Garbage Trucks Go Hybrid

Hydraulic Hybrid Developed By EPA Increases Garbage Truck Fuel Economy Up To 30 Percent

In the early morning hours across America, five days a week, an army of big-dog garbage trucks sets out to pick up our trash. They pull up, stop, idle, load and take off for the next stop, often only 100 feet or less away. This happens 300 to 1,200 times per day, per vehicle.

Peterbilt garbage truck

The city of Ann Arbor, Mich. is purchasing four Peterbilt garbage trucks with Eaton’s Hydraulic Launch Assist hydraulic hybrid system. The city expects a 30% increase in fuel economy as well as savings from fewer brake replacement jobs.

On a good day, a diesel garbage hauler will eke out 4 to 5 mpg. Then there are all those icky, nasty pollutants pouring out of the exhaust pipe.

But thanks to the United States Environmental Protection Agency (EPA), yes, those government folks who monitor environmental laws and fuel mileage testing, a system called “hydraulic hybrid” increases fuel economy up to 30 percent and reduces carbon dioxide emissions by 40 percent or more in heavy-duty truck applications.

Developed at EPA’s National Vehicle and Fuel Emissions Laboratory (NVFEL) in Ann Arbor, Michigan, the government agency partnered with Cleveland, Ohio-based Eaton Corporation, a global diversified power management company. The technology, called the Hydraulic Launch Assist (HLA) system essentially operates in the same manner as a gasoline-electric hybrid.
Like gasoline-electric hybrid versions, HLA works by recovering a portion of the energy normally lost as heat by the vehicle’s brakes. But instead of a battery pack, a hydraulic system uses pistons to capture the wasted energy by compressing nitrogen gas stored in a tank, called an accumulator. When the driver lets off the accelerator pedal, the wheels drive a hydraulic pump that pumps hydraulic fluid to compress the nitrogen gas and slows the truck down. When the driver accelerates, the nitrogen is allowed to expand and pushes a piston in a cylinder filled with hydraulic fluid. This action assists the diesel engine in turning the rear wheels.

An added advantage to the HLA system is reduced brake wear because Eaton’s technology hydraulically stops the truck. Typically, refuse haulers require several brake replacements each year, costing around $2,000 each time. The hydraulic regenerative braking system cuts this to less than once a year.

Several cities are testing the HLA equipped garbage trucks. The latest is, appropriately, Ann Arbor with four Peterbilt equipped trucks. The city is one of the first to obtain funding for them through the U.S. Department of Energy’s Clean Cities Program. The $156,000 grant offsets the nearly $40,000 cost difference over a conventional diesel hauler.

An aggressive variation of the HLA design is being tested in UPS Navistar parcel delivery trucks. Using an Eaton series-type hybrid design, the V6 diesel engines do not power the vehicles, but serve solely to actuate the hydraulic systems’ pumps. It’s estimated that these vehicles could see fuel economy improvements of as much as 60 percent and a reduction of greenhouse emissions of 40 percent.

Using hydraulic technology to increase fuel economy and lower emission isn’t an exclusive for the United States. Hydraulic hybrid buses are being tested on the streets of Beijing, China with the hope of introducing them to other parts of the country.

The hydraulic hybrid appears to offer huge benefits when applied to heavy vehicles that operate in stop-and-go driving conditions, but what about passenger cars and trucks?
The engineers at the EPA’s Michigan laboratory have built and tested many prototypes over the years, including a diesel-hydraulic Ford Taurus that chalked up more than 80 miles per gallon. In 2004, the EPA displayed a hydraulic hybrid Ford Expedition SUV with a small diesel engine replacing the large displacement gasoline V8. It delivered an 82 percent improvement in combined city and highway gas mileage. Ford was an early partner with the EPA in developing the system, but later dropped out.

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  • Yegor

    Why invent a new technology (Hybrid-Hydraulic) when there is already a 13 years proven one Hybrid-Electric?
    They spent lots of taxpayer’s money on development and they still do not know what will go wrong with it because you need years of experience to find out.

    Garbage trucks are an excellent choice for a hybrid-electric technology – sometimes they stop and go every 30 feet. I think fuel efficiency improvement should be something like 100%.

    Delivery trucks are also a very good choice for a hybrid-electric technology.

  • calvin

    Hydraulic accumulators have been in use for over 150 years. It is a proven technology.

    The reason that the EPA decided to fund their own research into hydraulic hybrids is likely due to the lack of research/funding in this field by the private sector. The EPA’s goal is to protect the environment, and funding alternative hybrid technologies certainly goes along with that goal.

    Garbage trucks require a lot more power than conventional vehicles, and using batteries at current prices is likely to be prohibitively expensive. Making use of the preexisting hydraulic systems in garbage trucks makes sense and would probably make conversions a lot easier, not to mention the maintenance cost reductions alluded to in the article.

    I think I trust the EPA’s research data more than random figures derives from blind speculation by someone who’s likely never designed a hybrid vehicle or done research in fuel economy.

  • Craig

    I agree with Calvin – the battery storage required to store the amount of energy required to stop a garbage truck is much greater than that recovered to stop a Prius.

  • simon@syd

    This is brilliant – seems sort of obvious now though. I wonder if streets could have points where garbage is taken to on garbage night, rather than the truck stopping outside of every house?

  • Anonymous

    It’s good to invest in some alternatives. I don’t think there will be one technology that fixes the gas dependency for all.

    People have different need, Trucks have even more different needs. Depending on the need (low milage commuter, long distance traveler, ‘sporty’ driver, local bus, long distance truck …) different technologies will have different efficiency results. We need to invest in many different technologies so that we can provide the optimal technology for the different use cases.

    I commute <15 miles a day - a small range EV would be perfect for me (I'm waiting for the Prius Plugin). But we also have the 'family' car for long distance trips (and otherwise used by my wife), for that, a small range EV would not do the trick.

    Also, if we now switch everything to electric, we change the oil dependency to battery dependency … I think it would be better to diversify the technology so that no big dependency on anything is created, much easier to switch (e.g. if the Arabs or Chinese have bought all the battery companies) if there are alternatives.

  • Old Man Crowder

    Simon: I like your thinking, although I think too many people are just too lazy. My next door neighbour won’t put his garbage next to mine because it would mean parking his car on the other side of his driveway! Heaven forbid!

  • Dump trucks

    Firstly I also want to say THANKS to United States Environmental Protection Agency (EPA), for doing their job very well.
    The Hydraulic Launch Assist (HLA) technology used by them is also very effective in nature.

  • alvin

    what brand of hydraulic motor/pump/accumulator used? what model/part number? can you provide us information? need additional components?

  • Scott Allerdice

    this is another new innovation but this time the work with trucks is truly admirable. blogviewz