How Hydraulic Hybrids Save Tons of Fuel Where It’s Needed Most

It’s a weekly cacophony of sounds that many are familiar with — the loud hiss of air brakes followed by a mechanical mayhem, and then the roar of a big, thirsty diesel engine.

Beginning in the early morning hours across America, five days a week, an army of big-dog refuse trucks set 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.

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, and this is just one example of where help has arrived from “hydraulic hybrid” technology which is saving fuel and emissions where it’s needed most.

Why is the need so great? Because there are lot of trucks out there, they use tons of fuel, and solutions are needed that will work for them. What’s more, making big, heavy, fuel-guzzling trucks even incrementally more efficient saves proportionally a bunch more fuel and emissions than, say, taking a Honda Civic, and improving its mpg by a comparable amount.

Working trucks that see a lot of stop-and go are an ideal fit for hydraulic hybrid technology.

Automakers and the public have tended to focus on making thrifty vehicles thriftier, but trucks and other gross emitters are at least as likely a target if the goal is cutting U.S. petroleum consumption and emissions.

And, wouldn’t you know, we can all thank the U.S. Environmental Protection Agency (EPA) for spurring the development of hydraulic hybrid tech in its efforts to increase fuel economy and reduces carbon dioxide emissions.

Hydraulic drive systems are not actually new, and have been used by heavy industrial machinery for quite some time. Where the EPA comes in, is its National Vehicle and Fuel Emissions Laboratory (NVFEL) in Ann Arbor, Mich. quietly began designing the hydraulic hybrid system for passenger vehicles in the 1980s, and worked on scaling the concept down. As part of former U.S. President Clinton’s “Supercar” initiative to develop an 80-mpg passenger vehicle for the U.S. market, the EPA focused with manufacturers on producing a vehicle that did just that.

The project was shelved in 2001 when the Supercar program was cancelled, but the EPA continued work on the system. In 2004, the government agency partnered with Cleveland, Ohio-based Eaton Corporation, a global diversified power management company. The collaboration resulted in a technology called the Hydraulic Launch Assist (HLA) system.

How It Works

The HLA system essentially operates in the same manner as a mild gasoline-electric hybrid to assist vehicle propulsion.

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.

Truck manufacturer Peterbilt began offering the system in 2010 in its low-cab forward Model 320 Class 8 refuse truck. Cities such as Ann Arbor, Mich. immediately saw the benefits.

Increased Fuel Economy and More

Eaton discontinued the HLA system three years ago leaving U.S. motion and control technologies firm, Parker Hannifin as the sole supplier for hydraulic hybrid systems. Named RunWise Advanced Series Drive, Parker’s system is a full series hydraulic hybrid that is combined with the company’s proprietary Power Drive Unit. It features two-speed hydrostatic drive (low speed 0-25 mph and high speed 26-45 mph) for urban driving, combined with mechanical direct drive for efficient operation at highway speeds (46-60-plus mph).

Partnered with truck maker, AutoCar, cities climbed onboard at a fairly quick pace for the Parker system. More than 30 of the AutoCar-Parker trucks have been delivered to municipalities including Santa Cruz, Calif., Orlando, Fla., Loveland, Colo., Oberlin, Ohio and Tacoma, Wash.

The cities have seen a significant fuel savings — about 33 percent, which translates to about $8,000 to $10,000 annual diesel fuel savings per truck. The fuel that the trucks do use is generally only when the vehicles travel at higher speeds, and that fuel is 20 percent biodiesel or compressed natural gas (CNG).

Hydraulic hybridization is used in the UK and Europe as well.

The trucks cost about 23 percent more than traditional versions. But in addition to fuel savings, the trucks require less maintenance. Brake pads last longer because the brakes don’t contact the drums until the truck slows to about 2 miles per hour. Typically refuse haulers require brake replacement every four to five months, costing around $2,000 each time. But with the hybrid trucks, the city anticipates brakes may only need to be changed every six years.

Another savings is tires. Garbage truck tires, which number ten per truck and cost upwards of $150 each, are expected to last longer due to reduced friction heat on the wheels.

Beyond the dollar savings, Parker’s hybrid garbage haulers reduce carbon dioxide (CO2) emissions by 40 percent or more.

Ford Gives Nod To Lightning Hybrids Hydraulic System For F-Series Trucks

While the hydraulic hybrid garbage haulers were laboring way, Loveland, Colo., based Lightning Hybrids was developing a hydraulic system that benefited vehicles that do a lot of urban stop-and-go driving such as delivery trucks and shuttle buses.

The company’s research and development resulted in a patented hydraulic hybrid system called Energy Recovery System (ERS) that has been installed in more than 120 vehicles, including 50 UPS delivery trucks operating in Chicago.

This apparently caught the attention of Ford Motor Company, who at last week’s The Work Truck Show in Indianapolis added Lightning Hybrids to its expanded Advanced Fuel Qualified Vehicle Modifier (QVM) program. The new eQVM lineup also includes two gasoline-electric hybrid manufacturers.

The original program includes more than 200 companies that Ford has identified as qualified to convert its commercial vehicles into motor homes, school buses, emergency vehicles as well as firms that convert Ford vehicles to run on natural gas and propane fuels.

In order to be named an eQVM or QVM, a company must meet Ford’s stringent standards for quality and reliability, which has the benefit that when a conversion is made by certified technicians will leave the Ford warranty intact.

Lightning Hybrids systems can be installed on the Ford E-350 and E-450 chassis, F-350 and F-550 Super Duty trucks, F-650 and F-750 medium-duty trucks and F-59 chassis.

Lightning Hybrids ERS Hydraulic Hybrid

Think of Lightning Hybrids’ novel Energy Recovery System as a “mechanical battery”. It is considered a parallel hybrid because there is no connection to a vehicle’s transmission or engine. It is similar to Eaton’s HLA system, but is smaller and lighter with a computer system called a power transfer module that manages the system’s operation.

A high pressure accumulator containing a nitrile bladder filled with dry nitrogen gas is with pressurized hydraulic fluid during regenerative braking and used to accelerate the vehicle from a stop.

A low pressure accumulator is a place to store the hydraulic fluid when it’s not in the high pressure accumulator.

The mechanical heart of the system is the driveshaft-mounted pump/motor(s). It converts mechanical energy to hydraulic when the vehicle is braking, and hydraulic energy to mechanical when accelerating. Medium duty vehicles use one pump; heavier vehicles use two.

The pump moves fluid from one accumulator to the next in a cyclical fashion as it stores and uses energy. Since the kinetic energy released by the pressurized hydraulic fluid is expended at speeds above 30 mph, the Lightning Hybrids solution is ideal for the urban and multi-stop routes used by delivery vans and shuttles.

Fuel savings of up to 25 percent or more occurs because the engine turns off until acceleration depletes the hydraulic fluid.

Like all hybrid systems, Lightning Hybrids’ ERS hydraulic hybrid also reduces harmful emissions.

“Our system reduces NOx emissions by half and CO2 emissions by 25 percent compared to vehicles without it,” said Tim Reeser, CEO of Lightning Hybrids.

Hop A Ride On A Lightning Hybrids Equipped Shuttle Bus

Going to Alaska for a summer vacation? If you visit Denali National Park and Preserve, a national park centered around the highest mountain in North America, formerly known as Mt. McKinley, two shuttle buses outfitted with the company’s hybrid system transport tourists.

Closer to home, Kiessling Transit, a Massachusetts-based paratransit bus company, doubled the size of its Lightning Hybrids hydraulic hybrid vans to 70 vehicles last year. After traveling close to one million miles, the company said the ERS hybrids have demonstrated improvements of 25 percent in fuel efficiency.

Additionally, two of its units also are on shuttles that carry passengers around the National Renewable Energy Laboratory in Golden, Colo.

As for delivery vans using ERS, in addition to UPS, Peapod, an online grocery delivery company, began using two delivery vans outfitted with ERS in Chicago, and AmeriPride Services, a leading U.S. uniform and linen supply company, is currently evaluating the hybrid system.

Lightning Hybrids has customers in Australia, Canada, China, India and Mexico. The company is expecting to break into the European market with a new, larger office in Great Britain’s MIRA Technology Park, a campus that has a presence of more than 30 automotive related companies.


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