After Gutenberg

Regenerative braking results from having a means to capture, store, and reuse the energy. It is possible to add this feature with hydraulic systems rather than relying upon electric drive. Research is needed to determine whether the addition of hydraulic “regen” is more cost effective than regenerative braking integral to an electric drive.

Tyler Hamilton is interested in seeing whether diesel-hydraulic hybrid technology will prove competitive with diesel-electric hybrid technology. One reason for such interest is that Toronto-based Azure Dynamics currently converts diesel vehicles to diesel-electric for governmental and non-govermental delivery fleets in Canada and the United States.

Jim Fraser notes:

In laboratory testing, the hybrid achieved a 60 percent to 70 percent improvement in fuel economy and a reduction of more than 40 percent in emissions, versus current UPS trucks. The EPA and UPS plan to conduct real-world testing this year.

A hydraulic hybrid has several advantages. One is that it can accept and deliver huge amounts of energy quickly, which batteries cannot. And its storage ability does not degrade over time, which is a fact of life with batteries available today. Generally speaking, though, hydraulic systems do not store as much total energy*.

* Note: Hampden Wireless reported that “the system can only store 2000 hp seconds of power. Or 100hp for 20 seconds. While that is a lot of power quickly its not a lot of total power.”

All three qualities can be said about ultra capacitors, as well; and, Azure Dynamics has been installing systems for ultra capacitor capture of kinetic energy. Beside making use of less hazardous materials, ultra caps have another advantage; they require far less maintenance than a hydraulic system does. Currently, the chief disadvantage of integrating ultra capacitors with regenerative braking is that such components make a potentially less expensive, electric drive, either prohibitively expensive or necessitating a much longer period to recoup cost.

What this blog would be interested in seeing (Tyler, Jim, or Mike Millikin) would a side by side comparison, to include five-year and ten-year ROI projections. Preferably, such a comparison between diesel hydraulic and diesel electric would

• Use the same type of diesel engine
• Have no difference in gearing or idle reduction methods
• Be installed in the same trucks, with other variables eliminated by experimental design
• Results come from UPS fleet managers interested in the bottom line rather than from the EPA with less obvious, political motives.

Rafael Seidl commented that hydraulic hybrids could be useful for trucks and buses “that need to make frequent stops but generally travel slowly.” He also perceived that such a system is cheaper than an electric hybrid. “Potentially suitable for retrofitting of stinky legacy diesels,” either type of regenerative system requires an electronic control unit “to fool the old engine.”