Energy, Exergy Analysis and Sustainability Assessment of a Thermal Power Plant Using Real Operational Data

Introduction and System Context

Global energy dynamics continue to be dominated by fossil fuels, which currently account for approximately 80% of global electricity generation. Within this framework, coal remains a primary and intensive source of energy, particularly in nations where it serves as the domestic fuel mainstay. This reliance persists despite the accelerating transition toward renewable sources, primarily because thermal power plants are essential for bridging the gap between energy availability and a global electricity demand that is growing at an annual rate of 6%. Meeting these requirements is a critical criterion for development, yet the surge in usage brings associated challenges regarding emissions and global warming.

The Necessity of Exergy Analysis

Traditional energy analysis, based on the first law of thermodynamics, provides a baseline view of a plant's current condition but is insufficient for optimizing modern thermal systems. Relying solely on energy balances often results in a coarse distribution of losses, which fails to reveal the specific potential for individual component development. In contrast, exergy analysis identifies the exact positions, amounts, and sources of irreversibilities. By accounting for the quality of energy and the impact of environmental conditions, exergy appraisals allow engineers to distinguish between simple energy dissipation and actual work potential loss. This distinction is vital for designing energy-efficient systems and identifying where enhancements can most effectively reduce fuel consumption and environmental impact.

Study Focus: Yeniköy Thermal Power Plant

This study utilizes real operational data from the Yeniköy Thermal Power Plant located in Muğla, Turkey. The facility consists of two separate units, each possessing a capacity of 210 MW, resulting in a total plant capacity of 420 MW. The research specifically examines one 210 MW unit, which operates on a standard steam power plant cycle comprising several complex sub-systems:

• The Turbine Group: Includes high-pressure (HPT), intermediate-pressure (IPT), and low-pressure (LPT) turbines.
• The Boiler System: The primary site of coal combustion and steam superheating.
• Heat Recovery: A network of three high-pressure feedwater heaters (HPHs) and four low-pressure feedwater heaters (LPHs).
• Auxiliary Components: Essential hardware including the condenser, deaerator, ejector, gland condenser, and various pump groups (CEP and BFP).

By establishing mass, energy, and exergy balances across these specific components at varying ambient temperatures ranging from 25 to 46 °C, the study aims to provide a comprehensive sustainability assessment. The focus on individual equipment nodes allows for the calculation of specific indicators, such as the sustainability efficiency indicator (SEI) and the exergetic ecological index (EEI), which have not previously been integrated in this manner for various environmental conditions.

Methodology: Thermodynamic and Sustainability Framework

The thermodynamic assessment of the Yeniköy Thermal Power Plant is grounded in a rigorous mathematical framework that integrates the first and second laws of thermodynamics. This methodology enables a dual-layer evaluation, determining both the energy quantity conservation and the quality of energy through mass, energy, and exergy balances across all primary and auxiliary components. To ensure high precision in the calculation of thermophysical properties—specifically enthalpy and entropy at various node points—the study employs Engineering Equation Solver (EES) V12.011. This software provides the necessary computational environment to model the steady-state open systems that characterize the plant’s steam cycle and heat exchange processes.

Exergy Balance and Chemical Analysis

While physical exergy is determined based on the deviation of a stream’s state from the reference dead-state (defined by temperature T₀ and pressure P₀), the assessment of the combustion process requires a detailed chemical exergy calculation. For the coal-fired boiler, the fuel exergy rate is not merely its heat content but a function of its elemental composition and the Lower Heating Value (LHV). The methodology utilizes the mass fractions of carbon (C), hydrogen (H), nitrogen (N), sulfur (S), and oxygen (O) to determine the chemical exergy of the coal. This is crucial for identifying the true magnitude of irreversibilities during the combustion process, where the highest rates of exergy destruction typically occur.

Sustainability and Ecological Indicators

To bridge the gap between thermodynamic performance and environmental impact, the framework incorporates exergy-based sustainability indices. These metrics quantify how effectively the plant utilizes available resources and the extent of its ecological footprint. The primary indicators used in this assessment are:

• Sustainability Efficiency Indicator (SEI): This metric provides a benchmark for the long-term viability of the energy generation process, relating exergetic efficiency to the potential for resource conservation.
• Exergetic Ecological Index (ECEI): This index evaluates the relationship between exergy destruction and environmental sustainability, offering a specialized lens through which the ecological cost of irreversibility is measured.

By applying these indicators alongside traditional parameters like the fuel depletion ratio and relative irreversibility, the methodology moves beyond simple efficiency percentages. It identifies the "Improvement Potential Rate" for specific components—such as the boiler and turbine groups—allowing for a targeted approach to enhancing both the technical performance and the overall sustainability of the facility under varying ambient conditions.

Component-Level Performance Assessment

A comprehensive thermodynamic appraisal of the Yeniköy Thermal Power Plant requires a granular analysis of its individual constituents to identify specific sources of irreversibility. By applying exergy balance equations to each node, the research distinguishes between the theoretical energy potential and the actual work produced, revealing significant disparities in performance across the steam cycle's components.

Exergy Destruction and Major Losses

The boiler was identified as the primary source of thermodynamic inefficiency within the facility. It exhibited the highest exergy destruction rate, calculated at 349,452.79 kW. In the context of the entire plant, the boiler accounted for 71.00% of the total exergy destruction at a reference temperature of 25 °C. This intensive irreversibility is primarily attributed to the chemical reactions and heat transfer processes inherent in coal combustion. The intermediate-pressure turbine (IPT) and low-pressure turbine (LPT) followed as the next most significant sources of exergy destruction, with relative irreversibility values of 5.42% and 4.22%, respectively.

High-Efficiency Constituents

While major subsystems like the boiler struggle with high destruction rates, specific auxiliary and turbine components demonstrate robust exergetic performance. The High-Pressure Turbine (HPT) achieved the highest exergetic efficiency among the major power-producing components at 86.12%. Furthermore, specific heat exchange and auxiliary units reached peak efficiency levels:

• Ejector: 98.62%
• High-Pressure Heater (HPH-3): 96.01%
• Low-Pressure Heater (LPH-2): 88.16%

Areas for Improvement

The analysis also highlighted critical low-efficiency areas that significantly detract from the system's overall exergetic sustainability. The gland condensers and boiler feed pumps (BFP) were noted for their poor performance, with efficiencies recorded at 28.30% and 37.51%, respectively. These figures indicate a high potential for technical improvement. Because exergy analysis locates the exact position and magnitude of these losses, these components represent primary targets for future optimization to reduce fuel consumption and environmental impact.

These component-level results provide the necessary data to evaluate the sustainability efficiency indicator (SEI), which was calculated at 2.50 for the plant. By identifying which constituents cause the most intensive irreversibility, engineers can prioritize interventions in the boiler and turbine groups to enhance the facility's total effectiveness.

Impact of Ambient Temperature Variation

The thermodynamic performance of the 210 MW coal-fired power plant exhibits significant sensitivity to changes in environmental conditions. As the reference temperature increases from a baseline of 25 °C to an extreme of 46 °C, the overall cycle exergy efficiency undergoes a notable decline, dropping from 59.94% to 56.00%. This reduction in efficiency is primarily driven by the exacerbation of irreversibilities across major plant components, particularly within the boiler and condenser subsystems.

The boiler remains the most critical component regarding exergy destruction, and its performance is directly hindered by rising outdoor temperatures. Quantitative analysis reveals that exergy destruction in the boiler increases from 349.45 MW at 25 °C to 360.05 MW at 46 °C. This rise in destruction indicates that higher ambient temperatures negatively impact the combustion and heat transfer processes, leading to a greater loss of potential useful work during steam generation.

The turbine group, essential for converting thermal energy into mechanical work, also demonstrates clear performance degradation under varying environmental states. The efficiency of each turbine stage shows a downward trend as temperature rises:

• High-Pressure Turbine (HPT): Efficiency diminishes as ambient conditions deviate from the standard reference state.
• Intermediate-Pressure Turbine (IPT): Shows increased susceptibility to exergy losses at higher temperatures.
• Low-Pressure Turbine (LPT): Experiences a drop in efficiency that contributes to the overall reduction in cycle performance.

Furthermore, the condenser's ability to maintain the required vacuum and effectively reject heat is compromised by higher ambient temperatures. This contributes to the total increase in irreversibilities, as the temperature difference between the system and its surroundings narrows, reducing the exergetic quality of the heat exchange. The combined effect of these component-level destructions results in a less sustainable and less efficient operation during periods of high environmental heat, highlighting the importance of considering local climate variations in the assessment of thermal power plants.

Would you like the summary of the next section, which covers the sustainability indices and exergetic ecological indicators?

Sustainability and Ecological Indicators

The assessment of a thermal power plant's environmental impact requires moving beyond simple energy balances to integrate exergy-based sustainability indices. These indicators provide a quantitative framework for evaluating how effectively a system utilizes natural resources and the degree to which its operation aligns with ecological preservation. In this study of a 210 MW coal-fired facility, the relationship between thermodynamic efficiency and environmental stewardship is articulated through the Sustainability Efficiency Indicator (SEI) and the Exergetic Ecological Index (ECEI).

Sustainability Efficiency Indicator (SEI)

The SEI serves as a primary metric for determining the baseline sustainability level of the thermal power plant. For the plant under investigation, the SEI was calculated at 2.50. This value is intrinsically linked to the system's ability to minimize waste; a fundamental assumption in this analysis is that a linear relationship exists between exergy efficiency and the sustainability index. As the exergy efficiency of the plant or its individual components increases, the sustainability index rises proportionally, reflecting a reduction in the exergy destruction that would otherwise lead to environmental degradation.

Exergetic Ecological Index (ECEI) and Component Performance

While the overall plant sustainability provides a macro-view, the Exergetic Ecological Index (ECEI) allows for a granular assessment of individual components. The ECEI measures the ecological quality of energy conversion within specific equipment. The study revealed significant variance across the plant’s architecture:

• High-Performance Components: The ejector achieved the highest ECEI value at 0.97, corresponding with its position as the most exergetically efficient component in the system (98.62%).
• Low-Performance Components: The condenser yielded the lowest ECEI values. Furthermore, specific auxiliary components, including the gland condenser and the feed pump, yielded negative or notably low ECEI values.

These variations are critical for identifying the potential for improvement. Components with low or negative ECEI values represent areas where the irreversibilities are so intense that they significantly detract from the plant's ecological standing. For instance, the low ECEI of the condenser is a direct reflection of high energy destruction and thermal rejection to the environment.

The Role of Irreversibility in Sustainability

The mechanism driving these sustainability indices is the management of irreversibility. Exergy analysis identifies the positions and sources of energy losses that traditional energy analysis may overlook. By quantifying the fuel depletion ratio and the improvement potential rate, researchers can correlate thermodynamic stability with ecological impact. The assessment demonstrates that high exergy destruction—particularly in the boiler, which accounts for 71.00% of the plant's total exergy destruction—is the primary bottleneck for both efficiency and sustainability. Consequently, reducing these irreversibilities is not merely an operational goal but a prerequisite for improving the plant’s ecological indicators and meeting the rising global demand for electricity with reduced environmental consequences.

Comparative Analysis and Improvement Potential

The thermodynamic evaluation of the Yeniköy Thermal Power Plant reveals significant performance gaps when measured against global industrial standards. The plant's overall exergy efficiency was determined to be 22.82%, a figure that underscores a substantial departure from international benchmarks. For comparison, reported exergy efficiencies for similar coal-fired installations in China and India reach 41.4% and 37.27%, respectively. This discrepancy highlights the necessity for a rigorous identification of systemic irreversibilities to bring the facility closer to modern operational norms.

Prioritization of Component Enhancements

To systematically address these inefficiencies, the research utilized relative irreversibility (RI) and Improvement Potential (IP) metrics. The boiler was identified as the primary source of thermodynamic loss, exhibiting a relative irreversibility of 79.43%. Because such a high percentage of the plant's total exergy destruction is localized within this single component, it represents the most critical target for technical intervention. Beyond the boiler, the turbine group and the condenser also demonstrated high IP rates, marking them as secondary priority areas for upgrades.

Factors Influencing Low Efficiency

The suboptimal performance observed at the Yeniköy facility is largely attributed to issues within the combustion and thermal transfer processes. Analysis suggests that the low efficiency levels stem from the following factors:

• Non-ideal Design: Architectural or systemic configurations that fail to optimize the extraction of useful work from the fuel source.
• Maintenance Inadequacies: Inadequate upkeep of high-destruction components, which exacerbates irreversibilities over time.
• Combustion Process Losses: Significant exergy is lost during the chemical reaction stage in the boiler, where the maximum destruction rate of 71.00% occurs.

By focusing on the boiler, turbine group, and condenser, the plant can significantly reduce its fuel depletion ratio and enhance its sustainability efficiency indicator. Improvements in these areas are essential not only for increasing electricity output per unit of fuel but also for mitigating the negative environmental impacts associated with high-consumption coal-fired power generation.

Key findings

• Boiler as Principal Irreversibility Source — The boiler accounts for 71.00% of the plant's total exergy destruction, primarily due to chemical reactions and heat transfer losses.
• Ambient Temperature Sensitivity — Increasing the dead-state temperature from 25 °C to 46 °C increases cycle exergy destruction by approximately 20 MW.
• Component Efficiency Hierarchy — The High-Pressure Turbine (86.12%) is significantly more efficient than the Intermediate (72.85%) and Low-Pressure (61.62%) units.
• Global Efficiency Gap — The studied plant shows a second-law efficiency of 22.82%, which is substantially lower than the 41.4% achieved by ultra-supercritical plants in China.

Method and assumptions

The study utilises real operational data from the 210 MW Yeniköy Thermal Power Plant. Thermodynamic analysis is performed using Engineering Equation Solver (EES) software. The methodology involves establishing mass, energy, and exergy balance equations for 17 individual components, including turbines, heaters, and pumps. Chemical exergy is calculated based on the elemental composition of the coal fuel (LHV of 1859.3 kcal/kg). A parametric study is conducted to observe the effects of varying ambient (dead-state) temperatures from 25 °C to 46 °C. The analysis extends to sustainability through specific indices: the Sustainability Efficiency Indicator (SEI) and the Exergetic Ecological Index (ECEI), which relate thermodynamic losses to environmental impact and resource depletion.

Where it applies

• Plant Modernisation Strategy — Provides a data-driven roadmap for prioritising component replacements, focusing on the boiler and turbine group.
• Operational Optimization — Assists plant operators in adjusting parameters to mitigate efficiency losses caused by high ambient temperatures.
• Sustainability Benchmarking — Offers a framework for energy researchers to use exergy-based indices to evaluate the environmental footprint of thermal utilities.

Terms used

• Exergy Destruction —
• Dead-state —
• Relative Irreversibility —
• Improvement Potential —
• Exergetic Ecological Index —

Questions and answers

Which component should be the priority for efficiency upgrades?

How does hot weather affect the power plant's performance?

Why is the High-Pressure Turbine more efficient than the Low-Pressure Turbine?

What software was used for the thermodynamic calculations?

How to cite

Gungor Celik, A.; Aydemir, U. Energy, Exergy Analysis and Sustainability Assessment of a Thermal Power Plant Operating in Various Environmental Conditions Using Real Operational Data. Sustainability 2025, 17, 1417.