Hydraulic hybrids rev up low-energy technologies

By the end of the decade, Ford Motor Co. hopes to have a pilot fleet of vehicles sporting a high-efficiency, hydraulic hybrid power train.

Technology development is underway now as Ford engineers collaborate with engineers at the U.S. Environmental Protection Agency (EPA). The agency developed the basic hydraulic hybrid technology in the late 1990s as part of the Partnership for Next Generation Vehicles initiative, a collaborative effort of the U.S. Council for Automotive Research, the federal government, the automotive industry, and the academic community to triple fuel economy and reduce automotive emissions. EPA's collaboration with Ford on hydraulic hybrid technology is reportedly the agency's first with an automaker.

"EPA came up with a great idea, and Ford helped transform that idea into a technology," says Jon Harmon, a spokesman for Ford. "With this agreement, Ford and EPA are taking the technology to the next level by working to incorporate it into a vehicle."

Designing a hydraulic hybrid powertrain will be more of a wild ride than a Sunday drive: The project will require a "radical reconfiguring of the existing power train design," says Harmon. It will also call for close collaboration among the dozens of design engineers from Ford and EPA who will work with their counterparts at FEV Engine Technology, Inc. (Auburn Hills, MI) and Eaton Corp. (Cleveland, OH) to develop and deliver a vehicle that is both fuel efficient and pleasant to drive.

The technology concept behind the hydraulic hybrid powertrain is similar to that used in electric hybrid vehicles. Each has a gasoline or diesel primary power source, and each incorporates an engine that is about 25% smaller than that found in traditional vehicles. That engine is designed to meet ordinary power demands. On those occasions when the car demands peak power-such as climbing hills or towing-an additional power source augments the primary engine. In hybrid electric vehicles, batteries provide electricity to a motor that drives additional power to the engine. Batteries recharge using regenerative braking, which captures energy normally lost as heat when the vehicle's brakes are applied. By harnessing that electrical energy to supplement the internal combustion engine, regenerative braking significantly reduces fuel consumption.

In the hybrid hydraulic system, hydraulic motors/pumps and hydraulic accumulators (high-pressure storage tanks located in the underbody of the vehicle) store energy and propel the vehicle. Regenerative braking pressurizes an inert gas, such as nitrogen, for releasing additional power when needed.

Large SUVs are the first vehicles that will benefit from the new powertrain. They have the space to accommodate all the components, engineers say.

The new Ford/EPA hydraulic hybrid initiative is the latest in a series of energy-efficient technologies and vehicles currently in development. Among others:

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