ITB Graduate School Conference

Harnessing the Indonesia’s Banda Sea Thermal Resources Through Comprehensive OTEC Potential Study

Reza Kurniawan Harnandika, Kevin Sahat Parsaulian, Muhammad Rais Abdillah — Wed, 29 Oct 2025 00:00:00 +0800

The Banda Sea, located in Indonesia's equatorial region, exhibits significant potential for Ocean Thermal Energy Conversion (OTEC) due to its deep-water layers and consistent surface temperatures. This study evaluates the OTEC feasibility in the Banda Sea by analyzing monthly and seasonal sea surface temperature (SST) data from 2015, obtained from Copernicus ERA5 reanalysis. Spatial and vertical temperature profiles were processed using Ocean Data View (ODV) to identify mixed-layer, thermocline, and deep-layer characteristics. Results indicate an average temperature gradient (ΔT) of 22.7°C between the surface (29–30°C) and 600–700 m depth (5–7°C), meeting the minimum ΔT requirement (20°C) for OTEC. The Carnot efficiency (η) reached 77%, surpassing the 70% benchmark for viable OTEC systems. However, long-term time-series analysis data from 2005 -2017 revealed intermittent periods where ΔT fell below 20°C, likely due to seasonal upwelling, El Niño-Southern Oscillation (ENSO) events, or anomalous ocean mixing. Those are posing reliability challenges for continuous power generation. While the Banda Sea’s thermal resources are promising, operational intermittency suggests the need for hybrid energy systems to ensure grid stability. This study provides critical insights for OTEC deployment in tropical regions, balancing renewable energy potential with technical constraints.

Projected Rainfall Trends and Variability in the Mrica Catchment under the SSP5-8.5 Scenario

Wed, 29 Oct 2025 00:00:00 +0800

This study analyzes changes in rainfall, inflow discharge, and electricity production at PLTA Mrica using historical data (1985–2014) from CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) and six global climate models (GCMs) under CMIP6 (Coupled Model Intercomparison Project Phase 6). Future projections are based on the SSP5-8.5 (Shared Socioeconomic Pathway 5 – fossil-fueled development) scenario to represent a worst-case pathway, enabling assessment of maximum potential climate impacts on hydropower reliability [2] scenario for the period 2021–2100. A delta-based statistical downscaling method is applied to produce high-resolution rainfall projections. This method is deterministic in nature; it applies a fixed anomaly (delta) between future and historical climatologies onto observed datasets, without simulating transient atmospheric processes as done in prognostic models. It is computationally efficient and widely used for impact studies where capturing long-term mean changes is prioritized over day-to-day weather variability [2][3]. The results indicate an increase in rainfall during the wet season and a significant decline during the dry season, particularly from January to March, with projected rises of up to +2.5 mm/day, or approximately +30–40%, compared to the historical baseline. Conversely, the dry season (June–September) is projected to experience a decline of up to 1.5 mm/day, equivalent to a reduction of 25–40%, depending on the month and future time slice. Historical data indicate that monthly rainfall of at least 100–120 mm is generally required to sustain sufficient reservoir inflow for optimal electricity generation at PLTA Mrica, especially during the dry season. Variability in rainfall, particularly prolonged dry spells or delayed wet season onset, can lead to inflow shortages, reducing turbine operation hours and ultimately affecting annual energy output. This study highlights the importance of using climate data such as projected rainfall thresholds and variability to guide reservoir operations, optimize electricity production, and reduce risks during dry periods. Integrating such information supports more adaptive and resilient hydropower planning under future climate uncertainty.

Optimization Strategy for Power Plant Asset Management Using Reliability Analysis and Life Cycle Cost: Case Study of Steam-Dominated Geothermal Power Plant Unit 1 at PT RST

Adam Kusuma Wardana, Raden Dadan Ramdan, M. Ali Ashat — Wed, 29 Oct 2025 00:00:00 +0800

PT RST is one of the largest power generation companies in Southeast Asia, with a total capacity of 21.08 GW. One of its units, the Steam-Dominated Geothermal Power Plant Unit 1, has been operating for over 40 years, presenting increasing challenges in maintaining reliability and cost efficiency. The aging condition of critical equipment in this facility necessitates a strategic asset management approach to support informed decision-making in maintenance and replacement planning.

This study integrates reliability analysis with economic life assessment to develop an optimized strategy for equipment replacement. The Equivalent Uniform Annual Cost (EUAC) is used to determine the most economical service life of each equipment unit, while the reliability index is calculated using a Weibull-based Non-Homogeneous Poisson Process (NHPP) model via AeROS software. Key input variables include equipment failure history, repair time, downtime, acquisition cost, and operation and maintenance (O&M) costs.

By combining cost and reliability indicators, a structured equipment replacement strategy is formulated, classifying assets into four categories: retain, prepare for replacement, immediate analysis required, and further evaluation. This integrated approach supports data-driven asset management decisions and contributes to improved performance and reduced electricity production costs at Steam-Dominated Geothermal Power Plant Unit 1

Evaluation of Performance Salak Geothermal Power Plant #1 based on Exergy Analysis

Anton Hermanto, Willy Ardiansyah — Wed, 29 Oct 2025 00:00:00 +0800

This study presents an exergy analysis of the Mount Salak Geothermal Power Plant Unit #1 to evaluate its thermodynamic performance and identify inefficiencies. Exergy analysis is employed to assess operational efficiency by considering both energy quantity and quality. Real operational data and CycleTempo simulation software were used to analyze key components, including the turbine, condenser, and gas removal system. Results indicate that the overall exergy efficiency of the system is 66.88%, with the highest exergy losses occurring in the turbine (13.76%) and condenser (10.01%). Two scenarios were simulated to improve performance: (1) adjusting turbine inlet pressure to 7.02 bara and (2) optimizing condenser pressure to 0.10 bara. These adjustments resulted in an increase in overall exergy efficiency to 68.81% and improved power output. The study emphasizes the importance of maintaining optimal operational parameters and addressing component inefficiencies to enhance power generation and extend the plant's operational life. It also highlights the value of exergy analysis as a tool for identifying potential improvements, offering valuable insights for operators seeking to optimize efficiency, reduce energy losses, and ensure the long-term sustainability of geothermal power plants.

The Impact of Local Temperature Variations on the Efficiency and Power Output of Solar Power Plants in Lombok Island

Wed, 29 Oct 2025 00:00:00 +0800

Indonesia, located in the equatorial region, possesses vast solar energy potential reaching up to 200,000 MW. However, its utilization remains significantly low at only 0.08% of the total potential. In remote regions like Lombok Island, solar power plants serve as a strategic solution for clean and sustainable electricity, especially where access to fossil fuels is limited and costly. This study investigates the impact of local temperature variation on the efficiency and power output of PLTS in Lombok, a tropical region with high solar irradiance (4–6 kWh/m²/day) and elevated daytime temperatures (26–33°C). Using temperature and solar radiation data from 2019 to 2024, along with electricity output records from three major Solar Power Plant facilities (Pringgabaya, Selong, Sengkol, each 7 MWp), the research applies statistical correlation and regression modeling to quantify the relationships among temperature, irradiance, and energy output. The findings are expected to reveal a negative correlation between increased ambient temperature and photovoltaic efficiency due to rising electrical resistance in solar cells. Conversely, higher irradiance generally enhances power output, although its benefits may be offset by excessive heat. This study also incorporates Dipole Mode Index (DMI) analysis to understand the regional climatic influence on local temperature trends. DMI is selected due to its direct representation of the Indian Ocean Dipole (IOD) phenomenon, which significantly affects weather patterns, sea surface temperature, and consequently, regional thermal variations in the Indonesian maritime continent. By focusing on DMI, this research captures a dominant mode of interannual climate variability that is particularly relevant to temperature fluctuations in Lombok. Furthermore, the study provides quantitative results for the Lombok region, including the percentage impact of each variable on power production. It also analyzes the seasonal and intraseasonal variations of temperature and solar radiation to identify periods of optimal and suboptimal solar plant performance. These findings are expected to support predictive energy output modeling and inform technical recommendations such as thermal mitigation strategies and material optimization for improving solar power performance in tropical environments. These insights are crucial for supporting Indonesia’s energy transition and achieving greater integration of renewable sources in its national energy mix.

Numerical Modeling Of A High-Temperature Geothermal System In A Volcanic Complex: Case Study From The Kepahiang Field, Indonesia

Wed, 29 Oct 2025 00:00:00 +0800

The Kepahiang Geothermal Working Area, located in Bengkulu Province, Indonesia, is a high-elevation, high-enthalpy geothermal system characterized by fumaroles, solfataras, and steaming grounds around Mount Kaba and Sempiang. This study aims to update the conceptual model using integrated geoscience data and numerical simulation. Three main reservoirs were identified: Kaba (up to 370°C), Sempiang (240–300°C), and Grojogan Sewu (200–250°C), overlain by a cap rock ranging from 500 to 1,500 meters thick. A numerical model using VOLSUNG software was developed, covering the natural-state conditions and calibrated with data from the KPH-01 temperature gradient well (452 m depth) and geothermometer surface manifestations. The model results align well with field observations, indicating upflow zones near Sempiang and lateral outflows toward Grojogan Sewu. However, further validation using deep exploration wells is necessary to confirm reservoir geometry and productivity. The study concludes that Kepahiang hosts a promising liquid-dominated geothermal system with structurally controlled fluid flow. It is recommended to drill at least three exploration wells in key upflow zones, particularly around Sempiang to support production planning

Analysis of MetOcean Changes in the Coastal Waters Surrounding Paiton Coal-Fired Power Plant, East Java

Wed, 29 Oct 2025 00:00:00 +0800

The Paiton Coal-Fired Power Plant (CFPP), located on the northern coast of East Java, Indonesia, has been operational since 1994 and is suspected of influencing the surrounding coastal environment. This study analyzes changes in MetOcean parameters, including sea surface temperature (SST), wind patterns, and wave characteristics, in the Paiton coastal area between 1993 and 2024. Results indicate a clear seasonal variation in SST following the Indonesian monsoon cycle, with warmer temperatures during the rainy season and lower temperatures during the dry season due to coastal upwelling. A warming trend of approximately 0.0178°C per year has been identified, with additional increases possibly linked to thermal discharges from the plant's cooling system. Wind analysis shows a dominant flow from the east to southeast during the dry season, with speeds of 2–3 m/s, influencing evaporation rates and corrosion risks for infrastructure. Wave data reveal that most waves are locally generated, with heights between 0.2 and 0.4 meters, and only rare occurrences of waves exceeding 0.4 meters. These oceanographic dynamics collectively affect the operational efficiency and cooling performance of the CFPP. Continuous oceanographic monitoring and integrated environmental management are essential to support the sustainable operation and long-term resilience of coastal power generation facilities.

Feasibility Study of Integrating Green Hydrogen Plant with Geothermal Power Plants in Renewable Energy Microgrid

Wed, 29 Oct 2025 00:00:00 +0800

In alignment with Indonesia’s national energy transition goals, PT PLN (Persero) has initiated a de-dieselization program aimed at replacing diesel generators with renewable energy sources, such as photovoltaic (PV) and geothermal power, as outlined in the Electricity Supply Business Plan (RUPTL 2021). This study investigates the economic feasibility of the proposed 10 MW Atadei Geothermal Power Plant (GPP), located within the Lembata microgrid in East Nusa Tenggara, a system currently challenged by increased PV penetration and the resulting “duck curve” phenomenon. This condition significantly reduces net load during midday, thereby constraining the minimum operational thresholds of geothermal generation. Two operational scenarios are evaluated: (1) reduced-capacity baseload operation, and (2) the integration of green hydrogen production to utilize excess power. Based on a post-dispatch average capacity factor of 77%, approximately 13% of geothermal generation remains unutilized. Incorporating green hydrogen production with Proton Electrolyzer Membrane (PEM) as a demand-response strategy enhances system flexibility, resulting in a net present value (NPV) of USD 0.16 million and an internal rate of return (IRR) of 12.5%. To maintain project viability, a minimum hydrogen price of USD 6.9 per kilogram is required. The findings underscore the potential of flexible, demand-side applications—particularly hydrogen production—to support both operational reliability and economic sustainability in isolated renewable energy systems

A Review of The Final Turbine Inspection Report at the Lahendong Geothermal Power Plant

Reza Muhamad, Raden Dadan Ramdan — Wed, 29 Oct 2025 00:00:00 +0800

In this paper, the author employs a review method based on the results of a turbine inspection conducted by the maintenance service unit of PT Indonesia Power in 2023. The review presents a comprehensive evaluation of the condition of rotor blades in the steam turbine of the Lahendong Unit 1 Geothermal Power Plant. The objective of this study is to assess the material integrity through a series of non-destructive testing (NDT) methods, as part of the Remaining Life Assesment (RLA) of the turbine components. The inspection included visual inspection, magnetic particle inspection (MPI), ultrasonic flaw testing, penetrant testing, in-situ metallography, hardness testing, as well as XRD and XRF analysis. Significant findings include pitting corrosion, rubbing, material loss, water droplet erosion, and cracks in several rotor stages. Microstructural analysis revealed the presence of martensite, retained austenite, and carbides, with indications of cavities along grain boundaries that have progressed to directional oriented cavities and even microcracks. Based on Neubauer’s classification, several blades have reached stage 4 and 5 (end of life), indicating substantial degradation. These findings provide a strong technical basis for predictive maintenance strategies and re-blading decisions in the next overhaul.

The Development of Vendor Performance Evaluation and Strategies Design Systems Using Fuzzy Best Worst Method (FBWM) and TODIM in PT PLN (Persero)

Dania Sita Ardhiana Reswari, Yosi Agustina Hidayat — Wed, 29 Oct 2025 00:00:00 +0800

In realizing its vision and mission, as well as in supporting electricity national fulfillment, PT PLN (Persero) is necessary to be supported by supply chain management, ranging from procurement to delivery activities. In the procurement process, one of the important aspects is the management of vendors, including the evaluation of their performance, to enable PT PLN (Persero) in selecting good performance vendors and determining appropriate development strategies for its vendor improvement. This paper discusses the development of vendor performance evaluation system by setting the criteria, sub criteria, and by a fuzzy multi-criteria decision making (MCDM). In the other hand, fuzzy best-worst method (BWM) is to determine importance weights of the evaluation criteria, while TODIM to asses vendor performance and subsequently to determine vendor development strategies based on its performance. Finally, this study is to develop framework in vendor performance evaluation system and strategies design.

Development of Vendor Selection Criteria and Its Relationship using Delphi Method, Best Worst Method (BWM) and Structural Equation Modeling-Partial Least Squares (SEM-PLS) in PT PLN (Persero) UPT Durikosambi

Anella Richi, Yosi Agustina Hidayat — Wed, 29 Oct 2025 00:00:00 +0800

An accurate vendor selection process is a critical factor in ensuring the successful execution of construction projects and asset maintenance within PT PLN UPT Durikosambi. This study aims to develop a more objective vendor selection framework using a Multi-Criteria Decision Making (MCDM) approach combined with statistical validation. The research process includes a preliminary study, development of conceptual and operational models, data collection, and analysis and interpretation. Criteria and subcriteria were identified based on existing conditions and relevant literature, then validated through the Delphi method to achieve expert consensus. The weighting of criteria was determined using the Best-Worst Method (BWM), recognized for its high consistency and efficiency in comparisons. The relationships among criteria were further analyzed using the Structural Equation Modeling-Partial Least Squares (SEM-PLS) approach to identify significant influences among variables. The findings of this research are expected to provide a strategic and adaptive foundation for decision-making in the procurement of construction services within PLN units or similar public infrastructure agencies.

Greenhouse Heating Using Geothermal Brine: A Case Study from Dieng

Rezha Aji Pradana, Willy Adriansyah — Wed, 29 Oct 2025 00:00:00 +0800

This study examines the feasibility of utilizing geothermal brine from the Dieng Geothermal Field to support greenhouse heating for highland potato cultivation. A thermodynamic simulation was conducted to estimate the heat load, mass flow, and heat exchanger requirements for a 70 m² greenhouse. Results indicate that a brine flow rate of 0.073 kg/s and a secondary fluid flow of 0.056 kg/s are sufficient to maintain internal temperatures of 18–21°C. The system requires only 0.26 m² of heat exchanger surface area, making it compact and scalable. The use of low-grade geothermal heat enhances the overall thermal efficiency of the plant and reduces dependency on fossil fuels. The proposed system offers agronomic benefits, including improved tuber quality and yield (estimated 15–25%) during cold seasons. Environmental advantages include reduced emissions and optimized energy use. Challenges such as silica scaling and initial investment are acknowledged, with recommendations for mitigation. This research highlights a sustainable pathway for integrating geothermal resources into protected agriculture, especially in highland regions.

Inventory Management Efficiency Strategy at UID Banten: A Study of Vendor Managed Inventory (VMI)

Argetra Halleiny, Darwin — Wed, 29 Oct 2025 00:00:00 +0800

Inventory management is critical to guaranteeing the efficiency and reliability of power distribution at PT PLN (Persero), notably at the Unit Induk Distribusi (UID) Banten. Challenges such as restricted storage space, installation delays owing to permit limits, and the buildup of heavy items such as medium-voltage cables have all had a substantial influence on operational performance. The purpose of this research is to investigate the feasibility of using Vendor Managed Inventory (VMI) as a strategic strategy to improve inventory efficiency at UID Banten. VMI enables suppliers to manage inventory levels based on real-time consumption data and demand projections, resulting in lower holding costs, increased stock availability, and reduced inventory buildup. Using literature review, the success of VMI implementations suggests that adopting VMI can provide substantial benefits, including streamlined warehouse operations, improved supplier collaboration, and greater responsiveness to demand fluctuations. However, several prerequisites, such as digital infrastructure readiness, data transparency, and mutual trust between stakeholders, must be met for successful VMI adoption. This study provides strategic recommendations for UID Banten to assess and prepare for VMI implementation as a means of achieving long-term inventory and distribution efficiency.

Supplier Selection and Order Allocation Based on Multi-Criteria Decision-Making Using AHP, Fuzzy TOPSIS, and Multi-Choice Goal Programming to Improve Local Content (TKDN)

Andi Muh Ade Ismail Bahar Bahar, Saskia Puspa Kenaka, Suprayogi — Wed, 29 Oct 2025 00:00:00 +0800

PT PLN Pusharlis menghadapi tantangan dalam pemilihan dan alokasi pemasok untuk komponen Control Board yang digunakan di Stasiun Pengisian Kendaraan Listrik Umum (SPKLU). Pemilihan pemasok yang tidak tepat dan alokasi pesanan yang tidak efisien dapat mengakibatkan keterlambatan pengadaan dan peningkatan biaya operasional. Penelitian ini bertujuan untuk mengembangkan model pengambilan keputusan terintegrasi yang memfasilitasi pemilihan pemasok yang paling sesuai dan alokasi pesanan yang optimal berdasarkan permintaan yang diproyeksikan. Tahap awal melibatkan peramalan permintaan Control Board menggunakan metode ARIMA. Proses pemilihan pemasok dan alokasi pesanan kemudian mengadopsi kerangka kerja pengambilan keputusan multikriteria. Analytical Hierarchy Process (AHP) diterapkan untuk menentukan bobot setiap kriteria, pemasok diperingkat menggunakan Fuzzy Technique for Order Preference by Similarity to Ideal Solution (Fuzzy TOPSIS), dan alokasi pesanan akhir dioptimalkan melalui Multi-Choice Goal Programming (MCGP). Kriteria evaluasi meliputi kinerja ekonomi, kepatuhan etika, dampak lingkungan, dan Persyaratan Kandungan Dalam Negeri (TKDN). Berbeda dengan pendekatan konvensional, kriteria TKDN dalam kajian ini dikembangkan sebagai indeks multiatribut, yang tidak hanya mencakup persentase bahan baku dalam negeri tetapi juga proses produksi lokal, pemanfaatan tenaga kerja, dan adopsi teknologi. Model yang diusulkan diharapkan dapat mendukung operasi SPKLU yang lebih akurat dan berkelanjutan.

Kata Kunci: ARIMA, AHP, Fuzzy TOPSIS, Multi-Choice Goal Programming, SPKLU, peramalan

Optimization of the Biomass Supply Chain for Co-Firing at Adipala Power Plant to Improve Cost Efficiency

Chandra Kharisma Margatama, Darwin — Wed, 29 Oct 2025 00:00:00 +0800

The utilization of biomass as a renewable energy source is becoming increasingly important to reduce dependence on fossil fuels and decrease carbon emissions. However, the efficient distribution of biomass in the co-firing system at the Adipala Steam Power Plant (PLTU) faces significant challenges related to high logistics costs. This study aims to optimize the distribution costs of biomass in the co-firing system at PLTU Adipala using Linear Programming (LP) methods. The primary objective of this research is to determine the optimal amount of biomass needed to meet the energy requirements of the power plant with efficient distribution costs, as well as to identify supply chain strategies that can enhance cost efficiency. The method employed is a Linear Programming optimization model that considers factors such as transportation costs, supply capacity, and energy needs. The results indicate that the application of LP can reduce logistics costs by up to 15% and improve the efficiency of biomass distribution. These findings make a significant contribution to enhancing the efficiency of biomass supply chain management at PLTU Adipala and can serve as a reference for the development of renewable energy policies in Indonesia. In conclusion, the application of LP in biomass supply chain management can provide efficient and sustainable solutions while promoting the reduction of carbon emissions in the energy sector.

Techno Economic Analysis of Hydrogen Production at the Songawayaua Geothermal Power Plant

A Agung Fadhilah P, Jooned Hendrarsakti, Ali Ashat — Wed, 29 Oct 2025 00:00:00 +0800

This study evaluates the techno-economic feasibility of integrating green hydrogen production with geothermal energy at the Songawayaua Geothermal Power Plant (GPP) in North Maluku, Indonesia. Although Indonesia holds a geothermal potential of 23.9 GW, utilization remains limited—especially in remote, low-demand regions—leaving substantial untapped resources. This research proposes a 30 MW geothermal development scenario, allocating 10 MW for grid electricity and 20 MW for hydrogen production using Proton Exchange Membrane (PEM) electrolysis, representing a novel configuration in the national context.

The techno-economic analysis reveals that electricity sales alone result in a negative Net Present Value (NPV) of USD –110 million under current tariff regulations. Conversely, hydrogen production achieves an output of 2,800 tons/year with a Levelized Cost of Hydrogen (LCOH) of USD 1.47/kg. The integrated system becomes economically feasible at a hydrogen selling price of USD 8.53/kg (NPV = 0) and commercially viable at USD 13/kg (IRR = 12%).

This study contributes new insights by quantifying critical economic thresholds and price sensitivities in geothermal-hydrogen integration. Unlike previous studies that examine each system separately, this work presents an integrated pathway that enhances renewable energy utilization and supports Indonesia’s Net Zero Emissions (NZE) 2060 target.

Techno-Economic Analysis of Kamojang Geothermal Power Plant as A Green Hydrogen Producer

Yusuf Satria Prihardana, Prihadi Setyo Darmanto — Wed, 29 Oct 2025 00:00:00 +0800

The utilization of renewable energy is becoming increasingly important in addressing the challenges of climate change and the need for clean energy. The potential to produce hydrogen from renewable energy sources, such as geothermal, offers an attractive solution to support the transition to clean energy. In this paper, the author uses a case study approach to analyze the hydrogen production potential of the Kamojang Geothermal Power Plant. The analysis method includes modeling the potential for hydrogen production based on the characteristics of the Kamojang Geothermal Power Plant, while the economic analysis includes planning investment costs, operational and maintenance costs, and Levelized Cost of Hydrogen. Based on the operational condition, it shows that the Kamojang Geothermal Power Plant has the potential to produce hydrogen using Alkaline Water Electrolysis technology. The economic analysis reveals that the hydrogen production infrastructure requires investment costs for Green Hydrogen Plant Infrastructure, operational costs must be considered to optimize LCOH and revenue from hydrogen sales can increase company profits in line with the PLN Group's Beyond kWh program. The results of this study are the basis for consideration, both from technical and economic aspects, in planning and implementing hydrogen production projects from renewable energy sources. The implication of this analysis is that the Kamojang Geothermal Power Plant has the potential to become a hydrogen producer in the future, where the hydrogen can be used commercially to support the PLN Group's Beyond kWh program and provide benefits to the environment by producing low-emission electrical energy fuel.

Pareto Analysis of Loss Output in Geothermal Power Plant Equipment for Prioritizing Auxiliary Equipment Investment Based on Operational Redundancy

Roland Christian Paruntungan Sihombing, Sutopo, M. Ali Ashat — Wed, 29 Oct 2025 00:00:00 +0800

This study aims to perform a Pareto analysis of output loss in Geothermal Power Plant equipment to identify priority investments in auxiliary equipment based on operational redundancy. The Pareto method is used to analyze the contribution of each piece of equipment to output loss and determine which equipment should be prioritized for further investment. The analysis shows that 20% of equipment, such as cooling towers and pumps, contributes the most to output loss. Based on these findings, it is recommended that investment should be focused on equipment that significantly impacts Geothermal Power Plant performance, with the goal of improving operational efficiency and reducing downtime. The Efficiency Optimization System (EOS) is used to monitor the performance of the plant in near real-time, identify inefficiencies, and provide improvement recommendations based on Pareto analysis to support decision-making in maintenance and investment.

Reliability Analysis as A Maintenance Optimization Strategy at PT PLN Indonesia Power Unit PLTP Gunung Salak

Moch Reza Zulfan, Willy Ardiansyah — Wed, 29 Oct 2025 00:00:00 +0800

The Gunung Salak Geothermal Power Plant (GPP), which has been operating for 30 years until now, has experienced several failures that tend to increase from time to time. Failure of power plant equipment and the length of repair time will result in the loss of production. Based on equipment failure data from GPP, there is an indication of ineffectiveness in the implementation of maintenance activities that have been carried out. Maintenance strategies can be determined from reliability analysis and failure prediction. Reliability analysis is expected to maintain power plant equipment from the risk of failure which causes force outage. This study applies a statistical model based on the Weibull-2 Distribution Parameter Method to determine the reliability of the model and failure prediction in power plant equipment. From the equipment failure data obtained, the Mean Time Between Failure (MTBF) value will then be determined. The results of the calculations that have been carried out, the Mean Time Between Failure (MTBF) values obtained for each piece of equipment are as follows: Turbine 20,156 hours; Cooling Tower 23,781 hours; Condenser 17,685 hours. The interval maintenance outage calculated by reliability analysis showed that turbine equipment, cooling tower, and condenser suggested to be overhaul every 2 years to reduce possibilities of failure.

A Conceptual Framework for the Selection of Biomass Alternatives for Coal Co-firing using Multi-Criteria Decision Making (MCDM) Approach

Imam Fachri, Yosi Agustina Hidayat — Wed, 29 Oct 2025 00:00:00 +0800

The increasing demand for sustainable energy and the need to reduce carbon emissions have driven the implementation of biomass co-firing in coal-fired power plants. Selecting appropriate biomass alternatives for co-firing is a complex decision involving multiple technical, economic, environmental, social, and regulatory considerations. This study aims to develop a conceptual framework for selecting biomass alternatives for co-firing in coal power plants. The framework integrates Analytic Hierarchy Process (AHP) and Structural Equation Modeling-Partial Least Squares (SEM-PLS) to identify and prioritize key selection criteria. The model consists of five main criteria technical, economic, environmental, social, and policy/regulation with a total of 14 validated sub-criteria. The dependent variable, Selection of Biomass Alternative, is measured by four biomass types: Rice Husk, Wood Pellet, Palm Kernel Shell, and Sawdust. The proposed framework provides a comprehensive tool to support decision-making and ensure the sustainable implementation of biomass co-firing.

Alternative Direct Use of Geothermal Energy in Atadei

Ressky Octa Pratama, Jooned Hendrarsakti — Wed, 29 Oct 2025 00:00:00 +0800

The development of geothermal energy in the Atadei 2 x 5 MW geothermal working area cannot be separated from social problems, namely the opposition of the local population in Lembata Regency. This is due to a lack of knowledge about the benefits of geothermal energy. To overcome this, direct use of geothermal energy can be a solution, so that the surrounding community can feel the benefits of geothermal development. One of the direct uses of geothermal energy is the use of a cascade system. The Atadei geothermal field has the potential for direct use of geothermal for the needs of the surrounding community. The results of this research are expected to provide an alternative to solve the problems that exist in the Atadei geothermal working area, so that the development of the Atadei 2 x 5 MW geothermal power plant can proceed smoothly.

Spatial Planning for Transmission Line Routing using Multi-Criteria Decision Analysis

Juzd Thoha Chairul Anam, Rinovia Mery Garnierita Simanjuntak, Anggi Afif Muzaki — Wed, 29 Oct 2025 00:00:00 +0800

Through the Electricity Supply Business Plan (RUPTL) 2021–2023, PT PLN (Persero) outlined plans for the development of transmission systems across Indonesia, projecting an expansion of 76,662 MVA in substation capacity and 47,723 kilometres of transmission lines by 2030. Transmission infrastructure development is further detailed for each major island system in the country. In particular, the transmission network in Sulawesi remains divided into two systems: Southern Sulawesi (SULBAGSEL) and Northern Sulawesi (SULBAGUT). The RUPTL document also highlights several strategic projects in the Sulawesi transmission system, including the 150 kV Tambu–Bangkir Transmission Line. Following an instruction from the Directorate General of Electricity to accelerate the Commercial Operation Date (COD) for the Tambu–Bangkir segment to 2024, the project timeline has been adjusted accordingly and designated as a priority assignment. Current transmission line construction planning still relies on manual methods, which have several weaknesses, including route inefficiency, potential cost overruns, challenges in accessing planning locations, and low planning accuracy that often does not reflect actual field conditions. This approach also inadequately considers disaster factors and the aspects of environmental, social, and corporate governance. This research aims to develop a more effective and efficient method for transmission line planning that reduces cost overruns while improving accessibility and planning accuracy. Additionally, this study will explore ways to incorporate land use, road access, disaster factors, and environmental, social, and corporate governance considerations. Spatial modeling using the Multi-Criteria Decision Analysis (MCDA) method can offer a more comprehensive approach, making transmission line planning more optimal and sustainable.

System Design for a Sustainable Returned Materials Management System at PT PLN UID East and North Kalimantan

Dimas Panji Endarto, Rachmawati Wangsaputra, Nur Faizatus Sa'idah — Wed, 29 Oct 2025 00:00:00 +0800

The Indonesian government through Presidential Regulation No. 111 of 2022 encourages the implementation of the Sustainable Development Goals (SDGs), including the efficient and responsible management of material resources. PT PLN (Persero), as a major energy provider, has responded through various sustainable transformation initiatives, including waste management based on the 3R principle. However, challenges are still faced in the management of returned materials, especially demolished materials (ATTB) at the distribution unit level such as PLN UID East Kalimantan and North Kalimantan. Problems such as the absence of standard classification procedures and the accumulation of unutilized materials indicate the need for a more effective system. Based on this, the problem formulation in this study is How is the design of a return material management business process that accommodates the 6R principles (Reduce, Reuse, Recycle, Repair, Refurbish, Remanufacture)? This research adopts the 6R-based closed-loop sustainable manufacturing approach to design a new digital-based business process for managing returned materials. The main focus is on designing a systematic classification mechanism into four categories based on technical, life, warranty, and economic aspects. This approach is expected to improve operational efficiency, support digital transformation, and strengthen PLN's contribution to the national sustainability agenda.

Enhancing Geothermal Energy Utilization Through Binary Power Plant and Absorption Chiller Technology: Songa Wayaua Case

Aria Pratama Putra, Jooned Hendrarsakti — Wed, 29 Oct 2025 00:00:00 +0800

The Songa Wayaua Geothermal Power Plant (PLTP) is planned for development with a 2x5 MW capacity using single-flash technology. The residual energy contained in the brine from the separator outlet can be further utilized before being reinjected. Referencing a study by PT. PLN (Persero), the brine stream from the single-flash plant, with a mass flow rate of 29.33 kg/s and a temperature of 164.9°C, will be directed into a cascaded system. This system comprises an Organic Rankine Cycle (ORC) for additional power generation and a Lithium Bromide-Water (LiBr-H₂O) absorption chiller for cooling purposes. This approach is particularly promising given the Songa Wayaua geothermal field's coastal proximity, making it suitable for future applications like fish refrigeration systems. The proposed design is projected to generate an additional 312.17 kW of power using Pentafluoropropane (R-245fa) as the working fluid. The ORC system's outlet temperature is maintained at a maximum of 125°C, allowing it to be subsequently used as the heat source for the absorption chiller. This chiller is estimated to produce a cooling capacity of 835.91 kW, with a Coefficient of Performance (COP) of 0.76 and an effectiveness (e) of 0.78. The results of this study indicate that the proposed system can significantly increase the overall energy efficiency and expand the application scope of the geothermal potential. This allows for the direct integration of geothermal energy with the local fishery industry, fostering a direct, mutually beneficial relationship between PT. PLN (Persero) and the community surrounding Songa Wayaua.

Design of a Computational Tool for Organic Rankine Cycle Performance Estimation Based on Geothermal Field Data

Singgih Imam Kurniawan, Ali Ashat, Prihadi Setyo Darmanto — Wed, 29 Oct 2025 00:00:00 +0800

This study evaluates the thermodynamic feasibility of additional power generation from separated brine at a high-temperature geothermal plant in Indonesia, referred to as the “XYZ geothermal plant” to maintain site confidentiality. The plant operates with a single-phase liquid-dominated reservoir, with temperatures ranging from 250 °C to 270 °C and a brine reinjection temperature of approximately 170 °C at a flow rate of 1400 tons per hour.

To ensure safe reinjection conditions, the Silica Scaling Index (SSI) was applied to determine the minimum allowable brine temperature. A finite difference-based Python simulation tool was developed to model heat transfer in the ORC system and assess performance across different working fluids and operating pressures. The results show that n-pentane achieves the best performance, producing a net power output of 5596 kW and a thermal efficiency of 17.21% at an optimal pressure of 1.80 MPa. Isopentane follows closely, while R-1233zd(E) performs less favorably due to pressure constraints.

Model validation against manual calculations resulted in deviations below 0.6%, confirming the simulation’s accuracy. This tool provides a fast and reliable method for evaluating ORC performance and supports practical decision-making for geothermal plant operators. It is intended to assist utilities such as PLN in optimizing geothermal resource utilization.

Prediction of Hydropower Plant Electricity Production Dependence on Weather Conditions Using Machine Learning Approach

Dennis Hasnan Zulfialda, Hakim Luthfi Malasan — Wed, 29 Oct 2025 00:00:00 +0800

To optimize the hydropower plant operations in the Sulawesi Generation Unit of PLN, this study proposes a data-driven approach to analyze electricity production by incorporating weather data. Utilizing historical data from January 2014 to December 2023, relevant indicators were extracted using machine learning algorithms. The integration of hydropower generation data, dam operational data, temperature, and rainfall enabled the prediction of electricity output through various models, including SARIMAX, Random Forest Regressor, Support Vector Regression, and Extreme Gradient Boosting. The dataset, consisting of 120 rows and 18 variables, demonstrated that combining diverse yet correlated data sources improve prediction accuracy. The best-performing model was validated and applied to forecast on new, unseen data. The findings indicate that machine learning offers a strategic advantage for PLN's decision-making in managing interconnected hydropower operations within the national power grid.

Numerical Simulation of the Atadei Geothermal Field: An Integrated Model Based on Updated Data

Muhammad Sholekan, Sutopo Sutopo, Heru Berian Pratama — Mon, 13 Apr 2026 00:00:00 +0800

Atadei geothermal system in southeastern Lembata remains unexploited due to insufficient subsurface constraints. This study formulates a calibrated three-dimensional reservoir model to address existing geological ambiguity and enable spatial delineation of productive zones. Multi-disciplinary inputs—comprising thermal logs, alteration mineralogy, resistivity cross-sections, and stratigraphic data—were synthesized and dynamically matched using VOLSUNG under natural-state conditions. The computational domain, exceeding 50 km², integrates deep convective boundaries, fault-aligned flow discontinuities, and phase transition indicators derived from synthetic wells. The simulation attained thermal convergence at log dt ≥ 11, reflecting hydrodynamic stabilization. Thermodynamic profiling indicates reservoir initiation at ~500 m depth, capped by a 600–1100 m thick low-permeability unit, with localized two-phase behavior observed at sub-vertical conduits. Peak reservoir temperatures exceed 240 °C, with steam saturation ranging from 0.2–0.65. Atypical vapor intrusion at shallow depth in ATS-4 indicates vertical migration through breached seal zones. The refined model reveals heterogeneity in phase distribution and offers a predictive basis for optimized well deployment.

System Dynamics for Policy Simulation of FABA (Fly Ash and Bottom Ash) Waste Utilization

Ferry Saputra, Saskia Puspa Kenaka, Suprayogi — Wed, 29 Oct 2025 00:00:00 +0800

Fly Ash and Bottom Ash (FABA) are by-products of coal combustion in power plants that pose environmental risks if not properly utilized. This study develops a System Dynamics model to evaluate policy scenarios for FABA utilization at the Nagan Raya coal-fired power plant, which produces an average of 2,295 tons of FABA per month. The model is based on historical data from 2016 to 2024 and simulates policy interventions for the 2025–2030 period, including biomass co-firing, public awareness campaigns, and subsidies for industrial users.

The simulation results for 2030 show that the combined policy scenario successfully reduces stored FABA from 98,352 tons to 37,011 tons and increases FABA utilization from 1,050 tons/month to 1,850 tons/month. CO₂ emission reductions also increase significantly, from 1,570 tons/month to 10,220 tons/month. The policy requires industrial subsidies of IDR 130 million/month and socialization costs of IDR 30 million/month. This study demonstrates that simulation-based waste policy modeling can effectively support the transition strategy toward achieving Indonesia’s Net Zero Emission 2060 target.

Development of a Warehouse Management System for Reusable Materials in Power Plant Maintenance, Repair, and Overhaul Activities

Ridho Muslimuda, Rachmawati Wangsaputra, Nur Faizatus Sa’idah — Wed, 29 Oct 2025 00:00:00 +0800

Ineffective management of reusable material warehousing at the Indralaya power generation unit has caused inefficiencies in material service time, primarily due to ineffective systems for receiving, storing, and issuing materials. These deficiencies have resulted in delays in the power plant's Maintenance, Repair, and Overhaul (MRO) processes. This study aims to develop an efficient and systematic Warehouse Management System (WMS) for managing reusable materials used in MRO activities, with the objective of improving warehouse operational efficiency and reducing material service lead time. The research methodology involved field observations, literature review, data collection, material classification, and service time analysis using Bizagi Modeler. The findings indicate that the development of a WMS—supported by redesigned business processes, improved warehouse layout, structured recording systems, and process digitalization—significantly enhances the efficiency of receiving, storage, and dispatch activities. These improvements contribute to faster material distribution and reduce search time, ultimately shortening the overall warehouse service time.

The Impact of El Niño on the incoming flow rate of the Saguling Hydroelectric Power Plant (PLTA) for Operational Sustainability

Andit Zelly Gunawan, Nurjanna Joko Trilaksono — Wed, 29 Oct 2025 00:00:00 +0800

This study investigates the impact of El Niño on the inflow dynamics of the Saguling Hydroelectric Power Plant (PLTA), located in West Java, Indonesia. Using 39 years of hydrometeorological data (1986–2024), including rainfall, reservoir inflow, and Oceanic Niño Index (ONI), the research identifies the climatic influence of El Niño–Southern Oscillation (ENSO) events on water availability and power generation sustainability. Results show a significant inverse correlation between ONI and both rainfall (r = –0.41) and inflow (r = –0.45), with El Niño years experiencing a 50–60% reduction in water inputs during dry months. La Niña events, in contrast, enhance inflow and precipitation, thereby supporting reservoir operations. Wavelet transform analysis reveals dominant periodicities in the 2–4 year range, consistent with ENSO cycles. These findings highlight the vulnerability of hydropower generation to climate variability and underscore the importance of adaptive reservoir management strategies based on ENSO projections. The study contributes to strategic planning in energy and water sectors, emphasizing the integration of climate forecasts in maintaining operational continuity of hydropower infrastructure.

Technical Study on The Design of Tangkuban Perahu Geothermal Power Plant

Gigieh Ramadhan Budyanto, Prihadi Setyo Darmanto — Wed, 29 Oct 2025 00:00:00 +0800

The Tangkuban Parahu Geothermal Working Area (WKP) possesses significant geothermal energy potential with high-temperature (high enthalpy) reservoir characteristics estimated at 240–270°C. This potential makes WKP Tangkuban Parahu one of the most promising areas for geothermal power plant development in Indonesia. This study aims to evaluate geothermal resource potential, design an optimal geothermal power generation system, and estimate the overall project development costs.

The analysis integrates geological, geochemical, and geophysical survey data from previous exploration studies. For power generation design, thermodynamic modeling was conducted using Excel with Coolprop extension, considering technologies single flash. This technology were selected for their advantages in utilizing geothermal resources with relatively high efficiency. This research is mainly focused on recalculation of Single Flash Cycle from Tangkuban Perahu Pre-FS Document that were conducted by PT.PLN and PT. New Quest

Based on Monte Carlo simulation results, the electrical power potential of WKP Tangkuban Parahu is estimated at 22 MW (P90) to 67 MW (P10), with a median value of 43 MW (P50).

The findings of this study are expected to serve as an important reference in designing an efficient and sustainable geothermal power plant at Mount Tangkuban Parahu WKP and support PT PLN in achieving its national renewable energy mix targets.

Preliminary Exergy Analysis for Performance Optimization at Ulubelu Geothermal Power Plant Unit 1

Ghoziah Putri Hardini, Willy Ardiansyah — Wed, 29 Oct 2025 00:00:00 +0800

Indonesia lies within the Ring of Fire, renowned for volcanic activity and geothermal energy potential estimated at 23.7 GW. By 2023, 18 geothermal power plants were operational with a combined capacity of 2,597 MW. The Ulubelu Geothermal Power Plant, supplying 25% of Lampung’s electricity, serves as a case study for a preliminary exergy analysis. Using Cycle-Tempo simulation, a thermodynamic model was developed to replicate actual operating conditions and evaluate exergy flows and losses. The system’s total exergy input was 50,136 kW, with 16,367 kW (32.6%) destroyed due to irreversibilities, resulting in an overall exergy efficiency of 67.34%. The turbine achieved the highest functional exergy efficiency (82.43%) but also accounted for the largest relative exergy loss (12.43%). Substantial inefficiencies were identified in the condenser (14.88%) and ejector (1.66%). These findings reveal critical sources of exergy destruction, forming the basis for targeted performance improvements. Optimization strategies are prioritized for the turbine and condenser, where losses are most significant.

A Validation of the Analytical Hierarchy Process (AHP) for Ranking Geothermal Potential for Next PLNs Project: An Academic Expert Perspective

Kiddy Nahli Aulia, Sutopo, Ali Ashat — Wed, 29 Oct 2025 00:00:00 +0800

The study evaluates the geothermal potential of Indonesia using the Analytical Hierarchy Process (AHP). AHP was employed to rank geothermal sites for development, considering criteria such as resource potential, infrastructure readiness, economic feasibility, and socio - cultural impacts. Academic expert judgment, while inherently subjective, is incorporated to provide structured comparisons among multiple geothermal fields. This study highlights the application of AHP in providing transparent, objective rankings for geothermal site prioritization, which is essential for strategic planning in Indonesia’s energy transition. The results suggest that economic feasibility and resource potential are key drivers in geothermal field selection, particularly for the Ulumbu and Tulehu fields that owned by PT PLN (Persero). These findings have direct implications for future geothermal investments and policy decisions in Indonesia. The study highlights the potential of AHP method in guiding policy and investment decisions for geothermal energy development PLN’s geothermal fields for further study.

The Projections of Solar Energy Potential in Indonesia under Climate Change Scenarios : A CMIP6 Multi-Model Ensemble Analysis

Wed, 29 Oct 2025 00:00:00 +0800

Indonesia holds significant solar energy potential, making it a key resource in the country’s pathway toward net-zero carbon emissions by 2060. However, climate variability introduces uncertainties that may impact long-term solar energy production and investment planning. This study investigates the projected impacts of climate change on Indonesia’s solar photovoltaic (PV) potential for the period 2030–2060, utilizing outputs from five global climate models (GCMs) of the Coupled Model Intercomparison Project Phase 6 (CMIP6). Two emission scenarios were considered: SSP1-2.6 (low emissions) and SSP5-8.5 (high emissions). Key climate variables influencing PV performance surface downwelling shortwave radiation, near-surface air temperature, and wind speed were analyzed. Model outputs were regridded to a 0.25° spatial resolution and bias-corrected through statistical downscaling. Results reveal spatially variable responses of PV potential to future climate change, with a projected decrease during the rainy season and an increase during the dry season in specific regions. These findings highlight the necessity of integrating climate projection uncertainties into national renewable energy strategies, ensuring adaptive and resilient solar energy development in Indonesia under future climate conditions.

Thermal Discomfort and Its Impact on Urban Residential Electricity Use: A Case Study in Bandung, Indonesia

Wed, 29 Oct 2025 00:00:00 +0800

Urban energy demand in tropical highland settings is increasingly sensitive to climatic stressors, particularly the combined effects of temperature and humidity on thermal comfort. This study quantifies the influence of the Thermal Humidity Index (THI) on monthly electricity consumption in Bandung, Indonesia, between January 2012 and May 2024. Daily THI values were derived from 2-meter air temperature and relative humidity observations, aggregated into monthly means, and paired with utility records of residential electricity use. Spearman rank correlation analysis indicates a moderate positive association (ρ = 0.35, p < 0.001) between elevated heat-stress conditions and increased consumption. However, this relationship is partly obscured by concurrent growth in household electrification, appliance ownership, and urbanization.

Despite these confounding trends, the findings highlight a growing reliance on mechanical cooling in Bandung, a city historically known for its naturally temperate climate. The results underscore the importance of incorporating dynamic thermal stress and demographic shifts into future energy planning. While Spearman's correlation offers a valuable starting point, future research should adopt multivariate or time-series models to better isolate causal factors. Furthermore, the behavioral assumption linking THI to air conditioning use remains unvalidated in this study; incorporating user-level data or surveys would enhance the robustness of the conclusions. Overall, this study contributes to the broader understanding of climate-sensitive energy behavior and offers a transferable framework for urban energy forecasting in tropical regions.