Transportation is one of the largest segment users of energy in the U.S., consuming 30 quadrillion (quads) of BTUs a year. Making up this segment are light-duty and beyond-light-duty transportation vehicles. Light duty refers to the cars that Americans drive every day. Beyond-light duty refers to everything else, from mobile machinery to large trucks. Mobile machinery—used in agriculture, construction, mining, and so forth—is a significant portion of this energy usage, said Zongxuan (Sunny) Sun, co-deputy director of the Center for Compact & Efficient Fluid Power (CCEFP).
“In a report published by the Department of Energy, off-road (transportation) consumes about 2.4 quads per year, which accounts for 8% of the total transportation energy consumption and 17% of the non-light utility vehicle energy consumption,” Sun said. “This is even larger than even the marine or aviation markets.”
Because of this, CCEFP researchers are working to secure government support and form collaborations between academia, industry and the national labs to conduct pre-competitive research in off-road vehicles. A group from the NFPA, CCEFP, Association of Equipment Manufacturers and member companies recently participated in a meeting with the Vehicles Technology Office (VTO) of the DOE to demonstrate the differences between on-road and off-road vehicles’ energy use.
Clearly, the biggest difference is that in on-road vehicles, internal combustion engines are used, while most of the energy produced by off-road vehicles goes through hydraulic power. Additionally, off-road vehicles are one input (ICE) and multiple output (drivetrain and working functions) systems with different hardware architectures and duty cycles than light-duty vehicles, said NFPA’s CEO Eric Lanke.
And not only are their drivetrains different, there is currently no dedicated program or offices in the federal government that fund the pre-competitive research in this area. Additionally, energy efficiency and productivity are key drivers for global competition in this area. Couple all this with the fact that NFPA’s research showed that the average efficiency of fluid power systems is only 22%, and you clearly can see there is a significant opportunity to improve efficiency in this area, said Sun.
In the meeting with VTO, Sun said the group highlighted four areas for potential research, with a fifth objective being the continued support of research by CCEFP universities.
1. Efficiency of fluid power systems enabled by more efficient components, such as modular power supplies, and optimized system architectures.
2. A tighter integration of fluid power systems with combustion engines, such as hybridization and Sun’s research into free-piston engines.
3. Develop connected and automated off-road vehicles to improve efficiency and productivity by reducing the losses of sub-optimal operations.
4. The development of systematic modeling and analysis tools to continue to develop new architectures, user interfaces, controls and connectivity.
Further details were given to the VTO about the free-piston engine and even Caterpillar’s hydraulic hybrid excavator to give the members of the VTO real-life examples of these efficiency improvements.
The free-piston engine combines the internal combustion engine and the hydraulic pump into one device, eliminating the crankshaft altogether. A linear engine moves back and forth, working combustion energy into fluid power directly.
“This device would enable efficiency improvement on both the engine side and the fluid power side,” Sun said. “Because you do not have a crank shaft, you have independent, individual modules so you could potentially place these modules at different locations of your vehicle so that you not only get improved efficiency, you also get a lot of flexibility in the design and packaging of your machine.”
Caterpillar’s hydraulic hybrid excavator is already commercially available, and offers significant improvements compared with its non-hybrid version of the same size excavator. This machine uses recovered energy from the swing to load trucks while using up to 33% less fuel than Caterpillar’s own 336D machine doing the same amount of work.
The CCEFP is also conducting research on a similar hybrid design, but Sun said they highlighted the Caterpillar product to demonstrate that manufacturers see the need in the industry and it’s not just a pipe dream created by professors.
“We also want to show that there are commercial products on the market that clearly demonstrate that with the right technology, you could significantly reduce energy consumption and emissions,” Sun said. “I think the key really is that fluid power is a dominant method for power transfer in this field and there are significant opportunities for improving energy efficiency. The CCEFP is working together with industry members to try to promote the pre-competitive research in this area.”