Hydraulic Hybrid Cars: No Batteries Required

[Fledermaus]

What if there was a hybrid vehicle technology that could at least double the gas mileage of passenger cars, SUVs and light trucks? What if it could slash emissions by 50 percent or more? And what if it could challenge our usual mileage expectations by offering better fuel consumption in the city than on the highway?

Even better from an engineering and manufacturing standpoint, what if this hybrid technology didn’t rely on expensive, heavy, bulky battery technologies that aren’t really ready for prime time and instead used a time-tested energy storage method?

Well, there is just such a hybrid-vehicle technology, and it’s one based entirely on hydraulic components rather than electric ones.

Kargul says the gains came from three sources — running the engine at its sweet spot on the engine map, operating the vehicle with the engine off and capturing braking energy. The regenerative braking capabilities of these systems in particular can far outshine the electric hybrids now available to consumers, something made possible by the high power density of accumulators. Kargul says the EPA’s hydraulic hybrids typically capture at least 70 percent of the braking energy that would otherwise be lost to heat. He estimates electric hybrids capture more like 20 to 25 percent, because their batteries, for all their energy density, have comparatively poor power density. “You would have to triple the size of the batteries to come close to 70 percent,” he says.

Another interesting aspect of the hydraulic hybrid involves the conditions under which they offer the biggest mileage gains. O’Brien says engine and mechanical transmissions already operate efficiently during highway driving cycles, so the fuel economy improvements offered by hydraulic hybrids are relatively minor on the open road. That’s not the case in cities, though, where start-stop driving and lower power requirements force engines to run at less efficient conditions. Here, hydraulic hybrids offer a bigger fuel economy edge. Achten makes a similar point. “For the first time, hydraulic hybrids allow better fuel consumption in the city than on the highway. And that’s the way it should be,” he says.

In terms of driving performance, hydraulic hybrids have something else going for them — the potential to leverage their high-power-density energy storage capabilities for short-term bursts of power that far outstrip the engine’s nominal power. How much power? O’Brien says Hybra Drive’s Hummer H1 conversion uses a 190 hp diesel engine yet can offer short bursts of power up to 600 hp.


http://www.designnews.com/article/CA6549294.html?industryid=43655#_self

Peterbilt showcases hybrid Model 320 Hydraulic Launch Assist vehicle at Waste Expo


The vehicle utilizes HLA technology by Eaton Corporation that captures the truck's kinetic energy during braking to assist in launching and accelerating the vehicle. Officials say testing has proven a significant improvement in fuel economy and indicated the potential to reduce annual brake re-alignment services by 50% annually.

"The Model 320 HLA is an ideal environmental option for refuse applications," says Bill Jackson, Peterbilt general manager and PACCAR vice-president. "Dramatic improvements in fuel economy, reductions in emissions and lower maintenance costs spotlight the Peterbilt Model 320 Hydraulic Hybrid as the environmentally responsible, fuel-efficient solution for municipal and residential solid waste transportation fleets."

http://www.trucknews.com/issues/ISArticle.asp?id=83861&issue=05052008

[madokie]

1. this from '02 by Ford

http://media.ford.com/newsroom/release_display.cfm?release=12525

FORD PREPARES DEMONSTRATION FLEET OF VANS WITH HYDRAULIC POWER ASSIST


DEARBORN, Mich., July 15, 2002 – Ford Motor Company announced plans for a demonstration fleet of E550 commercial vans for production prove-out of a promising hydraulic hybrid powertrain. The vans are expected to be up to one-third more fuel efficient in stop-and-go driving than today’s E550.


The demonstration fleet will be put into service in early 2004, likely in a fleet of delivery vehicles that would accumulate mileage quickly, mostly in stop-and-go duty cycles.


The Ford Hydraulic Power Assist (HPA) system will reduce fuel consumption while increasing vehicle performance. A reversible hydraulic motor and an energy-storage accumulator recover energy normally lost during braking – storing it as hydraulic pressure to be later released to provide a boost for acceleration. Launching a heavy vehicle from a stop requires much more energy than keeping that vehicle in motion. Adding a hydraulic boost allows the vehicle to accelerate much more quickly than the same truck without it, while greatly decreasing fuel consumption and exhaust emissions. Ford first showcased the hydraulic assist technology in a concept truck, the Mighty F350 Tonka, at the North American International Auto Show in January 2002.


Ford research indicates that the installation of a HPA system on a commercial van or medium-duty truck could increase fuel efficiency in stop-and-go driving by 30 to 35 percent and cut exhaust emissions by at least 20 percent.

[arendt]

2. This deserves to be seen. K&R. Interesting tech. FIrst I heard of it. n/t

[FourScore]

3. bookmarking and recommend

[gateley]

4. K&R -- nt

[wtmusic]

5. Batteries with regen directed to ultracapacitors is a more efficient solution

which is not even mentioned. How much energy is lost to friction in this system?

"Design concepts for hydraulic hybrids vary, but typically the car’s diesel or gas engine powers a hydraulic pump motor, which charges that high-pressure accumulator. The accumulator, in turn, drives one or more additional pump motors connected to the wheels. A second lower pressure accumulator typically completes the hydraulic circuit. Depending on the design, there may be one pump motor to drive a pair of wheels through a differential or one pump motor per wheel for an all-wheel-drive version with independent torque control. During braking, the pump motors on the wheels reverse themselves, re-charging the accumulator and capturing energy that would otherwise be lost to heat."

vs. to one with zero moving parts?

- Ultracapacitors perform well in cold weather, down to –40° Celsius, whereas, without heating, batteries do not operate reliably below 0° degrees Celsius. For transit busses,
- Ultracapacitors are a safe solution, as a pack with equalization is discharged over night.
- Ultracapacitors have a long life cycle, essentially lasting the lifetime of the machine into which they are incorporated. This low maintenance results in cost savings.
- Ultracapacitors are 85-95 percent efficient as compared to an average of 70% or lower for batteries in similar applications (as measured by ISE).
- Ultracapacitors are environmentally friendly, as they are 70 percent recyclable and do not include heavy metals.
- Ultracapacitors more than 10 times the power of batteries. In terms of vehicle acceleration, this is an essential attribute.
- Ultracapacitors provide a powerful energy storage solution, capable of capturing energy from one function, such as braking, and storing it for next energy requirement, such as acceleration.

http://www.evworld.com/article.cfm?archive=1&storyid=1138&first=5085&end=5084

Maxwell Technologies to Design and Produce Ultracapacitors for Mercedes Hybrid Program

http://www.greencarcongress.com/2007/09/maxwell-technol.html

Either Detroit can't think outside the mechanical box of pulleys, pumps, belts, and hoses -- or they make too much money from selling those items to even consider it.

[Fledermaus]

13. Power density of Maxwell ultracapacitor 1.6kW/kg. Accumulators have power densities of 500 kW/kg

Ultracapacitors will certainly show up in hybrid passenger cars, but I don't think they can compete with accumulators for dump trucks or city buses.

[wtmusic]

15. One order of magnitude off ain't bad

Maxwell BCAP0650 P270 Pmax (W/kg) 11,300

http://www.maxwell.com/ultracapacitors/products/large-cell/bcap0650.asp

Where are you getting your accumulator number?

[Fledermaus]

17. I don't think anybody has their numbers correct.

Ultracapasitors have a very good power density by them selfs. However, when they are assembled into a package their power density drops.

If you investigate the power density for Maxwell's power modules, you can see that the power density is drooping for larger modules.
http://www.maxwell.com/ultracapacitors/products/modules/bpak0020-15v.asp
They don't even state the power density for their largest module. Perhaps someone here can figure out the power density. At 58Kg, the best I can come up with is 1.7kW/Kg. Here is the spec sheet for their largest module.
http://www.maxwell.com/pdf/uc/datasheets/mc_power_series_125_1011161_rev1.pdf

I would like to know who is building 500kW/Kg accumulators. 500kW is probably a misprint.

[phantom power]

16. Also they're cheaper.

[losthills]

6. Oh, it's by "Fledermouse" (or "whatever...")

Must be bullshit, then......

[JohnWxy]

7. Recommended!!

[phantom power]

8. do these things use some kind of compressible hydraulic fluid?

I'm trying to figure out how they store energy. Typical hydraulic fluids aren't compressible, and so they can't store energy, at least via pressurization.

[madokie]

9. I would say with a bladder filled with an inert gas in the oil reservoir.

[Fledermaus]

12. Yes, Nitrogen in a blader.

http://www.wilkesandmclean.com/acc_size_3000_psi.html


An important characteristic of nitrogen gas is that as oil is pumped into the high-pressure accumulator during braking, the gas pressure increases exponentially. Energy is stored as more and more fluid is pumped into the accumulator at higher and higher pressures. In addition to increased pressure, the nitrogen gas also generally heats during compression, and this typically results in energy being lost to the environment. However, the integration of open-cell foam into the accumulator has improved the efficiency of accumulators significantly. Today, accumulators can have efficiencies as high as 98 percent when brake energy is stored for the period that most commuters spend in stop-and-go traffic.

http://www.swri.edu/3pubs/ttoday/Fall06/Balance.htm

[Ready4Change]

10. My guess:

They pump fluid into a rigid chamber that contains a trapped quantity of air (or maybe some specific, compressible gas that behaves well with their fluid of choice.)

Imagine an air tank with it's only opening on the bottom. Fluid pumped in compresses the air, which can't escape due to the fluid. Energy is extracted when the system allows the compressed air to push the fluid back out.

A problem I can see is how to store energy at variable rates. By that I mean that, when the tank is nearly empty, pumping fluid in will be fairly easy. But when the tank is nearly full, getting ANY fluid in there will take a lot of force. Those conditions might not be compatible with your braking needs of the moment. That's something that an electric system and charge controllers can handle well.

[CRF450]

11. Never saw this idea before, but it sounds damn cool!

[kristopher]

14. Isn't UPS using this on their trucks?

This is an application specific technology, great for stop and go driving - but very little benefit for most suburban, rural or over the road driving.