Hydraulics and motion controls company Parker Hannifin has been gaining traction in the refuse truck market since launching its RunWise hydraulic hybrid system for heavy commercial vehicles in 2010. More than 100 trucks are on the road with refuse fleets using the combined power transmission and energy storage system, and orders to Parker’s truck-building partner Autocar continue, says Tom DeCoster, business development manager for Parker’s hybrid drives systems division.
Today, much of the industry’s attention is fixed firmly on compressed natural gas (CNG). Last year, more than half of the refuse trucks sold featured CNG engines as fleet managers looked to cut fuel costs as quickly as possible. In that environment, DeCoster says Parker is talking to customers about its technology, explaining to them that no matter what the fuel choice, hydraulic hybrid technology can cut energy consumption in heavy commercial vehicles.
“We see the hybrid having a solid place in the market, regardless of the fuel choice,” DeCoster states. “Our national diesel fleet average is a 43% fuel savings, which is pretty amazing when you consider that these vehicles consume a lot of fuel every day.”
Hybrids boost low-speed performance
As with gas-electric hybrids such as the Toyota Prius, RunWise stores energy that traditional vehicles waste during braking. Electric hybrids store that regenerative braking power in batteries while RunWise stores it as pressurized fluid in a hydraulic accumulator. When the truck’s driver takes his foot off the brake pedal and onto the throttle, RunWise releases that stored energy, using it to power the vehicle up to about 20mph. The truck’s engine doesn’t have to rev up until the vehicle is already rolling at a decent speed.
Hybrids offer the biggest benefits in low-speed, start-stop traffic where they can constantly gather energy, a key point for garbage haulers because refuse trucks typically operate in those slow, energy-intensive conditions.
As refuse haulers have ordered more RunWise trucks, Parker has continued to invest in the system. The first generation of the trucks, for example, could only recapture braking energy down to about 5mph before the truck’s conventional brakes applied stopping power. The hybrid system on the newest trucks works all the way down to 1mph.
DeCoster notes, “There was still a considerable amount of energy to be recouped in those lower speeds.”
Fuel-saving competition
Steven Saltzgiver, vice president of fleet management for refuse company Republic Services, says his business is testing a prototype truck in California that uses both CNG and hydraulic hybrid technology. He likes what he’s seen so far, explaining, “We spend about half a billion dollars in fuel per year as an industry, so we have a strong vested interest in pursuing all of these technologies.”
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Hydraulics vs. electrics Gasoline-electric hybrids have gained a toehold in the passenger car market with vehicles such as Toyota’s Prius line. But refuse companies say electrifying the commercial world is more difficult because of higher weights and energy levels. The performance of electric systems tends to decline as batteries drain, much like a flashlight slowly going dim as power drains away. Electrified trucks give the highest boost levels at the start of the day when batteries and trucks are full. Refuse trucks, on the other hand, start the day with the lightest loads and take on more weight throughout the day. Republic Services fleet director Steven Saltzgiver comments, “We need a system that gives a big boost at the end of the day, when the trucks are their heaviest.” DeCoster says the electrical storage that works well in a 3,000 lb Prius can’t scale up to 50,000 lb refuse trucks. “In a refuse application, from 30mph down to zero, we’re capturing about 500hp. That’s a lot of energy to try to push into a battery storage system,” Tom DeCoster, business development manager for Parker Hannifin’s hybrid drives systems division states. “Most battery systems on the market today can’t handle that amount of energy that fast.” |
Many refuse fleets are looking at CNG as a way of cutting diesel use, so in a sense, CNG trucks compete for fuel-saving dollars with Parker’s hybrid system, Saltzgiver says. But longer-term, he believes companies should consider ways to reduce fuel use, not simply replace one higher-cost diesel with less expensive CNG.
“We’re all being careful with our fleet investments. You never put all of your eggs in one basket. You have to try a bunch of different technologies to see what fits your needs,” Saltzgiver says.
After testing several systems, Saltzgiver explains natural gas has a lot of potential because experts believe its costs will be low and stable for many years, and most refuse fleets also run landfills that give off fuel-grade methane.
However, “There’s a lot of sulfur that you have to remove, and that can get pretty costly. There’s some potential there (for waste gas fuel), but it’s pretty expensive to get started,” Saltzgiver explains.
Obstacles to CNG truck growth
While Saltzgiver likes the large number of CNG trucks that Republic Services has ordered, he says there are plenty of challenges in supporting such vehicles in the field.
It takes Republic Services about two years to go through the construction and regulatory approval process to support natural gas trucks in its fleet. Utilities have to build higher-volume gas lines to depots, and staging areas have to be set up to fuel large numbers of vehicles simultaneously. Expenses include changes to truck-yard layouts and compressors to take the utility natural gas feed and force it into truck tanks.
In addition, CNG has less energy than diesel fuel, so truck drivers have to go through more gear changes to get the load moving than with diesel. Slower startup means more time spent moving from stop to stop, increasing the time it takes for a collection crew to finish its route.
DeCoster notes that adopting diesel-hydraulic hybrid systems offers quicker savings because the trucks don’t require any infrastructure investments. Still, in the longer term, he sees a lot of potential for a future CNG RunWise as more fleets make the depot improvements necessary to support natural gas.
Parker and Autocar announced plans last year to work out a CNG version of its RunWise system, and though the companies have not announced a timeframe to bring such a vehicle to market, they are continuing to develop the technology. Such a combination could address performance differences between the two fuels. Providing hydraulic power to CNG engines at low speeds could give trucks comparable acceleration performance to diesel hydraulic hybrids.
“I can’t think of any other technology that can cut fuel consumption by 40% or more while still maintaining the rigors of the duty cycle,” DeCoster says. “We’re fuel agnostic, so we expect to see big fuel savings in CNG or diesel.”
Parker Hannifin Corp.
www.parker.com
Autocar LLC
www.autocartruck.com
About the author: Robert Schoenberger is the editor of TMV and can be reached at 330.523.5381 or rschoenberger@gie.net.
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