Combined Cycle Research Articles

Comparative and optimal study of energy, exergy, and exergoeconomic performance in supercritical CO2 recompression combined cycles with organic rankine, trans-critical CO2, and kalina cycle

The bottom cycle in supercritical carbon dioxide (sCO2) recompression Brayton combined cycle (RCBC) effectively recovers substantial waste heat for electricity generation, enhancing energy utilization. The recovery efficiency is significantly influenced by the bottom cycle configurations and specific working conditions. Besides, implementing these bottom cycles introduces challenges related to increased system dimensions and design complexity. The present study aims to understand and evaluate the characteristics and optimal trade-offs of various bottom cycles, including trans-critical, subcritical, and non-azeotropic mixed working fluids, by establishing 3E (energy, exergy and Exergoeconomic) models for sCO2/tCO2, sCO2/ORC, and sCO2/KC combined cycle systems. To analysis and enhance interpretability, statistical Global Sensitivity Analysis (GSA) alongside unsupervised learning-based Self-Organizing Map (SOM) techniques and parametric analysis are employed. These methods identify key parameters and discern system patterns. Subsequently, the Non-Dominated Sorting Whale Optimization Algorithm (NSWOA) and entropy weight-based Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) are applied to establish a Pareto-optimal decision space and identify compromised ideal design points for each combined cycle. The results quantitatively rank sensitivity for objective variables within the design space in different combined cycles and visually represent system nonlinearity and coupling relationships in 2D weight planes using SOM. The TOPSIS trade-off points based on the Pareto frontier for the three combined cycles are ηth = 45.08 %, cp,tot = 8.5199 $/GJ, ηth = 45.13 %, cp,tot = 8.3739 $/GJ, and ηth = 48.97 %, cp,tot = 8.4783 $/GJ, respectively. Integrating machine learning techniques provides a comprehensive understanding of system patterns, offering valuable insights for decision-makers in the design and optimization of combined cogeneration cycles.

Combined cycle gas turbine (CCGT) plants utilizing methane-hydrogen blends represent a significant element in Australia’s journey toward achieving net-zero emissions

To deliver 570 TWh of dispatchable electricity to the grid in Australia, it is necessary to build up wind and solar photovoltaic power plants generating capacity of 325 GW, and a long-term hydrogen energy storage system comprising 50–150 GW of electrolyzers, 50 TWh of hydrogen storage, and 165 GW of hydrogen power generation. While the addition of other renewable energy producers and energy storage technologies effective on shorter scales are certainly welcome and positively impact the above demand, the inclusion of inter-annual variability and safety negatively impacts these numbers. Fuel cells are currently less advanced compared to electrolyzers and hydrogen storage in salt caverns. Expanding hydrogen power generation will require exploring additional opportunities. Here we advocate for methane-hydrogen Combined Cycle Gas Turbine (CCGT) plants. Their adaptability to effortlessly integrate methane and green hydrogen mixtures positions them as a key player in the evolution toward net zero. This transition will be complete once a fully established wind and solar photovoltaic generation, coupled with an efficient hydrogen energy storage system, is in place. Notably, these CCGT plants consistently yield the lowest Life Cycle Analysis (LCA) carbon dioxide (CO2) emissions during the grid’s progression toward net zero.

B-227 Customized molecular tests for minimal residual disease: a tool for therapeutic decisions in follicular lymphoma patients

Abstract Background Monitoring of minimal residual disease (MRD) is based on accurate laboratory tests which can recognize a small fraction of malignant cells that survived the course of treatment. Several studies of the B-non-Hodgkin lymphoma group have been presented that MRD positivity at the end of treatment is a negative prognostic index. Follicular lymphoma (FL) is a chronic indolent malignancy, which response highly to immuno-chemotherapy followed by prolonged remissions but with inevitable relapse in most patients. The GALLIUM study showed that immuno-chemotherapy combinations, 6 cycles of bendamustine-obinutuzumab (BO), is the most efficacious treatment, but with severe side effects .In addition, 90% of patients achieved negative MRD from peripheral blood (PB) or bone marrow (BM) after only 3 BO cycles. These findings raise the possibility for MRD based treatment approach, where the duration of chemotherapy could be decided according to MRD status at mid-induction (MI). Identification of a marker in the PB and/or BM of each FL patient which will be use to the design of a sensitive RQ-PCR test for MRD detection for follow-up. Methods Qualitative PCR for translocation 14:18 and for the VDJ rearrangement sequence of the immunoglobulin heavy chain was used for marker identification. MRD monitoring was done by RQ-PCR. MRD monitoring for VDJ was designed specifically to each patients based on his VDJ sequence. MRD was assessed on PB and BM at MI. Results Marker for monitoring was identified at 11/21 patients in this study. After 3 combined therapy cycles, 7 patients were found to have MRD negativity by RQ-PCR therefore continue with immuno-therapy only. MRD positivity was assessed in BM of 3 patients (0.11%, 0.022%, and 0.133%). These 3 patients continued with the combined therapy. RQ-PCR sensitivity was 10-4-10-5. Conclusions This study will reveal the ability to use sensitive and specific MRD that has to be designed for each patient according to his marker and enable the establishment of a treatment with a high safety profile for FL patients. Correlation between MRD status and clinical and safety parameters will be assessed at the end of the study, 30 months after the first treatment, taking into account MRD status from different time point of the follow-up period.

Energy, exergy and advanced exergy analyses on Garri “1” combined cycle power plant of Sudan

Thermal power plants account for 39% of Sudan's electricity grid. Consequently, enhancing the performance of these plants is crucial for bolstering the Sudanese energy sector. This paper presents an analysis of energy, conventional exergy, and advanced exergy for 180-MW Garri “1” combined cycle power plant in Sudan. The study focuses on assessing the enhancement potential of this power plant to provide guidance for performance improvement and identify optimal areas for enhancement within the plant's components. The energy and classical exergy analyses results indicated that the highest energy losses occur in the stacks (55.1%), while the largest source of exergy destruction is combustion chambers (50.98%). Furthermore, the lowest contributions to energy and exergy losses are from the deaerators (0.15% energy and 0.32% exergy) and auxiliary systems (0.22% energy and 2.85% exergy). The overall energy and exergy efficiencies of the plant were found to be 36.1% and 34.1%, respectively. The advanced exergy analysis exhibited that the ratios of unavoidable to avoidable exergy destruction and endogenous to exogenous exergy destruction are 87.95% to 12.05% and 68.3% to 31.7%, respectively. Moreover, it was shown that the primary source of avoidable endogenous exergy destruction is the combustion chambers (48.53%). Furthermore, the improvement potential in the plant's exergy efficiency was found to be only 3%, suggesting the need for optimization of operational parameters to enhance overall performance. The current paper offers valuable insights into enhancing efficiency of Sudanese energy sector, with implications for optimizing the energy sector in similar developing countries.

The Application of Case-Based Learning (CBL) Combined with PDCA Cycle in the Clinical Teaching Practice of Breast Ultrasound in Standardized Residency Training

Background: The integration of case-based learning (CBL) with the plan-do-check-act (PDCA) cycle has potential benefits for clinical education, yet its efficacy in ultrasound residency training, particularly for breast ultrasound, requires evaluation. Aim: This study aimed to assess the impact of a combined CBL and PDCA cycle teaching model on the clinical thinking and skills of ultrasound residents compared to traditional teaching methods. Methods: A comparative study was conducted at Sichuan Provincial People’s Hospital’s ultrasound medicine base, from August 2020 to June 2023, focusing on residents in training. Sixty-one trainees were randomly divided into two groups: a joint group (n = 31) taught using a PDCA cycle-based model integrated with CBL and a traditional group (n = 30) taught with conventional methods. Both groups underwent a 20-hour course and were subsequently evaluated on theoretical knowledge, clinical thinking, and skills. Comparative statistical analysis was performed to evaluate the performance differences between the two groups. Results: The joint group demonstrated significantly better clinical thinking and skills operation than the traditional group (P < 0.05). No significant difference was observed between the groups regarding theoretical knowledge (P > 0.05). Conclusions: The combined CBL-PDCA cycle teaching mode significantly enhances the clinical thinking abilities and operational skills of residents in breast ultrasound training. This innovative approach shows promise as an effective educational strategy to foster intrinsic motivation and higher order learning capabilities among ultrasound residents.

Investigating the impact of nanofluids and exergy metrics for integrated solar-biomass SCO2 power and desalination cycles

Several strategies have emerged for utilizing waste heat across diverse sectors. Yet, integrated systems that merge power generation with freshwater production, especially those leveraging renewable energy, remain relatively unexplored. Addressing this gap, a novel solar biomass-driven system is under development for power generation and desalination facilities. In the suggested system, rather than wasting the energy of a supercritical CO2 power cycle, a bottoming cycle is proposed to augment energy utilization factor (EUF). By integrating humidification-dehumidification, thermal vapor compression, and reverse osmosis (HDH-TVC-RO) with a multi-effect distillation (MED) unit, freshwater production rate is significantly enhanced. The outcomes reveal a freshwater output of 29.36 kg/s, a gained output ratio (GOR) of 17.36, and the EUF of 3.372. Various nanofluids have been assessed for the solar collector and due to superior total exergy efficiency and less corrosion effects, Cu- and carbon-based nanoparticles are recommended. Sensitivity analysis indicates that increasing the pressure ratio of compressors boosts the total GOR. Furthermore, adjustments to both the parameters of pressure of steam fed to HDH-TVC, and the compressor pressure ratio demonstrate a linear effect on EUF behaviour.

A novel dual-split layout for transcritical CO2 power cycle adapted to variable heat sources

Transcritical CO2 power cycle is widely used as the bottom cycle of natural gas engine to recover waste heat. However, owing to the large variation in waste heat sources caused by changes in engine operating conditions, the adaptability of the CO2 power cycle is poor, reflected in severe performance deterioration in thermal match, components and system power output. Hence, to improve the adaptability of the CO2 power cycle to wide-range fluctuation in heat sources, a novel dual-split configuration is proposed in this paper. The freedom of regulation is effectively enhanced by the supplementary split branches, and the mass flow rate through different heat exchangers can be actively adjusted with high flexibility. Furthermore, off-design performance models and a calculation procedure are built to present the off-design performance of the different cycles under the engine operational profile. The results indicate that the proposed configuration can improves the adaptability of the CO2 cycle to fluctuating heat sources effectively. Specifically, for all engine operational conditions, the invalidated operating region was contracted from eight to four points, with the engine coolant and exhaust gas utilisation rates exceeding 90 % and 97.4 % respectively. In addition, under low engine operating conditions, the cycle pressure ratio and mass flow rate were maintained at relatively high values, contributing to enhanced pump and turbine efficiencies. The maximum net power output increased by 8.3 kW, and the minimum brake-specific fuel consumption decreased by 16.9 %.

Energy and exergy analyses on the high-pressure bleeding-air variable cycle designed for a wide-speed-range airbreathing propulsion system

The performance of the traditional turbojet decreases sharply with the increase of the Mach number in the supersonic flight, especially for the turbine-based combined cycle (TBCC) engine in the transition region of the turbojet and scramjet engine. This paper proposes a new high-pressure bleeding-air variable cycle engine (HB-VCE) concept that aims to ease the sharp contradiction between thrust output and fuel consumption of TBCC in the transition region. Through the energy and exergy analyses, the HB-VCE shows greater potential in energy utilization under high Mach flight conditions. The performance of HB-VCE significantly improves as the bleed ratio increases, with a more pronounced effect at higher Mach numbers. At Mach 1.5, the HB-VCE increases the specific thrust (ST) by 2.84 % and reduces the specific fuel consumption (SFC) by 2.73 %. At Mach 2.4, it increases the ST by 6.60 % and reduces the SFC by 6.52 %. Additionally, the controlling law of the critical bleeding ratio constrained by the turbine outlet temperature is proposed. Finally, the effect of the turbine inlet temperature, overall pressure ratio, and Mach number on the critical bleeding ratio is analyzed. This paper provides a promising HB-VCE concept with greater energy utilization for the TBCC design in the transition region.

Mixing enhancement assisted by dual plate cavity in supersonic flow

Fast and efficient mixing of high-speed shear flow formed by fuel and oxidizer is of great importance for the improvement of rocket-based combined cycle engine performance. Nevertheless, the existence of compressibility effects of high-speed flow significantly inhibits the growth process of a mixing layer. Moreover, a finite-length combustor of the engine calls for more effective enhanced-mixing strategies to complete mixing in a shorter streamwise distance. To this end, in present paper, the strategy called dual plate cavity (DPC) is proposed to promote mixing. Three cases including the benchmark, front-DPC and back-DPC cases are selected to perform the comparative study. By means of high-order direct numerical simulations, the structure evolution characteristics and turbulence intensity distributions are researched. The index of velocity thickness is utilized to assess the mixing layer growth. The results indicate that with the introduction of DPC, the mixing process is dramatically promoted. The penetration behavior of newly found T-shaped structures into the upper main stream can engulf more fluid into the mixing region. Specifically, in the back-DPC case, the coexistence of both large-scale and small-scale structures in the far flow field can improve the turbulence intensity. The spatial correlation analysis results show that with the influence of DPC, the structure sizes are much larger than that of the benchmark case in the same streamwise position. Meanwhile, the contour line equal to 0.5 possesses property of distortion for the back-DPC case. The drastic pulsation of a mixing layer edge can obviously promote the mixing process. Through exploration of the enhanced-mixing mechanisms, this work indicates that the proposed DPC strategy is a good candidate for efficient mixing, and in the future, more detailed work including three-dimensional simulations concerning the strategy optimization is suggested to be performed.

Numerical investigation of the distributed combustion in the thermal choked solid fuel combined cycle engine

In this study, a solid fuel combined cycle engine concept based on the distributed combustion and the self-adaptive thermal choking is proposed, which can operate effectively within a wide Mach number range. By regulating the heat release through the distributed fuel injection, the thermal choking can be formed in the fixed geometry combustor. The air intake controls the flow capture and circulation area through the movement of its head cone, ensuring stable air breathing over a wide range. Numerical simulations conducted under Ma = 3.0 and 6.0 conditions using the validated Eulerian-Lagrangian method coupled with gaseous and particle reaction models demonstrate the concept's capability to operate within the Mach number range of 3.0–6.0, delivering improved mixing, combustion, and specific impulse performance.

Evaluating the Harmonic Effects on the Thermal Performance of a Power Transformer

Harmonics in the power grid contribute to increased power losses in both the core and windings of power transformers. These losses lead to abnormal rises in temperature causing overheating and reduce the efficiency of the transformer. If the losses and temperature exceed the values set during the design stage for linear load conditions, it can damage the transformer’s insulating materials and shorten its lifespan. To assess the thermal impact of power system harmonics on transformers under steady-state and transient conditions, the rated losses and harmonic losses of the transformer are calculated. These losses are then inputted into a developed thermal 3D finite element method (FEM) performance model to determine the temperature distribution of transformer components. The numerical results from the thermal model will be compared with data from a Hyundai test report and real measurements from Egypt’s Kureimat power plant, specifically a 750 MW combined cycle power plant. The thermal modeling is focused on a step-up (16.5/240 kV), 240 ± 4 × 2.5%, 180/240/300 MVA power transformer operating in ONAN, ONAF1, and ONAF2 modes. This paper shows that the developed model aligns closely with actual measurements and the HYUNDAI test report. The loss calculations reveal that the discrepancy in total losses, with and without accounting for harmonics, becomes more pronounced as the load increases. Using this model, the presence of grid harmonics results in a higher temperature distribution across transformer components, leading to an increase in the hot spot temperature.

Analysis of various system designs for adsorption cycle in building heating applications

Buildings are major energy consumers, highlighting the need for efficient thermal energy storage to reduce reliance on non-renewable sources. Adsorption-based systems offer significant energy savings for heating applications. This research compares four critical adsorption-based cycles: adsorption thermal energy storage, adsorption heat transformer, adsorption mass recovery with heating and cooling, and a novel combined cycle. The study uncovers new insights into temperature and pressure control challenges through lumped parameter modeling. These dynamic modeling results advance our understanding and optimization of adsorption systems, enhancing their feasibility and efficiency for building heating. The adsorption mass recovery cycle demonstrates superior energy storage density (289 kW h/m³) compared to the adsorption heat transformer cycle (240 kW h/m³) and the adsorption thermal energy storage cycle (157 kW h/m³). It also has the highest water uptake (0.56 kg/kg), surpassing the other two cycles. Despite its pressure fluctuations and temperature instability challenges, the adsorption mass recovery cycle outperforms the adsorption heat transformer and adsorption thermal energy storage cycles in energy storage density. The novel combined cycle optimizes heat storage and release, achieves the highest energy storage density (302 kW h/m³), and outperforms the individual cycles. The combined cycle's performance was evaluated in a home in South Korea, revealing significant energy savings and proving an effective solution for enhancing energy efficiency in building heating systems. This research addresses a crucial gap and provides a foundation for future advancements in thermal energy storage.

A Surrogate Model Approach to Predict Operations and Maintenance Cost for Combined Cycle Power Plant

Abstract In the transition toward carbon neutrality by 2050, renewable energy sources are gaining prominence. The variability of renewable energy poses challenges for power grid stability. Gas turbine combined cycle (GTCC) power plants play a crucial role in grid stabilization, especially during peak loads. In GTCC power generation, operations and maintenance (O&M) cost is the next most important after fuel and initial investment cost, and it is necessary to predict O&M cost according to changes in the operating environment for efficient and stable operation of GTCC power plant. However, various uncertainties exist when estimating O&M costs because actual design information is limitedly disclosed due to maintenance contracts between operators and manufacturers, and it is difficult to obtain accurate variables according to the operation condition. In this paper, the correlation was analyzed considering the uncertainty of the factors affecting the O&M cost of the GTCC power plant through sensitivity analysis, and the main factors were defined. In addition, a surrogate model was proposed that can quickly calculate fixed and variable O&M cost according to changing operating scenarios such as shortening startup time, enhancing ramp rate, or lower minimum load. Through the case study, short-term and long-term O&M costs can be estimated in the operating environment of the GTCC power plant currently being operated. Additionally, the model facilitates cost projections for new hybrid GTCC facilities (combining gas turbines with energy storage systems), aiding long-term investment planning.

Novel Recuperated Power Cycles for Cost-Effective Integration of Variable Renewable Energy

The ongoing transition to energy systems with high shares of variable renewables motivates the development of novel thermal power cycles that operate economically at low capacity factors to accommodate wind and solar intermittency. This study presents two recuperated power cycles with low capital costs for this market segment: (1) the near-isothermal hydrogen turbine (NIHT) concept, capable of achieving combined cycle efficiencies without a bottoming cycle through fuel combustion in the expansion path, and (2) the intercooled recuperated water-injected (IRWI) power cycle that employs conventional combustion technology at an efficiency cost of only 4% points. The economic assessment carried out in this work reveals that the proposed cycles increasingly outperform combined cycle benchmarks with and without CO2 capture as the plant capacity factor reduces below 50%. When the cost of fuel storage and delivery by pipelines is included in the evaluation, however, plants fired by hydrogen lose competitiveness relative to natural gas-fired plants due to the high fuel delivery costs caused by the low volumetric energy density of hydrogen. This important but uncertain cost component could erode the business case for future hydrogen-fired power plants, in which case the IRWI concept powered by natural gas emerges as a promising solution.

Investigating different scenarios of integrating solar-assisted carbon capture with combined cycle power plant and water desalination system

In this work, an optimal algorithm-based integration of solar thermal energy with carbon capture and desalination processes were proposed. The stripper columns, identified as the most energy-consuming equipment, were designed with constant capacities to ensure practicality and applicability. Results show that, without affecting the power plant's efficiency, using a solvent tank as an energy storage system (scenario-2) increases total CO2 capture from 45 % to 98 % compared to a part-time solar power system (scenario-1). Utilizing two solvent tanks reduces waste energy from 87 % to 67 % (scenario-3), while achieving 100 % CO2 capture. Using three different stripper columns (scenario-4) lowers the levelized cost of energy by 20 %. Incorporating an additional multiple effect distillation system (scenario-5) reduces levelized cost of energy and energy loss by 26 % and 74 %, respectively. Approximately 28 % of the total solar energy collected (4.64 × 106 MWh) was used to capture 1.57 × 106 ton.year−1 of CO2. The remaining energy was used in desalination to produce 9.4 × 106 m³.year−1 of fresh water, increasing overall energy efficiency from 28 % to 81 %, and reducing waste energy to 0.88 × 106 MWh, just 26 % of previous scenarios' waste.

Model-based evaluation of ammonia energy storage concepts at high technological readiness level

Ammonia is a promising carbon-free energy carrier since it can be stored as a liquid at mild conditions and its production process from hydrogen and nitrogen is established and efficient. Several Ammonia-to-Power concepts have been proposed in the literature, many of which employ not-yet-mature electrochemical technologies. We model the charging and discharging phases of three ammonia energy storage concepts in Aspen Plus seeking a compromise between efficient concepts and mature technologies. In the charging phase, ammonia is produced via the Haber–Bosch process using hydrogen from low-temperature water electrolysis for all the considered concepts. For the discharging phase, three ammonia conversion processes are modeled: (i) ammonia is thermally decomposed into nitrogen and hydrogen by using thermal energy from storage, and hydrogen is converted into electricity in a fuel cell; (ii) ammonia is thermally decomposed by using heat generated through the combustion of a fraction of the ammonia stream, and the produced hydrogen is supplied to a fuel cell; (iii) ammonia is used as a fuel in a combined power cycle. We compare these concepts with respect to roundtrip efficiency and levelized cost of electricity. The roundtrip efficiency and the levelized cost of electricity of the modeled concepts are ca. 30–34 % and 0.28–0.31 €kWh−1 (for an electricity purchase price of 0.03 €kWh−1). Concept (i) has both the highest roundtrip efficiency and the lowest levelized cost of electricity. We identify the process bottlenecks via an exergy analysis.

The Impact of Retrofitting Natural Gas-Fired Power Plants on Carbon Footprint: Converting from Open-Cycle Gas Turbine to Combined-Cycle Gas Turbine

Since retrofitting existing natural gas-fired (NGF) power plants is an essential strategy for enhancing their efficiency and controlling greenhouse gas emissions, this paper compares the carbon footprint of natural gas-fired power generation from an NGF power plant in Brazil (BR-NGF) with and without retrofitting. The former scenario entails retrofitting the BR-NGF power plant with combined-cycle gas turbine (CCGT) technology. In contrast, the latter involves continuing the BR-NGF power plant operation with open-cycle gas turbine (OCGT) technology. Our analysis considers the BR-NGF power plant’s life cycle (construction, operation, and decommissioning) and the natural gas’ life cycle (natural gas extraction and processing, liquefaction, liquefied natural gas transportation, regasification, and combustion). Moreover, it is based on data from primary and secondary sources, mainly the Ecoinvent database and the ReCiPe 2016 method. For OCGT, the results showed that the BR-NGF power plant and the natural gas life cycles are responsible for 620.87 gCO2eq./kWh and 178.58 gCO2eq./kWh, respectively. For CCGT, these values are 450.04 gCO2eq./kWh and 129.30 gCO2eq./kWh. Our findings highlight the relevance of the natural gas’ life cycle, signaling additional opportunities for reducing the overall carbon footprint of natural gas-fired power generation.

A multi-stage lithium-ion battery aging dataset using various experimental design methodologies

This dataset encompasses a comprehensive investigation of combined calendar and cycle aging in commercially available lithium-ion battery cells (Samsung INR21700-50E). A total of 279 cells were subjected to 71 distinct aging conditions across two stages. Stage 1 is based on a non-model-based design of experiments (DoE), including full-factorial and Latin hypercube experimental designs, to determine the degradation behavior. Stage 2 employed model-based parameter individual optimal experimental design (pi-OED) to refine specific dependencies, along with a second non-model-based approach for fair comparison of DoE methodologies. While the primary aim was to validate the benefits of optimal experimental design in lithium-ion battery aging studies, this dataset offers extensive utility for various applications. They include training of machine learning models for battery life prediction, calibrating of physics-based or (semi-)empirical models for battery performance and degradation, and numerous other investigations in battery research. Additionally, the dataset has the potential to uncover hidden dependencies and correlations in battery aging mechanisms that were not evident in previous studies, which often relied on pre-existing assumptions and limited experimental designs.

Hybridization of Concentrated Solar Thermal With Geothermal and Biomass Power

While Geothermal Power Plants (GPPs) can be a reliable renewable energy source, this reliability can decrease over the years due to brine mass flow declining. This reduced mass flow causes extra capacity unused in the GPP turbines. This problem can be overcome by hybridizing GPPs with CST and biomass. These three thermal technologies can, in theory, complement each other if all the resources are present at the exact location. This is the scenario for this study, as the location for the case study is the Kızıldere 2 (KZD2) GPP in Denizli, Turkiye, operated by Zorlu Energy. This region has sufficient potential for all three technologies: CST, geothermal, and biomass. Furthermore, by building a topping cycle using CST and biomass, it is possible to generate additional power. This study utilizes a topping steam Rankine cycle run equally by CST and biomass, and, as a result, the 20% excess capacity in the GPP turbine is used while generating an additional 20 MWe of power.

Performance Evaluation of a Condenser at a Combined Cycle Power Plant Using the LMTD Method

This study evaluates the performance of the condenser at the Cilegon Combined Cycle Power Plant (CCPP) using the Logarithmic Mean Temperature Difference (LMTD) method to measure the heat transfer rate. Routine maintenance carried out on the condenser in the form of cleaning the condenser water box and condenser tube from garbage and crust on the condenser tube wall. Currently, condenser maintenance follows a routine schedule that is tied to steam turbine maintenance, without taking actual condenser performance into account. This can lead to inefficiencies and unnecessary downtime. The goal of this research is to assess the heat transfer rate of the condenser before and after maintenance to judge its effectiveness. Data on temperature changes were gathered in June 2023, before maintenance, and again in July 2023, after an overhaul. The analysis shows that the heat transfer rate increased from 51,362,294.48 kcal/h to 127,246,219.7 kcal/h, while the LMTD value rose from 0.76°C to 1.86°C. Based on these results, the study suggests a new approach to maintenance that focuses on performance. Specifically, maintenance should be done when the heat transfer rate drops below 110,000,000 kcal/h. This approach will help ensure the condenser works at its best, improve the plant's overall efficiency, and prevent the need for unnecessary maintenance. By aligning maintenance with performance data, the plant can boost output while lowering costs and downtime.