Abstract
Keywords - Air Conditioning, Stop-start, Cold storage, Phase change material, A/C compressor.
Abstract - The stop-start function strongly contributes to lower the fuel consumption of petrol vehicles. Its drawback is air conditioning disruption, since this is mechanically driven by the engine. Therefore, a choice must be made between stop-start advantages (lower fuel consumption, pollutant emissions and noise) and thermal comfort. Keeping all the above benefits calls for modified air conditioning systems.
An analysis of requirements reveals that the system specification should target maintaining of thermal comfort for 45 seconds at an ambient temperature of 35°C, which covers more than 90% of real conditions.
Different solutions have been explored, including electrical air conditioning. This has proven to be adaptable to highly electrified cars, namely from 6kW under 42V, but not in the initial 14V stop-start context.
A comparison between all reviewed concepts has shown that thermal storage is the right solution. It is better than electrical concepts in terms of efficiency and weight. Its principle is cold storage in a phase change material during normal A/C operation, and release at engine standstill.
The system that has been developed consists of two main parts: the HVAC with cold storage and the adapted control strategy.
Wind tunnel tests have been performed to demonstrate the benefits of the new system.
Compared to the normal one, it cancels temperature peaks experienced at engine standstill, and it provides a lower cabin temperature during the whole driving cycle.