Application of an organic rankine cylce [sic] cycle for waste heat recovery using the exhaust and coolant of a diesel generator

Abstract

A dual organic Rankine cycle (ORC) system in diesel engines was proposed and analyzed based on several working fluids. More than one third of the energy released by the combustion of the fuel is wasted in the exhaust heat and the cooling water, this is why it is important to recover such energy. In this report, a simple ORC configuration was adopted, and an analysis was carried out to select a suitable working fluid for both the high temperature loop and the low temperature loop. The choice was based on parameters such as the net power of the system (Pnet), the ORC efficiency ({cedil}{9D}{9C}{82} orc), the cycle efficiency ({cedil}{9D}{9C}{82} cycle) and the power ratio (Pnet/Pengine). In addition a basic heat exchanger design and an economic study were made in order to determine the feasibility of the system in hand. Results show that dodecane and toluene (heavy hydrocarbons) deliver the highest net power and efficiency values for the high temperature loop, ranging from 14.54% to 16.41% ORC efficiency, and from 11.92% to 13.48% cycle efficiency, and 98.69 kW to 111.34 kW net output power; respectively. Meanwhile, R134a and R410a were the promising working fluids for the low temperature loop with an ORC efficiency ranging from 7.73% to 8.58%, and a cycle efficiency ranging from 6.71% to 7.08%, and net power ranging from 28.58 kW to 31.7 kW. The payback period of the dual system was found to be in the range of 11 years for 12 hours of operation per day. The payback period of the HTL applied alone was found to be in the range of 7.5 years to 8 years for the same hours of operation per day.