Sweden’s Volvo Trucks is trying to squeeze more fuel economy out of modern-day big rigs in Europe by using an “autopilot” style system in an attempt to control and capture the kinetic energy created when using a truck’s brakes—helping boost fuel economy by 5%. Dubbed “I-See,” this new system aims to harness such kinetic energy to aid in truck propulsion, explains Anders Eriksson, who headed up Volvo’s development group for this autopilot system.
That kinetic energy is the mechanical work needed to reduce an object’s speed to zero, he says, meaning that when an object in motion is slowed down, its energy gets transformed into some other form of energy. Thus, when a truck hits the brakes, its kinetic energy is converted into heat, Eriksson notes.
Volvo’s I-See system aims to harness the kinetic energy produced by a truck’s brakes to help “push” the vehicle up hills, then use that same energy on downhill gradients for acceleration—all without tapping the engine. Eriksson says Volvo’s tests so far show that using kinetic energy in this manner can reduce fuel consumption by 5%. For a truck in normal operation in Europe covering about 86,992 mi. annually, fuel savings should total a little over 264 gals. per year, he says.
“If kinetic energy can be exploited to a greater extent, it may help cut fuel consumption,” Eriksson points out. “This will benefit both the environment and the industry’s economy, something that is very important today as fuel costs are becoming an increasingly heavy burden on many haulage firms.”
This is how it works: The I-See controller gets linked to the transmission’s tilt sensor, obtaining information about the road topography digitally and then making gear changes accordingly. Basically, I-See carries out six different operations to tap into a truck’s kinetic energy. For instance, I-See accelerates up hills, remains in a high gear for as long as possible, and then “freewheels” on descents to exploit the truck’s weight as a propulsion motor. It also requires use of the cruise control, and Volvo’s data indicates that on average European truck drivers use cruise control about half the time, Eriksson says.
“I-See works best in undulating terrain,” he notes. “With moderately long and steep slopes, I-See ensures that you can freewheel for long distances without using the engine. It is this freewheeling capability that makes the system special. When the truck rolls freely, virtually no fuel is used.” But in order to successfully freewheel, a whole lot of data is required, he stresses. “It imposes high demands on precision,” Eriksson says. “For instance, you have to know whether your speed will drop or increase over the next stretch of road. A gradient of just a few percent can be the decisive factor.”
Air resistance and truck weight are other factors that make a difference. All told, the system has to keep track of and process a lot of information, he explains.
