Accurate evaluation of vehicles' transient total power
requirement helps achieving further improvements in vehicle fuel
efficiency. When operated, the air-conditioning (A/C) system is the
largest auxiliary load on a vehicle, therefore accurate evaluation
of the load it places on the vehicle's engine and/or energy
storage system is especially important. Vehicle simulation models,
such as "Autonomie," have been used by OEMs to evaluate
vehicles' energy performance. However, the load from the A/C
system on the engine or on the energy storage system has not always
been modeled in sufficient detail. A transient A/C simulation tool
incorporated into vehicle simulation models would also provide a
tool for developing more efficient A/C systems through a thorough
consideration of the transient A/C system performance. The dynamic
system simulation software MATLAB/Simulink® is frequently used by
vehicle controls engineers to develop new and more efficient
vehicle energy system controls. A MATLAB/Simulink-based transient
A/C system simulation model is easier to incorporate into
MATLAB/Simulink-based vehicle simulation software; therefore, the
availability of a transient A/C system simulation tool developed in
the MATLAB/Simulink platform is important.
NREL has recently developed an A/C simulation tool to address
these needs. This paper describes in detail the modeling methods
used for this new simulation tool. Comparison with measured data is
provided to demonstrate the validity of the model. The agreement
between simulation and measurement was shown to be good on both the
component and system level. The capabilities of the model are also
demonstrated by the example of simulating the SC03 cycle.
