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HEVs idle their engine during the stops to meet the cooling loads. However, idling reduces fuel economy and increases emissions and engine wear. The paper focuses on exploring alternative strategies for air conditioning the HEV during stop times. Simulation analyses are used to identify fundamental differences and new technology tradeoffs encountered in HEVs. An analysis of cooling loads on a car under typical weather and driving conditions is combined with efficiency estimates for an advanced a/c system to compare different cooling strategies in terms of fuel usage and overall system COP. Options considered include belt-and electrically-driven compressors, with thermal and electrical storage technologies. The results of this parametric analysis narrow the range of cooling strategies to be considered for detailed analysis and prototype testing.

This paper presents a dynamic model of a transcritical air-conditioning system, specifically suited for multivariable controller design. The physically-based model retains sufficient detail to accurately predict system dynamic response while also being simple enough to be of value in determining appropriate control strategies. The control focus would be quasi-steady transitions between operating states by modulating flow rates of both air and refrigerant to meet changing constraints on capacity, efficiency, noise, etc. The model structure is highly modular, accommodating various system configurations and component types. The modeling results are programmed as a library of components for use in Simulink, a graphical programming package.