Thermoeconomic Optimization Design of the ORC System Installed on a Light-Duty Vehicle for Waste Heat Recovery from Exhaust Heat

The organic Rankine cycle (ORC) has been widely studied to recover waste heat from internal combustion engines in commercial on-road vehicles. To achieve a cost-effective ORC, a trade-off between factors such as costs, power outputs, back pressure, and weight needs to be carefully worked out. However, the trade-off is still a huge challenge in engine waste heat recovery. In this study, a thermoeconomic optimization study of a vehicle-mounted ORC unit is proposed to recover waste heat from various exhaust gas conditions of a light-duty vehicle. The optimization is carried out for four organic working fluids with different critical temperatures, respectively. Under the investigated working fluids, the lower specific investment cost (SIC) and higher mean net output power (MEOP) of ORC can be achieved using the organic working fluid with higher critical temperature. The maximum mean net output power is obtained by taking RC490 as working fluid and the payback period (PB) is 3.01 years when the petrol is EUR 1.5 per liter. The proposed strategy is compared with a thermodynamic optimization method with MEOP as an optimized objective. It shows that the proposed strategy reached SIC results more economically. The importance of taking the ORC weight and the back pressure caused by ORC installation into consideration during the preliminary design phase is highlighted.

Automated summary

This study proposes a thermoeconomic optimization strategy to recover waste heat from various exhaust gas conditions of a light-duty vehicle. By selecting organic working fluids with higher critical temperatures, lower investment costs and higher net output power can be achieved. Compared with a thermodynamic optimization method with net output power as the optimized objective, the proposed strategy is more economically efficient.