ITB Graduate School Conference

Kinetic Modeling of Lignite Devolatilization: Comparative Perspectives of DAEM and Iso-conversional Methods

2025-05-19T15:46:54+08:00

DAEM and iso-conversional methods are reviewed for kinetically modeling lignite devolatilization, a critical initial stage in coal utilization that profoundly impacts energy efficiency and emissions. Lignite presents unique challenges due to its high volatile content () and complex multi-stage decomposition reactions. DAEM addresses this by assuming devolatilization as a series of parallel, first-order reactions with a continuous distribution of activation energies, mostly Gaussian or Weibull; multi-Gaussian DAEM extensions further enhance accuracy for intricate decomposition profiles. Conversely, iso-conversional methods like Friedman, FWO, and KAS estimate effective activation energies () at various conversions, offering a robust way to analyze kinetic data from multiple heating rates. Comparative analyses indicate that multi-Gaussian DAEM more effectively captures the staged devolatilization of lignite, with reported for low-rank coal ranging from 142 to and significantly improved sum of squared error (SSE) ratios (e.g., ). While iso-conversional methods are computationally efficient and provide consistent profiles (), DAEM yields more complete kinetic parameters. Both require quality TGA data and primarily describe chemical kinetics, often neglecting physical transport limitations pertinent to reactor design. Future research focuses on refining these models and integrating them with broader system simulations.

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

2025-05-20T00:38:32+08:00

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.

Simulation of Filter Cake Co-firing Characteristics in Circulating Fluidized Bed Coal Fired Power Plant

2025-05-19T16:10:41+08:00

A study on co-firing using coal and filter cake biomass was conducted on a circulating fluidized bed boiler power plant varying the co-firing biomass ratio from 0 to 50%. The mixing of coal fuel and filter cake biomass in the model is carried out before entering the mill. After the model iteration shows convergence, the output simulation is validated by comparing the simulation output value with the design and actual parameter values. The evaluation is carried out by comparing the simulation results of baseline conditions with co-firing conditions on the parameters of performance, power output, equipment condition, energy consumption itself, and the impact on emission products. The addition of 1% of the co-firing ratio using rice husks showed a decrease in boiler efficiency (HHV) by 1.3%. Net plant heat rate and SFC increased by 5% and 0.2171%. Furthermore, co-firing using filter cake also reduces SO2 emission by 1.642 ppmv@6% O2, dry.

The Potential of Carbon Trading and Carbon Tax Analysis to Enchance the Economic Feasibility of Geothermal Power Plant in Indonesia

2025-05-30T16:52:53+08:00

Global climate change, driven by the increasing concentration of greenhouse gases in the atmosphere, has emerged as one of the most pressing challenges confronting humanity. The energy sector, particularly its continued reliance on fossil fuel combustion for electricity generation, is a major contributor to greenhouse gas emissions. In response to the urgent need to mitigate these negative impacts, various countries and international organizations have developed policies and mechanisms aimed at reducing carbon emissions. One such mechanism is the carbon trading system, a market-based instrument that enables countries or companies to buy and sell carbon emission allowances. Under this scheme, entities that successfully reduce emissions beyond their assigned targets may sell their surplus allowances to others who are unable to meet their reduction obligations. This approach fosters both efficiency and innovation in emissions reduction, with economic incentives serving as a primary driver. Geothermal Power Plants, as a renewable energy source, play a pivotal role in reducing dependence on fossil fuels. Compared to fossil power plants, Geothermal Power Plants generate significantly lower levels of carbon emissions. Therefore, analyzing the potential integration of Geothermal Power Plants into the carbon trading system could offer financial incentives and enhance the economic viability of geothermal energy. This mechanism has the potential to support the further development and expansion of geothermal power infrastructure.

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

2025-05-30T16:59:31+08:00

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.

Application of United Nations Framework Classification for Resources (UNFC) in Ulumbu Geothermal Field, East Nusa Tenggara, Indonesia

2025-05-20T01:05:09+08:00

The Ulumbu Geothermal Field, located in East Nusa Tenggara and operated by PT PLN (Persero), is strategically supporting Indonesia’s renewable energy goals. Ulumbu Geothermal Power Plant currently operates at a total capacity of 10 MW (4 × 2.5 MW) and has an estimated additional potential of at least 40 MW for future development. Although the field has been in operation for several years, PLN has not yet implemented an internationally recognized classification framework such as the United Nations Framework Classification for Resources (UNFC) to manage its geothermal assets. This paper explores the application of the UNFC to the Ulumbu Geothermal Field by assessing its geothermal resources through three fundamental criteria of environmental-socio-economic viability (E-axis), technical feasibility (F-axis), and degree of confidence in the estimate (G-axis). Utilizing publicly available data and internal reports, the study evaluates how the field’s current status aligns with each UNFC axis. The results provide classification of the Ulumbu geothermal resources according to UNFC and highlight the challenges and opportunities of adopting such a system in PLN. The findings suggest that applying UNFC can enhance project transparency, optimize decision-making, and support more sustainable geothermal development in Indonesia.

Greenhouse Heating Using Geothermal Brine: A Case Study from Dieng

2025-06-03T11:40:18+08:00

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)

2025-05-30T17:16:38+08:00

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.

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

2025-05-30T17:08:01+08:00

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.

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

2025-05-30T17:16:02+08:00

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.

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

2025-05-30T17:01:06+08:00

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.

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

2025-05-19T15:57:09+08:00

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.

Techno-Economic Analysis of Exhaust Steam Utilization – Ulumbu Geothermal Power Plant Using Organic Rankine Cycle (ORC) with Pentane as Working Fluid

2025-06-10T01:24:29+08:00

Ulumbu Geothermal Field is one of the existing water-dominated geothermal field in Indonesia, high enthalpy (230°C - 240°C) and located on Flores Island, East Nusa Tenggara. PT PLN as developer for Ulumbu Geothermal Field operates an existing geothermal power plant with 4x2,5 MW capacity, utilizing two types of steam turbines: condensing (2x2,5 MW) and back pressure (2x2,5 MW). The exhaust steam from back pressure turbines has a temperature around 98°C - 105°C, with a maximum steam flow rate approximately 62 Tons per hour. Several studies have been conducted by PT PLN for utilization plan of Ulumbu exhaust steam, for direct and indirect use. This research aims to assess the optimum power that can be generated by ORC (Organic Rankine Cycle) plant, regarding the parameters on site, such as thermodynamics of exhaust steam, ambient temperature, and water availability. ORC (Organic Rankine Cycle) system used in this research is ORC (Organic Rankine Cycle) with Pre-Heater, Evaporator, Expander, Condenser and Pump. Using pentane as working fluid and ASPEN HYSYS for simulation, this ORC (Organic Rankine Cycle) can generate about 2.77 MW, with 9.38 % thermal efficiency. The development cost for this project approximately 9.9 million USD, with IRR Value of 13.97%, dan NPV of 2.86 million USD, if the electricity is sold at 11.71 cent/kWh for first 10 years and 9.96 cent for next 15 years, regarding to Indonesian Government tariffs for Nusa Tenggara.

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

2025-05-19T23:07:05+08:00

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.

Analysis of Geothermal Fluid Pipe Behavior in Dry Steam Geothermal Power Plant under Dynamic Load

2025-06-02T09:31:22+08:00

This study investigates the dynamic behavior of a dry steam geothermal fluid piping system located in a seismically active region of West Java, Indonesia. Given the potential for resonance under earthquake-induced dynamic loads, modal analysis was conducted using ANSYS finite element software to determine the piping system's natural frequencies and mode shapes. The piping system, spanning 186 meters, was modeled with fixed and roller supports to reflect realistic boundary conditions. Analysis results revealed that while the first mode (10.31 Hz) falls within the critical earthquake frequency range, its low mass participation indicates minimal influence on system response. In contrast, the twenty-fifth mode (31.12 Hz) exhibits deformation patterns more aligned with expected seismic excitation, with its frequency exceeding the dominant earthquake spectrum. Thus, the system is not considered highly susceptible to resonance. This study underscores the importance of modal analysis in assessing seismic resilience and confirms the structural adequacy of the piping design under dynamic loads.

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

2025-05-19T23:18:41+08:00

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.

Encouraging Geothermal Investment in Indonesia: Evaluating Government Strategies to Address Exploration Risks and Comparative Insights from Successful Countries

2025-05-30T14:48:23+08:00

Exploration is the most expensive and high-risk phase in the geothermal development chain. This condition has resulted in low private sector participation, particularly during the early stages of development. This study aims to evaluate the Indonesian government's policy strategies to address geothermal exploration risks and conduct a comparative analysis with successful approaches implemented in Kenya, the Philippines, and Turkey. Using a qualitative-descriptive method, the study draws on policy literature and actual exploration data to examine regulatory frameworks, fiscal incentives, and public risk-sharing mechanisms. The findings reveal that while Indonesia has initiated exploration through government agencies such as Center for Mineral, Coal, and Geothermal Resources “PSDMBP” and offers fiscal incentives and risk guarantees (via Geothermal Risk Mitigation Facility “GRMF” and PT Penjaminan Infrastruktur Indonesia “PII”), the implementation still faces major challenges, including limited budget, weak inter-agency coordination, bureaucratic inefficiencies, and restricted access to geoscientific data. In contrast, exploration models in Kenya (public exploration via Geothermal Development Company “GDC”), the Philippines (Build-Operate-Transfer “BOT” scheme with feed-in tariffs), and Turkey (cost-sharing with the private sector) show more integrated and investor-friendly approaches. This study concludes with strategic recommendations, including the establishment of a state-owned exploration company, improved data transparency, regulatory reforms, and the implementation of output-based fiscal incentives to enhance geothermal investment attractiveness in Indonesia.

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

2025-06-04T11:42:23+08:00

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.

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

2025-06-03T11:43:06+08:00

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

Implementation Analysis of Emission Reduction System for SO₂, NO₂, and Hg Emission Reduction Equipment in Coal-Fired Power Plants

2025-05-19T15:45:20+08:00

Coal-Fired Power-Plants (CFPP) have four main emission parameters: SO₂, NO₂, particulate matter, and Hg. Currently, many existing CFPP have yet to install emission reduction equipment for SO₂, NO₂, and Hg emission. This study aims to evaluate the technical and economic impacts of implementing emission reduction equipment in existing CFPP with capacities between 50 and 1000 MW. This study is conducted using SteamPro–Thermoflow, a well-known software in the thermal power plant industry for heat and mass balance analysis. The simulations show that Selective Catalytic Reduction (SCR) achieves 80% NO₂ reduction efficiency, higher than Selective Non-Catalytic Reduction (SNCR) at 40%. For SO₂ reduction, Wet and Sea Water Flue Gas Desulfurization (WFGD and SWFGD) reach 95%, while Semi-Dry FGD (SDFGD) achieves 90%. Activated Carbon Injection (ACI) for mercury (Hg) reduction achieves 60%, and up to 85% when combined with FGD. For auxiliary power consumption, at 0.01–0.03% of gross power for NO₂ reduction, 0.25–0.50% for SO₂ reduction, and 0.17–0.22% for Hg reduction. Investment costs are 50–120 USD/kW for SNCR, 5–20 USD/kW for SCR, 10–35 USD/kW for ACI, and 32–110 USD/kW for FGD. The study results are expected to guide emission reduction policies in power generation sector.

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

2025-05-30T17:00:34+08:00

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.

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

2025-06-09T14:26:53+08:00

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.

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

2025-06-11T05:14:54+08:00

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.

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

2025-06-10T00:46:07+08:00

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.

Cost Recovery Frameworks for Geothermal Projects: Insights from Oil and Gas and Their Relevance to PLN’s Geothermal Operations in Indonesia

2025-05-30T16:54:15+08:00

Some of PLN’s Geothermal Working Area (GWA) has suboptimal resource quality, which leads to high exploration costs and longer development times that hinder national geothermal targets. To address this, PT Perusahaan Listrik Negara (Persero) (PLN) has established a strategic partnership model called the Geothermal Exploration & Energy Conversion Agreement (GEECA) to improve efficiency and share exploration risks with partners, including cost recovery schemes similar to those in oil and gas. The development processes for oil, gas, and geothermal projects are similar: identifying reserves, exploration drilling, facility development, production, and site closure. The risks associated with geothermal, oil, and gas projects share similarities. The cost recovery scheme and GEECA include a mechanism for reimbursing exploration costs to partners or contractors. While they share fundamental concepts, the reimbursement methods differ significantly. In the cost recovery system, reimbursement occurs from production income before profits are shared between the government and the contractor. In contrast, GEECA employs a more definitive approach, ensuring that PLN will reimburse all exploration costs within two years after the power plant starts commercial operations. In Indonesia's geothermal development, especially with PLN's GWA, GEECA can enhance the appeal of partnerships. For other GWAs, PLN should consider enriching the data to reduce uncertainty and attract more partners.

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

2025-05-19T17:58:11+08:00

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.

Hazard And Operability Study for Determining Safety Integrity Level on Surface Above Ground System and Unit 1 And Unit 2 Geothermal Power Plant in Ulumbu Field

2025-06-13T17:29:04+08:00

This study applies the Hazard and Operability (HAZOP) method to identify potential process risks and determine the Safety Integrity Level (SIL) of the Surface Above Ground System (SAGS) and Units 1 and 2 at the Ulumbu Geothermal Power Plant. Using process documentation, maintenance records, and operational data from 2020–2024, eight critical nodes were analyzed. Risk was evaluated using a matrix based on severity and likelihood, with failure probabilities derived from Mean Time to Failure (MTTF) and the OREDA database. The SIL assessment was conducted in accordance with IEC 61511. Results showed that most nodes operated under SIL 2, indicating a generally adequate safety system. However, several nodes—particularly those in the demister and lube oil systems—fell under SIL 1, suggesting the need for improvement. The study recommends additional shutdown valves to enhance protective functions, particularly in scenarios involving rupture disks. Overall, the findings provide insights into system vulnerabilities and support recommendations for improving the safety integrity of geothermal plant operations.

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

2025-06-03T10:16:32+08:00

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

2025-06-01T22:21:07+08:00

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.

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)

2025-05-30T17:05:05+08:00

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

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

2025-05-19T16:05:24+08:00

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.

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

2025-05-30T16:57:57+08:00

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.

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

2025-05-19T16:08:08+08:00

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.

Optimizing Financial Feasibility and Resource Utilization in Binary Geothermal Systems: A Case Study from the Dieng Geothermal Field, Indonesia

2025-05-30T16:55:30+08:00

This study evaluates the technical and financial feasibility of developing a binary geothermal power plant by utilizing residual brine from the Dieng geothermal field in Central Java, Indonesia. As one of the most geologically complex and active regions in Southeast Asia, the Dieng field represents significant untapped potential for secondary energy through binary cycle technology. By using data from reservoir simulation, brine chemistry analysis, and economic modeling, the study examines multiple development configurations across several scenarios. Technically, the study finds that several wells will have sufficient brine temperature and sustainability for the project, although there is a risk of silica content, which poses a scaling problem. Finally, the base scenario of the financial project is not viable under the current tariffs of USD 6.23 cents/kWh but becomes attractive when paired with optimized tariffs and resource integration from Dieng Unit-2. The findings support the pathway for enhanced geothermal utilization in Indonesia, emphasizing the importance of flexible development strategies, regulatory alignment, and technological optimization to ensure long-term project viability.

Technical Study on The Design of Tangkuban Perahu Geothermal Power Plant

2025-06-01T22:18:22+08:00

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.

Analysis of the Earthquake Load Effects on the Cooling Tower Structure of the Ulumbu Geothermal Power Plant Using the Pushover Method

2025-06-10T02:14:55+08:00

Earthquake loads pose a critical threat to the structural integrity of infrastructure in geothermal power plants, particularly cooling towers, which are essential for thermal regulation. This study aims to evaluate the seismic performance of the cooling tower structure at the Ulumbu Geothermal Power Plant through a nonlinear static pushover analysis. The analysis was performed using structural modeling software and applied the ATC-40 guidelines to assess performance levels under lateral seismic loads. The capacity spectrum method was utilized to transform the pushover curve into an equivalent single degree of freedom (SDOF) system, allowing the identification of the performance point. Results indicate a proportional relationship between base shear and displacement, with the structure capable of resisting a maximum lateral load of 730.383 kN. According to ATC-40 criteria, the structure meets the Immediate Occupancy (IO) performance level, demonstrating sufficient seismic resilience and indicating that the cooling tower remains safe and operational following a moderate earthquake. This research contributes to the understanding of seismic vulnerability in geothermal infrastructure and supports improved structural design and risk mitigation strategies.

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

2025-05-20T00:41:25+08:00

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.

Numerical Modeling of the Songa-Wayaua Geothermal Reservoir Incorporating Seawater Intrusion Effects

2025-05-30T16:32:57+08:00

The Songa-Wayaua Geothermal Working Area (GWA), located in South Halmahera, North Maluku, is a high-enthalpy geothermal system with planned development for 2 × 5 MW power generation. Despite considerable progress in exploration and early-stage modeling, challenges remain in accurately simulating subsurface behavior near the coastline, particularly with regard to seawater intrusion and its impact on reservoir performance. This study presents the development of an updated numerical reservoir model using the Brynhild module within the Volsung geothermal simulation platform. By integrating geological, geophysical, and geochemical data, a refined 3D conceptual model was constructed in Leapfrog and subsequently imported into Brynhild. The model incorporates a multi-component equation of state (H₂O + CO₂ + NaCl) to capture the thermodynamic effects of saline intrusion. Boundary conditions and reservoir properties were carefully calibrated to replicate natural state conditions and surface manifestations. Simulation results successfully reproduce pre-exploitation temperature and pressure profiles and demonstrate the extent and direction of seawater intrusion. History matching mass flow and chloride concentrations further validates the model’s ability to represent dynamic reservoir behavior. This integrated modeling approach provides critical insights for sustainable geothermal development in coastal settings.

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

2025-05-19T23:30:46+08:00

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.

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

2025-05-30T17:03:55+08:00

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.

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

2025-05-19T23:16:41+08:00

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

Alternative Direct Use of Geothermal Energy in Atadei

2025-05-23T17:29:27+08:00

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.

Characterizing the Two-Phase Geothermal System of the Ulumbu Field Through Updated Data and Numerical Reservoir Modeling to Support Capacity Expansion Planning

2025-06-01T22:11:10+08:00

The Ulumbu geothermal field in Flores, Indonesia, exhibits a two-phase system characterized by steam-dominated conditions at shallow depths and liquid-dominated conditions at greater depths. An existing facility currently generates 4 × 2.5 MW, with a planned expansion of 2 × 20 MW as outlined in the 2021–2030 RUPTL. However, uncertainties concerning subsurface structure, heterogeneous permeability, and long-term reservoir sustainability necessitate a comprehensive re-evaluation. Earlier studies relied on exploratory conceptual models with limited geoscientific data. The studies introduced the first natural state model using TOUGH2, confirming the presence of a steam cap overlying a liquid-dominated zone.

This study presents an updated and integrated conceptual and numerical model of the Ulumbu geothermal system based on recent geoscientific, geophysical, and well data. Numerical simulation was conducted using the Volsung simulator to improve natural state representation and inform future development. A potential upflow zone is identified beneath the Lungar area, directly connected to the heat source and underlying a steam-supplying two-phase zone. The model achieves calibration with well data, reproducing key reservoir characteristics: a ~600 m thick steam cap (saturation 0.6–0.7, ~260°C), a ~200 m thick boiling zone (~290°C), and a deeper liquid-dominated reservoir (~300°C) below –1000 m asl. While this study successfully reconstructs the natural state of the system, future production simulations are still required to confirm long-term deliverability and the feasibility of 2 × 20 MW expansion.

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

2025-05-20T00:46:02+08:00

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.

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

2025-05-19T23:05:46+08:00

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

A Study on Renewable Energy Certificates as Enabling Instruments for Geothermal Energy Advancement

2025-06-13T07:42:06+08:00

Indonesia, home to the world’s second-largest geothermal reserves, holds strategic potential to accelerate the clean energy transition through expanded geothermal development. This paper examines the role of Renewable Energy Certificates (RECs) as a market-based instrument to support this agenda. Despite the introduction of geothermal RECs in Indonesia’s voluntary market, their sales performance remains lower than those of hydropower and solar sources. Through a multi-phase analysis—encompassing sales trends, international price benchmarking, techno-economic simulations, and market strategy formulation—this study identifies key barriers and opportunities for improving geothermal REC utilization. Benchmarking indicates that REC prices in Indonesia are among the lowest in Asia, with limited financial impact on geothermal project economics at current levels. However, techno-economic modeling reveals that rising REC prices could significantly enhance project bankability. The study proposes a set of targeted marketing strategies, including RE100 corporate engagement, premium product positioning, and integration with ESG policy frameworks. These strategies aim to ensure full recognition and monetization of geothermal electricity via REC markets. The findings offer actionable insights for PT PLN (Persero) and stakeholders to optimize REC deployment and strengthen geothermal’s role in Indonesia’s renewable energy mix.

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

2025-06-03T11:42:04+08:00

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.

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

2025-05-30T16:51:00+08:00

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.

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

2025-05-30T17:08:40+08:00

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.

Analysis of Geothermal Direct Use in Agriculture and the Social Economic Effects on Local Communities

2025-05-28T12:26:14+08:00

The direct use of geothermal energy offers a promising solution to diverse energy requirements. However, the focus on utilizing geothermal direct use is less explored in Indonesia. The vast geothermal potential suggests more exploration for direct applications, especially in the agricultural industry. This study analyzes the performance of geothermal direct use utilization at two locations: PLTP Wayang Windu (coffee drying) and PLTP Lahendong (drying agricultural products and palm sugar production), with the socioeconomic effect on local communities in the geothermal work area based on literature review. In Wayang Windu, 147°C brine is processed through a closed heat exchanger system, producing 32.65 kW of energy to dry 1,000 kg of coffee for 12.5 hours. In Lahendong, heat waste is used to make a 12-ton/day palm sugar. Heating efficiency for Paddy drying of the dryer is 82.50%, and total drying efficiency reached 51.10%. This direct use of utilization has the potential to reduce carbon emissions from the production process that still uses fossil fuels or wood. Local communities welcomed the direct use of geothermal technology for drying agricultural products. It is also essential to ensure the regulatory and policy landscape surrounding the geothermal work area is safe and sustainable for public.

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

2025-05-20T00:11:03+08:00

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.