
So, don't use bursts disks, pick another (more reliable) version of a release valve (it's not like burst disks are the only way to do it).
Advanced Open Water certified since 1994. (Score:2)
Re:Scuba tank's burst disc ... (Score:5, Interesting)
Yes, SCUBA tanks (in the U.S.) are supposed to undergo annual visual inspection (basically an interior/exterior idiot check for bad rust, chips, cracks, beat up valves, etc) as well as hydrostatic testing every 5 years*. The cylinders most likely to have a catastrophic failure (typically the neck) were a bunch of aluminum 80's manufactured something like 30 years ago. Back when I worked in a dive shop we would do an eddy-current test on the necks of ALL aluminum cylinders during the annual visual inspection even though it was only really necessary for the one batch. If you take halfway decent care of a tank and don't let moisture get in (by draining the tank too low), they'll last for ages. We had decades old steel cylinders in our rental fleet that had probably outlived many a valve!
The concern is probably warranted but I would imagine the auto industry's safety measures will be far greater than those of the average diver. If the vehicles only go in for maintenance once every few years, the tanks ought to be fine. I would worry more about them being punctured during a collision. Frankly though, assuming they've done at least a minor amount of planning with collisions in mind, the severity of a collision strong enough to puncture the tank would make a sudden release of pressure the least of your concerns.
* Disclaimer: I've been out of the dive industry a while, my numbers might be off.
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Many moons ago I had a part time job delivering 45KG LPG cylinders in a country town. One day whilst negotiating a mild left turn at a fork in the road, one of empties fell off the mazda easyloader tray. The noise was the loudest Donnnngggg Donnngg Donngg" I have ever heard, but the mandatory protection cover ring around the valve ensured no problems.
The funniest thing was watching the head of the local fireservice dive to the ground in the nearby service station when he saw it happen. I just chucked it bac
Perfectly safe, not reliable. (Score:5, Informative)
For those who are not into car repair et al, Audi used hydraulic pressure accumulators for power brake assist. It's a great system, particularly for turbocharged cars, which spend a considerable amount of time in normal driving with low or no manifold vacuum (which is created by the pistons trying to draw air past a restriction, aka, the throttle vane. That big round thing your brake master cylinder comes out of? That's the vacuum servo. It uses surface area to multiply force from the vacuum.) Citroen used the same idea to power the extensive hydraulics used in their famous suspension systems. Mercedes did as well for their cars which had hydraulic power windows (!!), door-closers, and suspensions. Nowadays, the idea of hydraulic assist has largely gone by the wayside, with auxiliary electric vacuum pumps used where necessary. It's a shame, because the hydraulic system had a HUGE amount of reserve; you could pump the pedal hard almost thirty times.
The reservoirs are lovingly nicknamed "the bomb" by enthusiasts and owners of mid-80s-to-early-90's Audis, strictly on appearance; they look sort of like a large-ish cartoon bomb. I have NEVER heard of one exploding or failing (in terms of the pressure vessel, say, by cracking) in any way, and they've been in use for almost thirty years.
The way they DO fail, very predictably, is via the internal bladder that separates the nitrogen charge from the hydraulic fluid. Eventually the bladder fails, or the nitrogen simply diffuses through the bladder. Also, hydraulic systems are pretty horribly unreliable; with age, everything rubber fails eventually. Citroen did a pretty good job of proving that too, but on Audis, pretty much all the hydraulic hoses eventually fail. The hazard, in this case, is that when this system fails, it'll dump gallons of very slippery hydraulic fluid all over the road. If you're lucky, it won't also spray it all over, say, your hot exhaust. Atomized oil is pretty damn flammable.
Another danger: with the Audi system, all you had to do was pump the brake pedal until it was hard, and the system was safe to work on. This system would involve higher pressures and larger quantities of fluid...and it would become a real danger for anyone working on the car to do so with the system charged, as fluid over a certain pressure will either break skin or worse. I imagine they'll develop an easy way to discharge it, but people are still idiots.
The thing is also going to be a total bitch in a fire; I'm sure they'll put a pressure relief on the nitrogen side, but even then, you've got 10-15 gallons of flammable oil to deal with.
I really don't see Chrysler having any incentive to make the thing more durable than Audi/VW/Citroen did. It'll be made so it lasts about 60-70K, and then you'll be looking at replacing a huge, high-pressure tank. Expect the hilarity 3-4 years from whenever they go on sale, probably sooner.
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"Citroen used the same idea to power the extensive hydraulics used in their famous suspension systems"
Yeh they sure did. My dear late friend Harry had a big Citroen Pallas, and when the hydraulics failed he ran up the back of the same car twice. Once originally and again when they pulled over to exchange details, the car in front braked too quickly AGAIN and Harry ran up the back of it once more!
(:
Pointlessly small amount of storage. (Score:5, Insightful)
The amount of energy you can store in a 14 gallon hydraulic accumulator is pretty small. Even if they're cranking the pressure up to 6-7,000 psi the energy density is around 50kw-sec/gallon or somewhere around the equivalent of a car battery.
Perhaps not so pointless (Score:5, Insightful)
Perhaps not pointless. In the city, it's the start-stop aspect which is the mileage killer. Regenerative systems capture some of the energy used to decelerate, and use it to re-accelerate later. This is responsible for a large part of the efficiency of electric hybrids in city usage. I'm not sure if the hydraulic system described in TFA is linked to braking, or would by nature of its design capture energy during deceleration, but if so it would definitely help in city use. In fact, that may be the only place in which it shows gains, but let's not underestimate that. Most minivan use IS city use.
There is also the advantage that it's not based upon rare earths or lithium, which have their own political "sourcing" issues and their own limitations on how much is available. In short- to medium-term timeframes, that could be more important than ultimate efficiency comparisons with electric hybrids.
The safety concern is a serious one. Unlike present applications mentioned in TFA (garbage trucks, busses), there is much less structure in a minivan-sized platform to protect the pressure vessel. Anyone remember the Pinto problem [wikimedia.org]? This is solvable, though it will require more structure (meaning more weight) to protect it. Overall, the hydraulic subsystem + the weight of the protective structure are probably less than the weight of the electric subsystem including its batteries, so that may be a net gain over electric hybrids, but we won't know til we see specs.
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Well, 80% of the US population lives in urban areas and 20% in rural. So that means slightly more than one urban family needs to own a minivan for every four rural families that do in order for the majority of minivans to be owned by urban dwellers.
If you think the ratio is that far skewed, the onus of proof is on you.
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It would indeed be pointlessly small if the intention was to charge up the reservoir and use it to drive around with.
However that isn't the intention. I will confess that I glanced at the summary. Perhaps you - and the assclowns with mod points - should try it?
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Dear GOD please learn about units. kw*sec = kJ.
Given the prayer, I'd say you have an unusual relation with your GOD.
Compressed gases aren't *too* bad (Score:5, Insightful)
I routinely work with compressed gases (~2500psi, medical oxygen on an ambulance). The tanks are tremendously well-built, and if you drop one you're worried about the valve because it protrudes - not the tank itself. And by my envelope calculations, there's something like 603k pounds trying to turn my tanks inside out.
Yes, I'd want to be damn sure I knew what that tank was doing, and how well it was built - but we're pretty good at making pressure vessels that won't rupture on their own, and equally good at making ones that are solid enough to withstand impacts.
Frankly, 15 gallons of gasoline worries me more. The kind of impact that would rupture a tank would aerosolize the gas, and I'd rather be in an explosion than an explosion with fire.
Re:Compressed gases aren't *too* bad (Score:5, Informative)
Finally someone who has something intelligent, constructive and relevant to say rather than the myriad of knee-jerk, living in mom's basement, I watch Discovery Channel experts.
Are you on the right site?
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I don't know anything about Chrysler's tanks, but I do know that MDI has got tank storage figured out [aircarcomp...nology.com] for their own purposes.
Re:Compressed gases aren't *too* bad (Score:5, Interesting)
avoid allowing ANY oil and high pressure air to com into contact (to avoid the accumulator turning into a very short lived one cycle/stroke diesel ...)
Oh that brings back memories. We used to have an power station in the Melbourne CBD. Back in the day it run steam powered elevators all over the city. It had a big steam boiler which was shut down at the end of the day. They would let it cool then pump diesel into it to clean the gunk out. One day a bit of gunk was still hot and the diesel blew up. The tank was measured as being about a foot bigger in all three dimensions. They got an engineer out who scratched his head and suggested they fire it up to see how it went. It worked fine.
No citation sorry. Its an old old story.
I don't know when Chrysler started their project.. (Score:2)
I don't believe it's quite the same thing, but this group [www.mdi.lu] has been working on a similar idea for a few years now. Only problem is I don't think the latter vehicle would be so splendid in the snowy North.
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Even bicycle-type tricycles: those that go at any significant speed have a single drive wheel in the back and two wheels up front.
I'm not saying that a "standard" tricycle will tip over at the drop of a hat, but they are less stable when cornering, especially when braking while cornering. The two-wheels-in-front configuration is provably more stable.
They've solved some serious problems (Score:5, Informative)
http://en.wikipedia.org/wiki/Compressed_air_car [wikipedia.org]
The compressed air car has been under development for a long time. It shows great promise but nobody yet has been able to make a practical vehicle.
The advantage of a hybrid vehicle is that it doesn't have to store enough energy for a complete trip. In particular, it stores energy (thereby heating the engine) and releases energy (thereby cooling the engine) over a short period of time. The pure compressed air vehicle has the problem that the engine is permanently in cooling mode. If the engine is hot, because it has just been compressing gas, it is far more efficient. The longer it operates as an engine, the less efficient it becomes.
The advantage of compressed gas for short time energy storage is that the storage is simple and does not take much sophisticated material as compared with batteries.
People raise the problem of a tank of gas stored at very high pressure. The hybrid vehicle doesn't need as big a tank. Also, they've been working on this for a long time. The problem is basically solved. It isn't nearly as much a problem as a tank of gasoline.
F1 KERS (Score:2)
KERS [wikipedia.org]
This isn't new tech... (Score:2)
Tata is making subcompacts in India which use this exact method as a propulsion source to get around. However, what works over there might not work over here.
But, if the technology makes it over, just the fact that it can keep a vehicle running with the gasoline or diesel engine off at idle to low speeds in city traffic would save a good amount of fuel.
UPS has been testing these for a few years (Score:2)
http://articles.cnn.com/2008-10-28/tech/ups.hybrid.trucks_1_hybrid-trucks-hydraulic-hybrid-hydraulic-fluid?_s=PM:TECH [cnn.com]
olde tech (Score:2)
This sounds reminiscent of the starting system used in the good old Yakovlev Yak-52 aircraft. They first started flying them in 1976 according to Wikipedia .... ah well, what is old is new again.
... and they are already behind. (Score:2, Interesting)
http://www.scuderigroup.com/our-engines/
This engine is a split-cycle four stroke air hybrid that fires After Top Dead Center (ATDC) effeciently. The engine already holds far more pressure than standard combustion engines and reduces NOx by up to 80% and CO2 emissions by ~30% over similar hybrids and standard combustion engines - without the need of an ancillary system for power management (an electrical system for example). The engine presses out nearly 100% of the gas from the exhaust piston which leads to
Flywheels (Score:2)
Whatever happened to flywheels for energy storage? Popular Science couldn't shut up about them 40 years ago. Example: http://3.ly/Ccxs [3.ly]
It's worse then that. (Score:2)
There is a theoretical limit to how efficient a compression/expansion 'battery' can be.
I don't recall the formula, I'm sure some /.er with more recent thermo then I will come up with it.
I do recall that to get decent efficiency the high pressure side needs to be very high pressure.
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There is a theoretical limit to how efficient a compression/expansion 'battery' can be.
Ideally speaking, if you prevent heat loss, PV=nRT says that it can be 100% efficient.
I do recall that to get decent efficiency the high pressure side needs to be very high pressure.
Like 5000psi?
Re:It's worse then that. (Score:5, Informative)
The problem can be with the T. The hot compressed gas cools to ambient over time, dissipating energy (seen as a loss of pressure). I suppose, though, the energy is used before much heat has a chance to leak away. Barring that the limit on efficiency is the mechanical losses in the motor you drive with the gas.
You don't need particularly high pressures to make it theoretically efficient. You may be thinking of heat engines based on Otto (piston) or Brayton (turbine) cycles where efficiency is related to the pressure and temperatures at combustion, the higher the better.
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The problem can be with the T. The hot compressed gas cools to ambient over time, dissipating energy
If only I had said something like:
if you prevent heat loss
I don't think this compressed gas storage system is meant to be a "plug-in hybrid" that you "charge up" at night so you can drive to work on stored energy, but is meant more to efficiently recapture energy lost to braking, so heat loss can be minimized since the energy is only stored for minutes, not hours.
I don't think you necessarily need high pressures to make it efficient but you need high pressures to keep the storage tank, compressor/motor piston, and interconnect hos
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TFA refers to using the "engine overrun torque". Presumably they're referring to the situation where you take your foot off the gas pedal and engage a lower gear, thus causing the momentum of the vehicle to drive the engine - colloquially referred to as "slowing down using the gears".
I see three problems with this. One, most US cars are automatics. Two, your typical minivan driver thinks one or the other pedal has to be pressed flat to the floor at all times. Three, your typical minivan driver doesn't
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Not quite. Overdrive is a larger ratio gear. Back in the olden days, top gear ( in the car, not the TV series ) was a 1:1 ratio between the input and output of the transmission. Overdrive is a bigger ratio than that. It, and the 1:1 that "D" gives you can have a "freewheel" to them, which is more like what you describe ( allows the engine to go slower without that causing compression deceleration ). So, if you commonly run in "D" rather than overdrive, you might be wasting a bit of fuel on a lower gear
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Generators cause drag so you loose some energy but this type of system would add friction into the mix which would waste more energy. Seems more like an energy shell game with looses from friction along the way.
Why is it that this system would necessarily waste more energy than a electrical system? You say that this system would add friction, which is just another word for the "drag" that the generator adds in an electrical system. Why is this more of an energy shell game than an electric hybrid? It's just replacing the generator/battery combo with a compressor/accumulator combo.
Assuming that it's mostly a short-term compress/decompress cycles, as long as the accumulator is well insulated to prevent heat loss, it
Re:Sounds inefficent (Score:5, Informative)
What people sometimes forget about is that such a cycle can be theoretically 100% efficient: it's called the reversible adiabatic process -- completely reversible! As long as your gas storage system is well insulated and has low thermal masses, that is. You simply compress and heat up the gas and store it. Later on, you decompress and cool down.
Think of a gas sealed in a well-insulated, low thermal mass cylinder. You do some work to move the piston in, the gas heats up and compresses. You release the piston, the gas does the same work going out as it expands and cools down. If the system is perfectly isolated and there is no friction, you get exactly the work you put in.
This has the theoretical potential of being a rather nifty thing, but I don't know how the practical (engineering) side of things works out. It may be impractical, or may be not. Time will tell.
Re:Sounds inefficent (Score:4, Interesting)
As a scientist who lives off the grid on solar PV (for decades now), I've pretty much investigated every way there is to store energy, and it's not so simple a problem. Vanadium redox batteries (utterly impractical for autos and that membrane ain't cheap) look about the best so far in terms of simple and good while being efficient. Most things that do heat storage are only efficient if huge enough that the surface area to volume ratio can be really small.
The above approach might work out fine for small amounts of energy and for short times, however, and having some is better than nothing -- it probably is pretty reliable unlike most batteries which tend to have much shorter cycle life than is claimed. I think we're going to see a big backlash against battery cars at some point because of that one.
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It's a good system that was implemented years ago by these guys:
http://www.permo-drive.com/tech/index.htm [permo-drive.com]
From my quick perusal the systems look the same.
They even sold it to the US military for use in their FMTVs.
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Doesn't a perfectly reversible adiabatic process also need to be quasi-static? I don't know the details of this specific case, but I don't expect the piston would always be moving very slowly.
Side effect (Score:5, Interesting)
Adiabatic heating on compression would be pretty serious. A diesel engine only has 15:1 to 20:1 compression ratio, and develops enough heat thereby to ignite diesel fuel. In this system we are looking at upwards of 300:1. The temperature would be absolutely fierce.
If on the other hand you design the system to dissipate the adiabatic heat, you are rejecting a good proportion of the compression energy, which then you will not get back on expansion. So either you must withstand incredible heat in the system, or you sacrifice efficiency.
The mirror image is adiabatic cooling on expansion. If you do reject the adiabatic compression heat, then on expansion you will have problems with supercooling and moisture freezing.
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Thank you for raising the point that different gases undergo different degrees of adiabatic effect. However, it is my understanding that your exposition is incorrect. First, all common gases are near enough to ideal gases under the conditions of interest. The volume exponent, gamma, is indeed different for monatomic gases (helium, neon, argon, etc) as compared to diatomic gases (nitrogen, oxygen, etc); however, the difference is only one of degree - both are above unity. Gamma is 5/3 for monatomic and 7
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On the other hand, any thermal leak is a very big energy loss. You're running a heater and throwing away heat on "charging", a cooler and then absorbing heat into the cooled gas on "discharging".
This is why compressed air is a rotten energy storage and transport medium. (In factories, however, it IS used as an energy transport medium because the inefficiency is offset by various design advantages in the devices it powers - typically linear actuators, large clutches on stamping presses, compact refrigerati
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I do agree that I was ahead of myself. Now for nitpicks:
Aerogel isn't a daydream. You can buy it. Costs reasonable amounts, even. If you wanted to insulate particularly hot CPU/GPU heatsinks in a laptop from the bottom of the case, a few mm of aerogel would be my choice, at a cost of maybe $10 or so. Maybe not in a $200 netbook, but Apple sure could pull that off if they needed to. Hot heatsinks are much easier to cool.
Superconductors are problematic due to rather theoretical reasons, too: good luck when yo
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Generators cause drag so you loose some energy but this type of system would add friction into the mix which would waste more energy
A bigger engine with 2 extra cylinders (to match the performance of this 4-cylinder hybrid) also adds friction, and it does so all the time the engine is running.
I would assume that this gas compressor can be disengaged with a clutch when not needed, so the friction losses could actually be less overall for the same max power output.
Re:Boom! (Score:4, Funny)
If it's holding 5000 PSI it will be pretty difficult to crush.
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A two-ton SUV moving at 80 miles an hour agrees with you, but doesn't give a fuck
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Now there's an idea! If crushed in a wreck, it would be holding more energy. Storing the energy of wrecks could become the new eco-friendly feature in cars.
Re:Boom! (Score:4, Insightful)
If you have ABS, you already have something like this in your car. It's a little (1qt) metal sphere with a rubber diaphragm in it. It holds about 3,000PSI of Nitrogen in order to cycle the ABS when it activates.
As for the safety...well... how safe is it to carry around 20 gallons of highly flammable gasoline?
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Really? Where do I find this on my car? I don't see it anywhere [realoem.com].
Nor have I seen it on any of the other ABS-equipped vehicles that I've owned.
Can I have some of what you're smoking, though?
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Dearest AC,
I've been looking for several minutes and still haven't found anything.
This link [demon.co.uk] indicates that some BMWs have a device called a hydraulic accumulator which is pressurized and used for braking purposes, but does not indicate that mine does.
I'm very interested in this yet-unseen part on my car.
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Funny that the "hydro unit" is shaped just like an electric motor: It's the ABS pump.
I know it has a pump. I'm looking for the highly-pressurized quart-sized sphere of nitrogen which is proclaimed to exist.
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Right. The ABS pump. The thing with the moving parts, not the thing with the stored energy.
Still waiting.
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Gasoline is just a liquid until it is ignited (Mythbusters found out that a dropped cigarette is not enough to ignite gasoline), so in a crash you need a source of a lot of heat for the gasoline to ignite. OTOH, Li-Ion batteries ignite if they are punctured. A high pressure tank can explode if punctured. Again, no need for a flame (though if you heat the high pressure tank it explodes more violently, since the internal pressure depends on the temperature).
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(though if you heat the high pressure tank it explodes more violently, since the internal pressure depends on the temperature)
Use a sacrificial valve (introduce a "defect" on purpose to control in which point in which the tank will blow. No explosion when over-pressurized/heated).
Re:Boom! (Score:5, Interesting)
In an accident, it will remain intact. If not, then the car won't pass standard safety tests, and the manufacturer knows it won't sell. In the event that some freak crushing blow strikes the tank (like, for example, getting caught between a freight train and a reinforced bunker, or perhaps dropped from an airplane) It'll most likely burst open at the one spot that the engineers intentionally design to be slightly weaker than the rest of the case, which conveniently releases the contained gas in a harmless direction.
5000 PSI is like having an average American car, including all passengers, with all its weight sitting on a single square inch. That's the maximum operating pressure, implying that the tank itself will actually hold significantly more pressure before having any problems. I feel pretty confident that the engineers involved know what they're doing, and can prevent catastrophic failure during a collision.
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Agree, I don't think safely containing nitrogen at 5000psi is a major engineering problem. I recall reading a while back that BMW had a tank that can hold hydrogen at 20,000psi and passed EU saftey standards for use in a car. Also hydrogen is a much more difficult gas to contain under pressure since it seeps right thru traditional materials such as steel.
The idea itsel
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I feel pretty confident that the engineers involved know what they're doing, and can prevent catastrophic failure during a collision.
Most people probably would have said the same thing about the engineers at Ford who designed the Pinto. And even if the engineer designs it right, you still need to worry about someone cutting corners because the safe design takes longer and/or costs more money.
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Let's not forget a carjacking gone bad.
LK
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Since they aren't holding much more energy than a gas tank or battery, can the risks due to catastrophic failure really be significantly greater?
Re:Boom! (Score:5, Funny)
CNN describes the tank as a "bladder".
Damn! Now that's two bladders I'll be emptying when an accident occurs.
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Mythbusters successfully demonstrated that a SCUBA tank, which have pressures up to 30 MPa (4400 psi) and internal volumes up to 18 liters, will turn itself into a missile [mythbustersresults.com] if its regulator catastrophically fails. The tank proposed in TFA would have a pressure of 34 MPa and a volume of 54 liters, meaning that it will store even more energy.
An over-pressurized liquid nitrogen tank caused major damage to a Texas A&M building when it failed (read: exploded). According to the engineer's report [ucdavis.edu] (pdf):
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SCBA tanks are required to be tested every 5 years at 5/3 of their rated pressure. I wonder if the Chrysler tanks will be due similar scrutiny...
In terms of "bladder," it's probably not a misnomer: Similar to an expansion tank [wikipedia.org] on a hot water system, or a pressure tank on a well system, the factory-installed nitrogen will be separated inside the tank from the newly-introduced compressed gas by rubber.
FWIW.
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I wonder if the Chrysler tanks will be due similar scrutiny...
doubt it. scba tanks are strapped to our backs and providing us life-air while deep under water. a tank failure would probably kill a diver so this extreme cautionary preventative maintenance is warranted.
Re:Boom! (Score:4, Insightful)
This will be tested up the wazoo, and then some.
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Batteries and liquid fuels have the huge advantage that when they blow up, most of the energy is released as heat.
I dunno about you, but 99.9999% of the world's population considers that to be a very serious DISadvantage in an accident.
If the pressure cylinder can be held in place, then the sudden, explosive release of an inert gas, such as Nitrogen, might actually be of some value in an accident. Fire suppression, perhaps?
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If the force applied to the tank in question is sufficient to cause a catastrophic rupture/explosion, then I would hazard to say that none of the parties directly involved in the collision are likely to care, as they're already dead.
Simply piercing the sides won't do it, you'd have to completely crush it. And considering the location and construction materials used, that's not going to be easy to do.
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Quite correct, these same issues were raised when LPG tanks became populr here, but it is very rare for one to be ruptured, they have to be damn strong just to work, in most cases stronger than any object they are attached to or hit by.
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the energy stored per kilogram is much lower than current lithium batteries.
For a non-plug-in hybrid, it doesn't really matter that much. What you're really after is a buffer to take up otherwise wasted energy and re-dispense it at the earliest available opportunity. The key isn't so much overall capacity - you just want something that can be charged and discharged fast enough and efficiently enough to satisfy the needs of normal city driving.
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Yes, a regular hybrid "only" needs to store as much energy as needed to bring the car to a stop and accelerate it to highway speeds.
Which means that when the pressure vessel bursts, you have one car-at-highway-speed's worth of kinetic energy blowing up in your face.
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Yes.
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Gasoline needs oxygen to burn. If the gas tank ruptures, and catches fire it still burns at a certain rate. If that tank ruptures it releases all the energy at once.
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I've seen tires from semi's explode, and take peoples hands, fingers, and critically injure them if the rim shatters along with it. And depending on the type you're only looking at 50-250psi. Voltages we can deal with, car coils kick out 100k-500k volts or more for ignition.
Yeah I seriously don't see this ever getting off the ground unless the container is designed to 'not' ever explode but in the even of a crash will only bleed pressure at a low level.
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if crash=1 then dump-pressure
(Yep, I'm no programmer. But I don't think it'd take a rocket surgeon to tell the programmers how to make this work, given the myriad of accelerometers and such in modern vehicles.)
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(Yep, I'm no programmer. But I don't think it'd take a rocket surgeon to tell the programmers how to make this work, given the myriad of accelerometers and such in modern vehicles.)
Considering how many screw ups there have been over simple things like roll sensors, and ignition modules that are supposed to cut fuel in the event of a crash or roll over? Yeah...I don't know about that.
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I think it'd be OK. Most of the complaints you speak of are of safety systems operating when they shouldn't be, as in the case of the roll bar that deploys when there is no accident imminent.
If the tank ejaculates prematurely*, then all that is lost is a bit of fuel economy. After all, it doesn't cause a new safety hazard when this happens, as do roll sensors that fire pyrotechnic roll bars ($$$+possible injury), fuel pump cutoffs that require one to crawl into the trunk to reset it before proceeding, and
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If you thought a high-voltage hybrid was dangerous... ...then you're a moron.
Seriously, there's about fifteen billion "dangerous" things in an average car - adding a small battery and a few wires doesn't change that. The total energy stored in the battery of most hybrids is about the same as the energy in a few tablespoons of gasoline. And unlike the parts of the car that carry your fuel, the high-voltage parts are clearly indicated with bright orange coloring. The airbags are probably more dangerous than t
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hmm short a super cap with some steel or aluminium bar, and let me know how it goes.... or simply ground one end to the car body and watch it light up a rescue worker/bystander when it ground through them.
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bugger the ethical treatment of gases.
i finally found a way to make popping candy!
when pressure cookers just aren't enough.
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Wait a minute... isn't that why people didn't want hydrogen cars in the first place?
No, it is because pure hydrogen has a lower energy density the hydrocarbons and it's highly difficult to store hydrogen (the tiny bastard uses the pores of the steel container to escape). See hydrogen storage [wikipedia.org].
What about supercapacitors?
Expensive like hell.
Those would be much safer than high-pressed nitrogen.
Would it, now? Just what you think happens when the hundreds of ampere*hours discharges through you body in the shortest time possible? Ah, you say: why through my body and not through the car's body? I ask you in return: why the nitrogen tank should explode instead of releasing all
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Your inflatable date will be ready for fun in no time!
There. Fixed it for you. (I like my women with hard bodies. But #2500? Sheesh!)
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Your inflatable beach toys will be ready for fun in no time!
And the stout is so much smoother when using N2 instead of CO2.
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Composite, carbon fiber. They've developed some that turn into somethin akin to cotton candy when they disintegrate rather than shrapnel.
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Already done by Porsche...
http://jalopnik.com/5728504/how-the-porsche-918-rsrs-amazing-hybrid-works/gallery/ [jalopnik.com]
They have a flywheel driven by a motor/generator powered by the motor/generator at the wheels when the car is breaking.. the flywheel can then dump power into the motor/generator for a power boost.
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If the car is BREAKING it wont go very far anyway.
It it is braking it should be OK.
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One variant of KERS [formula1.com] in Formula 1 racing used it.
For those readers left of the pond, F1 is like IndyCar but the cars can turn both right and left.
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I hope there's a turbo button that vents the nitrogen to a rocket nozzle for when you want to pass someone.
Only if your van uses a 486 CPU. After that, it's just nothing or adjusting your BIOS setting (which requires a cold-reboot most of the time).
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So if I can't start my engine and my pressure tank is empty, how do I jump start it? Connect a high-pressure line from another vehicle with the same kind of accumulator? Or do I have to tow-start it?
Would help if you'd have had baked beans for the dinner a night before. Though... mileage may vary.
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But they're not *that* bad, just lousy. More like you lose about 40% round trip, not 75% as you say, and that 40% is at end of life, when you
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Don't carbon fiber flywheels in a vacuum chamber have a higher energy density? (and very high cost)
I read about special extremely long life (but lower energy density) nickle-iron batteries that last an extremely long time. And the electrolyte in them can be swapped after they do wear out to rejuvenate them.
Have you tried those? How well do they work for your off-grid system.
How do you live without A/C?
Re:Chemical battery efficiency is quite poor (Score:4, Informative)
The typical chemical battery used in hybrids have very poor efficiency. It stores only 50% of the energy given and releases only half of the stored energy
Nope. Lithium-ion is around 90+ percent efficient round trip. See the note in the wiki article [wikipedia.org]. Lead acid is around 70% round trip. Molten sodium is a very old technology that is actually quite safe, but has durability and power density problems.
Flywheels are great, but they're really scary. Flywheel hybrid research was mostly stopped when a wheel blew up and killed a technician at Chrysler. The problem with compressed air is that their is heating of the air during compression and cooling during expansion. If that heat does not stay in the air, there is efficiency loss.
What we need is really electricity priced the way cell phone minutes are sold. Peak hour, off peak and night rates. Then there will be an incentive for people to buy these things to store cheap electricity at night and use it in the day and reduce the grid load on hot summer days.
There already is for large industrial customers. The smart grid would bring that to homes. One of the consequences is negative electricity prices due to excess wind power. Even so, I did some bath that showed you could expect to make around 0.1 and 0.2 dollars per kWh of capacity per day. That's around 30-70 dollars a year per kWh. The cheapest batteries I know of are around 50-60 dollars per kWh and will be toast before they pay for themselves.
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What we need is really electricity priced the way cell phone minutes are sold. Peak hour, off peak and night rates. Then there will be an incentive for people to buy these things to store cheap electricity at night and use it in the day and reduce the grid load on hot summer days.
They DO have these options: For industrial and commercial use. Residential just doesn't make sense for that.
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Source please? Last I've heard, Nickel-based chemistries (early hybrids such as the Prius use(d?) Ni-MH) achieve 90% charging efficiency if fast-charged [batteryuniversity.com] (that is, the battery stores 90% of the energy provided to it). And Li-ion's charge efficiency reaches an impressive 99.9% [batteryuniversity.com].
While compressed air may have many advantages over modern batteries, charging/discharging efficiency is unlikely to be one of them.