Techno-economic studies of low GWP-organic Rankine cycle for low-level geothermal waste heat utilization in Remote Island of Indonesia

• Published in: Case studies in thermal engineering 2025-01, Vol.65, p.105385, Article 105385
• Main Authors: Tanbar, Fefria, Febriyanto, Rusdi, Ariyadi, Hifni Mukhtar, Nugraha, Ariyana Dwiputra, Simaremare, Arionmaro Asi, Supriyanto, Eko, Triani, Meiri, Muflikhun, Muhammad Akhsin
• Format: Article
• Language: English
• Subjects: Geothermal; Organic Rankine Cycle; Technoeconomic; Thermal efficiency
• ISSN: 2214-157X; 2214-157X
• DOI: 10.1016/j.csite.2024.105385

With global decarbonization trends, the energy supply challenge persists, especially in archipelagic nations like Indonesia. The Ulumbu Geothermal Power Plant at Flores Island of Indonesia currently uses a type of back pressure where the expanded steam is discharged directly to the atmosphere at a pressure of 0.98 bar and a temperature of 98.7 °C. This steam could be harnessed to generate electrical energy using Organic Rankine Cycle system. This study thermodynamically and economically assessed two ORC systems: Binary Cycle-Organic Rankine Cycle (BC-ORC) and Recuperator (BC-ORCR), both using low global warming potential (GWP) working fluids of R1233zd (E), R1224yd (Z), R1234ze (Z), R1234ze (E), R1243zf, and R1234yf, paired with air- and water-cooled condensers. The results indicate that the BC-ORCR system with a water-cooled condenser using R1233zd (E) as the working fluid achieved the highest net output power value and system efficiency of 2213 kW and 10.14 %, respectively. This could support up to 65 % of the electricity load of the GI Ulumbu and GI Ruteng substations. Economically, this system also emerged as the most favorable option, offering the highest production capacity, with a TL Sales Target of 16,476,847 USD, a net present value (NPV) of 3,982,761 USD and a Payback Period of 9.39 years, outperforming other systems in the analysis.