Combined Cycle Gas Turbine Plant Research Articles

Model for the techno-economic analysis of common work of wind power and CCGT power plant to offer constant level of power in the electricity market

Wind power varies over time, mainly under the influence of meteorological fluctuations. The variations occur on all time scales. Understanding these variations and their predictability is of key importance for the integration and optimal utilization of wind in the power system. There are two major attributes of variable generation that notably impact the participation on power exchanges: Variability (the output of variable generation changes and resulting in fluctuations in the plant output on all time scales) and Uncertainty (the magnitude and timing of variable generation output is less predictable, wind power output has low levels of predictability). Because of these variability and uncertainty wind plants cannot participate to electricity market, especially to power exchanges. For this purpose, the paper presents techno-economic analysis of work of wind plants together with combined cycle gas turbine (CCGT) plant as support for offering continues power to electricity market. A model of wind farms and CCGT plant was developed in program PLEXOS based on real hourly input data and all characteristics of CCGT with especial analysis of techno-economic characteristics of different types of starts and stops of the plant.The Model analyzes the followings: costs of different start-stop characteristics (hot, warm, cold start-ups and shutdowns) and part load performance of CCGT. Besides the costs, the technical restrictions were considered such as start-up time depending on outage duration, minimum operation time, and minimum load or peaking capability.For calculation purposes, the following parameters are necessary to know in order to be able to economically evaluate changes in the start-up process: ramp up and down rate, time of start time reduction, fuel mass flow during start, electricity production during start, variable cost of start-up process, cost and charges for life time consumption for each start and start type, remuneration during start up time regarding expected or unexpected starts, the cost and revenues for balancing energy (important when participating in electricity market), and the cost or revenues for CO 2 -certificates. Main motivation for this analysis is to investigate possibilities to participate on power exchanges by offering continues guarantied power from wind plants by backing-up them with CCGT power plant.

Effect of external conditions and steam parameters on performance of combined-cycle power plants with back-pressure steam turbine

The cogeneration combined-cycle gas turbine plant with back-pressure steam turbine is considered. A simple circuit of the plant increases its reliability, and the use of optimal temperatures of the heating and return water allows obtaining the highest thermal efficiency of the plant taking into account the ratio of its electric and heat power. The technical and economic efficiency of the combined-cycle plant with back-pressure steam turbine is studied to estimate the capital investment. The parameters and conditions to maximize the net present value growth relative to the base version are determined.

Technical and economic analysis of the combined-cycle plant with back-pressure steam turbine

The cogeneration combined-cycle gas turbine plant with back-pressure steam turbine is considered. A simple circuit of the plant increases its reliability, and the use of optimal temperatures of the heating and return water allows obtaining the highest thermal efficiency of the plant taking into account the ratio of its electric and heat power. The technical and economic efficiency of the combined-cycle plant with back-pressure steam turbine is studied to estimate the capital investment. The parameters and conditions to maximize the net present value growth relative to the base version are determined.

Optimum Performance Improvements of the Combined Cycle Based on an Intercooler–Reheated Gas Turbine

The performance enhancements and modeling of the gas turbine (GT), together with the combined cycle gas turbine (CCGT) power plant, are described in this study. The thermal analysis has proposed intercooler–reheated-GT (IHGT) configuration of the CCGT system, as well as the development of a simulation code and integrated model for exploiting the CCGT power plants performance, using the matlab code. The validation of a heavy-duty CCGT power plants performance is done through real power plants, namely, MARAFIQ CCGT plants in Saudi Arabia with satisfactory results. The results from this simulation show that the higher thermal efficiency of 56% MW, while high power output of 1640 MW, occurred in IHGT combined cycle plants (IHGTCC), having an optimal turbine inlet temperature about 1900 K. Furthermore, the CCGT system proposed in the study has improved power output by 94%. The results of optimization show that the IHGTCC has optimum power of 1860 MW and thermal efficiency of 59%. Therefore, the ambient temperatures and operation conditions of the CCGT strongly affect their performance. The optimum level of power and efficiency is seen at high turbine inlet temperatures and isentropic turbine efficiency. Thus, it can be understood that the models developed in this study are useful tools for estimating the CCGT power plant's performance.

Reducing water usage with rotary regenerative gas/gas heat exchangers in natural gas-fired power plants with post-combustion carbon capture

It is possible to greatly mitigate the increase of water usage associated with the addition of carbon capture to fossil fuel power generation. This article presents a first-of-a-kind feasibility study of a series of technology options with rotary regenerative gas/gas heat exchangers for the management of the water balance around post-combustion carbon capture process integrated with CCGT (Combined Cycle Gas Turbine) plants with and without EGR (exhaust gas recirculation). Hybrid cooling configurations with a gas/gas heat exchanger upstream of the direct contact cooler reduce cooling and process water demand by 67% and 35% respectively compared to a wet system where the flue gas is primarily cooled prior to the absorber in larger direct contact coolers. The CO2-depleted gas stream is then reheated above 70 °C with enough buoyancy to rise through the stack. Dry air-cooled configurations, relying on ambient air as the cooling medium, eliminate the use of process and cooling water prior to the absorber and the temperature of the flue gas entering the absorber is unchanged. Rotary regenerative heat exchangers do not introduce significant additional pressure drop and gas leakage from a high CO2 concentration stream to a stream with lower concentration can be minimized to acceptable levels with available strategies using a purge and a scavenging slipstream from the higher pressure flow.

Fuel flexibility, stability and emissions in premixed hydrogen-rich gas turbine combustion: Technology, fundamentals, and numerical simulations

Abstract The objective of this paper is to review the progress made in understanding the effects of fuel composition on premixed gas turbine combustion, with a special emphasis on system stability and emissions, for hydrogen-rich synthetic gas (syngas) mixtures. This is driven by the rising interest in the use of hydrogen blends and syngas in combined cycle power plants, as an alternative to standard natural gas. Typical applications where such mixtures are used include the recycling of hydrogen by-product from industry as well as promising pre-combustion carbon capture methods like fuel reforming or gasification integrated with gas turbine combined cycle plants. Syngas is mainly a mixture of H2, CO and CH4; its composition can vary due to fluctuations in the process’s conditions but can also dramatically change if the feedstock is modified like coal or biomass grades in gasification. Due to the substantially different chemical, transport and thermal properties that distinguish the syngas components, especially H2, when compared with conventional hydrocarbon fuels, these non-standard fuels pose several challenges in premixed combustion. These challenges are reviewed in this paper along with the combustion fundamentals of these fuels. A survey of available technologies able to handle syngas and hydrogen-rich fuel in general is provided reflecting the difficulties encountered while using these fuels in real large scale commercial applications. We find that a limited number of options exist today for fully premixed combustion, but promising designs are under development. Finally, the ever growing use of numerical simulation to cost-effectively study full scale combustion systems—with Large Eddy Simulations (LES) being at the forefront as a compromise between accuracy and computational cost—justifies the simultaneous review of the different numerical attempts to simulate hydrogen-containing fuel mixtures and syngas in premixed combustion. Challenges specific to performing LES calculations for these reacting flows are highlighted. We find that, while the literature on premixed LES methane combustion is abundant, LES of premixed syngas and hydrogen-rich fuels combustion is comparatively scarce. Only few attempts were made so far showing the need for more research effort in this area to help tackle the challenges presented by these fuels.

Reprint of: Performance analysis of a CCGT power plant integrated to a LNG regasification process

This paper examines the performance of a combined cycle gas turbine plant (CCGT) when integrated to the cold energy released during the regasification process of liquefied natural gas (LNG). A growing number of LNG import terminals supply regasified natural gas for power generation, with an adjacent CCGT plant providing an anchor market for the facility itself. Two integration alternatives with mutual energetic gains are proposed and simulated, and compared to a reference case without any use of the LNG cold potential. The first alternative consists on exchanging heat among LNG and the Brayton cycle air intake. The second alternative adds to the first one a novel recovery opportunity by exchanging heat with the Rankine cycle condenser. On both cases, heat from the CCGT is rejected to a lower temperature level than the one of the regular dead state. From the regasification side, the process is performed without any help of extra external energy. Both integration alternatives led to an electrical efficiency enhancement when comparing to the non-integrated cycle: 6.32% and 9.09%, respectively. The energy return on investment (EROI) of each alternative was also analyzed and gains of 12.92% and 18.57% are predicted by upon the simulation data.

Performance analysis of a CCGT power plant integrated to a LNG regasification process

This paper examines the performance of a combined cycle gas turbine plant (CCGT) when integrated to the cold energy released during the regasification process of liquefied natural gas (LNG). A growing number of LNG import terminals supply regasified natural gas for power generation, with an adjacent CCGT plant providing an anchor market for the facility itself. Two integration alternatives with mutual energetic gains are proposed and simulated, and compared to a reference case without any use of the LNG cold potential. The first alternative consists on exchanging heat among LNG and the Brayton cycle air intake. The second alternative adds to the first one a novel recovery opportunity by exchanging heat with the Rankine cycle condenser. On both cases, heat from the CCGT is rejected to a lower temperature level than the one of the regular dead state. From the regasification side, the process is performed without any help of extra external energy. Both integration alternatives led to an electrical efficiency enhancement when comparing to the non-integrated cycle: 6.32% and 9.09%, respectively. The energy return on investment (EROI) of each alternative was also analyzed and gains of 12.92% and 18.57% are predicted by upon the simulation data.

Themoeconomic optimization of triple pressure heat recovery steam generator operating parameters for combined cycle plants

Original scientific paper DOI: 10.2298/TSCI131124040M The aim of this work is to develop a method for optimization of operating parameters of a triple pressure heat recovery steam generator. Two types of optimization: (a) thermodynamic and (b) thermoeconomic were performed. The purpose of the thermodynamic optimization is to maximize the efficiency of the plant. The selected objective for this purpose is minimization of the exergy destruction in the heat recovery steam generator. The purpose of the thermoeconomic optimization is to decrease the production cost of electricity. Here, the total annual cost of heat recovery steam generator, defined as a sum of annual values of the capital costs and the cost of the exergy destruction, is selected as the objective function. The optimal values of the most influencing variables are obtained by minimizing the objective function while satisfying a group of constraints. The optimization algorithm is developed and tested on a case of combined cycle gas turbine plant with complex configuration. Six operating parameters were subject of optimization: pressures and pinch point temperatures of every three (high, intermediate, and low pressure) steam stream. The influence of these variables on the objective function and production cost are investigated in detail. The differences between results of thermodynamic and the thermoeconomic optimization are discussed.

Integrated Environmental Assessment of Future Energy Scenarios Based on Economic Equilibrium Models

The future evolution of energy supply technologies strongly depends on (and affects) the economic and environmental systems, due to the high dependency of this sector on the availability and cost of fossil fuels, especially on the small regional scale. This paper aims at presenting the modeling system and preliminary results of a research project conducted on the scale of Luxembourg to assess the environmental impact of future energy scenarios for the country, integrating outputs from partial and computable general equilibrium models within hybrid Life Cycle Assessment (LCA) frameworks. The general equilibrium model for Luxembourg, LUXGEM, is used to evaluate the economic impacts of policy decisions and other economic shocks over the time horizon 2006-2030. A techno-economic (partial equilibrium) model for Luxembourg, ETEM, is used instead to compute operation levels of various technologies to meet the demand for energy services at the least cost along the same timeline. The future energy demand and supply are made consistent by coupling ETEM with LUXGEM so as to have the same macro-economic variables and energy shares driving both models. The coupling results are then implemented within a set of Environmentally-Extended Input-Output (EE-IO) models in historical time series to test the feasibility of the integrated framework and then to assess the environmental impacts of the country. Accordingly, a disaggregated energy sector was built with the different ETEM technologies in the EE-IO to allow hybridization with Life Cycle Inventory (LCI) and enrich the process detail. The results show that the environmental impact slightly decreased overall from 2006 to 2009. Most of the impacts come from some imported commodities (natural gas, used to produce electricity, and metalliferous ores and metal scrap). The main energy production technology is the combined-cycle gas turbine plant “Twinerg”, representing almost 80% of the domestic electricity production in Luxembourg. In the hybrid EE-IO model, this technology contributes to around 7% of the total impact of the country’s net consumption. The causes of divergence between ETEM and LUXGEM are also thoroughly investigated to outline possible strategies of modeling improvements for future assessment of environmental impacts using EE-IO. Further analyses focus first on the completion of the models’ coupling and its application to the defined scenarios. Once the coupling is consistently accomplished, LUXGEM can compute the IO flows from 2010 to 2030, while the LCI processes in the hybrid system are harmonized with ETEM to represent the future domestic and imported energy technologies.

A Holistic Approach to GTCC Operational Efficiency Improvement Studies

Because of the increasing share of renewables in the energy market, part load operation of gas turbine combined cycle (GTCC) power plants has become a major issue. In combination with the variable ambient conditions and fuel quality, load variations cause these plants to be operated across a wide range of conditions and settings. However, efficiency improvement and optimization studies are often focused on single operating points. The current study assesses efficiency improvement possibilities for the KA26 GTCC plant, as recently built in Lelystad, The Netherlands, taking into account that the plant is operated under frequently varying conditions and load settings. In this context, free operational parameters play an important role: these are the process parameters, which can be adjusted by the operator without compromising safety and other operational objectives. The study applies a steady state thermodynamic model with second-law analysis for exploring the entire operational space. A method is presented for revealing correlations between the exergy losses in major system components, indicating component interactions. This is achieved with a set of numerical simulations, in which operational conditions and settings are randomly varied, recording plant efficiency and exergy losses in major components. The resulting data is used to identify distinct operational regimes for the GTCC. Finally, the free operational parameters are used as decision variables in a genetic algorithm, optimizing plant efficiency in the operational regimes identified earlier. The results show that the optimal settings for decision variables depend on the regime of operation.

The effect of political cycles on power investment decisions: Expectations over the repeal and reinstatement of carbon policy mechanisms in Australia

Political uncertainty over global greenhouse gas (GHG) mitigation policy is likely to defer investment in cleaner technologies. It may also incentivise short-lived, high-cost interim investments while businesses wait for the uncertainty to subside. The range of possible policy responses to the issue has created uncertainty over the future of national mitigation pathways. Given that the electricity sector, globally, is a major emitter of GHGs, this represents a systematic risk to investment in electricity generation assets. This paper uses a real options analysis framework informed by a survey of experts conducted in Australia – used as a proxy to model the degree of the uncertainty – to investigate the optimal timing for investment in the conversion of a coal plant to a combined cycle gas turbine plant using the American-style option valuation method. The effect of market and political uncertainty is studied for the Clean Energy Act 2011 in Australia. Political uncertainty is addressed bi-modally in terms of: (1) uncertainty over the repeal of the carbon pricing policy, and (2) if it is repealed, uncertainty over the reinstatement of the policy, to represent the effect of electoral cycles and the possibility of more stringent future global mitigation efforts. Results of the analysis show that although political uncertainty with respect to GHG mitigation policy may delay investment in the conversion of the coal plant, expectations over the reinstatement of the carbon pricing reduces the amount of option premium to defer the conversion decision.

Optimization of CCGT power plant and performance analysis using MATLAB/Simulink with actual operational data.

In the Modern scenario, the naturally available resources for power generation are being depleted at an alarming rate; firstly due to wastage of power at consumer end, secondly due to inefficiency of various power system components. A Combined Cycle Gas Turbine (CCGT) integrates two cycles- Brayton cycle (Gas Turbine) and Rankine cycle (Steam Turbine) with the objective of increasing overall plant efficiency. This is accomplished by utilising the exhaust of Gas Turbine through a waste-heat recovery boiler to run a Steam Turbine. The efficiency of a gas turbine which ranges from 28% to 33% can hence be raised to about 60% by recovering some of the low grade thermal energy from the exhaust gas for steam turbine process. This paper is a study for the modelling of CCGT and comparing it with actual operational data. The performance model for CCGT plant was developed in MATLAB/Simulink.

A life cycle comparison of greenhouse emissions for power generation from coal mining and underground coal gasification

Underground coal gasification (UCG) is an advancing technology that is receiving considerable global attention as an economic and environmentally friendly alternative for exploitation of coal deposits. UCG has the potential to decrease greenhouse gas emissions (GHG) during the development and utilization of coal resources. In this paper, the life cycle of UCG from in situ coal gasification to utilization for electricity generation is analyzed and compared with coal extraction through conventional coal mining and utilization in power plants. Four life cycle assessment models have been developed and analyzed to compare (greenhouse gas) GHG emissions of coal mining, coal gasification and power generation through conventional pulverized coal fired power plants (PCC), supercritical coal fired (SCPC) power plants, integrated gasification combined cycle plants for coal (Coal-IGCC), and combined cycle gas turbine plants for UCG (UCG-CCGT). The analysis shows that UCG is comparable to these latest technologies and in fact, the GHG emissions from UCG are about 28 % less than the conventional PCC plant. When combined with the economic superiority, UCG has a clear advantage over competing technologies. The comparison also shows that there is considerable reduction in the GHG emissions with the development of technology and improvements in generation efficiencies.

An Agent-Based Implementation of Hidden Markov Models for Gas Turbine Condition Monitoring

This paper considers the use of a multiagent system (MAS) incorporating hidden Markov models for the condition monitoring of gas turbine (GT) engines. Hidden Markov models utilizing a Gaussian probability distribution are proposed as an anomaly detection tool for GTs components. The use of this technique is shown to allow the modeling of the dynamics of GTs despite a lack of high-frequency data. This allows the early detection of developing faults and avoids costly outages due to asset Failure. These models are implemented as part of an MAS, using a proposed extension of an established power system ontology, for fault detection of gas turbines. The multiagent system is shown to be applicable through a case study and comparison to an existing system utilizing historic data from a combined-cycle gas turbine plant provided by an industrial partner.

Evaluation of power investment decisions under uncertain carbon policy: A case study for converting coal fired steam turbine to combined cycle gas turbine plants in Australia

Greenhouse gas (GHG) intensive fuels are currently a major input into the Australian electricity sector. Accordingly, climate change mitigation policies represent a systematic risk to investment in electricity generation assets. Although the Australian government introduced carbon pricing in 2012 and announced a commitment to the continuation of the Kyoto protocol beyond 2012, the opposition at the time signalled that should they be provided the opportunity they would repeal these policies. This paper uses a real options analysis (ROA) framework to investigate the optimal timing of one potential business response to carbon pricing: investment in the conversion of coal plant to lower emission CCGT plant. An American-style option valuation method is used for this purpose. The viewpoint is from that of a private investor assessing three available options for an existing coal plant: (1) to invest in its conversion to CCGT; (2) to abandon it, or; (3) to take no immediate action. The method provides a decision criterion that informs the investor whether or not to delay the investment. The effect of market and political uncertainty is studied for both the Clean Energy Act 2011 (CEA) and high carbon price (HCP) policy scenarios. The results of the modelling suggest that political uncertainty after the implementation of carbon pricing impedes the decision to switch to cleaner technologies. However, this effect can be mitigated by implementing higher expected carbon prices.

Improved Load Tracking Performance for Combined Cycle Gas Turbine Plants through Flatness Based Feedforward Control

The increasing competition on the energy market along with the highly variable feed-in from renewable energy sources have a far-reaching impact on the operation of conventional power plants. In order to stay competitive, utility companies need to adopt an operation regime that is characterized by fast cycling. At the same time, the operation has to remain as efficient as possible. In combined cycle gas turbine (CCGT) plants, the total power output is the combination of gas turbine (GT) power output and steam turbine (ST) power output. These are coupled through the dynamic behavior of the heat recovery steam generator (HRSG). A model based feedforward control concept can be used to improve the performance during load changes. Thereby, the process dynamics of the HRSG and the turbines are taken into account in the feedforward control algorithm. Thus, GT and ST power output are coordinated in an optimal way which in turn improves the load tracking capabilities as compared to standard control concepts. This is demonstrated in this contribution by simulations studies.

Maintaining the Power Output of An Existing Coal Plant with the Addition of CO2 Capture: Retrofits Options With Gas Turbine Combined Cycle Plants

Abstract It is likely that a significant number of existing pulverised coal-fired power plants will be retrofitted with post-combustion capture as part of a global rollout of carbon capture and storage. Previous studies have demonstrated that the energy penalty for post-combustion carbon dioxide (CO2) capture can be greatly minimised by effective integration of the capture system with the power cycle. Nevertheless, the power output of the site is, in most cases, reduced and the volume of electricity sales would drop. For other plants, the existing steam cycle may not be able to be integrated effectively for steam extraction, or space and access around/to the steam cycle may be impossible. As an alternative to steam extraction, it is possible to retrofit existing coal plants with a gas turbine combined cycle plant (CCGT) to maintain, or even increase, the site power output. The gas turbine can be integrated to the existing coal plant in various ways to supply all the heat, or a fraction of the heat, and the power required for the capture systems. An important consideration is whether carbon emissions from both, the combined cycle and the retrofitted coal plant are captured, or from the latter only. This paper examines these different options for carbon capture retrofits to existing coal plant and presents a novel configuration with the sequential combustion of gas turbine flue gas in the existing coal boiler while capturing carbon emissions from the combustion of coal and natural gas.

Integrated environmental assessment of future energy scenarios based on economic equilibrium models

The future evolution of energy supply technologies strongly depends on (and affects) the economic and environmental systems, due to the high dependency of this sector on the availability and cost of fossil fuels, especially on the small regional scale. This paper aims at presenting the modeling system and preliminary results of a research project conducted on the scale of Luxembourg to assess the environmental impact of future energy scenarios for the country, integrating outputs from partial and computable general equilibrium models within hybrid Life Cycle Assessment (LCA) frameworks. The general equilibrium model for Luxembourg, LUXGEM, is used to evaluate the economic impacts of policy decisions and other economic shocks over the time horizon 2006−2030. A techno-economic (partial equilibrium) model for Luxembourg, ETEM, is used instead to compute operation levels of various technologies to meet the demand for energy services at the least cost along the same timeline. The future energy demand and supply are made consistent by coupling ETEM with LUXGEM so as to have the same macro-economic variables and energy shares driving both models. The coupling results are then implemented within a set of Environmentally-Extended Input-Output (EE-IO) models in historical time series to test the feasibility of the integrated framework and then to assess the environmental impacts of the country. Accordingly, a disaggregated energy sector was built with the different ETEM technologies in the EE-IO to allow hybridization with Life Cycle Inventory (LCI) and enrich the process detail. The results show that the environmental impact slightly decreased overall from 2006 to 2009. Most of the impacts come from some imported commodities (natural gas, used to produce electricity, and metalliferous ores and metal scrap). The main energy production technology is the combined-cycle gas turbine plant “Twinerg”, representing almost 80% of the domestic electricity production in Luxembourg. In the hybrid EE-IO model, this technology contributes to around 7% of the total impact of the country’s net consumption. The causes of divergence between ETEM and LUXGEM are also thoroughly investigated to outline possible strategies of modeling improvements for future assessment of environmental impacts using EE-IO. Further analyses focus first on the completion of the models’ coupling and its application to the defined scenarios. Once the coupling is consistently accomplished, LUXGEM can compute the IO flows from 2010 to 2030, while the LCI processes in the hybrid system are harmonized with ETEM to represent the future domestic and imported energy technologies.

Cost allocation in cogeneration power-desalination plant utilising gas/steam combined cycle (GTCC) in Kuwait

Gas turbine combined cycle (GTCC) plants have high overall thermal efficiency, and are used for large base-load power plants (PPs) to produce electric power (EP) and desalted seawater (DW) at the lowest cost per units of EP and DW. Allocating the cost of each product (EP and DW) is the subject of this paper. Energy and exergy analyses as well as the power loss due to supplying steam to desalting units rather than expand it to conventional condensers are used in the analysis. This paper develops a mathematical model using the engineering equation solver (EES) Software to evaluate the performance of Al-Shuaiba CPDP. A sensitivity analysis is carried out to investigate the effects of some combined cycle parameters on the overall efficiency, specific fuel energy to desalination as well as the desalinated water cost. The selected parameters are ambient temperature, compression ratio, air to fuel ratio, turbine inlet temperature and stack temperature.