Why have I never heard of hydraulic hybrids before?

[mrspeedybob]

Ran across this recently...
http://www.mobilehydraulictips.com/hydraulic-hybrid-vehicles-future-driving/

Peugeot apparently has a hydraulic hybrid car in development...
http://www.extremetech.com/extreme/146450-peugeot-unveils-hydraulic-air-hybrid-80-mpg-car

From what I've read from Wikipedia and other sources this technology is simpler, less expensive, more energy efficient, and requires less toxic materials then electric hybrids.

What's the down side?
Why have we spent the last 20 years developing electric hybrids instead of this?
Is it just a marketing problem? No ones figured out how to make hydraulic equipment sound sexy?

 

[OmCheeto]

As to your header title question, my guess is, that you haven't been paying attention.

Ran across this recently...
http://www.mobilehydraulictips.com/hydraulic-hybrid-vehicles-future-driving/

Peugeot apparently has a hydraulic hybrid car in development...
http://www.extremetech.com/extreme/146450-peugeot-unveils-hydraulic-air-hybrid-80-mpg-car

From what I've read from Wikipedia and other sources this technology is simpler, less expensive, more energy efficient, and requires less toxic materials then electric hybrids.

What's the down side?

My guess is that it was economically unfeasible until now.

Hydraulics are inefficient in this application. Electricity is more efficient, easier to regenerate and to control.

With hydraulics there will be a loss of about 20% at each stage, you will need to factor that into the calculations. 80% pump * 80% motor = 64%. You will need a hydraulic fluid cooler to radiate the wasted 36%.

But as I always say, capturing 64% of something's energy is infinitely more efficient than throwing it all away.

Why have we spent the last 20 years developing electric hybrids instead of this?
Is it just a marketing problem? No ones figured out how to make hydraulic equipment sound sexy?

I find all forms of improvements in automotive efficiency, sexy.
My guess to your questions is, that other people fixate on the latest craze, and don't look at all the alternatives.

And then there's; "Holy Mary! Has the price of technology really changed that much in 15 years?"

I was all ready to argue this point until I saw the price of super-capacitors has fallen to a reasonable rate.
Gads.
$1.28 per kJoule!
This means to absorb the energy of a 3500 lb vehicle from 35 mph to zero will only cost $250, vs. $55,000 in 1996.
I should really double check that calculation. If true, my hobby just got a lot simpler.

This is something I constantly have to kick myself for: Living in the past.

 

[Jobrag]

I note that they don't say what the range of a full hydraulic charge would be, probably not far. High pressure hydraulic equipment is heavy and expensive so sorry I can't see this as ever being practical.

 

[OmCheeto]

...
And then there's; "Holy Mary! Has the price of technology really changed that much in 15 years?"
...

...
Hydraulic motors and pumps might get to 90% efficiency. A pump driving a motor will therefore have 90% * 90% = 81% efficiency. You will need to pay for that 19% inefficiency, you will also need an oil cooler to remove the 19% waste heat. A manual change gearbox will be closer to 98% efficient.

And look at that! Baluncore's efficiency for hydraulic thingamajigs jumped from 80 to 90% in only 8 months!

 

[OmCheeto]

I note that they don't say what the range of a full hydraulic charge would be, probably not far. High pressure hydraulic equipment is heavy and expensive so sorry I can't see this as ever being practical.

I see it as practical.

Can Hydraulic Hybrids Compete With Electric Hybrids?
10/21/2013
”Everyone we talked to said the technology is reliable, offers good performance, and costs a lot less than electric hybrid technology,” Alexander told Design News. “You get the benefits when you’re starting and stopping a lot, so it’s good for garbage trucks, delivery trucks, and city buses.”

But then, I spent most of my working life, stuck in stop-and-go traffic.
You don't live in Texas, do you? I've heard they've got big long roads out there, that, go, forever...

​

 

[Baluncore]

“With hydraulics there will be a loss of about 20% at each stage”,
“Hydraulic motors and pumps might get to 90% efficiency”.

And look at that! Baluncore's efficiency for hydraulic thingamajigs jumped from 80 to 90% in only 8 months!

One is a best performance specification. The other is a typical value. They are consistent.

But as I always say, capturing 64% of something's energy is infinitely more efficient than throwing it all away.

I agree, but I prefer to capture much more than 64% by using electricity.
.

 

[Baluncore]

Hydraulic regenerative braking keeps raising it's head. Then each time, it has slowly lowered it again and gone quiet. The inefficiency of hydraulic systems in automotive applications is well known to the automotive industry.

The article referenced was “Contributed by Tom McShane, engineering blogger and writer for UK-based Apex Hydraulics”. http://www.mobilehydraulictips.com/hydraulic-hybrid-vehicles-future-driving/ The title asks “Are hydraulic hybrid vehicles the future of driving?” My answer is NO.

That article misrepresents comparisons between hydraulics and electricity. For example; “Hydraulic hybrids have been proven to be more cost-effective than electric hybrid systems. This is mainly due to the absence of expensive materials used in it, unlike those required for batteries.” The question I ask is how cost-effectiveness in use, can be compared with cost of manufacture.

“Hydraulics systems can recover about 75% of the kinetic energy during braking and deceleration, as compared to the 25% recovery from electric hybrids, which clearly indicates the high efficiency of hydraulic hybrid systems.” Where does that quoted 25% come from?

“Smaller, lighter, and more efficient designs for pumps and accumulators have helped in applying the system to both small consumer vehicles, as well as large, heavy-duty, commercial vehicles.”
Where are those vehicles or test reports? The picture at the head of the article is of a Toyota Prius which is an electric hybrid, not hydraulic. The future is electric, not hydraulic.

 

[OmCheeto]

“With hydraulics there will be a loss of about 20% at each stage”,
“Hydraulic motors and pumps might get to 90% efficiency”.

One is a best performance specification. The other is a typical value. They are consistent.

I agree, but I prefer to capture much more than 64% by using electricity.

I'm curious how efficient electrical recovery systems are, at various speed ranges.
30-20 mph
20-10 mph
10-0 mph

I'll have to google that, when I get back from the river this evening.

As I said, a few years back;

If this keeps up, I may have to give up all my research, and just sit at the beach.

Ciao!

 

[Ketch22]

I worked on a project when in school (this was in 79-80) that was a hydraulic hybrid. We had gray results but the weight and unusual drive made it unmarketable add a car. A couple years ago United Parcel Service commisioned several of their big brown trucks for urban delivery using the same principals. It seems to work very well in the delivery truck realm where the weight and bulk is less of a concern.