Analysis on the waste heat recovery in a light duty vehicle

Waste heat recovery through organic Rankine cycles can improve the efficiency of automotive engines. However, the integration on board vehicle of a new auxiliary system must be evaluated in all its aspects. This paper investigates the potential of an ORC-based heat recovery system sized for a light duty vehicle driven by a SI engine. Louvered heat exchangers and a scroll expander are the main components of the system. The integrated system has been modelled considering the vehicle traveling at different cruising speeds in two operational scenarios. Parametric analyzes have been carried out in order to investigate the influence of the system control parameters. Subsequently, the impact of the recovery system installation on vehicle performance has been also evaluated. Results show that the recovery system operation must be carefully adjusted according to the engine operating point. In optimal conditions, almost 6% of the heat carried by the exhaust gases can be recovered on average. That increases of about 3.5% the overall power delivered by the powertrain. Regarding the integration on board vehicle, for each driving scenario, the powertrain fuel consumption increases, but the overall energy balance improves.