Proposal for a Vehicle-Level Test Procedure to Measure Air Conditioning Fuel Use

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Real world. To measure real world fuel use, the control should not be defined and the A/C system should be allowed run as designed, with vehicle and climate control design decisions impacting A/C fuel use. A soak and cooldown would be required for this approach.

Rugh recommends vehicle-level A/C fuel use test procedure that includes:

• Soaking the vehicle with solar lamps that meet SCO3 requirements or with an alternative heating method such as portable electric heaters.

• Operating vehicle over repeated drive cycles or at a constant speed until steady-state cabin air temperature is attained.

• Running A/C off and A/C on tests to calculate a cooldown and steady-state A/C fuel use.

The procedure measures the approximate real-world A/C fuel use. Data are gathered for both cooldown and steady-state passenger compartment thermal conditions. The impact of thermal load reduction technologies can be measured using this procedure. This procedure can be used to characterize the impact of energy use for climate control on advanced vehicles as well as conventional vehicles.

While this paper focused on passenger compartment cooling, measuring the impact of passenger compartment heating on vehicles with electric powertrains is also critical. Thermal preheating of the passenger compartment using grid power can increase the electric range of PHEVs and EVs in the winter in addition to precooling in the summer.

—Rugh, 2010

Resources

• J. Rugh (2010) Proposal for a Vehicle Level Test Procedure to Measure Air Conditioning Fuel Use. (Preprint) (NREL/CP-540-47273)