Freight vehicles, the behemoths of the road, haul as much as 80,000 pounds of product from coast to coast and pole to pole. Commercial vehicles consume as much as one-third of all motive fuel and are a significant emissions contributor, according to the Center for American Progress.

Unless they employ returnable packaging/racking systems, delivery  of freight is the last leg of a manufacturer’s production cycle. Whether a manufacturer purchases and manages its own freight fleet or outsources it to a freight transport company, transporting sustainably produced goods by less than ecofriendly means can be a last-round black eye on an otherwise green production process and can
muck up the works for even the greenest of manufacturers.

Increasingly, fuel cost increases, government regulations (see Government Regulations sidebar), and concern for the environment are driving manufacturers to explore alternative fuel and power sources for the freight fleets that deliver their products (see Trucking Industry Heavyweights Develop SuperTrucks
sidebar).

Several new and newer alt-powered vehicles and fuel types were showcased at the Mid-America Trucking Show in April in Louisville, Ky.

Six major types of alternative-powered systems and alternative fuels include electric drive trains, hybrid-electric drive trains, hydraulic hybrid power systems, natural gas-, biodiesel-, and propane-fueled.

So how do the drive trains or fuel systems work? How are they different from traditional propulsion systems? What are their best applications?

1. Electric

Electric drive systems are powered by an electric motor or generator, with power stored onboard in battery packs. They consume no fossil fuels for propulsion or operation.

Freightliner Custom Chassis Corp. (FCCC) a Daimler Trucks NA company, Gaffney, S.C., has begun full production of an all-electric, light-freight delivery truck chassis—the first in the industry. The chassis is currently undergoing testing with major U.S. pickup and delivery fleets (see Figure 1).

“In partnership with Enova, we have developed an all-electric chassis to meet the environmental, economic, and performance needs of our commercial vehicle customers,” said FCCC President Bob Harbin. This is the only walk-in van chassis in the industry to be completely electrically powered, Harbin said.

Figure 1
An all-electric chassis, co-developed with Enova Systems and using Tesla lithium-ion batteries, powers FCCC’s E-Cell walk-in van. The E-Cell is the only domestically engineered all-electric chassis, and the industry’s first in North America. Image courtesy of Enova Systems, Torrance, Calif.

Enova, Torrance, Calif., contributes “enabling technologies” in alternative-energy propulsion systems for light- and heavy-duty vehicles. The project involved the engineering and integration of Enova’s 120-kilowatt (kW) all-electric drive system technology into FCCC’s new MT-45 chassis.

The electric chassis’ power storage—including its HVAC system—uses Tesla Motors lithium-ion batteries. FCCC is the first company within the industry to use Tesla batteries for commercial applications, said Mike Staran, president and CEO of Enova Systems. The drive system’s 120 kW battery packs have a maximum100-mile driving range on a single charge. The battery pack charges from fully depleted
to fully charged in six to eight hours.

The batteries also capture and store energy during the regenerative braking phase of the vehicle’s operation. The regenerative braking system saves energy by recycling and storing it, instead of losing it to heat, which can then be reused to propel the vehicle.

Because the range of an electric vehicle is limited by weight, design, and the type of battery used, EVs are particularly well-suited to short-distance, high-use applications—those that demand frequent starts and stops, such as light-duty delivery vehicles.

2. Hybrid Electric

Eaton Corporation, Cleveland, develops and manufactures hybrid electric power systems for freight vehicles, which boost fuel economy and reduce particulate emissions in trucks as well as buses and service vehicles, according to Eaton’s James Parks, manager of global communications fleets (see Figure 2).

“By definition, a hybrid vehicle uses two or more distinct power sources to move,” Parks said. “Our hybrid system combines a truck’s traditional internal combustion engine with an electric motor and batteries to move the vehicle forward. Then, through regenerative braking, the system recharges itself.”

On average, hybrid electric power systems can reduce fuel consumption by 35 percent—in some applications, the reduction can be even higher. The applications that realize the best fuel efficiencies using this hybrid power system are commercial vehicles that stop and start frequently or that idle at work sites to run accessories or tools, Parks added.

Figure 2
Hybrid electric power systems combine a truck’s traditional internal combustion engine with an electric motor and batteries to move the vehicle forward. They can reduce fuel consumption by 35 percent. Image courtesy of Eaton Corp., Cleveland.

Eaton’s patented hybrid electric power system uses a parallel configuration that maintains the vehicle’s conventional drive train layout and uses patented controls to blend engine torque with electric torque to move the vehicle.

The system recovers power normally lost during braking and stores the energy in batteries. It can provide engine-off power, take off and work-site capability for those needing hydraulic operations and an auxiliary electric power source from the vehicle.

“To build the system, we couple the vehicle’s engine with our own UltraShift® automated manual transmission and clutch,” Parks said. “Between the output side of the clutch and the transmission, we integrate an electric motor/generator that is connected to a power inverter and lithium-ion batteries and controlled with our own electronic control module.”

Diesel/Electric. Florence, Ky.,-based ePower Engine Systems LLC, a developer of hybrid drive train technology, debuted the company’s proprietary diesel/electric engine system for the over-the-road transportation industry at the Mid-America Trucking Show.

The hybrid technology reduces fuel consumption—and hence CO₂ production—by as much as 65 percent under normal conditions of use and without reducing performance, according to the company.

The system can be retrofitted and uses off-the-shelf components.

No advanced battery technology is employed in the epower engine system. Instead, standard lead acid batteries are used.

3. Hydraulic Hybrid

Eaton also produces hydraulic hybridpower trains. The company’s patented Hydraulic Launch Assist™ or HLA® hydraulic hybrid system has two main parts—regeneration and acceleration, Eaton’s Parks said.

For acceleration, the fluid in the high-pressure accumulator is released to drive the pump/motor as a motor. The motor then propels the vehicle by transmitting torque to the driveshaft.

During regeneration, the vehicle’s kinetic energy that is normally lost during braking is captured and used to drive the pump/motor as a pump. The pump action transfers hydraulic fluid from a low-pressure reservoir to a high-pressure accumulator, he explained. As the fluid pumps into the accumulator it compresses nitrogen gas and pressurizes the system. The regenerative braking captures about 70 percent of the kinetic energy produced during braking.

“Accumulatively, customers using our hybrid systems globally have reduced their fuel consumption by 6 million gallons and harmful emissions by 60,000 metric tons over more than 150 million miles,” Parks said.

4. Natural Gas

Natural gas is emerging as a domestically available and economical alternative to diesel fuel.

Natural gas, comprised mostly of methane, is one of the cleanest burning fossil fuels, according to the Center for American Progress. It says natural gas produces less than half as much carbon pollution as coal for electricity and up to 25 percent less than oil for transportation.

But methane has some drawbacks. One is its low energy content. It takes about 100 cubic feet of methane to deliver the same amount of horsepower as a gallon of gasoline. Consequently, natural gas must be compressed (CNG) or liquefied (LNG), and it requires heavy, high-pressure fuel tanks.

LNG and CNG are replacements for petro-diesel and are suitable to fuel heavy-freight vehicles, as well as cars, the center states.

Compressed. To provide adequate driving range, CNG must be stored onboard a vehicle in tanks at high pressure—up to 3,600 pounds per square inch, according to the U.S. Dept. of Energy (DOE). A CNG-powered vehicle gets about the same fuel economy as a conventional gasoline vehicle on a gasoline gallon equivalent (GGE) basis, according to the DOE. (A GGE is the amount of alternative fuel that contains the same amount of energy as a gallon of gasoline. A GGE equals about 5.7 lbs. of CNG.)

Liquefied. One way to extend the driving range of a natural gas-powered vehicle is to liquefy the natural gas (LNG). Chilling methane to -260 degrees F reduces its volume by a factor of 630-to-1, allowing more fuel to be stored in a smaller tank. During this process, when the natural gas is cooled below its boiling point, certain concentrations of hydrocarbons, water, carbon dioxide, oxygen, and some sulfur compounds are either reduced or removed.

LNG is also less than half the weight of water, so it will float if spilled on water. At atmospheric pressure, LNG occupies only 1/600 the volume of natural gas in vapor form. A GGE equals about 1.5 gallons of LNG, the DOE says.

Because it must be kept at such cold temperatures, LNG is stored in double-wall, vacuum-insulated pressure vessels. LNG fuel systems typically are used only in heavy-duty vehicles.

But a supercold cryogenic fuel tank cannot keep the methane liquid cold indefinitely. As the fuel warms up, it begins to vaporize and must either be vented or used.

LNG costs more than CNG because of the costs of the chilling equipment.

As a motor fuel, LNG has the highest octane rating—130—of any of the other alternatives, which means it can handle compression ratios of up to 15-to-1.

Landfill Gas. Waste Management, based in Houston, is evaluating and developing a range of technologies that could create fuel, such as LNG, for fleet and other vehicles from landfill gas.

The company is not only a leading provider of waste services that include collection, transfer, recycling, and resource recovery and disposal, it is also the largest residential recycler and a leading developer, operator, and owner of waste-to-energy and landfill gas-to-energy facilities in North America, according to Wes Muir, director of corporate communications for Waste Management.

Waste Management has the world’s largest fleet of heavy-duty natural gas refuse and recycling trucks—853: 351 compressed natural gas and 491 liquefied natural gas, Muir added.

“Our company is committed to extracting the maximum value from the materials it manages by converting materials’ waste into beneficial reuse products such as renewable energy, transportation fuels, and chemicals,” Muir said.

5. Biodiesel

Common compression-ignition internal combustion engines are traditionally fueled by diesel derived from petroleum oil. Biodiesel can completely or partially replace diesel fuel. It is an organically based product and is renewable.

Biodiesel is relatively easily produced from plant and animal oils, fats, and greases and often is a byproduct of food processing. (see “Biodiesel—ready to rumble; Engine-ready, less toxic than table salt, more biodegradable than sugar.”)

Compared to diesel fuel, biodiesel is cleaner-burning, made from natural, renewable sources such as vegetable oils; and produces lower carbon emissions than diesel, according to the National Biodiesel Board.

“Biodiesel can be operated in any compression-ignition (diesel) engine with little or no modification to the engine or the fuel system,” the bBoard said in the article.

“Biodiesel is the first and only alternative fuel to have a complete evaluation of emission results and potential health effects submitted to the U.S. Environmental Protection Agency (EPA under the Clean Air Act Section 211(b),” according to the board.

The results show that pure biodiesel (B100) has 67 percent fewer total unburned hydrocarbons; 48 less carbon monoxide; and 47 percent less particulate matter than diesel fuel.

6. Propane

Propane, also known as liquefied petroleum gas (LPG), is another alternative to petrol. Like natural gas, propane is a gaseous fuel, so it is a vapor at room temperature and must be contained in a special high-pressure fuel cylinder. About 60 percent of the propane that is produced comes from natural gas wells; the rest is a byproduct of crude oil refining.

“Propane offers an environmentally friendly alternative to diesel and gasoline, increases energy security, and provides significant economic savings,” said Brian Feehan, vice president of the Propane Education & Research Council at an Alternative Fuels & Vehicles National Conference & Expo in May 2010.

Cummins,www.cummins.com
Daimler Trucks North America, www.daimlertrucksnorthamerica.com
Eaton,www.eaton.com
Enova Systems, www.enovasystems.com
Freightliner Custom Chassis Corp., www.freightlinerchassis.com
National Biodiesel Board (NBB), www.biodiesel.org
Navistar Inc., www.navistar.com
Peterbilt, www.peterbilt.com
Propane Education & Research Council, www.propanecouncil.org
U.S. Department of Energy, www.energy.gov
Waste Management Co., www.wm.com