Analisis 3E (Energy, Exergy, and Environmental) pada Pemanfaatan Panas Gas Buang Pembangkit Listrik Tenaga Mesin Gas Sei Gelam Menggunakan Sistem Organic Rankine Cycle

Anthony Nathaniel, Dr. Ir. Hifni Mukhtar Ariyadi, S.T., M.Sc., IPM.

2026 | Tesis | S2 Teknik Mesin

Pemanfaatan panas gas buang pada pembangkit listrik berbasis mesin gas merupakan salah satu upaya untuk meningkatkan efisiensi energi dan mengurangi emisi tanpa menambah konsumsi bahan bakar. Pada PLTMG Sei Gelam, gas buang dari mesin gas masih memiliki temperatur tinggi sehingga berpotensi dimanfaatkan sebagai sumber panas untuk sistem Organic Rankine Cycle (ORC). Penelitian ini bertujuan untuk menganalisis pemanfaatan panas gas buang PLTMG Sei Gelam menggunakan sistem ORC berdasarkan pendekatan energi, eksergi, dan lingkungan, serta menentukan fluida kerja yang paling optimal di antara butane, pentane, hexane, dan toluene. 

Penelitian dilakukan melalui pemodelan dan simulasi sistem ORC menggunakan Aspen HYSYS. Sistem ORC yang dianalisis terdiri dari pompa, evaporator, turbin, dan kondensor. Kondisi sumber panas menggunakan temperatur gas buang masuk evaporator sebesar 380°C dengan laju aliran massa 17,28 kg/s. Kondisi kondensor ditetapkan pada temperatur udara pendingin masuk 30°C, dan udara pendingin keluar 40°C. Simulasi dilakukan pada dua skenario. Pada simulasi 1, temperatur outlet gas buang dijaga tetap sebesar 150°C dengan variasi temperatur evaporator 100–140°C. Pada simulasi 2, temperatur evaporator dijaga 15°C lebih rendah dari temperatur outlet gas buang dengan variasi temperatur evaporator 130–150°C. Hasil simulasi digunakan untuk menghitung daya bersih ORC, efisiensi termal, total exergy destruction, efisiensi eksergi, fuel saving, dan reduksi emisi CO?.

Hasil penelitian menunjukkan bahwa peningkatan temperatur evaporator mampu meningkatkan daya bersih ORC, efisiensi termal, dan efisiensi eksergi, serta menurunkan total exergy destruction. Toluene memberikan performa terbaik pada kedua skenario. Pada simulasi 1, toluene menghasilkan daya bersih 618,57 kW, efisiensi termal 15,68%, efisiensi eksergi 35,72%, total exergy destruction 1005,11 kW, fuel saving 0,01279 kg/kWh, dan reduksi emisi CO? 0,03333 kg CO?/kWh. Pada simulasi 2, toluene menghasilkan daya bersih 618,86 kW, efisiensi termal 16,74%, efisiensi eksergi 37,38%, total exergy destruction 936,70 kW, fuel saving 0,01281 kg/kWh, dan reduksi emisi CO? 0,03336 kg CO?/kWh. Berdasarkan analisis gabungan energi, eksergi, dan lingkungan, toluene merupakan fluida kerja paling optimal untuk sistem ORC pemanfaatan panas gas buang PLTMG Sei Gelam.

Exhaust gas waste heat utilization in gas engine power plants is one strategy to improve energy efficiency and reduce emissions without additional fuel consumption. At PLTMG Sei Gelam, the exhaust gas from the gas engine still has a relatively high temperature, making it potential as a heat source for an Organic Rankine Cycle (ORC) system. This study aims to analyze the utilization of exhaust gas waste heat from PLTMG Sei Gelam using an ORC system based on energy, exergy, and environmental approaches, and to determine the most optimal working fluid among butane, pentane, hexane, and toluene.

This study was conducted by modeling and simulating the ORC system using Aspen HYSYS. The ORC system analyzed in this study consists of a pump, evaporator, turbine, and condenser. The heat source condition was set using an exhaust gas inlet temperature of 380°C and a mass flow rate of 17.28 kg/s. The condenser condition was set at a working fluid condensation temperature of 50°C, a cooling air inlet temperature of 30°C, and a cooling air outlet temperature of 40°C. Two simulation scenarios were investigated. In Simulation 1, the exhaust gas outlet temperature was fixed at 150°C, while the evaporation temperature was varied from 100°C to 140°C. In Simulation 2, the evaporation temperature was maintained 15°C lower than the exhaust gas outlet temperature, with an evaporation temperature range of 130°C to 150°C. The simulation results were used to calculate ORC net power output, thermal efficiency, total exergy destruction, exergy efficiency, fuel saving, and CO? emission reduction.

The results show that increasing the evaporation temperature improves ORC net power output, thermal efficiency, and exergy efficiency, while reducing total exergy destruction. Toluene shows the best performance in both scenarios. In Simulation 1, toluene produces a net power output of 618.57 kW, thermal efficiency of 15.68%, exergy efficiency of 35.72%, total exergy destruction of 1005.11 kW, fuel saving of 0.01279 kg/kWh, and CO? emission reduction of 0.03333 kg CO?/kWh. In Simulation 2, toluene produces a net power output of 618.86 kW, thermal efficiency of 16.74%, exergy efficiency of 37.38%, total exergy destruction of 936.70 kW, fuel saving of 0.01281 kg/kWh, and CO? emission reduction of 0.03336 kg CO?/kWh. Based on the combined energy, exergy, and environmental analysis, toluene is the most optimal working fluid for the ORC waste heat recovery system at PLTMG Sei Gelam. 

Kata Kunci : Organic Rankine Cycle (ORC), Waste Heat Recovery (WHR), Aspen HYSYS, Energi, Eksergi, Lingkungan