- *The hybrid controller monitors the driver's acceleration and braking, and commands the hybrid system components. The high-pressure accumulator stores energy just like a battery would in a hybrid electric vehicle. However, it uses hydraulic fluid to compress nitrogen gas.
- *The engine pump/motor transfers hydraulic fluid to the rear drive pump/motor.
- *The rear drive pump/motor converts the pressure from the hydraulic fluid into rotating power for the wheels, and recovers braking energy which is stored in the high-pressure accumulator.
- *The low-pressure reservoir stores the low-pressure fluid after it has been used by the pump/motor unit.
The above configuration provides three key design features that provide maximum fuel efficiency:
- Regenerative Braking. The vehicle uses its own stored braking energy for starts and accelerations. This process recovers and reuses more than 70 percent of the energy normally wasted during braking.
- Optimum Engine Control. In the full series hybrid design, there is no conventional transmission and driveshaft connecting the engine to the wheels. This frees the engine to be operated at its maximum efficiency.
- Shutting Engine Off When Not Needed. The unique hybrid design also enables the engine to be completely shut off during certain stages of operation, such as idling at a stoplight. As a result, in stop-and-go urban city driving engine use is cut almost in half.
This technology is currently being evaluated by UPS in real-world package delivery. This vehicle has delivered both packages and environmental benefits to doorstops across Michigan. This evaluation is the next in a series of steps to bring this technology to neighborhoods throughout the entire nation.
UPS expects to see an increase of 60 to 70 percent in urban settings - where most delivery vehicles are driven. The EPA estimates these trucks can save 1,000 gallons of fuel each year. (Imagine the fuel savings for an entire fleet.)
And as efficiency jumps, pollution and greenhouse gas emissions also drop. This technology produces 40 percent fewer greenhouse gas emissions as compared to a conventional delivery truck. Because the hydraulic hybrid system is so cost-effective, UPS estimated that its upfront costs can be recouped within three years. This means the net savings over the vehicle's lifespan could exceed $50,000.
FUTURE OF HYDRAULICS
Using the full hydraulic drive in conjunction with the EPA's Clean Diesel Combustion technology is projected to improve fuel economy even more. Today we are seeing that energy innovation solutions, like hydraulic hybrids, can power our nation's economy, and drive our environmental success.
More than 14 million Americans rely on public transit services to get to work, to school and to neighboring cities. Because of its safety, reliability and efficiency, diesel is the predominant power source for bus services nationwide. More than 95 percent of the nation's full-sized transit buses are powered by diesel. It is less flammable than gasoline, and engine maintenance and durability are unmatched.
Though once in danger of being banned in the United States because of their emissions, diesel vehicles are undergoing a number of revolutionary advancements.
Buses have always been able to be counted on to deliver people, and now they are delivering something even more welcome: clean air.