Electric power conversion of exhaust waste heat recovery from gas turbine power plant using organic Rankine cycle

Abstract

In this study, an examination of a bottoming organic Rankine cycle for power conversion of the flue gases from a 5.75 MW gas turbine power plant was carried out. First law of thermodynamics was applied to the four major components of the system and simulated using developed MATLAB codes, while the thermo-physical properties at each state were supplied by engineering equation solver database. Five organic working fluids were compared based on selected performance indices. Toluene exhibited the best performance at full and partial electric generator load conditions with net power outputs of 532.70 kW at full load and 412.95 kW at partial load of 75%, while at 50% partial load, R245fa has the highest net power output of 469.09 kW. The cycle efficiency of the organic Rankine cycle system was improved from 34.67% at full load to 40.51% with exhaust gases from the power plant considered as sources of low-grade heat. R245fa showed the best adaptability at 50% partial load but at excessively high mass flow rate of 13.62 kg/s. It is evidently shown from this study that, waste heat recovery technologies can effectively generate about 16.8% of the nominal power of a gas turbine power plant and hence, reduce emissions per kW generated, suitable for sustainable environment as well as promoting energy security.