Combined Cycle Units Research Articles

Разработка методики расчета составляющих резерва тепловой экономичности парогазовых установок

The components of the thermal efficiency reserve of thermal power plant equipment are the overexpenditure or savings of fuel due to the deviation of the actual values of the equipment performance from their nominal values. They are determined in tons of reference fuel for a certain period. The components of the thermal efficiency reserve are the most essential element of the technical record-keeping and reporting systems of power plants. They allow us to quantitatively assess the technical condition of the equipment and, on this basis, effectively plan repair programs. The methods to calculate the components of the thermal efficiency reserve of steam power plants are well developed and regulated according to the regulatory documents. Regulatory requirements for combined-cycle plants in this area contain inaccuracies and do not cover a full list of the components of the thermal efficiency reserve. Thus, it is necessary to develop a method that allows us to calculate the components of the thermal efficiency reserve of combined-cycle plants. When developing the methodology for combined-cycle plants, the authors have applied the approaches to calculate the components of the thermal efficiency reserve that are used for steam power plants. In addition, available methods for assessing the thermal efficiency of thermal power plant equipment have been used. The developed methods have been tested based on actual data on the operation of combined-cycle plant PGU-116. A methodology to calculate the components of the thermal efficiency reserve of combined-cycle plants with waste-heat boilers without fuel afterburning has been developed. The methodology has been tested in assessing the thermal efficiency indicators of combined-cycle plant in operation. Shortcomings in regulatory documents of the energy industry in terms of calculating the components of the thermal efficiency reserve of combined-cycle equipment have been identified. The developed methodology can be recommended for use in the systems of technical record-keeping and reporting of power plants when monitoring the indicators of thermal efficiency of combined-cycle plants. To ensure the objectivity of the results of the analysis of the efficiency of operated combined-cycle power units in Russia, it is necessary to adjust industry regulatory documents. They should contain uniform scientifically substantiated methods for calculating the components of the reserve of thermal efficiency of combined-cycle equipment.

Investigation of control strategies for the hydrogen fueled R-Graz cycle

In the context of large-scale hydrogen power generation, the Graz cycle and its improved version, the R-Graz cycle, exhibits excellent performance and technological feasibility. For such semi-closed, split cycles, apart from the conventional adjustments of fuel consumption and compressor IGV angle, compressor inlet pressure and split ratio are two additional crucial control parameters. In this study, six control strategies are firstly formulated and compared. The results indicate that the control strategy aiming to maintain the turbine inlet temperature outperforms the strategy aiming to maintain the exhaust temperature in terms of efficiency. Among them, the inventory control strategy demonstrates superior efficiency compared to the split ratio and IGV control strategies. Taking into account the advantages of various strategies, a hybrid inventory control strategy suitable for the R-Graz cycle is proposed. Based on this strategy, at 40% load and the ambient temperature of 19 °C, the efficiency reaches 87.06% of the design point, surpassing conventional F-class gas-steam combined cycle units. When the ambient temperature varies, under winter conditions of 10 °C and summer conditions of 30 °C, the full load net efficiency of the cycle reaches 72.06% and 69.60%, respectively. This research holds practical guidance value for the engineering application of the R-Graz cycle and the efficient utilization of hydrogen energy.

A complete dynamic modeling of two-by-one gas-steam combined cycle unit for coordinated control design

The high penetration of renewable energy can potentially change the role of combined cycle gas turbines (CCGT) from load suppliers to flexible suppliers. However, the slow process in the dynamic modeling of the CCGT complete system restricts the design of its best flexible operation strategy. Therefore, this paper adopts the composite modeling method to establish a complete nonlinear dynamic model of a 2 × 1 CCGT including two gas turbines, two three-pressure heat recovery steam generators (HRSG), one steam turbine, and one heat exchanger. This model can reflect the dynamic characteristics of pressure and flow in the bottom cycle due to the changes in operating mode, which can guide the design of the flexible operation control strategy of the 2 × 1 CCGT. To verify the model’s accuracy, the simulated data were compared with the field data from a 900 MW cycle with the same configuration. The results show that the established model can accurately reflect the changing trend of variables during mode switching. The range errors of essential variables such as gas turbine (GT) power is 3.8 %, GT outlet temperature is 1.4 %, high-pressure drum pressure is 4.5 %, and the range errors of other variables are below 5 %, proving the fidelity of the established control model. The dynamic model established in this paper will be the basis for model-based controller design which can handle multi-objective optimization and constraints in flexible operations. Moreover, this model will be used to guide the design of multi-mode control and energy management strategies.

Model development and parameter calibration of a combined-cycle power generation unit via metaheuristic optimization techniques

Mathematical modeling of combined-cycle units has produced a variety of valuable results, primarily significant advances in their energy efficiency and education of power plant operators. These positive results motivate the need for more complex modeling and simulation techniques with the goal of greater accuracy and accessibility. This study presents a simplified and enhanced version of a gas turbine model for dynamic performance simulation. The theoretical improvements have been proved through modeling philosophy and simulation accuracy attained by metaheuristic optimization techniques. The model has been constructed using thermodynamic and mathematical concepts, with parameter optimization and calibration performed using metaheuristic optimizers. The suggested model’s resilience has been demonstrated by simulation results.

A note on hydropower as a marginal price setter for Spain's electricity market in 2021–2022

From January 2021 to March 2022, wholesale Spanish spot electricity prices reached a record high of €700/MWh. Surprisingly, hydropower set the marginal market price for 52% of the hours in 2021 and 43% in the first quarter of 2022. Combined-cycle gas-fired units, which typically determine the marginal price, were marginal in only 16% and 21% of the hours in 2021 and 2022, respectively. Hydropower set prices between 3% and 12% higher than an estimate of their opportunity cost, and they were responsible for charging 69% of the prices above €500/MWh. The empirical evidence suggests that 2021 was an unusual year compared to 2018 and 2019 because the role played by hydropower as a marginal price setter was relatively more prominent.

Self-Unit Commitment of Combined-Cycle Units with Real Operational Constraints

This paper highlights the importance of accurately modeling the operational constraints of Combined-Cycle Gas Turbines (CCGTs) within a unit-commitment framework. In practice, in Colombia, when given an initial dispatch by the Independent System Operator, CCGT plants are operated according to the results of heuristic simulation codes. Such heuristics often omit technical operating constraints, including hot, warm, or cold startup ramps; the minimum operation hours required for a gas turbine to start a steam turbine; the relationship between the dispatched number of steam and gas turbines; the load distribution among gas turbines; and supplementary fires. Most unit-commitment models in the literature represent standard technical constraints like startup, shutdown, up/down ramps, and in some cases, supplementary fires. However, they typically overlook other real-life CCGT operating constraints, which were considered in this work. These constraints are crucial in integrated energy systems to avoid equipment damage, which can potentially put CCGT plants out of service and ultimately lead to lower operating costs.

Institute Teploelektroproyekt - 105 years in the service of the country's energy industry

The article is devoted to the 105th anniversary of Institute Teploelektroproyekt. Thermal power plants built according to the Institute's designs over the past twenty years, with installed combined-cycle and steam-power units running on gas and coal, are presented. The article describes the current environment of the institute's activities, the limitations of centralized financing of projects, the withdrawal from the market of power equipment of a number of foreign manufacturers of gas turbines due to sanctions, the adjustment of business plans of traditional customers of energy projects. The Institute actively accepts challenges, works with Russian manufacturers of gas turbine units, capitalizes on the accumulated experience of designing combined-cycle power plants (CCPP). An experience of construction and operation of the first stage of Sakhalinskaya SDPP-2 operating on coal, with a seismicity of the site at 9 points on the MSK scale on the coast of the Tatar Strait, is presented. During the time of operation of the station, the Sakhalin coal was found to be extremely viscous, which is associated with the presence of bentonite in its mineral part. The measures taken to partially reconstruct the fuel supply path led to a significant improvement in the operation of the path. The Institute-designed Svobodnenskaya thermal power plant (TPP) was put into operation, generating electricity and steam to provide consumers of the Amur Gas Processing Plant. Gas fuel is supplied from the main gas pipeline Power of Siberia-1. This implemented project is one of the examples of choosing a gas-fired steam turbine unit in favor of CCGT. The project Boiler House as Part of Ethane-Containing Gas-Processing Combine in the settlement of Ust-Luga on the Baltic Sea coast is unique as an example of the full integration of thermal power plant into a large industrial enterprise in order to solve the problem of minimizing the possible consequences of a major accident at the combine. The design of combined-cycle power plants of Novocherkasskaya SDPP and Artemovskaya CCPP-2 on the basis of domestically produced GTUs with a unit power of 110 and 160 MW, construction projects of new power units of Norilskaya CCPP-3 and Yakutskaya SDPP-2 for permafrost conditions are close to completion. The projects for the successive modernization of the Kirishskaya SDPP and Surgutskaya SDPP-1 power units with the replacement of steam turbine units are at the stages of designing and implementation. Institute Teploelektroproyekt is, as before, holding one of the leading positions among the design organizations of the industry, making a significant contribution to the development of the country’s energy industry.

Digital Twin is an Effective Tool for Digital Transformation of Industrial Enterprises

The article presents the results of a study of digital transformation processes taking place on scientific and industrial enterprises using digital twin technology. The degree of introduction of digital technologies and the level of labor productivity in the developed countries and in Russia were considered. The concept, definition, properties and characteristics of digital twin technology were studied. The applied methods of digital design and modeling in the digital twintechnology were investigated. The author analyzes the features of creation, functionality, and the advantages of digital twin technology at various stages of the object's life cycle - during design, production and operation. Practical examples of digital twins application in the domestic industry are given: the design of a premium-class car of the 'Tuple' project, the optimization of technological grinding operations of product manufacturing, the introduction of a predictive prognostic system and monitoring of modern high-tech equipment of the combined-cycle unit of the Izhevsk CHP-1 PSU for monitoring the operational condition, reliable forecasting of technological processes, protection from incidents and accidents. The application of digital twin technology as a training complex to train the operational personnel of industrial facilities based on modeling of rarely encountered and critically dangerous operating modes of industrial facilities is investigated. The Russian market of digital design and modeling is studied and key leaders were identified. The top digital technologies to achieve technological leadership of domestic companies are summarized. As a result of the research, the key capabilities of digital twin technology and barriers constraining the processes of full-scale digital transformation of scientific and industrial enterprises are identified. Recommendations for the successful implementation and development of digital twin technology are proposed. The motivating factors of state support for the digital transformation of domestic business are summarized.

Synergetic performance of gas turbine combined cycle unit with inlet cooled by quasi-isobaric ACAES exhaust

Gas power generation units are challenged with peak regulation in the new power system characterized by high proportion of renewables. In aim to enhance the part-load performance and the peak-regulation capacity of gas turbine combined cycle (GTCC) power units, a synergetic power system of GTCC integrated by an isobaric and adiabatic compressed air energy storage (IACAES) was proposed, where the compressor inlet air in the gas turbine was directly mixed and cooled by the ACAES exhaust. Based on the demand load distribution of a GTCC unit and the off-design performance, the parameters of the IACAES were designed for the proposed synergetic system (SS), and comparatively for the benchmark integrated system (BS) without compressor inlet cooling. The peak-regulation performances of the proposed synergetic system were investigated and compared with those of the standalone GTCC as well as the benchmark system. The case study in a 67.3 MW GTCC indicates that, in the range of the ambient temperature from 283.15 to 308.15 K, the GTCC operative efficiency considerably enhances by averagely 0.943% resulting from the power shifting. The IACAES discharging power and roundtrip efficiency in SS are 10.5% lower than those in BS. An average negative gap of system efficiency in SS reaches 0.199% versus BS. However, GTCC inlet cooling by IACAES exhaust enhances the power capacity of the unit averagely by 1330.88 kW, and the peak-regulation capacity increases averagely by 10.59% compared to that in the standalone GTCC. The peak-regulation capacity enhances by 1.98% versus BS. The synergetic cooling effect weakens with the reduction in the ambient temperature and the charging air pressure.

Coal-derived synthetic natural gas as an alternative energy carrier for application to produce power --- comparison of integrated vs. non-integrated processes

This work addresses clean utilization of coal through thermo-chemical processes (i.e., gasification & methanation) that convert solid carbonaceous feedstock to gaseous fuel for power generation, which features potential advantages for environmental benignity and energy security. It would be beneficial to convert coal to synthetic natural gas (SNG) that can feed the combined cycle units in the regions like Taiwan where natural gas (NG) is imported, which would help stabilize the price of electricity and alleviate the energy security concern. The objective of this study is to investigate the performance as well as the pros and cons between integrated and non-integrated SNG plants. The characteristics of power and chemical plants differs in various aspects, thus the concept of non-integrated approach to produce SNG and power offers better system resilience, availability and market flexibility at the expense of reduced efficiency. Fuel switch strategy would be one of the key pillars for the pathway toward Net-Zero Emissions (NZE) by 2050. Alternative energy carriers (AECs), generally synthesized from conversion of other energy sources, may provide solutions to decarbonization and low-emission environment. In summary, the thermo-chemical conversion processes studied in the present work address the core issues in clean and efficient utilization of carbonaceous resources.

Gas turbine operating as part of a thermal power plant with hydrogen storages

Over the past few years, much attention has been paid to hydrogen energy. The development of hydrogen technologies leads to a reduction in the cost of both the hydrogen fuel itself and hydrogen systems, which leads to a wider use of this type of fuel in various branches of the fuel and energy complex. At the moment, the primary task is to increase the efficiency of combined cycle power units, reduce wear and tear of equipment during peak electricity consumption, reliable backup of energy supply, and reduce harmful emissions during the generation of heat and electricity. One of the modern methods for implementing these challenges is the use of energy storage devices. A new solution to this problem can be the introduction of hydrogen storage in the cycle of a thermal power plant. The article considers the modernization of a combined-cycle power unit with a gas turbine PG6111FA manufactured by « General Electric» with a rated power of 80 MW, a waste heat steam boiler manufactured by JSC « EnergoMashinostroitelny Alliance», and a steam turbine KT-33/36–7.5/0.12. During periods of night unloading, the effective efficiency of the power unit drops, so it is necessary not to unload the equipment, but to turn on the electrolyzers for the production of hydrogen fuel for further use in hydrogen fuel cells. The operating time of the hydrogen system with an electrolyzer is not limited in time, the operation of the electrolyzer takes place during night unloading periods (from 4 to 7 h a day), while the hydrogen storage works constantly, in this mode of operation, the service life is about 15 years, for stable operation it is necessary hydrogen fuel and periodic maintenance. An important component of the hydrogen system is a hydrogen battery with minimal storage losses, in contrast to traditionally installed thermal storage. Studies of the use of hydrogen storage in the circuits of thermal power plants have shown their effectiveness, including their implementation allows you to increase the efficiency, reduce the cost of own needs of the power plant, reduce emissions in the production of electricity, a leveled load schedule allows you to increase the life of the gas turbine, as the turbine works in basic mode. The use of accumulators in thermal power plants increases the competitiveness among traditional energy generation systems.

Import Substitution of Chemicals for Water Treatment at Series-Configuration Combined-Cycle Units

Import Substitution of Chemicals for Water Treatment at Series-Configuration Combined-Cycle Units

Exergy analysis of naphtha‐based combined cycle captive cogeneration plant for a petrochemical complex

AbstractThe primary objective of the present paper is to assess the performance of a naphtha‐based combined cycle power plant using the first and second laws of thermodynamics. Heat loss and energy efficiency of each component are calculated by using energy equations. Cogeneration efficiency and efficiency standard have been applied for calculating energy efficiencies. The cogeneration efficiency and efficiency standards are found as 57.87% and 41%, with heat recovery steam generators and auxiliary boilers as the most inefficient units. Further exergy efficiency is found as 30%, with combustion chambers and auxiliary boilers as the most inefficient units. At the end of the analysis, an elaborate appraisal has been made to critically judge the plant as a combined cycle unit. Finally, a few suggestions have been made for further improvement of the plant.

Incorporation of market signals for the optimal design of post combustion carbon capture systems

Recent studies have shown that fossil generators equipped with post-combustion carbon capture (PCC) systems are needed to reduce the cost of deep decarbonization. Such generators need to be flexible and responsive to grid conditions, particularly in a high variable renewable energy (VRE) environment. In this work, we evaluate the net present value (NPV) of retrofitting an existing natural gas combined cycle (NGCC) unit with a flexible PCC system while incorporating market signals from a high VRE grid. We use our industrial partner’s NGCC configuration as representative of existing NGCC units and Svante’s rapid-temperature swing adsorption (TSA) for PCC. Because of its ability to rapidly startup/shutdown and ramp-up/ramp-down, the chosen capture technology is very attractive for load-following operations. For a given set of market signals, we formulate a two-stage stochastic multi-period optimization problem, under the price-taker assumption, to simultaneously optimize the design of the capture system and operation of the entire plant. Rigorous models for the NGCC unit, PCC system, and compression system are developed using commercial process simulators and validated with either plant or vendor data. For computational tractability, we develop surrogate/reduced-order models for use in the optimization problem. The surrogate model for the NGCC plant is constructed by linearizing the rigorous dynamic model at 75% load, while data-driven nonlinear surrogate models for the capture and compression systems are constructed using simulation data from the rigorous models. The optimization problem, formulated as a mixed integer bilinear program, is implemented in the IDAES® integrated platform and solved to global optimality using Gurobi 9.5. Using this formulation, we determine the profitability of retrofitting an existing NGCC unit with the chosen capture system for multiple regions in the U.S. under two scenarios with different carbon prices. The results show that the optimal decision strongly depends on the region and on the carbon price, thereby demonstrating the importance of the inclusion of market signals in the design process.

Reserve provision of combined-cycle unit in joint day-ahead energy and reserve markets

With the continuous development of natural gas-fired combined cycle power generation technology, the combined cycle (CC) unit's installed capacity is gradually increasing in the power system because of its flexible operation characteristics. Participating in the energy and reserve markets and taking advantage of flexible mode transfer characteristics, the CC unit can provide the system with energy and sufficient reserve capacity. This paper proposes a bi-level strategic bidding model to study the CC unit’s bidding behavior in the day-ahead energy and reserve markets. The upper-level model is an optimal bidding model for the configuration-based CC unit aiming to maximize its profit. The lower-level model is the joint market clearing model of the energy and reserve markets managed by the independent system operator (ISO). CC unit and ISO in this model influence each other by the locational marginal electricity prices (LMEP) and the locational marginal reserve prices (LMRP) obtained from the lower-level market-clearing model. The CC unit submits the bids to the ISO and arranges the generation plan according to the market clearing results of the lower-level market-clearing model carried out by the ISO. The proposed bi-level optimization model is transformed into a mathematical equilibrium constraint (MPEC) problem by Karush-Kuhn-Tucker (KKT) conditions and duality theory. In this paper, the improved IEEE-6 bus and IEEE-57 bus systems are used as case studies to verify the effectiveness of the proposed bidding strategy for the CC unit. The results show that the proposed bidding strategy can effectively improve the profits of the CC unit in the electricity market. Compared with the case of the CC unit only participating in the energy market, the profits of the CC unit in the market increased by 8.84% and 12.3%.

Fault diagnosis analysis of combined cycle based on the structural theory of thermo‐economics

AbstractIn this paper, an improved thermo‐economic diagnosis model based on the structural theory of thermo‐economics combined with advanced exergy analysis is proposed in a combined cycle fault diagnosis model. Diagnosis model simulation of a 590 MW combined cycle unit is implemented by EBSILON Professional in terms of advanced exergy analysis method. The characteristic fault value (CFV) required for diagnosis is quantitatively presented and precisely located in the diagnosis model. The results show that with 3% performance deterioration fault of the compressor, gas turbine and intermediate pressure cylinder of the turbine, gas turbine failure leads to three times fuel consumption to the unit compared to the compressor. In contrast, multiple fault diagnosis results show that the fault value generated by each component under multiple faults is not a simple superposition of a single fault. The impact of some component faults is partially offset or increased. However, the increased fuel consumption of the whole unit under multiple faults or malfunctions must be greater than the sum of the increased fuel consumption under a single fault. CFV can effectively perform precise positioning and quantitative analysis on single and multiple fault scenarios of the combined cycle unit. In addition, CFV has strong sensitivity and changes linearly with the performance deterioration of the components, which paves the way for a reliable approach for early‐stage warning and diagnosis.

Part-load performance analysis of a dual-recuperated gas turbine combined cycle system

To undertake peak shaving tasks, gas turbine combined cycle (GTCC) units often deviate from the design operating point. In order to improve the off-design performance of GTCCs, a dual-recuperated gas turbine combined cycle (DRGTCC) system based on partial recuperation and compressor inlet air heating is proposed in this paper. The operating characteristics of the novel system using the proposed operation strategy are investigated, and the effects of pressure drop in recuperators and ambient temperature on system performance are discussed. The results indicate that, compared with the GTCC system, the DRGTCC system has higher turbine inlet temperature (TIT) and turbine expansion ratio at the same power output, and the performance has been improved especially at lower power outputs. When the inlet temperature of the compressor is increased from 0 °C to 45 °C, the air mass flowrate can be regulated between 46.0% and 100% of the design value. The combined cycle efficiency of the DRGTCC system is improved by 2.55 percentage points at 45.5% design combined cycle load. Moreover, the sensitivity analysis shows that the system performance decreases with the increase of the pressure drop in recuperators, and the ambient temperature affects the load regulation range and efficiency.

Multi-Objective Optimization of Economy, Safety and Emissions for the Startup Scheduling of a Steam Turbine

Abstract With the rapid development of renewable energy, traditional power generation such as combined cycle unit needs to startup or change load quickly to balance the variability brought by renewable resources. In the combined cycle unit, the startup of steam turbine has a great influence on the whole set, and it is necessary to ensure safety, shorten the startup time, and reduce pollutant emissions. These optimization objectives are inter-related and have complex contradiction, which is the difficulty for multi-objective optimization. Costs function consisting of startup costs, fatigue life damage costs, pollutant emissions costs, and revenue gained from electricity is proposed to balance the contradiction more objectively. Finite exhaustive method (FEM) combining thermal-structural finite element calculation and multi-objective optimization is proposed for multi-objective startup process optimization, and its results are compared with those of minimum startup time and minimum fatigue life damage optimization. It can automatically search for a unique global optimal solution for engineering practice, rather than solution sets obtained by Pareto Optimality, which is beneficial for application in different combined cycle steam turbines and startup process. Multi-objective optimization scheduling shortens startup time from 105 to 93 min, reduces maximum stress from 493 MPa to 440 MPa, and reduces costs function by 66.6%. The comparison with the multi-objective optimization results of the response surface method (RSM) proves the reliability and validity of this method. The practical inspection results prove that the optimal scheduling is safe and effective.

Thermochemical Recuperation of the Exhaust Gas Heat in Combined-Cycle Units: Thermodynamic Analysis

Thermochemical Recuperation of the Exhaust Gas Heat in Combined-Cycle Units: Thermodynamic Analysis

Modeling and analysis of thermodynamic performance of 6F unit based on Thermoflow

With the continuous development of combined cycle technology, mastering the thermal performance of combined cycle unit is beneficial to the system performance analysis, operation optimization and debugging. In this paper, the mathematical model of each component of the gas-steam combined cycle was established. Thermoflow software was used to calculate the thermodynamic performance of the system, and the influence of inlet temperature and gas turbine load on the thermodynamic performance of the system was analyzed. The results show that the model is reliable and the maximum error is 1.47%. When compressor inlet temperature increases by 10°C, gas turbine power decreases by about 5.8% and power generation thermal efficiency decreases by 0.15%. When the gas turbine load decreases by 10%, the thermal efficiency of combined cycle power generation decreases by 1.4%.