I’ve been spotting plug-in electric cars all over the Bay Area recently. Nissan Leafs and Chevy Volts are a nearly dime a dozen and the plug-in Prius sightings have been adding up recently. I just spotted a Tesla roadster last week quietly engaged in my neighborhood’s evening ritual of locating a parking spot, as well as a Fisker Karma stuck in downtown San Francisco traffic. But amongst all these electrified passenger car sightings, I’ve also noticed an increasing number of hybrid delivery trucks, including one I spotted while biking home the other day.
It turns out that many of the same technologies being used in passenger cars, such as vehicle hybridization and battery electric drive, are also being implemented to meet the needs of trucks. The goals are essentially the same — reducing oil consumption (usually diesel fuel) and reducing emissions. And in the case of plug-in electric trucks, taking advantage of lower-cost electricity in place of volatilely priced diesel fuel.
Doubling the fuel efficiency of our nation’s trucking fleet is a key part of our Half the Oil plan for cutting our nation’s projected oil consumption in half in the next 20 years. Use of electrification technologies is poised to play a significant role in keeping our freight system moving while reducing oil consumption. Our newly released survey takes a look at the state of truck electrification technologies today and in what applications they are showing the most promise.
This blog post, the first in a series, provides an overview of the electrification technologies for medium- and heavy-duty trucks, while subsequent posts will take a look at how these technologies are being used in different applications — like port trucking, delivery truck fleets, and tractor-trailers.
Electric drivetrain technology
The vehicle drivetrain, the components responsible for moving the truck down the road, can incorporate electric motors and batteries or fuel cells to reduce or eliminate the need for an internal combustion engine. Many of the electric drivetrain technologies for trucks are similar to those being used or developed for passenger vehicles.
Hybrid-Electric (HEV): HEV trucks combine a conventional internal combustion engine (burning gasoline, diesel, biofuels, or alternatives such as natural gas) with an electric motor, batteries, and braking-energy capture (called regeneration). The internal combustion engine may be smaller than that of a standard truck because the electric motor provides added power. And hybrid-electric trucks can travel farther than their conventional diesel counterparts before refueling, while improving fuel economy and extending brake life. Hybrid-electric powertrains are the most mature electric-drive truck technology presently on the road.
Plug-in Hybrid-Electric (PHEV): PHEV trucks are similar to conventional hybrid-electric vehicles, but they have a larger battery pack. In addition to plugging in to recharge its batteries, the truck captures braking energy. The plug-in hybrid system may be designed to allow all-electric operation of the vehicle for a limited number of miles, or it may be intended primarily for providing power to accessories such as refrigeration equipment or tools at a job site.
Battery Electric (BEV): BEV trucks are propelled by an electric-drive motor that is powered by on-board batteries. These trucks, which have no internal combustion engine, must be plugged in to recharge their batteries. The range of a present-day BEV truck varies, depending on the load it carries and the capacity of its batteries.
Fuel Cell Electric (FCEV): These electric trucks are powered by a fuel cell, which converts hydrogen and air into electricity while emitting only water vapor. An FCEV also has a battery to store captured braking energy and provide additional power when necessary, as in an HEV. But fuel cell electric trucks refuel with hydrogen instead of plugging into an external source of electricity.
External Electric Power: As with light-rail trains or trolley cars, trucks could run on electricity that is supplied as needed, through over headlines or a connection in the roadway, instead of being stored in an on-board battery. These trucks would require dedicated lanes and be most viable on heavily traveled routes, but they would avoid range limitations and reduce battery costs. The trucks could also be fully electric or diesel electric hybrids, which would allow them to operate away from the dedicated roadway when required.
Electrification of vehicle systems and accessories
A large category of truck electrification technologies do not directly involve moving the truck, but can reduce fuel consumption by powering systems on the vehicle typically powered by the diesel or gasoline engine. Many of these electrification opportunities are unique to medium- and heavy-duty trucks.
Electrified Accessories: Truck components that are usually directly driven by the internal combustion engine via belts can be made electric. Air compressors, water pumps, air conditioners, heaters, power steering, and other systems common to trucks can operate more efficiently when decoupled from the engine.
Electric Auxiliary Power Units (APUs) and Refrigeration Units (Reefers): These are units that provide electric power to the truck when it is not running, such as providing electricity to the truck cab overnight while the driver sleeps to run heating and air conditioning systems, television, radios, computers, etc. Reefers specifically provide power for cargo refrigeration systems critical to many kinds of shipping, such as perishable food.
Electric Export Power or Power Take-Off (PTO): Trucks are often driven to a work site and then continue to run their engines to provide power to tools used at the work site. Export power or PTO systems supply the energy to run external equipment mounted on the truck: fans, lights, pumps and other work tools. Booms or lifts — which are traditionally powered by the truck hydraulic system via the internal combustion engine — can also be electrified. Such systems save fuel, but also provide the additional benefits of quieter operation and emissions reduction.
As you might imagine, some electrification strategies are better suited to certain applications — in the upcoming posts to this blog series, I’ll discuss some of the applications where these electrification technologies are currently being used or demonstrated. Be sure to check back in the coming weeks to learn about how truck electrification can save fuel and reduce emissions at ports, in urban delivery applications, and in big-rig trucks.
Support from UCS members make work like this possible. Will you join us? Help UCS advance independent science for a healthy environment and a safer world.