Parker’s hydraulic hybrid recovers quickly

  • 19-Jun-2008 08:21 EDT
Parker's testbed system uses two large accumulators to store energy that can get a vehicle moving without burning much fuel.

As oil prices rise, equipment makers are racing to develop technologies that reduce fuel consumption. Parker Hannifin is developing a hydraulic system that stores energy that can be used to get vehicles moving without burning much fuel.

Parker’s Runwise technology is based on an energy recovery system that collects energy when brakes are applied and when the engine is idling, storing this energy in a hydraulic accumulator. The hybrid technology was developed in conjunction with Autocar, a garbage truck developer, but Parker is also examining systems that can be used in wheel loaders and other vehicles that often start and stop.

“Hydraulics provide a significant advantage over electric hybrids. Hydraulics can take a lot of energy in a short time, while batteries have to be charged slowly over longer periods,” said Lewis Kasper, Business Unit Manager at Parker.

Parker’s series system uses the vehicle’s internal-combustion engine to augment the regenerative braking system when the accumulator capacity falls below 50 to 60%, which happens only rarely.

“The engine only comes in about one in 20 times. Otherwise, the accumulator is charged by the brakes,” said Kasper said.

He noted that in addition to fuel savings, a key advantage is that vehicle engines can be sized for peak speeds, not for the amount of low-end torque they provide. That can provide some substantial benefits.

“In something like a delivery truck, we could reduce engine size by 25 to 30%,” said Kasper.

He noted that fuel savings are significant. “We’re seeing mileage improvements of 40 to 117% for dump trucks, depending on their routes. That’s without reducing engine size, which could save another 10 to 20%,” said Kasper.

Another benefit of hydraulic hybrids is that they provide instant acceleration, without the ramp-up needed for electric motors. Accumulators could have longer lifetimes than batteries, Kasper added.

Other hydraulic system suppliers are also developing hybrid systems. Eaton has worked with UPS and the U.S. EPA. Bosch Rexroth is also developing another approach that uses hydraulics to conserve energy.

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