Hydraulic Hybrid

[bwilson4web]

Originally Posted by roflwaffle

The biggest problem w/ hydraulic hybrids in passenger vehicles is the weight of the accumulator. Even low weight CF accumulators still run about 240lbs for ~.3kWh of energy storage. A battery pack in something like the Prius is ~100lbs and has ~.7kWh of useful energy, so even low weight accumulators would clock in above 500lbs to get to the same amount of energy storage a 100lb NiMH battery pack has.

I would like to suggest the hybrid system has a substantially higher, peak power compared to the electric hybrid. So I'm thinking:

• garbage truck - with very short, start-stop cycles with tons of mass to move and stop, use hydraulic hybrid.
• passenger car - needing to climb the occasional hill with light mass, longer distances and substantial energy-to-mass changes, use electric hybrid.

I'm a "right tool for the right job" guy who believes there is more than one solution based upon the requirements. For a commuting car, light mass and a high ratio of commuting energy to mass, use electric (and plug-in.) For a big honker vehicle, hydraulic makes a lot of sense.

Bob Wilson

[dcb]

Found a hydrostatic motorcycle. No mention of an accumulator so not technically a hybrid, and the mpg isn't great, but it isn't too horrible either (~65mpg average).

Top speed 75 mph, engine rated at 24.8HP.

For comparison, Suzuki GZ250 top speed is 76mph, 20hp, rated @ 82 mpg

So the hydrostatic lost 1/5 of its horsepower somewhere, and 1/5 of its efficiency. I don't know that the bikes have significantly different CDAs with an upright rider on them, it is all pretty blunt. Plus the diesel seems to have lost any advantage of being a diesel.

Hydrostatic Drive Diesel Motorcycle

Of course recapturing braking would make a lot of sense, but this is just trying to compare apples to apples and break down to the detailed efficiencies. You can add a hydraulic motor-pump and accumulator in parallel to a "regular" bike too, and on the surface it would would yield even better results than forcing all the engine power through the hydrostatic drive.

[basslover911]

what I don't understand is why we don't use air hybrids... now not those crappy french cars that only have an "air" motor... but simply use air tanks to get regen energy.

Think about it, you don't have to have two tanks for a reservoir, no fluid, and less weight. Sure its less efficient... but its all give and take (weight and cost vs efficiency). We could use scuba tanks (3000psi) for an extremely high energy storage.

[Boreas]

Without putting much thought into it yet, My first thought is there would be a lot of energy loss through heating the air when it's compressed. Thats an interesting thought if it could be made efficient.

[user removed]

One of the most basic problems with using the atmosphere or any other gas containing oxygen is when you compress it above 500 PSI, then you run the risk of "dieseling" if there are any trace amounts of lubricants in the pressure vessel.

Now you can always turn that around and make a system that intentionally injects combustible vapor into a specially designed pressure vessel where the spontaneous ignition of the vapor increases the pressure reserve in the vessel for power production.

Compressing a gas increases its temperature, but that same temperature drops when the pressure is released. Various theories concerning the insulation of the pressure vessel and maximization of heat retention could be applied to an atmospheric driven hybrid.

Another issue with such a design is the necessity to create something like 50 atmospheres of pressure with only a single stage of compression, which requires some unique designs that have no poppet or reed valves and virtually no chamber of unmoved atmosphere in the pump providing the pressure. This also runs the same risk of spontaneous combustion of the high pressure atmosphere when exposed to lubricants.

Potential development of non combustible lubricants (some may already exist) that are solutions to the "dieseling" issue may be a solution.

I believe the basic rotary piston engine like the WW1 examples has much room for modern development and application in vehicles, apparently a position that is not shared or very well understood by most. The lack of reciprocation in that design from so long ago is intriguing, to me at least.

regards
Mech

[dcb]

I guess in a sense, a hydraulic hybrid is "sort-of" an air hybrid considering what you are doing with an accumulator, only you can probably store twice as much energy or more in an empty air accumulator than in a half-filled hydraulic accumulator. an "air" car could be a closed system filled with nitrogen or c02 also, like they move the hydraulic fluid from high to low pressure tanks. Though you need a place/form for the low pressure n2 tank (could be part of the car structure I suppose ).

Another thought, if you need additional braking beyond what the motor is providing, you can transfer that braking heat to the low pressure accumulator somehow and assist the migration back to the high pressure side. Inboard calipers might help. Ah nevermind, not worth it, just stay off the brakes

[user removed]

Ford F-150 Used to Develop 40 MPG Hydraulic Hybrid Powertrain - PickupTrucks.com News

Who would have guessed, a CVT and HH powertrain, with the towing capacity of the original truck. Sorry battery electrics need not apply.

regards
Mech

[roflwaffle]

I'll believe it when I see it! Back in 2006 it was a 60mpg pickup.

[user removed]

Yep and in 2006 the miracle battery was only 5 years away.

regards
Mech

[roflwaffle]

Miracle battery? Will it heal the sick and balance the budget?

In 2006 battery electric hybrids had already been mass produced for almost a decade. If Ford can get the price of HH pickups down to where they're competitive then kudos to them, however the track record so far consists of exaggerated claims and no mass produced consumer autos. They look good for industry in dump trucks/etc, but only time will tell in pickup trucks.