Putting the hy in hybrid cars

January 22, 2011 10:35 AM

Hydraulic hybrid cars to be mass produced by Chrysler. Using a brake-stored "launch assist" technology developed and tested by the EPA since 2004, the lesser known hydraulic hybrid vehicle is relatively clean-burning and fuel efficient, easy to deliver, and isn't powered by batteries. How it all works.
posted by Brian B. (56 comments total)

UPS is experimenting with this on the streets, also.
posted by Exchequer at 10:46 AM on January 22, 2011 [1 favorite]

So the idea is to save fuel by using alternate power for the parts of the process that wastes the most fuel, starting from dead stop and accelerating from low speed?

Hm. Not a bad idea. Interesting that it says UPS trucks are already using this.
posted by zoogleplex at 10:46 AM on January 22, 2011

The article mentions Chrysler, but not GM. Typo?
posted by indubitable at 10:55 AM on January 22, 2011

Headline on first link: Chrysler announces battery-free hydraulic hybrid tech, compresses gas to make power. CHRYSLER, not GM. There's a difference. As my uncle who worked for GM for 40 years and hated his job for 38 of them would tell you.
posted by oneswellfoop at 10:57 AM on January 22, 2011 [3 favorites]

Awesome. Seems like a way to power a toy, not a real road-going vehicle.

Still, I'm looking forward to the day I can drive an auto powered by an Elastic Hybrid Drive System.
posted by notyou at 10:57 AM on January 22, 2011 [1 favorite]

MUST...NOT...BUILD...ELECTRIC...CAR...
posted by ryanrs at 11:01 AM on January 22, 2011 [3 favorites]

The article mentions Chrysler, but not GM. Typo?

Typo indeed. Maybe a mod could replace GM with Chrysler.
posted by Brian B. at 11:01 AM on January 22, 2011

zoogleplex, the hydraulic system captures energy that would otherwise go to waste, stores it, and uses it to accelerate the vehicle. It's regenerative braking using pressure instead of potential.
posted by polyhedron at 11:02 AM on January 22, 2011

Man, I remember when howstuffworks wasn't almost completely worthless and covered with ads. Regenerative braking recharges the accumulator - no shit. How? The accumulator uses high pressure nitrogen to drive the drive shaft? That's not how any hydraulic accumulators I've ever seen work.

Great post, though.
posted by ctmf at 11:05 AM on January 22, 2011 [1 favorite]

[Chryslis averted, carry on.]
posted by cortex at 11:08 AM on January 22, 2011 [7 favorites]

So, it's like slowing down by winding up an elastic band, and speeding up again by letting the elastic band go?
posted by Flashman at 11:11 AM on January 22, 2011 [2 favorites]

Also, every single hydraulic accumulator I've had the dubious pleasure of working with leaks oil like crazy. Hope the engine comes with a drip tray mounted underneath.

And plenty of warning placards to depressurize the system before working on it. People don't expect a parked and turned off car to have a high energy hazard in there.

I think these engines would be perfect for the golf cart like things we bop around in at work, though.
posted by ctmf at 11:15 AM on January 22, 2011

ctmf: leaking oil+pressure - how true! I can imagine the result of an accident, where a pressurized oil system suddenly blows all the oil out on a roadway. Or even better/worse, adding to a car fire like a can of shaving cream in a fire.

But your golf-cart-like-things are probably using propane like a forklift, yes?
posted by Old'n'Busted at 11:18 AM on January 22, 2011

The nitrogen simply stores the energy. The shaft is driven by hydraulic fluid.

Energy recapture is not a new idea, engineers have been thinking about it since about the time they started building cars. Of course, the market is all about price and cost, which is why these ideas don't get implemented sooner. The market has to bear the cost of the technology, and until fuel prices rise enough to make it cost effective for consumers, nothing will happen. I honestly don't think fuel prices are there yet, but manufacturers are responding to consumer desire based on consumer perceptions. That, and establishing a foothold in the market for energy efficient vehicles is a necessary position for when prices actually do force everyone to go fuel efficient.

Fuel prices in Europe have been much higher those in the U.S. for a very long time, and while the cars there are generally more efficient on average, they have been made so by being smaller and lighter. Energy efficient technology was still considered by the manufacturers to be not commercially feasible. One thing to think about is that the cost isn't just the initial capital outlay, but the cost of maintenance, particularly any items that fall under the manufacturers warranty.

Nevertheless, this is good news that they think energy recapture is a viable feature. Just think how much fuel could have been saved if this had been done since the beginning. Socialism!
posted by Xoebe at 11:20 AM on January 22, 2011 [3 favorites]

while the cars there are generally more efficient on average, they have been made so by being smaller and lighter

You say this like it's a bad thing.
posted by ryanrs at 11:24 AM on January 22, 2011 [3 favorites]

So, it's like slowing down by winding up an elastic band, and speeding up again by letting the elastic band go?

They have ideas like that too. And there is an entire category of flywheel related concepts, some very low tech and heavy (and once used in cars), and some recent ones charged with electricity using composite materials and deemed slightly dangerous. In general, they all encompass a no-idle bonus.
posted by Brian B. at 11:25 AM on January 22, 2011

The accumulator uses high pressure nitrogen to drive the drive shaft?

Yeah, I'd like more explanation of that. Calling it "hydraulic" suggests the pressure is the primary energy source, but it sounds like nitrogen is really the primary energy source and the pressure is only used to move the nitrogen. Is nitrogen readily available? How quickly is the nitrogren depleted? Where would it be recharged?

The nitrogen simply stores the energy.

How exactly does that work without running out of nitrogen? Is the nitrogen recaptured somehow? Or is there some system of converting energy to more nitrogen?
posted by scottreynen at 11:33 AM on January 22, 2011

In a normal accumulator, the N2 doesn't get "used". It acts like a spring for the oil to be pressed against and stored, then provides the motive force when the oil is let out again. I'm sure thats what was meant, just poorly worded.

Of course, the nitrogen will periodically have to be recharged (not often, but sometimes). I guess gas stations could have that. Or they could use air instead, and put bigger compressors at gas stations. Either way, it would be nice if the fitting was incompatible with some moron trying to inflate a tire to 3000 lbs by accident. Heh.
posted by ctmf at 11:43 AM on January 22, 2011 [2 favorites]

ctmf: leaking oil+pressure - how true! I can imagine the result of an accident, where a pressurized oil system suddenly blows all the oil out on a roadway. Or even better/worse, adding to a car fire like a can of shaving cream in a fire.

I would assume that the vehicle is stopped during this accident, so at least it isn't used as an exploding missile.
posted by Brian B. at 11:44 AM on January 22, 2011 [1 favorite]

scottreynen: If I understand it correctly, the energy is stored by compressing/expanding nitrogen in a closed container; nitrogen isn't lost or vented. (Here are a couple of cutaway views of a gas type hydraulic accumulators for example). The energy storage is pneumatic; the hydraulic system is just used for moving the energy back and forth between the axle and the pressurized gas.
posted by hattifattener at 11:45 AM on January 22, 2011 [2 favorites]

I know, the nitrogen doesn't have to be the same pressure as the oil. Funnier my way, though.
posted by ctmf at 11:46 AM on January 22, 2011

ctmf, lots of motorcycles have external nitrogen reservoirs on the rear shock. Recharging the nitrogen is not a regular maintenance item, as far as I know. Recharge kits are available, but I think they're mostly for people who compulsively work on their motorcycles. Normal riders go to a repair shop and tell them that the suspension feels funny.
posted by ryanrs at 12:01 PM on January 22, 2011

reminds me of Bagucigalpi's springs, except those are explicitly 'wound,' and therefore likely to have been conceptualized as non-hydraulic.
posted by mwhybark at 12:34 PM on January 22, 2011 [1 favorite]

I hate to go there, but this sounds so steampunk to me.
posted by tommasz at 12:52 PM on January 22, 2011

The short announcement doesn't make it clear whether this is a parallel or series hydraulic system; though it's linked to the UPS vehicles which -- if I read it right -- are series.

The difference appears to be that while the parallel system only reclaims braking energy (aka "launch assist") and is not involved in distance driving, in the series system the engine power is delivered indirectly through the hydraulic system, which allows engine speeds to be somewhat decoupled from demand and be managed for maximum efficiency.

So this system seems like it's roughly comparable to a Chevy Volt in its approach, but less lossy than batteries, with less dead weight and, I'm guessing, smaller ecological footprint in manufacturing. Sounds pretty cool.
posted by George_Spiggott at 12:55 PM on January 22, 2011

Hydraulics hybrid are also used in garbage trucks.
posted by Monday, stony Monday at 12:57 PM on January 22, 2011 [1 favorite]

If I understand it correctly, the energy is stored by compressing/expanding nitrogen in a closed container; nitrogen isn't lost or vented

That makes more sense. It also means the explanation on How Stuff Works is wrong:

the accumulator sends its energy (in the form of nitrogen gas) directly to the driveshaft

And on further research, everything about How Stuff Works seems to be wrong now. Ugh. I rememeber when it was a really useful site, but now the front page has a "Are you friends with your boss on Facebook?" poll and a Sudoku puzzle. Looks like they're just desperately seeking page views at all costs.
posted by scottreynen at 1:00 PM on January 22, 2011 [3 favorites]

lots of motorcycles have external nitrogen reservoirs on the rear shock

Yes, Nitrogen springs working with pressurised fluid transfer is how most high end shock absorbers work. Re-pressurising the cylinders doesn't need to be done all that often - we rebuild them more regularly for performance reasons (super picky tolerances really) and the gas pressure has remained stable in dozens of sets that I have been closely monitoring for over a year with racing loads working on them. So yearly checks on your nitrogen levels, when the only issue if it leaks is loss of regenerative power seems like a small issue to me. Lots of garages are starting to hold nitrogen for tyres anyway, so this would be a minor issue, so a high pressure fitting and approved filling stations would be easy to do within the current infrastructure.

I don't know about the transfer losses in the system, nor how well the system copes with higher levels of braking performance - that'd be interesting to know. It'd be nice if this system was as efficient or more than the Prius style so we're not digging all the planet up and shipping non-recyclable battery cells around.
posted by Brockles at 1:05 PM on January 22, 2011

If it's a Chrysler, every penny you save on gas will be spent on repairs.
posted by eatyourlunch at 1:27 PM on January 22, 2011 [2 favorites]

I want to make an energy recapture car that looks like a forklift carrying a Monty Python-sized giant 1 ton weight. All power will come from the falling of the weight, and all storage of power from the raising of the weight. Brake: weight goes up. Accelerate: weight goes down.
posted by zippy at 1:32 PM on January 22, 2011

For those unfamiliar with reasons why a hybrid car warrants an incentive to buy it over a smaller car with the same gas mileage: they reduce the worst pollutants which are produced during acceleration (smog making nitrous oxides), and if they feature regenerative braking or hydraulics, they promise a major reduction in brake pad replacement costs, which are ground to dust, and which are among the three main costs of maintaining a vehicle, behind tires and preventive maintenance.
posted by Brian B. at 1:42 PM on January 22, 2011

Development on this has been going on for a while, sort of a close cousin to the flywheel systems that are now starting to pop in racing. Porsche ran a 911 variant at the 24 hours of The Ring a while back and did well with it. Williams GPE was also RDing a flywheel hybrid (actually, they're the folks that sold it/worked with Porsche).

There's a lot of engineering pluses to going with this kind of hybrid system over batteries. It weighs less and takes up less room (packaging-wise) and from what I gather, a setup like this can exhibit explosive acceleration off the line.

If you can make it small enough and light enough, then I say put it in there and let's see what she'll do.
posted by Relay at 1:55 PM on January 22, 2011

Re: recharging nitrogen, depends on what kind of accumulator you have, I guess. I've worked with big hydraulic power plants that use the piston-type accumulators, and also some smaller applications like emergency backups for hydraulic valve operators, which tend to be bladder-type.

The piston type ones are hit and miss - sometimes you never have to touch them, and sometimes you get a lemon that seems to need recharging every few days no matter how many times you replace parts and fittings.
posted by ctmf at 2:00 PM on January 22, 2011

they promise a major reduction in brake pad replacement costs, which are ground to dust, and which are among the three main costs of maintaining a vehicle, behind tires and preventive maintenance.

tee hee, not if your car is over 20 years old....
posted by ennui.bz at 2:05 PM on January 22, 2011

Is nitrogen readily available?

Air is 78% nitrogen, so yes. It is extremely readily available.
posted by schmod at 2:15 PM on January 22, 2011

while the cars there are generally more efficient on average, they have been made so by being smaller and lighter

...

You say this like it's a bad thing.

You say that like safety isn't a good thing.
posted by ericost at 2:39 PM on January 22, 2011

You say this like it's a bad thing.

>You say that like safety isn't a good thing.

Smaller and lighter is safer. When some idiot drives into me, the smaller and lighter their vehicle, the better.
posted by -harlequin- at 2:53 PM on January 22, 2011 [8 favorites]

our vehicle was made in 2004, yes, 6 years old, in 6 more years, we will be ready for a new vehicle, maybe this new hybrid will have all the early model kinks out of it, and sign me up to get a new hybrid.
posted by tustinrick at 2:56 PM on January 22, 2011

while the cars there are generally more efficient on average, they have been made so by being smaller and lighter

You say this like it's a bad thing.

It kind of is, indicating that real technology advances are really coming slower than what's ideal. Making a car that is made from less stuff is kind of the quick and dirty kludge to make for better efficiency. The end result of going smaller and lighter is that we all adopt motorcycles, scooters and mopeds in lieu of autos. Unfortunately, such vehicles simply do not address the needs of most travelers. Addressing the needs of car buyers, the limitations of materials and safety requirements hits a wall after a while. Improving the means of propulsion is the real prize.

Ironically, most motorcycles, scooters and mopeds even today have engines that are much more primitive and relatively inefficient compared to modern autos. Real innovation comes from propelling the hunk of steel down the road more economically, by doing something other than simply shrinking the hunk of steel.
posted by 2N2222 at 3:16 PM on January 22, 2011

If recent history is any indication, improvements to energy efficiency are often used not to reduce the amount of consumption of energy overall, but to keep the status quo average energy consumption of vehicles by simply increasing the size of the vehicle (see jumbo hybrid SUVs). That may be innovative, but it's not helping out the real problem: increasing atmospheric CO₂.

I'd love to see a move toward smaller cars. There's absolutely no need to cart 2 tons of steel with you to work. Of course, that doesn't mean we all have to drive Smart Fortwos. Improvements to safety technology means that smaller cars can be safer as well, but we're all safer when the average vehicular mass decreases.
posted by Existential Dread at 3:40 PM on January 22, 2011

"Hydraulic" is a bit of a misnomer. "Hydropneumatic" would be more accurate. It's strange that Chrysler is the first carmaker to consider bringing this to market: Citroën has been using Hydropneumatic suspensions for almost 60 years now. Despite that, and Peugeot-Citroën's confirmed interest in hybrids, there has been no indication of them taking this path.
posted by Skeptic at 4:29 PM on January 22, 2011 [1 favorite]

Old'n'Busted writes "leaking oil+pressure - how true! I can imagine the result of an accident, where a pressurized oil system suddenly blows all the oil out on a roadway. Or even better/worse, adding to a car fire like a can of shaving cream in a fire."

Several antilock systems work like this (obviously with smaller volumes). I don't recall any sorts of horror mongering about these systems. Heck Hydraulic power steering systems can develop pressure in excess of 1000 psi.

Skeptic writes "It's strange that Chrysler is the first carmaker to consider bringing this to market"

Despite their recent troubles they've always been both an innovative engineering company and, because of their somewhat rocky business health, willing to take risks that larger automotive makers seem to avoid.
posted by Mitheral at 6:49 PM on January 22, 2011

Ford was talking about doing this to the F-150 several years back, but my guess is they either couldn't scale it well, or it wasn't worth the extra cost/weight.
posted by spiderskull at 6:49 PM on January 22, 2011

The short announcement doesn't make it clear whether this is a parallel or series hydraulic system; though it's linked to the UPS vehicles which -- if I read it right -- are series.

The difference appears to be that while the parallel system only reclaims braking energy (aka "launch assist") and is not involved in distance driving, in the series system the engine power is delivered indirectly through the hydraulic system, which allows engine speeds to be somewhat decoupled from demand and be managed for maximum efficiency.

So sort of like what diesel-electric locomotives have done for about the last 80 years? I was wondering when we’d see that sort of thing showing up in automobiles. I know the Prius and so on are capable of running in a mode where the gasoline motor diverts all of its output into the generator to power the traction motors, but they also have a direct mechanical transmission.
posted by spitefulcrow at 7:37 PM on January 22, 2011

I was wondering when we’d see [train-style series systems] showing up in automobiles

I'm surprised we haven't already. I read somewhere that one of the big American makers developed a prototype car with an electric transmission, well before hybrids became a thing, simply because the electric system was lighter and no more complex nor less efficient than a traditional mechanical gearbox+differential+etc. (It's surprising how much energy you can lose in gears.) I'd think there are other engineering advantages, like more freedom in how you position the engine, continuously-variable transmission, etc.
posted by hattifattener at 8:27 PM on January 22, 2011 [1 favorite]

Smaller and lighter is safer. When some idiot drives into me, the smaller and lighter their vehicle, the better.

I believe that safety really is about the ratio of the involved cars' masses. If everybody on the road had cars that were half as massive, we wouldn't be any safer.
posted by Jpfed at 2:16 AM on January 23, 2011

Actually Jpfed, safety is a combination of the engineering & design of the car, and how it is operated.
posted by Relay at 9:35 AM on January 23, 2011

Thanks for the post! I have a 2010 Prius and it does really suffer in terms of acceleration when you stomp on the gas pedal. I wish they'd bolt on a mechanical storage system so the car would have more pep and avoid the lossiness of storing brake energy in the battery. I'm glad to have it and I'm glad to get 50 MPG, but having a guilt-free mechanical turbo boost would be all the better.
posted by efbrazil at 9:51 AM on January 23, 2011

The IIHS put out an interesting video showing an offset crash between a '58 Chevy Bel Air and an '09 Malibu. The Bel Air has a 300 lb. weight advantage, so it's not a good measure of the weight theory of safety, but it really does illustrate how much safer a modern car is in a crash.
posted by electroboy at 1:44 PM on January 23, 2011

I'm a little sad that they ruined a 50 year old car like that.
posted by Pruitt-Igoe at 4:46 PM on January 23, 2011

Actually Jpfed, safety is a combination of the engineering & design of the car, and how it is operated.

and

it really does illustrate how much safer a modern car is in a crash.

What I said was in response to "smaller and lighter is safer". I and presumably the person I was responding to meant "all other things being equal". So, engineering practices unchanged, smaller and lighter is not safer if both cars are smaller and lighter.

When you get into a crash, your velocity will change. From the conservation of momentum equations, the mass ratio plays a part in how much your velocity will change. The engineering helps determine how quickly your velocity will change.

Human bodies are damaged by accelerations that are too fast. Acceleration is dv/dt; great engineering helps increase dt, but the mass ratio plays a part in dv. Therefore, both play a factor in human safety, and engineering practices being equal, smaller and lighter is not safer.
posted by Jpfed at 4:49 PM on January 23, 2011

Human bodies are damaged by accelerations that are too fast.

That's one way human bodies are damaged, but if you watch the video you'll see that the entire body of the older car deforms and the passenger compartment is completely crushed. You can certainly be injured by quick deceleration, but having your chest pierced by the steering column will do it too.
posted by electroboy at 9:00 PM on January 23, 2011

You can certainly be injured by quick deceleration, but having your chest pierced by the steering column will do it too.

engineering practices being equal, smaller and lighter is not safer. The phrase "engineering practices being equal" means that I'm talking about when both cars have spikes jutting from their steering wheels, or when both cars have seat belts, air bags, roll cages, frames made out of space-age materials, etc.

Now that I'm repeating myself, I should bow out.
posted by Jpfed at 4:31 AM on January 24, 2011

Well, you also should've read the part of my original post that said:

The Bel Air has a 300 lb. weight advantage, so it's not a good measure of the weight theory of safety, but it really does illustrate how much safer a modern car is in a crash.

posted by electroboy at 8:20 AM on January 24, 2011

So, engineering practices unchanged, smaller and lighter is not safer if both cars are smaller and lighter.

This false assumption that both people must be in a car is part of why you think it makes no difference. A small car drives into you, you go over the hood and quite likely walk away (i have firsthand experience of that). A large SUV by contrast, hits above your center of mass, you get knocked down, your head slammed into the concrete, and you go under the wheels. And you die.
posted by -harlequin- at 1:37 PM on January 24, 2011

(I'd also put money on the driver of a smartcar t-boned on the drivers side by another smartcar, surviving better than the same scenario with larger SUVs. This is because side-impact resistance does not scale by mass as rapidly as kinetic energy does, and a side-impact starts only inches from the driver. In both cases, the driver will suffer the same rapid acceleration to his vehicle, but in the case of the SUV, there is the additional devastating injury of a door often being unable to stop the 4-tonne missile in the inches before it starts travelling through the driver.)
posted by -harlequin- at 2:45 AM on January 25, 2011