Mack Trucks has shown a refuse truck featuring Wrightspeed’s turbine-powered electric “Route” powertrain. Designed to reduce fuel and maintenance costs, the retrofitted Mack LR was shown at the Waste Expo 2016 (yes, that’s a thing) in Las Vegas this week.
The Mack LR refuse collection truck (aka “garbage truck”) chassis has been retrofitted with Wrightspeed’s Route 1000 turbine and electric powertrain, replacing its conventional combustion engine. The showcase builds on Wrightspeed’s earlier work with other truck users such as FedEx and New Zealand Bus.
The Route 1000 system is designed to power vehicles with a gross vehicle weight of up to 66,000 pounds up grades as steep was 40 percent. The total system utilizes an 80 kW Fulcrum Turbine Generator as its hub, which is capable of burning a number of combustible fuels. To augment this, there’s also a 730 kW regenerative braking system.
A geared traction drive (GTD) powers each of the two rear axles on the Mack, providing both slip control and motive power. Batteries supplied by A123 Systems are installed in a modular fashion to increase or decrease on-board storage according to specification, and a plug-in charging system is also included so that those batteries can be fully charged during the truck’s down time. No battery capacity was specified for the retrofitted Mack LR shown in Vegas.
The Fulcrum turbine generator was introduced by Wrightspeed last year as a power generator specifically designed for use in heavy-duty vehicles up to Class 7-8 trucks. The Fulcrum is a radial inflow, axial turbine, intercooled and recuperated design that uses a two-stage compression process. The generator is about 1/10th the size of a similarly-capable combustion engine in a traditional piston design, weighing only 250 pounds (113 kg) and with a 10,000 hour expected running lifetime. This makes the Fulcrum lighter weight than a similar, competing turbine from Capstone, which weighs about 300 pounds (136 kg).
The Fulcrum is capable of running on diesel/biodiesel, compressed and liquid natural gas (CNG/LNG), landfill gases, kerosene, propane, heating oil, and more. It also features very low noise and vibration characteristics. Because of its high-temperature, clean burn, the Fulcrum does not require emissions equipment for the exhaust. In the Wrightspeed design, an intercooler feeds air to the combustor, which is injected with fuel. The combustion process pushes the exhaust out in a funnel, turning the turbine. As it spins the turbine, the hot air escapes through a port and is sent back to the intercooler. The spinning turbine’s shaft turns a generator which produces power to be sent to the drivetrain.
The GTD used in the Mack on display is Wrightspeed’s two-speed gearbox with integrated motor, designed specifically for heavy use. No clutch is required as the speed of the motors can be controlled and changed on the fly, allowing for gear mesh without heavy clutch and synchros. Each drive axle has two GTD units attached, one for each side, allowing for full traction control through control of the motors’ speed to each wheel. Thus a truck with two drive axles (such as this Mack LR) can use four motors, each delivering about 200 horsepower (186 kW) continuously and 10,600 pound-feet (14,372 Nm) of torque to the axle as a whole. Braking power in regeneration is similarly over the top, combining on the Mack LR to become about 730 kW in all. The entire system also eliminates the need for gear-up units such as differentials.