Can hydraulic systems fuel the next generation of hybrid cars?

[Fledermaus]

It’s a little known fact that when it comes to fuel efficiency, some garbage trucks can put hybrid cars to shame — thanks to a hydraulic hybrid system that does away with batteries altogether.

Now, Chrysler Group has partnered with the U.S. Environmental Protection Agency to adapt the same technology for minivans. They have invested $2 million dollars each to make it happen, with road testing planned for as early as next year.

The system offers considerable key advantages over battery-operated electric hybrids, as Technology Review magazine points out:

Hydraulic systems are bulky and loud, which has limited their use to large vehicles such as garbage trucks. But they’re attractive because pumps and air storage tanks are cheap compared to batteries. Also, hydraulic hybrids have the potential for larger fuel economy improvements than battery hybrids because hydraulic systems can store energy very quickly, allowing them to capture more energy from braking. While conventional battery hybrid systems for minivans might improve fuel economy by 25 percent compared to gas-powered cars, hydraulic systems could improve fuel economy by 30 percent to 35 percent under most conditions, says David Haugen, manager of the technology development group at EPA’s National Vehicle and Fuel Emissions Laboratory. In city driving, the improvement could be as much as 60 percent. Chris Cowland, Chrysler’s director responsible for advanced powertrains, says the 60 percent improvement is “way more significant than any other technology that we know of today.”

[Pab Sungenis]

1. The in-line hybrid, which the Prius was based on, was invented in 1969

by GM. It took almost four decades to bring it to market.

What are the odds that we'll see hydraulic hybrids or that new super-efficient turbine motor that was the talk of everyone a month ago in production in our lifetimes?

[ret5hd]

2. it's different than what i am used to!

it won't accelerate as rapidly as i am used to!
it will be too loud!
it will be too quiet!
it won't be able to drive from new york to LA without re-fueling!

(pre-emptive whining)

[PamW]

3. Unfortunately, it's just a replacement for the tranmission / drive train.

Can hydraulic systems fuel the next generation of hybrid cars?
===============================================================

The hydraulic system referred to here are actually just replacements
for the transmission and drive train.

Hydraulic systems do not extract energy - they are not "engines".

An "engine" is something that extracts energy from a fuel. Even in the
graphic, there is an "engine" up front in the car.

Just as you can't have a car with just a mechanical transmission and drive
train and no engine, you can't have a car with just a hydraulic drive train.

Even in electric cars, the electric motor is actually more analogous to the
transmission and drive train than it is to an "engine".

For an electric car, the true "engine" that powers it is not the electric
motor. The true "engine" in scientific parlance is the powerplant that provides
the electricity. That's also where you will find the pollution and waste heat
that would otherwise be discharged by the internal combustion engine of a
conventional car.

However, I see this error made a lot. People compare the efficiency of the
electric motor to the efficiency of the IC engine in a car. That comparison makes
no scientific sense whatsoever. If you want to make that comparison, you
compare the efficiency of the IC engine to the powerplant that made the electricity,
and you compare the motor to the transmission and drive train of the IC car. That's
the only comparison that makes sense, scientifically and in the context of
the 2nd Law of Thermodynamics.

PamW

[txlibdem]

5. Sorry to disagree, Pam. The graphic clearly shows both transmission and drive train

This is just a substitute for an electric motor + battery combo like the Prius and every other current hybrid has.

[PamW]

10. I have to disagree with your disagreement.

This is just a substitute for an electric motor + battery combo like the Prius and every other current hybrid has.
============================

Scientifically, and thermodynamically, an electric motor and battery are also
NOT engines but are really a part of the drive train.

The "engine" for a all-electric vehicle is NOT the electric motor, but is
the power plant that is used to charge the batteries.

That's why it is called a "motor" and not an "engine". Science and physics makes
a very clear distinction between what is called an "engine" and what is called a
"motor". That distinction appears to be lost to the general public.

"Motors" convert one type of "work" ( entropy-free energy ) to another form of
"work". Electricity is "work" and an electric motor converts electricity to
either translational or rotational motion ( also entropy-free energy or work ).

An "engine" extracts energy from a fuel. You don't feed an "engine" "work".
You feed an engine a fuel that contains energy. The release of the energy by
the engine also entails release of entropy, and hence the limit on the efficiency
of an engine by the 2nd Law of Thermodynamics:

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html

There's no such limit placed on the efficiency of a "motor". So how come we
don't just use motors? Because there's no place in the environment that you
can go get entropy-free energy in the form of "work".

You always have to have some type of "engine" to get you the energy.

As the above states, you can never have a 100% efficient engine:

Second Law of Thermodynamics: It is impossible to extract an amount of heat QH
from a hot reservoir and use it all to do work W . Some amount of heat QC must
be exhausted to a cold reservoir. This precludes a perfect heat engine.


Even if you get your electricity from solar, you still have waste heat. There's
no solar cell that is 100% efficient, and the laws of physics say there NEVER
will be one that is 100% efficient.

PamW

[txlibdem]

12. I meant functionally, not thermodynamically

I just meant that in the Prius, there is a gasoline engine + transmission + electric motor/battery + the rest of the drive shaft. While in this hydraulic gizmo, there is a gasoline engine + transmission + hydraulic storage + the rest of the drive shaft.

[PamW]

17. Yes - but it's the thermodynamics...

I meant functionally, not thermodynamically
========================

Yes - but it's the thermodynamics that tells us how efficient the system
is and how much waste heat it has to expend, and how much pollution - both
thermal and chemical that the vehicle is going to emit.

Isn't this last point what we are really interested in?

The mechanical transmission and drive train is extremely efficient - high 90s-
like 98% or 99% efficient.

If the only thing you did was replace a 99% efficient mechanical transmission
with a hydraulic one that was 99.5% efficient; but still kept the old internal
combustion engine driving the whole thing - how much "improvement" have you really
made?

I agree that we need to get rid of the internal combustion engine.

The problem I have is with people that put the cart before the horse. An electric
car or hydraulic car is no cleaner than the power plant used to run it.

I think too many think that all we have to do is switch over to electrics or hydraulics,
or whatever and we've solved the problem. We haven't solved anything but replace
a portion of the drive train.

The thing that pollutes is the "engine" and electrics and hydraulics merely substitute
a fossil fuel power plant for the gasoline-fueled internal combustion engine.

Before electrics and hydraulics can help us, we need a cleaner electric power system;
which contains a sprinkling of solar and wind, but the real "heavy lifting" will have
to be done by nuclear. It's really the only choice.

PamW

[txlibdem]

18. Electric vehicles are a definite must, along with efficiency mandates

and removing coal, oil and natural gas from our lives for good.

The unfortunate truth is that nearly every damn thing we do today is wrong, is killing the planet, and will eventually kill us all if we're stupid enough not to change.

[DCKit]

4. Hydraulic storage is 85% efficient. The best batteries only capture 15%.

A mix of "All Three" makes serious sense.

[Tesha]

6. "The best batteries only capture 15%" -- Nonsense.

Batteries are a lot more than 15% efficient. And
combined with ultracapacitors, electrical systems
can store energy almost as rapidly as can these
hydraulic systems.

The real problem with these hydraulic systems,
though, is likely energy density. A hydraulic
accumulator probably stores far less energy than
does a modern lithium-ion battery. Enough energy
to power a garbage truck the hundreds of feet
from stop to stop, but not enough to operate
for tens of miles without the internal combustion
engine operating.

Tesha

[txlibdem]

7. Batteries are over 90% efficient, chargers are 95% efficient. Where did you get your facts?

Here's a quote from Stanford re the Tesla:
------------------------------------------------------------------
"The energy cycle (charging and then discharging) of the lithium-ion batteries in the Tesla Roadster is about 86%
efficient."
... from PDF http://www.stanford.edu/group/greendorm/participate/cee124/TeslaReading.pdf
----------------------------------------------------------------

I guess you must be using solar batteries, aka OIL, which are nothing but millions of years of concentrated and compressed sunshine (and a little help from mother nature in the form of pressure and heat).

-------------------------------------------------------------------
"An electric vehicle (EV) starts with a huge advantage over an internal combustion engine (ICE) vehicle: ICE vehicles generally run at about 20% efficiency, meaning that 80% of the energy content of their fuel is wasted, versus EVs which put about 80% of their input energy into turning the wheels."
,,, from http://www.saxton.org/EV/efficiency.php
-------------------------------------------------------------------
... That's including the charger loss, battery loss, DC converter loss, electric motor loss, and drivetrain loss. You still get 80% of the energy when the rubber hits the road -- versus less than 20% for the dinosaur battery (OIL) powered car.

[PamW]

11. Nonsense - this is an apples and oranges comparison.

"An electric vehicle (EV) starts with a huge advantage over an internal combustion engine (ICE) vehicle: ICE vehicles generally run at about 20% efficiency, meaning that 80% of the energy content of their fuel is wasted, versus EVs which put about 80% of their input energy into turning the wheels."
========================================

This is the type of specious argument that shows the people who wrote it don't
understand thermodynamics. It is an "apples and oranges" comparison.

For the IC engine, it takes the total energy content of the fuel as a base, and then
shows that only 20% ends up at the wheels, and 80% goes as waste heat.

For the electric vehicle, they start with the entropy-free work as the base, and show
that 80% of that ends up at the wheels.

But where did that entropy-free energy in the form of electricity come from? It came
from a power plant. By the time you add up the waste heat from the power plant - about
60% and the transmission line losses (7%) and other loses; you end up with the
electric car delivering about 20% of the energy content of the fuel of the power plant,
which is the comparison that should be made to the energy content of gasoline.

Sorry but battery charges are not 90% efficient - they are about 70% to 80% efficient.
Don't believe me - go get a charger from your auto supply and charge your car battery.
You will feel the heat coming off the charger.

Additionally, batteries like Nickel Metal Hydride batteries ( NiMH ) are only about 70%
efficient in terms of electricity out vs. electricity in.

http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery

Charge/discharge efficiency 66%


Lithium-Ion are a little better, but not that much:

http://en.wikipedia.org/wiki/Lithium-ion_battery


Charge/discharge efficiency 80-90%<3>


Usually Lithium-Ion is closer to the 80% unless you charge them REALLY SLOW
That's where a lot of your charging energy goes - heat in overcoming the intrinsic
resistance of the battery. You can minimize that by slow charging.

In terms of total efficiency as a percentage of the total energy contained in
the fuel fed to the power plant, electric cars and internal combustion engines
are essentially "on par".

The "huge efficiency difference" is really marketing hype by the electric car
proponents who are playing "fast and loose" with the Laws of Thermodynamics and Physics.

PamW

[txlibdem]

13. We don't have to agree on everything but on this we are at polar opposites for sure

Repeat from my earlier post:
Here's a quote from Stanford re the Tesla:
------------------------------------------------------------------
"The energy cycle (charging and then discharging) of the lithium-ion batteries in the Tesla Roadster is about 86%
efficient."
... from PDF http://www.stanford.edu/group/greendorm/participate/cee...
----------------------------------------------------------------

How far back in the process do we go back? Do we take it to the electrical generation + line losses till it gets to your plug? Do we go back to mining the fuel for that electrical power plant and transporting the fuel? Do we include the satellites and man hours to locate the fuel?

How about for gasoline/diesel? Do we include the energy used to pump it into your car (gas pumps use electricity to pump it)? Do we include the big truck that drove how many miles to bring the gas to the station? Do we include the fuel used at the refinery and the electricity used to pump it into those huge storage tanks at the refinery? Do we include the energy expended to transport the crude oil from the well to the refinery? Do we include the energy used to drill an unknown number of holes till they "struck oil?" Do we include the satellites and man hours to locate where to attempt to drill those test wells?

How far back do we go? It sounds like you seem to want a one-sided comparison. The gas didn't magically appear in your tank...

[DCKit]

8. I'm answering myself, so y'all don't get confuded.

It's not about battery charging, it's about regenerative braking.

15% for batteries, 85% for hydraulic.

[TheWraith]

9. Still wrong.

Regenerative braking is a LOT more efficient than that. And I don't for a second believe a purely physical system is going to compete with a nearly solid state electrical drive.

[txlibdem]

15. Can you please post a link for that info.

Tesla says 80%: http://www.teslamotors.com/blog/magic-tesla-roadster-regenerative-braking
... unless you're talking about from the wall to the battery, to the wheels, and back to the battery, where Tesla says 64%.

The GM Volt forum says up to 72% efficiency: http://gm-volt.com/forum/showthread.php?740-What-is-efficiency-of-regenerative-braking

PriusChat forum says:
----------------------------------------------------------
Attila's study tells the efficiency of regeneration braking is approx 50% on the Gen2.

http://priuschat.com/forums/gen-iii-2010-prius-technical-discussion/90455-just-how-lossy-regenerative-breaking-3.html
----------------------------------------------------------

[DCKit]

19. I guess they have, in fact, improved greatly since the first Prius hit the road.

The original did only capture 15% in regenerative braking and the rest was lost to the heat of conventional braking.

Sorry, but I'm so used to being disappointed by all the things that are reported on, but never come to be.

[Gregorian]

14. Except the manufacturing energy of hydraulics is crap.

As an interim solution hybrid makes sense. But the problem is, there shouldn't even be an interim period. We should be done with internal combustion.

I say full steam ahead with solar and wind, and battery technology, and then just use electric motors.

Hydraulic is similar to internal combustion in terms of steel, machining, and manufacturing. If everyone has hydraulics in their cars that is a huge carbon footprint in itself.

[Turbineguy]

16. As I see it

The problem with ICE cars are the transients. The engine has to be capable of producing the highest power required for short periods. That sets the lower limit for horsepower and size. The hybrid, by storing power in the battery breaks down this transient into the average power required, corrected for charge/battery/motor losses. But even then there are still transients due to starts and stops. Therefore the addition of hydraulic system would help smooth those out. This could compensate for inefficiency in the basic hybrid train. The hydraulic system would kick in for an uphill acceleration from a stop thereby reducing the power requirement of the electric motor.

The biggest influence on fuel efficiency is the driver anyway.

I once did not reset my car computer for 35,000 miles, about 5 years. I found that my average speed was 28 miles per hour. So that would be my IC engine requirement. Most of the time there were one or two people in the car, never the less it would have to be designed for 5 persons.

If the car weighed 3000 lbs including the driver and needed 28 HP to go 28 mph average speed, we would have to add 6.5 HP for 4 passengers, and then account for hybrid loss of about 20% or 41.5 HP. Etc. All the vehicle losses would have to be accounted for. The ICE engine could run on a duty cycle at its lowest specific fuel consumption. This is more economical than the 200 HP ICE it replaces. In addition the engine can be located anywhere since it is not mechanically connected to the wheels.

The hybrid essentially reduces the biggest loss, from the driver by smoothing out the transients.

High pressure hydraulic systems would bring their own problems with fluid, safety, seal problems etc.