Cooling fans located behind the radiator draw cool air across the radiator and into the engine compartment. The traditional fans are simple on or off devices. In its simplest form, the vehicle cooling system consists of an engine-driven water pump that moves coolant through a series of passages to keep the engine components cool from the extreme heat generated through combustion. This heat is then rejected to the atmosphere through the vehicle radiator/cooling fan system.
There are a number of options available in the marketplace that help reduce fuel consumption due to the cooling fan. They include 2-speed/modulating fan drives and fully modulating fan drives. Depending on the application, savings for a 2-speed/modulating cooling fan would be perhaps one-third of the fuel burned due to fan operation.
Some fully modulating fans are available to further reduce the fuel consumption during fan-on operation. The control system for these fans can vary the speed from 0 to full on and add only enough fan speed to meet the necessary cooling requirements of the vehicle.
It is important to note that cooling fans typically consume 0.2–0.4% of the truck’s fuel to perform their function, so any fuel economy gains from new technology will be modest.
The study team developed a Confidence Matrix, an OEM Availability Matrix and an Engine-driven Accessories Power Use Chart to assist fleets. The Confidence Matrix is designed to inform fleets of the study team’s confidence in the technology being studied vs. the payback the fleet should expect to receive from the technology. Technologies in the top right of the matrix have a short payback, usually thanks to their low upfront cost, and moreover are found to have enough performance data that fleets can be highly confident in those short payback times, usually because the technology is more mature or otherwise has a more substantial track record of results. The OEM Availability Matrix shows the current availability (as of March 2017) of these engine-drive accessories at the various truck builders. The Engine-driven Accessories Power Use Chart shows the various places the energy from fuel is used in a Class 8 truck.