Energy Focus Is on Mobile Hydraulics

With annual energy usage estimated at 1 percent of all energy consumed in the U.S., off-highway construction equipment consumes more energy each year than all the dehumidifiers, refrigerators, microwaves and TVs combined. From skid steers to backhoes, the potential for energy savings is putting a new focus on innovative hydraulic solutions.

"In the past, hydraulic system optimization focused on controllability, cost and reliability," says Joe Pfaff, vice president of Engineering at INCOVA Technologies. "Today, the fourth dimension in the value proposition is efficiency." In the U.S. and even more so in Europe, India and China, fuel costs and the percentage of operating cost related to fuel is getting higher. This is driving OEMs and the entire supply chain to innovate solutions that provide higher fuel efficiency.

Many companies are working to optimize hydraulic efficiency by using variable displacement pumps and load sense systems. But one thing that HUSCO has learned is that understanding the vehicle duty cycle is critical for designing optimal hydraulic systems. Pfaff says an enormous amount of work has been done at HUSCO and INCOVA to create a foundation of know-how related to efficiency that is drawn upon to optimize hydraulic systems. If the focus is on valve operation in a laboratory environment, it will lead to sub-optimal solutions. It is critically important to understand how the valve works in the machine to provide high value, differentiated products.

"Within the last 18 months, we have done testing and analysis on over a dozen machines ranging from skid steers, to excavators (4 tons up to 25 tons) and backhoes. This allows us to decode the power transfer all the way from the engine to the actuators," says Pfaff. "We want to understand in a thorough way where power is being lost and what sort of design changes can be implemented to improve the overall machine efficiency." He says that HUSCO and INCOVA are pursuing several innovative new valve solutions that improve hydraulic efficiency while at the same time lowering the hydraulic system cost.

"With electronics, sensors and closed loop control, there is a tremendous opportunity to improve fuel efficiency but the value statement has to be strong," says Dwight Stephenson, senior vice president of Engineering at HUSCO International. "We could build an experimental vehicle with lots of electronics and sensors that would demonstrate a large leap forward in fuel efficiency. But you can't triple the cost of the hydraulic system and expect to win in the marketplace. The key is to judiciously use advanced technology to achieve high fuel efficiency without adding incremental costs."

"Some of the really exciting things that are going on here merge a little bit of the old know-how with the new know-how," says Pfaff. "The valve business, in general, has seen a lot of incremental improvements over the years, but there hasn't been a lot of big innovation since pressure compensation and load sensing became common 15 or 20 years ago."

"Within the next couple of years, you're going to see a number of new technology offerings from HUSCO," Pfaff continues. "The market demand for higher fuel efficiency is creating opportunities for innovative companies to expand their market share. This dynamic is exciting the supply base into doing some new things, not necessarily radical, but significantly new."

According to Pfaff, one of the eye-opening results of HUSCO's machine efficiency testing is the power transfer through the different components. He says that, in general, an engine is about 30 to 35 percent efficient at maximum operating efficiency. A pump is 85 percent at maximum efficiency, and a control valve typically runs depending on the application between 25 percent on a skid steer up to 60 percent efficiency on a 20-ton excavator.

"The efficiency opportunity in the valving area is huge. And clearly there is opportunity in the engines and the pumps also, but the opportunity for adding science and know-how to improve control valve efficiency is probably the highest out of the three areas," he says.

"We find this tremendously exciting as an opportunity to differentiate our existing products and develop new products. If you can double valve efficiency from 25 percent to 50 percent, with a very small cost impact or in some cases even a cost reduction, that is a major step forward. It's really just by including the efficiency analysis into the engineering design process that we are able to realize those kinds of gains."

Pfaff say the corollary to the development of control valves could be the internal combustion engine on cars. For 20 years, we have heard that the end will come for internal combustion engines. But solid, incremental improvements have been made in the efficiency of those engines without a significant cost impact. Direct injection, variable valve timing, and other new technologies have refined the internal combustion engine to a very high level. Now you can buy a direct injection diesel car that gets 60 miles to the gallon, which will beat a hybrid in most cases. To some degree, he says the same opportunities exist with valves.

"Right now the valve efficiency is not nearly as good as it can be with the application of our engineering know-how," says Pfaff. "Because of the poor efficiency of hydraulic control valves, some people see an opportunity to transition to hydrostatic solutions. But for me, after seeing the data from these 12 machines and knowing some of the solutions, I think from a technology standpoint the control valve technology trajectory is going to be very similar to engine technology."

"We are going to have fantastic levels of refinement over the next decade that drastically improve control valve efficiency without a significant effect on the cost and while continuing to improve reliability. We all remember back to the carburetor days with engines, and I don't think anyone wants to go back there from a reliability standpoint. This rate of increase in hydraulic technology can happen, and I think that is what we are going to see in valving in the next 10 years."

Photo: A Bobcat 435H five-ton mini-excavator used as the demonstration system, utilizing a pump to control the displacement and motion of each actuator, has produced energy savings up to 50 percent in simulation. Source: Purdue University

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