They aren't going away (hydraulic hybrids)

[jamesqf]

Note a couple of points on that. 1) It's 2013, why are they still working on 2008? 2) This:

In both cases, the maximum energy capacity of the pressurized accumulator is reached in just ten seconds.

Which supports what I've been saying all along: hydraulic or pneumatic hybrids are a good match for a mostly stop & go driving cycle, not good at all for over-the-road applications.

[payne171]

One advantage for pneumatics that I haven't seen countered is the availability of rare earth metals. Eventually they will get very scarce. I seriously don't there are enough on the planet to supply all cars. I could definitely see an automotive landscape where plug-ins and EVs use almost all of the rare earth metals. The other cars will use pneumatics.

[NeilBlanchard]

Rare earths are hard to refine, but they are not actually uncommon. Once you get them, they can be recycled. And by the way, the two largest uses for rare earth magnets are hard drives and cell phones.

[user removed]

Green Car Congress: Bosch offers more details on the light-duty hydraulic-hybrid drive developed with PSA

A little more info.

regards
Mech

[acparker]

When trying to maximize efficiency, one must choose the right tool for the job. A vehicle optimized for city driving in relatively flat terrain may not do as well in hilly or mountainous terrain or over long distances. Most vehicles are used in city driving in relatively flat terrain, so there is definitely a strong market for the Peugeot HYbrid Air Car (great marketing approach, by the way) and other hydraulic hybrids that may be manufactured.

Hydraulic hybrids are certainly not going away. Peugeot already sells a full line of electric hybrids. If hydraulic hybrid had no merits, they wouldn't be wasting their resources on it. I welcome Peugeot's aggressiveness and hope they sell many "air" cars. It will encourage their competitors to duplicate their success.

The hh system I am most impressed with is the one designed by Folsom Technologies (you will have to google it, as I haven't posted enough to include links).

[user removed]

FTI - Hybrid Vehicle Powertrains

Here is a link.

regards
Mech

[Topdawg_135]

Wish I would have found this thread when it started. I have been working in the HH field for almost two years now and could have answered some of the questions more accurately(although Mech has been doing a good job). I'll be following this from now on and am more than happy to answer questions.

[user removed]

If you can get the overall powertrain efficiency high enough, then you can use P&G techniques while maintaining a constant speed, even at freeway speeds. This is the crucial factor which can not be done electrically.

If this level of efficiency is achieved, then you can design the engine to only operate at it's best BSFC and you now have a vehicle that is capable of significantly greater efficiency under all but the most severe scenarios, like climbing Pikes Peak.

The energy density of a hydraulic accumulator is a function of it's working pressure. In the Bosch-Peugeot design it's around 4300 PSI. Americas cup racers are 12,000 PSI, almost 3 times the energy density.

That's not a future prediction or a theoretical possibility, it's being done right now. Basically the energy density means the amount of horsepower-seconds of energy you have that can be released in seconds. This provides and energy recovery-application storage capacity that has a lefespan measured in hundreds of thousands of miles.

Increasing the aero efficiency of any car means the engine efficiency is reduced as you make the engine produce less power for a constant speed. if the HH vehicle can be built then increasing the aero efficiency means the system requires less average power delivery so the engine simply runs for less time, while maintaining peak efficiency, and the mileage improves in direct proportion to the reduced average loads.

The arguments about total storage capacity and comparisons to battery packs miss the point. With energy storage efficiencies of above 80% and infinite ratios for constant power application regardless of storage. A battery is like a fuel tank. A powertrain with capacitive regenerative storage and the capability of matching engine BSFC to the precise amount of power to the wheels to maintain velocity is a completely different animal.

If you choose to not believe that then consider using a battery as the energy storage unit but use the HH powertrain to provide regeneration and allow peak BSFC of the battery and motor regardless of the vehicles speed or load.

I was looking at the newest Brammo Enertia motorcycle, would love to have one. It has a liquid cooled electric motor and a 6 speed transmission. Why would they have either component if it was not necessary and or more efficient. The answer is they have those components becasue they are both necessary and more efficient, when you consider all of the potential operational parameters. I just can't see 16 grand for a bike, when I can ride my TU250 for $2300 and 85 MPG.

regards
Mech

[IamIan]

Originally Posted by Old Mechanic

If you can get the overall powertrain efficiency high enough, then you can use P&G techniques while maintaining a constant speed, even at freeway speeds. This is the crucial factor which can not be done electrically.

While I'll agree with many potential benefits of a HH ... I will disagree with the part above indicated in bold.

[P-hack]

I like the idea, I don't understand all the losses in the hydraulic system but it looks like a promising approach for improving regenerative braking over modern electrical approaches by a huge margin, both in terms of overall efficiency and in terms of providing much more braking power and returning more of the captured energy.

Energy density isn't much of an issue if absorbtion is limited to %200 of a typical decel/accel cycle. Can swap in a larger accumulator if you have hills. Current electric regen is returned as a fraction of total braking energy. While it is convenient to use electric regen, that hardly makes it the most efficient choice. There is a lot of room for improvement and options beyond electrical, which has it's own limitations.

Still I wouldn't put it in-line with the ICE, not without understanding the losses. Coupled to the front wheels? absolutely (and it can still modulate engine load from there anyway)