Analysis of environmental and economic benefits of integrated Exhaust Energy Recovery (EER) for vehicles

Differing from those traditional vehicle exhaust heat recovery systems which just provided thermal energy directly for cabin warming, integrated Exhaust Energy Recovery (EER) which is researched and developed mainly in recent years aims to convert exhaust thermal energy to mechanical or electric energy for increasing the total thermal efficiency and the total power of powertrain. In the study presented in this paper, an analytic model was built for examining the environmental and economic benefits of integrated EER systems. Then the improvement on the total powertrain efficiency and net reduction of CO₂ emissions were investigated, in terms of the average vehicle used in the UK. Results show that, for light duty vehicles fitted with thermal cycle EER system, the cost increase could be paid back in 10.1years and CO₂ emission could be paid back in just 1.9years, compared to Hybrid Electric Vehicle's (HEV's) 11.9years and 1.4years for cost and CO₂ emission, respectively. When the annual fuel price increase is considered, the cost pay-back is reduced to 8.1years for EER vehicles and 8.9years for HEVs. Higher mileage vehicles will have more obvious advantage for fitting EER system. When doubled annual mileage is considered, EER system can reduce the cost and CO₂ emission pay-back times to 2.7years and 0.6years, compared to HEV's 8.5 and 2.7years, respectively.