CompositesWorld
Issue link: https://cw.epubxp.com/i/791367
Hydraulic-powered hybrid vehicles prove effective, ACMA Executive Forum gauges Trump effect on composites, supplier investments take effect in oil and gas market. MARCH 2017 14 CompositesWorld TRENDS Hydraulic hybrids boost fuel economy without batteries A hybrid vehicle uses two or more power sources, typically gasoline supplemented by batteries and/or regenerative braking. This reduces power demand on the engine, which reduces fuel consumption and emissions. However, a hybrid vehicle does not necessarily have to involve batteries or electrification. The US Environmental Protection Agency's (EPA, Washington, DC) own investigation tends to support Lightning Hybrids' (Loveland, CO, US) contention that hydraulic hybrids are more efficient and easier to imple- ment, especially as heavier vehicles. The EPA has been experimenting with the technology since the late 1980s, and the United Parcel Service (UPS, Atlanta, GA, US) recently added 50 vehicles, using Lightning Hybrids' patented Energy Recovery System (ERS) to its fleet in the Chicago metropolitan area. Lightning Hybrids CEO Tim Reeser says his customers report a 15-55% reduction in fuel use and CO2 emissions and a 50% cut in NOX emissions. Other benefits include: • R equires less space and payload sacrifice vs. battery hybrids; • Much les s expensive than electric hybrid drivetrains; • R educes engine exhaust during acceleration; • A dds power/torque (e.g., 600-800 ft-lb) enabling engine downsizing; • 100% or better improvement in brake component life. The systems are reportedly easy to install, fitting between the frame rails towards the center of the vehicle (see photo). Ultimate cost can be reduced to as little as US$5,000 by means of alternative-energy and clean-air grants. UPS, for one, anticipates for its Chicago hydraulic hybrid fleet a return on investment within a short 1-2 year period. Instead of batteries, hydraulic hybrids use a lightweight hydraulic system comprising a low-pressure reservoir (aluminum tank with bladder) for storing hydraulic fluid (nonflammable) and a pump to move the fluid from the reservoir to a high-pressure accumulator (composite tank with bladder). This accumulator holds not only the fluid brought over by the pump but also pressurized nitrogen gas in the bladder. During regenerative braking, kinetic energy from the vehicle's motion powers the pump via the driveshaft, moving fluid from the reservoir to the accumulator. This slows the vehicle — the hybrid system acts as the primary braking system. During this phase, pressure builds in the accumulator as the nitrogen gas is compressed: This functions like a mechanical battery, storing energy to be released when the vehicle needs to accelerate again. As the vehicle accelerates, the accumulator sends its energy, in the form of pressurized hydraulic fluid, to the pump, which now acts as a motor, turning the vehicle's driveshaft and, thereby, reducing the load on the engine. As the vehicle accelerates, the hydraulic fluid returns to the reservoir, ready to charge the accumulator again, during the next braking event (see endnote). Composites play a key role in Lightning Hybrids' ERS high-pressure accumulators. These are Type 3 pressure vessels made by Steelhead Composites (Golden, CO, US). "Accumulators are one of the most ubiquitous compo- nents in hydraulics, yet little is known about them," says Mateo Cantu, business development head for Steelhead Composites. For example, accumulators are used to change the pitch of wind blades in turbines > 3MW, to actuate ship rudders and stabilizers, to move aircraft flight controls, landing gear and thrust reversers AUTOMOTIVE Source (both photos) | Lightning Hybrids (continued on page 16)