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NREL - National Renewable Energy Laboratory
About NRELEnergy AnalysisScience and TechnologyTechnology TransferTechnology DeploymentEnergy Systems Integration

About the Project

The Vehicle Technologies Office supports the development of technologies that will achieve transportation energy security through a U.S. highway vehicle fleet that consists of affordable, full-function cars and trucks that are free from petroleum dependence and harmful emissions, without sacrificing mobility, safety, and vehicle choice.

With support from the Department of Energy's Vehicle Technologies Office, NREL's Vehicle Ancillary Loads Reduction Project (VALR) aims to help reduce the use of petroleum in the United States. Ancillary systems affect not only the fuel economy of internal combustion and gasoline-hybrid engines of the present day, they can be expected to have the same effect on fuel cell power sources of the future.

The largest ancillary load is the air-conditioning system when it is operating. (Typically it imposes a mechanical load of 1.5-3.5 kilowatts on a light-duty vehicle engine.) About 7 billion gallons of fuel, equivalent to about 5.5% of total national light-duty vehicle fuel use, are used annually to cool and dehumidify light-duty vehicles. Current air-conditioning systems are not optimized to reduce fuel use and fail to use waste heat energy being rejected from the engine. Much of the energy produced by an engine is rejected as low-grade waste heat. That's a potentially significant source of energy for air-conditioning systems.

Our goal at NREL is to help the automotive industry reduce the fuel used for air conditioning. NREL is investigating techniques to reduce the peak soak temperature, which allows the air conditioning system size to be reduced. We are also looking at improved air delivery systems and alternative methods to cool the passenger compartment, which will reduce the power requirements of a climate control system.

As we develop and test solutions to reduce fuel use of ancillary loads, an emphasis is put on maintaining or improving occupant comfort. Our focus is on complete system integrated modeling, concentrating on air conditioning and emissions. Our approach simulates climate control and ancillary systems to determine their impact on vehicle fuel economy, tailpipe emissions, and the occupants' response to the thermal environment.

Learn more about NREL's research and development efforts focused on using a systems approach to improve vehicle ancillary loads.