Hydraulic Hybrids

Most people by now are at least familiar with hybrid electric and internal combustion engine technology. The use of electric motors and batteries can significantly extend the range and efficiency of fuel-burning cars and trucks, depending on how they're driven.

But there’s another type of hybrid technology, one that requires no batteries or sophisticated electric power management systems. Hydraulic hybrid drive systems capture the energy that's normally dissipated in braking and store it as hydraulic pressure that can power the axles in driving. While that might not make much sense for a long-haul tractor that makes infrequent stops, it makes perfect sense for a delivery truck, garbage truck and other vehicles that make lots of stops in the course of their daily routes. Package delivery company UPS is one high-profile user of hydraulic hybrids, having fitted the technology to many of its delivery trucks.

Hydraulic hybrids are one form of regenerative braking, a broad term that describes the process of capturing the momentum energy of deceleration, then using it later to propel the vehicle.

In a hydraulic hybrid, two major components are at work. Accumulators are containers for holding high-pressure hydraulic fluid. Hydraulic drive pumps serve both as motors to drive the wheels and as pumps to re-pressurize hydraulic fluid.

Here are some advantages of hydraulic hybrids:

  • Their technology is simple -- no need for major breakthroughs to make them practical.
  • They call for less brake maintenance.
  • The system is clean, reducing emissions by up to 40 percent.
  • They’re efficient, with hydraulic hybrid drivetrains providing a 60- to 100-percent increase in fuel efficiency.

Equally important as fuel choice is how efficiently that fuel is used. After all, efficiency is a big part of environmental responsibility (and yes, saving money). Next, another fleet-minded fuel-saving strategy.