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Considerations for HYDRAULICS in Electric Off-Highway Equipment
Independent metering valves, such as Eaton’s CMA valve shown here, can better control metering losses to reduce hydraulic power consumption.
contributed by Shelley Nation, Senior Engineering Specialist, Emerging Technologies, and Aaron Jagoda, Senior Engineering Specialist, Advanced Technology, Eaton
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s emissions standards around the world grow more stringent, non-road mobile machinery (NRMM) manufacturers are leveraging new strategies to create more efficient vehicles. Electrification is one of the most prominent. A variety of electrified machines are being brought to market, helping to dramatically reduce carbon dioxide (CO2) and nitrogen oxide (NOx) emissions compared to traditional, diesel-fueled equipment. But electrification is a newer trend that comes with certain challenges. Consider that batteries remain expensive—and for end users, the machine’s ability to perform a full day’s work on a single charge is imperative. Original equipment manufacturers (OEMs) must balance battery cost with the power and range requirements of the machine without creating a priceprohibitive product. Striking this balance can be tricky. Luckily, there are opportunities to
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OEM Off-Highway | AUGUST 2021
achieve power savings, particularly through the deployment of efficient hydraulic components and architectures.
Electrification methodologies While electrification methods differ, there are commonalities in the types of vehicles being electrified. Power requirements, efficiency, total cost of ownership and noise all affect electrification adoption rates. Smaller machines with less horsepower demand will transition more rapidly. So will vehicles used in low-emissions zones, particularly construction and material handling platforms. Mini excavators are primed for growth, while aerial work platforms are already heavily electrified. Electrification affects all aspects of a machine’s power architecture, from source to conversion, transmission, consumption and management. In terms of power source, the traditional prime mover of a mobile machine is an internal combustion engine. Technology alternatives range from hybrid elec-
tric and plug-in hybrid, which maintain the diesel engine, to tethered electric and battery electric, which remove it. As for power consumption, there are three good opportunities for electrification: The machine’s propel circuit, rotary work functions and linear work functions. • A machine’s propel circuit is how it moves around, via its wheels or tracks. Fully electric propel systems (either on the axle or wheels) are an alternative to traditional hydraulic or mechanical propel systems. Advantages of electric propel solutions include minimized energy conversions and reduced hydraulic leaks. However, system costs are considerably higher than hydraulic propel solutions due to higher electric component costs and battery power requirements. They’re also not as rugged as hydraulic systems; which can present challenges in harsh environments. • Rotary work functions, such as
