They aren't going away (hydraulic hybrids)

[jamesqf]

Originally Posted by darcane

I've been wondering why these systems aren't more widely used too. Other than some delivery trucks, there really aren't any Hydraulic Hybrids in production yet that I'm aware of.

Ever scuba dive? Remember how heavy those tanks were?

To store energy in a hydraulic hybrid (or pneumatic - same principle), you need to hold gas at high pressure. That means you need a strong storage tank, which - material properties being what they are - means the tank is going to be heavy. (It also means the tank is potentially subject to catastropic failure - search for "scuba tank explosion"). Put this together, and you have a pretty bad energy/weight ratio, which means the hydraulic hybrid doesn't really work for normal driving, but is suited to applications like delivery & garbage trucks, where the drive cycle is almost all stop & go.

[user removed]

Originally Posted by NeilBlanchard

How much range is provided with the 'Energy Storage System' and the 'Low pressure storage' tanks?

What is the all electric range of a first generation Insight? You are missing the point, which is the storage and release capacity of hydraulics allows for highest efficiency operation of an IC engine or a battery powered car that does not need voltage control for speed control.

As far as accumulator explosions, that is a matter of simple shielding, position in the vehicle, and one other fact james did not address. The gas in an accumulator is an inert gas, same type used in some types of fire extinguishing systems. That is completely different from scuba tanks which supply oxygen which is highly flammable when combined with any combustible.

We have all driven vehicles with many gallons of gasoline in tanks which can be ruptured in collisions. Rupturing a nitrogen filled accumulator would release around 5-20 cubic feet of inert nitrogen, which if it ever happened would block the air from the area of the vehicle for a short period of time and actually act as a fire retardant.

Accumulator technology is ancient, dating even before WW2. How many times have you heard of an accumulator "explosion" in any application that ever cost a single human life. Compare that to traffic fatalities that number 2 million in the US in my lifetime.

Comparing high pressure oxygen tanks to high pressure nitrogen tanks? Would you use a scuba divers tank to put out a fire?

There are numerous examples of bombers in WW2 that suffered flak hits to the reserve LOW pressure oxygen systems, while I don't remember a single instance of a death related to hydraulic accumulator failure. Maybe james can provide us with some examples?

regards
Mech

[niky]

As far as "fuels" go, a high pressure nitro tank is a heck of a lot safer than gasoline, modestly high pressure LPG, ultra-high pressure CNG or insanely-pressurized H2.

[jamesqf]

Originally Posted by Old Mechanic

What is the all electric range of a first generation Insight? You are missing the point, which is the storage and release capacity of hydraulics allows for highest efficiency operation of an IC engine or a battery powered car that does not need voltage control for speed control.

Nope, not missing the point - which is how much an hydraulic energy storage system would need to weigh to store the same amount of energy as the Insight's battery.

The gas in an accumulator is an inert gas, same type used in some types of fire extinguishing systems.

Irrelevant, because what causes the damage is the sudden release of pressure as the storage tank ruptures and sends shrapnel flying in all directions, not chemical reactions.

Accumulator technology is ancient, dating even before WW2. How many times have you heard of an accumulator "explosion" in any application that ever cost a single human life.

And I would bet that all those accumulators are a) very strong and heavy; and b) at comparatively low pressure. To be of practical use in a passenger vehicle, they need to be light and work at very high pressures.

while I don't remember a single instance of a death related to hydraulic accumulator failure.

Any accumulator in an airplane would have to be pretty small (about the only practical use I can think of is landing gear, and perhaps hydraulic controls).

Maybe james can provide us with some examples?

Now how am I supposed to do that, when this type of accumulator basically doesn't exist yet? But if you do a search, you'll find lots of product literature (all pdf, so I can't quote it) with warnings about how improper use can cause serious injury or death.

[jamesqf]

Originally Posted by niky

As far as "fuels" go, a high pressure nitro tank is a heck of a lot safer than gasoline, modestly high pressure LPG, ultra-high pressure CNG or insanely-pressurized H2.

Not if you consider the size of the storage vessel needed to contain an equivalent amount of energy.

[user removed]

James seems to lack a lot of knowledge about hydraulic accumualtors and their application in a hybrid vehicles. Try studying the UPS hydraulic hybrid trucks which have been on the road for years.

When you have acquired some knowledge and understanding the size of the UPS accumulators, in relation to the gross weight of the trucks (26,000 lbs), you will be better informed to make judgements about the amount of weight and space necessary, especially in a car weighing less than 10% of that amount. The weight penalty issue is non existant.

Plenty of accumulators available today, with operating pressures of 3000 PSI which is what is used in many commercial applications right now, with no further development necessary. The catastrophic failure issue has been resolved long ago. If you want to get into the state of the art in accumulators, look at the America's cup racing sailboats, where cost is no issue, with accumulators operating at 12,000 PSI.

You dodged the issue about failures costing lives. Keep picking apart that which you have not researched, the result will be your points have no merit.

As far as size and weight, to quote one of the EPA heads of the research in 2006, Charles Gray, "I can hold a 500 HP hydraulic motor in my hand." Another quote by the same Engineer who was very familiar with the state of the technology, 7 years ago.

"The hydraulic hybrid will be as important to the auto industry, as was the assembly line."

They produced an 80 MPG test mule that weighed 3800 pounds, the same as a Ford Taurus of the same age.

7 years ago.

While YOU may choose to not believe facts, that is an internal issue. On a forum dedicated to improving mileage in any and every vehicle on the planet, the hydraulic hybrid has a place and if you go back to that same time frame andread all the predictions about the drastci improvements in battery technology predicted by research organizations that were heavily funded, those same predictions have proven to be very optomistic.

The same 2006 paper predicted that powertrain improvements alone would result in an 80% improvement in fuel economy. Not sure what you are trying to say when you state something about the accumulator design not being produced, when they are available off the shelf from several well known manufacturers. Used ones are available on ebay today.

regards
Mech

[user removed]

Exploding hydraulic accumulators indeed. Lets just put them on a school bus.

Students convert traditional school bus to hydraulic hybrid | MNN - Mother Nature Network

Built by a bunch of high school students. I guess the gospel according to james means they will blow themselves up. . With the support of Ford and the Atlanta school system!!!!!!!

regards
Mech

[niky]

Gasoline cars burn. And explode, if there's enough vapor sitting in the tank when they catch fire.

CNG tanks explode. Gruesomely. Spectacularly. Awesomely. With much fire and shrapnel.

LPG/LNG tanks explode. With fire. Though in automotive use, they're designed with safety valves to release pressure long before they get close to CNG pressures.

Batteries explode. With fire.

A properly designed hydraulic tank will blow pressure out whatever safety valve or failsafe is built into the system in whichever direction said safety valve is facing.

The only system actually safer than a hydraulic bottle would likely be a diesel, since diesel fuel doesn't explode at ordinary pressures.

[NeilBlanchard]

The original Insight was a mild hybrid. I think that if a hydraulic hybrid is going to be justified (from an engineering standpoint) then it needs to exceed the performance of a full hybrid like the Plugin Prius or the Volt or any of the plugin hybrids now on the market.

The problem with a hydraulic hybrid is that it cannot be used like a plugin hybrid; which is the most efficient portion of driving one.

Even a comparison with the regular Prius would be useful. Does the weight and cost and energy storage capacity of this hydraulic system justify using it instead of an electric system like the Prius? Would using it result in better overall efficiency?

[user removed]

Neil, I have explained this to you before on this forum. Any hydraulic hybrid does not by design need to be limited to IC primary power. Since the primary (fuel tank, electric or liquid fuel) is not relevant to the increased efficiency of the HH in recovering and reapplying recovered energy, then you should try to investigate and understand the capabilities of a HH.

The mild hybrid is called launch assist, but even in a launch assist design you can still use P&G techniques at constant speeds (beyond launch assist and beyond any electric drive to date). The belief that a direct drive all electric vehicle can recover any significant proportion of regenerative forces is also not true from an engineering perspective. No way you can generate enough electricity in any direct drive electric car at low speeds, because you can not spin the motor high enough to recover the energy. I have heard claims of 50% recovery efficiency by you and others here, but have never seen any evidence to confirm that claim.

I have also posted documentation (on this forum) that shows 33% for electric hybrids and 78% for HH designs. That documentation was avaialble from the EPA's paper in the collaberation with Ford, the University of Michigan and other manufacturers,
that was headed by Charles Gray ending in 2006.

Bottom line is in any electric powered vehicle, regardless of the configuration you could add hydraulic energy recovery and improve efficiency. It's not a matter of your preferred design or my preferred design. They are not mutually exclusive.

regards
Mech