Hydraulic Hybrids

Hydraulic HybridsKieron Kohlmann

What are hydraulic hybridsFirst used in 1982Hydraulic hybrids are similar to electric hybrids but use fluid instead of electricity.Similar to electric hybrids, hydraulic hybrids are either series or parallel.Commonly used by trucks, buses with frequent stops.

How they workHydraulic Hybrids consist of 3 main componentsLow pressure tank(reservoir)High pressure tankPump/motor

AccelerationDuring acceleration high pressure fluid is transferred from the high pressure tank through the pump, turning the driveshaft. The now low pressure fluid is routed to the low pressure tank for storage.

Acceleration

Image courtesy of EPA.gov

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CruisingOnce the high pressure reservoir is depleted, the engine provides power to either a pump or driveshaft.

Cruising

Image courtesy of EPA.gov

brakingDuring braking, fluid is pumped from the low pressure reservoir to charge the high pressure accumulator.The fluid is then stored for later use during acceleration.

braking

Image courtesy of EPA.gov

PARALLEL V SERIESIn a parallel hydraulic hybrid, the engine still has a mechanical connection through the pump to the drive wheels.

Parallel hybrid

Image courtesy of EPA.gov

Series hybridIn a series hydraulic hybrid, the engine is directly connected to the hydraulic pump with no direct connection to the wheels.

Series Hybrid

Image courtesy of EPA.gov

Benefits of hydraulic over electric hybridsNo expensive batteries to go badSafer for technicians to work onLess electronics=less trainingLack of transmission

Compared to electric hybrids

Compared to Electric hybrids

Who uses hydraulic hybrids?UPS operates a fleet of about 40 hydraulic hybrid trucks.Thousands of fleets around the world are adding hydraulic hybrids.

Eaton parallel systemEATON offers an add on hydraulic hybrid systemSystem bolts in between transmission and drive axle.Allows fleets to slowly convert without purchasing completely new equipment.

Chrysler town and countryIn 2012 Chrysler announced partnership with the EPA to develop hydraulic hybrid mini-vans.EPA estimated a 30-35% reduction in fuel consumption during city driving.Testing recently ended.

Sourceshttp://www.epa.gov/otaq/technology/research/how-it-works-parallel.htmhttp://www.diva-portal.org/smash/get/diva2:373607/FULLTEXT01.pdf