Diesel’s main contenders: Natural gas series, Part 3
Plant-based ethanol supplies also continue to grow in every sense of the word. The 209 ethanol refineries in 29 states generated 14 billion gallons of the fuel in 2011, according to the Renewable Fuels Association. That’s up from 1.6 billion gallons in 2000.
Since ethanol contains less energy per volume, a Flex Fuel Vehicle (FFV) – equipped with corrosion-resisting fuel systems that can handle fuel with higher oxygen content – will see its fuel economy drop 25 to 30 percent when running on E85, which contains 85 percent ethanol and 15 percent gasoline.
The fuel undeniably is easier to source when compared to some alternatives. More than 2,860 gas stations can pour E85, even though most supplies are at E10 levels. This supports light-duty FFV fleets in a large number of locales.
Typical ethanol levels likely will grow to E15 now that EPA has approved the fuel for cars, light-duty trucks and SUVs built since 2001. But Mouw questions just how many of the FFVs will ever burn anything other than gasoline.
Electric and hybrid
Some light- and medium-duty fleets are looking at vehicles that abandon the traditional fuel tank altogether. PepsiCo’s Frito-Lay – the seventh-largest private fleet in the United States – is deploying 176 Smith Electric Vehicles known as the Newton, a Class 4-7 truck that can travel up to 100 miles on a single charge, reducing traditional greenhouse gases by 75 percent. The trucks also are virtually silent, which can be a selling point in an urban setting.
In contrast, hybrid options combine several energy sources in a single package. Every offering includes some unique components, but most designs tend to fall into one of two categories.
The first is hydraulic systems, such as those adopted by several leading waste haulers. They use the kinetic energy from a braking truck to drive a combined pump and motor. When working as a pump, the system transfers hydraulic fluid from a low-pressure reservoir to a high-pressure accumulator. This stored energy is released to drive the motor, which helps the truck accelerate – either on its own or by combining the power of a combustion engine.
The other category is electric hybrids. These power a growing number of urban package delivery vans, using a combined generator and motor mounted between the transmission and the flywheel. The braking energy captured with the generator is stored in a battery, which can be used to drive the electric motor that can help move the truck or drive the power take-off for tools such as cherry pickers, reducing the need to idle.