Thermodynamic, economic, and carbon emission evaluation of various Organic Rankine cycle configurations for maximizing waste heat recovery potential

Abstract

Waste heat recovery using the Organic Rankine Cycle (ORC) enhances energy efficiency, lowers emissions, and reduces costs. This study evaluates ORC systems for high-temperature waste heat recovery (515.14 °C) using DWSIM software. Various ORC configurations, including simple ORC (sORC), series ORC (S-ORC), single-stage regenerative ORC (SR-ORC), double-stage regenerative ORC (DR-ORC), and multi-evaporating pressure ORC (ME-ORC), were analyzed with different working fluids, including Toluene, Dodecane, Benzene, and Cyclopentane. Toluene was identified as the best working fluid, achieving a thermal efficiency of 24.33 % and a net power output of 1,839.66 kW in the sORC. The S-ORC demonstrated superior performance, delivering 3,679.32 kW of net power at the same efficiency. A parametric study examined the effects of operating pressure, exhaust gas temperature, and mass flow rate on efficiency. Results showed thermal efficiency peaked at 40.08 bar, with optimal performance at an exhaust gas temperature of 520 °C and a mass flow rate of 44.5 kg/s. Exergy analysis identified the evaporator as the main source of inefficiency, highlighting opportunities for improvement to boost overall system efficiency. Economically, the S-ORC achieved a Net Present Value (NPV) of 3.98 million EUR, a payback period of 5.75 years, and an Internal Rate of Return (IRR) of 12.66 %. It also reduced CO₂ emissions by 12,971.36 metric tons annually, translating to 1.04 million EUR in revenue through carbon credit trading under the EU ETS. In summary, the S-ORC configuration offers the best balance of thermodynamic, economic, and environmental benefits for industrial waste heat recovery systems.