Organic Rankine Cycle Waste Heat Recovery for Passenger Hybrid Electric Vehicles

Abstract

Electrification of road transport is a major step to solve the air quality problem and general environmental impact caused by the still widespread use of fossil fuels. At the same time, energy efficiency in the transport sector must be improved as a steppingstone towards a more sustainable future. Multiple waste heat recovery technologies are being investigated for low-temperature waste heat recovery. One of the technologies that is being considered for vehicle application is the Organic Rankine Cycle (ORC). In this paper, the potential of ORC is discussed in detail for hybrid vehicle application. The modelling and testing of multiple systems such as the hybrid vehicle, engine, and ORC waste heat recovery are performed using the computational approach in GT-SUITE software environment correlated against available engine data. It was found that the maximum cycle efficiency achieved from the ORC system was 5.4% with 2.02 kW of delivered power recovered from the waste heat available. This led to 1.0% and 1.2% of fuel economy improvement in the New European Driving Cycle (NEDC) and Worldwide Harmonised Light Vehicle Test Procedure (WLTP) driving cycle test, respectively. From the driving cycle analysis, Hybrid Electric Vehicles (HEV) and ORC are operative in a different part of the driving cycle. This is because the entire propulsion power is provided by the HEV system, resulting in less engine operation in some part of the cycle for the ORC system to function. Apart from that, a brief economic analysis of ORC Waste Heat Recovery (WHR) is also performed in this paper and a comparative analysis is carried out for different waste heat recovery technologies for hybrid vehicle application.