Quantifying energy-related CO2 emissions reduction potential of a proposed organic rankine cycle system for exhaust heat recovery application in commercial trucks

Abstract

The transportation sector is presently among the most deciding sectors in fossil fuel use and CO₂ emissions. More than 30% of the fuel energy content is released to the environment in the form of exhaust heat and recuperating part of this heat has the potential of achieving reductions in the adverse effects of CO₂ emissions on our environment in tandem with efficiency improvement of the internal combustion engine (ICE). This study assesses the feasibility of incorporating a proposed organic Rankine cycle (ORC)-based exhaust heat recovery (EHR) system in a highway truck for recovering exhaust heat from the 206-kW diesel engine and further quantifies the energy-related CO₂ reduction potential of the proposed module. A simple ORC system layout with recuperating is considered due to additional weight concerns that could negate the recovery goal of the study. The model uses R245fa as a working fluid because of its application in ICEs for EHR. A preliminary result of the proposed model achieved electrical power outputs of 0.42–3.48 kW, thermal efficiencies of 1.96–6.36%, and up to 4% reduction in fuel consumption, all measured as the primary performance indicators of the system when running at truck speeds of 66–119 km/hr. The model further achieved up to 4,767kgCO₂ reduction in carbon emissions, representing a 4% reduction in the CO₂ emission of a typical highway truck engine. The exergo-economic analysis experienced up to 17.28 kW of exergy destruction in the evaporator and 0.89 kW as the minimum exergy destruction realized in the condenser. The highest cost rate of exergy destruction of 142 £/yr observed in the evaporator.