Combined Cycle Gas Turbine System Research Articles

Onboard pre-combustion carbon capture with combined-cycle gas turbine power plant architectures for LNG-fuelled ship propulsion

This paper investigates the concept of pre-combustion carbon capture (Pre-CCS) with a combined cycle gas turbine (CCGT) propulsion system to achieve energy efficient carbon capture onboard a Liquid Natural Gas fuelled vessel. A basic CCGT model with energy efficiency of 51.6 % when using LNG as fuel was integrated with a Pre-CCS system composed of a steam methane reformer, water–gas shift reactors, pressure swing adsorption (SMR-PSA), and liquid CO2 storage. Various waste heat utilisation schemes integrated with the CCGT-reformer were modelled in Aspen HYSYS. The modelling of the waste heat recovery networks as energy streams integrating between various processes and unit of operations has facilitated a closed-loop simulation of various systems. It was concluded that a proper utilisation of the high-grade heat from the gas turbine (GT) exhaust and from the reformer is crucial to improve the overall energy efficiency and carbon capture rate, exemplified by a scheme where the heating needs for the SMR and the cooling needs from the water–gas-shift reactors are fully integrated. When optimised, the integrated system had an overall energy efficiency of 41.5 % and 43.2 % (i.e. an efficiency loss of 10.2–10.5 percentage points from the base CCGT system) accompanied with specific GHG emission reduction of 51.2 % and 52.3 % for operation of the GT at a turbine entry temperature of 1700 K and 1850 K, respectively. Intermediate levels of reforming, where the GT uses a mix of LNG and reformate gases, were also simulated, showing an almost linear evolution from the 100 % LNG feed to the GT to the 100 % reformate case. Such a strategy could be used for gradual evolution to meet the required CO2 reduction timeline. It was determined that the 100 % reformate case provides the highest CO2 capture rate. Estimates of other emissions from the GT assuming typical combustor residence times for the whole range of fuel blends were also carried out, showing that the overall greenhouse gas emission is dominated by CO2, given that the GT emits negligible N2O and unburnt methane. Some capital cost estimates were also made to determine the unit price of hydrogen fuel produced onboard, suggesting that the CAPEX was not prohibitive. These findings support the pre-combustion CCS − CCGT integrated system as a promising long-term decarbonisation and propulsion strategy to comply with emissions regulations, displaying good performance in terms of cost, energy consumption, and CO2 reduction. The scalability and adaptability of the proposed system for existing and new-built ships across the decarbonisation timeline is also discussed.

Design and energy efficiency analysis of hydrogen - fueled SOFC-‘GT+ST’ combined cycle system

In order to enhance electricity generation efficiency of hydrogen-fueled fuel cell gas turbine combined cycle system abbreviated as SOFC-GT system, a new combined system of fuel cell with turbine abbreviated as SOFC-GT+ST system is based on the feature of high concentration of water vapor in the anode of hydrogen fuel cell and the introduction of steam turbine, and a system model based on ebsilon software is built to compare the system under the same parameter conditions. The system model is built based on ebsilon software, and the system power, power generating efficiency, and the loss of the electricity is comparatively studied under the same parameters, and improved SOFC-GT+ST is proposed. Research results show the following: the second system, which utilizes the spent gas of cathode and anode separately, effectively utilizes the thermal energy of water vapor in the anode spent gas and improves the power generation efficiency of the system; the improved SOFC-′GT+ST The improved SOFC-‘GT+ST’ system further improves the power generation efficiency of the system by recycling the hydrogen in the SOFC that does not participate in the electrochemical reaction, which reaches 65.88%. The research in this paper provides a reference for improving.

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.

Modeling and thermodynamic analysis of gas-supercritical carbon dioxide combined cycle system

ABSTRACT Gas turbine power generation has the advantages of flexibility, efficiency, and lower carbon emissions compared with coal-fired power generation. Under the situation of energy structure transformation and upgrading, gas turbine power generation will have bright prospects. In this paper, the modeling and thermodynamic analysis of various gas-supercritical carbon dioxide(sCO2) combined cycle systems are carried out based on the calculation method of total physical properties, and six typical combined cycle layouts are selected for detailed research. In order to obtain the optimal state of the combined cycle system, the parameters of the sCO2 bottom cycle are optimized within a certain range of the gas turbine pressure ratio. It is found that the combined cycle system has high thermal efficiency when the top cycle adopts the air preheating cycle, and a higher top cycle regenerative degree does not represent a better performance. In fact, the optimal regenerative degree is related to the bottom cycle performance. The study also found that the air preheating-dual heated cascade combined cycle system has the highest thermal efficiency of the layouts studied, reaching 65.3%, but it comes at the cost of a complex operating system. The heat recovery performance of the sCO2 partial heating bottom cycle is relatively poor, and its mass flow rate is the highest, so it is not suitable for the bottom cycle of the combined cycle. The sCO2 dual heated cascade cycle has the highest output work and the smallest CO2 flow, so this paper considers this bottom cycle as the most suitable bottom cycle for the combined cycle system. This research can provide a certain basis for the design of gas turbine combined cycle system.

Multi-objective optimization of gas turbine combined cycle system considering environmental damage cost of pollution emissions

Currently, most of the performance analysis and optimization design of the gas turbine combined cycle (GTCC) units ignore the economic loss to the environment caused by the pollutant emissions. In this paper, based on the structure theory of thermoeconomics, an environmental thermoeconomic cost model is established. And then an annual total cost model is established, which can reflect the real economic performance. Based on the comprehensive analysis of the energy, economy and environment, with the objectives of the higher exergy efficiency, less annual total cost and lower specific CO2 emission rate, a multi-objective optimization study of the GTCC unit is conducted using the genetic algorithm (GA) in this paper. Pareto frontiers for the multi-objective optimization has been obtained with GA, and in turn a design plan can be selected from the Pareto frontier according to the preference. The multi-objective optimization results show that the optimized system can greatly increase the system environmental thermoeconomic performance. Moreover, the effects of main variables on the economic performance index of the optimized system are investigated. The results show that the natural gas price has the greater impact on the economic performance index compared with the pollutants environmental damage cost and the non-energy cost.

Integration of Hydrogen and Synthetic Natural Gas within Legacy Power Generation Facilities

Whilst various new technologies for power generation are continuously being evaluated, the owners of almost-new facilities, such as combined-cycle gas turbine (CCGT) plants, remain motivated to adapt these to new circumstances and avoid the balance-sheet financial impairments of underutilization. Not only are the owners reluctant to decommission the legacy CCGT assets, but system operators value the inertia and flexibilities they contribute to a system becoming predominated with renewable generation. This analysis therefore focuses on the reinvestment cases for adapting CCGT to hydrogen (H2), synthetic natural gas (SNG) and/or retrofitted carbon capture and utilization systems (CCUS). Although H2, either by itself or as part of SNG, has been evaluated attractively for longer-term electricity storage, the business case for how it can be part of a hybrid legacy CCGT system has not been analyzed in a market context. This work compares the power to synthetic natural gas to power (PSNGP) adaptation with the simpler and less expensive power to hydrogen to power (P2HP) adaptation. Both the P2HP and PSNGP configurations are effective in terms of decarbonizations. The best results of the feasibility analysis for a UK application with low CCGT load factors (around 31%) were obtained for 100% H2 (P2HP) in the lower range of wholesale electricity prices (less than 178 GBP/MWh), but in the higher range of prices, it would be preferable to use the PSNGP configuration with a low proportion of SNG (25%). If the CCGT load factor increased to 55% (the medium scenario), the breakeven profitability point between P2HP and PSNGP decreased to a market price of 145 GBP/MWh. Alternatively, with the higher load factors (above 77%), satisfactory results were obtained for PSNGP using 50% SNG if with market prices above 185 GBP/MWh.

Utilization of electric vehicles in combined voltage‐frequency control of multi‐area thermal‐combined cycle gas turbine system using two degree of freedom tilt‐integral‐derivative controller

AbstractThis paper conveys the unified control pattern of frequency and voltage of interconnected multi‐area power system through the automatic load frequency control (ALFC) loop and automatic voltage regulator (AVR) loop. Each area includes a single‐stage reheat thermal plant, combined cycle gas turbine (CCGT) plant, and electric vehicles (EVs). Pertinent generation rate constraint for thermal and CCGT plant and governor dead band for the thermal plant is considered. A maiden attempt has been made to introduce the two degree of freedom tilt‐integral‐derivative (2DOFTID) controller for both the ALFC and AVR loops. In this study, a meta‐heuristic algorithm called Harris Hawks optimization (HHO) is implemented to optimize the controller parameters. Study divulges that performance of the 2DOFTID controller predominates when compared with TID and proportional‐integral‐derivative with filter (PIDF) controller apropos time‐domain indices. By juxtaposition, the superiority of the proposed algorithm and performance index is observed. Also, improved system dynamics were independently exhibited by the influence of the lumped EV model and AVR. For the predominance of the 2DOFTID controller, different patterns of disturbances such as random and sinusoidal varying load perturbation have been investigated. Eventually, the sensitivity studies were accomplished to determine the sturdiness of the proposed controller for substantial variations in the system parameters.

Exergy Analysis of a Natural Gas-Fired Gas Turbine Combined Cycle Power Plant with Post-Combustion Carbon Capture

Post-combustion carbon capture (PCC) plays an important role in reducing the greenhouse gas emissions. In the present study, an exergy analysis is conducted to assess the exergy destruction and exergetic efficiency of a natural gas-fired combined cycle gas turbine (CCGT) system coupled with the PCC unit. The overall exergetic performance of the system is compared against the baseline CCGT by using realistic data. The working temperature and composition of the exhaust flue gas are two critical parameters that have significant impact on the performance of the absorption liquid and equipment operation. Results show that the highest exergy destruction occurs in the combustion chamber and condenser are 15.69 MW and 11.78 MW, occupying more than 45 % of the exergy destruction of the overall system for the conventional CCGT system. For the CCGT system with PCC unit, the exergy destruction of absorber is relatively high with an exergetic efficiency of 56.18 %. The highest exergetic efficiency is found in the units of combustion chamber and heat recovery steam generator (HRSG), which are 90.23 % and 87.01 %, while the condenser has the lowest efficiency. Identification of the low efficiency component presents an opportunity for improvement of the system.

Performance enhancement comparison of a gas turbine combined cycle system by introducing a refrigeration cycle using environment-friendly refrigerants to recover waste heat

Performance enhancement comparison of a gas turbine combined cycle system by introducing a refrigeration cycle using environment-friendly refrigerants to recover waste heat

Combined cycle gas turbine system optimization for extended range electric vehicles

In order to meet the Corporate Average Fuel Economy standards for passenger vehicles in 2025, car manufacturers are exploring several alternative energy converters to replace the Internal Combustion Engine, which has demonstrated limited efficiency improvement. Recent studies explored the use of a Gas Turbine as the primary vehicle driver in a hybrid powertrain; however, none evaluated the implementation of a Combined Cycle Gas Turbine, which offers higher efficiency. This study presents a methodology for the design and optimization of the most optimal combined cycle system configuration, suitable to replace the engine in a series-hybrid extended-range electric vehicle, and investigates its potential fuel savings. The two-steps methodology consists of conducting first an exergo-technological analysis using a Non-dominated Sorting Genetic Algorithm to identify the best suitable combined cycle configuration for integration in a series hybrid powertrain. Second, a series-hybrid extended range vehicle model is developed, to assess the consumption savings of the prioritized combined cycle on the Worldwide Harmonized Light Vehicle Test Cycle. The Reheat Gas Turbine combined to a Turbine Reheat Steam Rankine Cycle system is prioritized, for offering the highest efficiency and an acceptable vehicle integration complexity among the other investigated systems. Consumption results show fuel savings up to 23.6% with the prioritized system as compared to a reference extended-range electric vehicle equipped with an engine and savings up to 17% compared to other gas-turbine systems presented in the literature, depending on the battery size, the trip length, and the maximum turbine inlet temperature. Consequently, combined-cycle gas-turbine systems present a serious alternative to replacing internal combustion engines on series hybrid electrified vehicles if the cost-effectiveness of these systems was proven.

Development and implementation of mathematical models of working mediums for gas part of combined cycle gas turbine system in Python programming environment

The working mediums in the gas turbine systems are: atmospheric air, natural gas and exhaust gases. For the detailed analysis of thermodynamic performance and values at characteristic points of the cycle it is necessary to know the relations defining: specific volume, specific isobaric and isochoric heat capacity, isentropic exponent, specific enthalpy and specific entropy. Mathematical models of thermodynamic parameters for the mentioned mediums were developed based on dependencies for mixtures of ideal and semi-ideal gases. The functions obtained for semi-ideal gas mixtures were extended by pressure correction factors derived from the Redlich-Kwong and Peng-Robinson equations of state. The thermodynamic parameters of the working mediums were dependent on the mass fractions of the components, temperature and pressure. Developed models approximated the behaviour and parameters of real gas mixtures. All calculation algorithms were implemented and optimized using appropriate numerical methods in the Python programming environment. As a result, mathematical models of working mediums for the gas part of the combined cycle gas turbine system were obtained.

Incorporating combined cycle gas turbine flexibility constraints and additional costs into the EPLANopt model: The Italian case study

The planning of an energy system with high penetration of renewables is increasing in complexity as only an effective implementation can allow the tackling of environmental and energy security issues. The aim of this study is to present the integration of combined cycle gas turbine cycling costs in EPLANopt, a simulation software consisting of EnergyPLAN coupled to a Multi-Objective Evolutionary Algorithm. The model is then applied to the Italian energy system which is characterized by a very high capacity and electricity production from combined cycle gas turbine systems. The proposed approach established a first step in the direction of modelling their role for load modulation accounting for technical constraints and additional costs related to start-up and partial load condition. Results show the importance of considering cycling costs of combined cycle gas turbine system within energy system modelling as the nature of these costs at the increasing of intermittent renewable generation can reach peaks of 33.5 €/MWh. Additionally, the inclusion of CCGT cycling costs in high penetration non programmable renewable energy sources scenarios opens up favorable business models for other load modulation strategies (e.g. electric batteries).

Identifying key process parameters for uncertainty propagation in environmental life cycle assessment for sewage sludge and food waste treatment

Life cycle assessment (LCA) results are often subject to uncertainty, which may lead to erroneous conclusions. This paper aims to tackle the parameter uncertainty involved in LCA. Hong Kong is selected as the reference city for the treatment of sewage sludge and food waste. A selection approach with sensitivity analysis is proposed to identify the key process parameters and Monte Carlo simulation is further conducted to propagate the uncertainty of the key process parameters identified. The results show that climate change is the major impact category among various impact categories that are generally considered in waste LCA studies. Scenarios 5 and 6, which consider anaerobic co-digestion (coAD) treatment, achieve the best performance in regard to the climate change impact. Scenario 6 which includes a combined cycle gas turbine system for biogas utilization has −6.75 × 104 kg avoided CO2e emissions and it is equal to 44% more avoided emissions compared to scenario 5 which applies a combined heat and power system. For the key process parameters identified, it is found that the electricity generation efficiencies in different waste treatment facilities, such as the incineration plant and the anaerobic digestion plant, have the greatest sensitivity to the result. Uncertainty propagation is then conducted to obtain the probability distribution functions in environmental performance of different scenarios. Scenario 6 has a 95% probability of achieving at least −5.32 × 104 kg avoided CO2e emissions, while the probability of scenario 5, which is the second best scenario, achieving the same avoid emissions is below 5%. It indicates a significant advantage of using combined cycle gas turbine over combined heat and power unit for biogas utilization in Hong Kong. The methodologies and results of this study provide comprehensive material that can be adapted for other areas planning sustainable sewage sludge and food waste treatment, as well as in tackling parameter uncertainty in general LCA studies.

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.

Development of Simultaneous Corrosion Barrier and Optimized Microstructure in FeCrAl Heat-Resistant Alloy for Energy Applications. Part 1: The Protective Scale

Coarse-grained Fe-based oxide dispersion-strengthened (ODS) steels are a class of advanced materials for combined cycle gas turbine systems to deal with operating temperatures and pressures of around 1100°C and 15–30 bar in aggressive environments, which would increase biomass energy conversion efficiencies up to 45% and above. This two-part paper reports the possibility of the development of simultaneous corrosion barrier and optimized microstructure in a FeCrAl heat-resistant alloy for energy applications. The first part reports the mechanism of generating a dense, self-healing α-alumina layer by thermal oxidation, during a heat treatment that leads to a coarse-grained microstructure with a potential value for high-temperature creep resistance in a FeCrAl ODS ferritic alloy, which will be described in more detail in the second part.

Theoretical Calculation and Economic Assessment of the Integrated Solar Combined Cycle Power Plants

The ISCC technology representing an integrated solar combined cycle and the economic assessment of ISCC are investigated. Comparisons conducted by theoretical calculation method among two cases, that is, an integrated solar combined cycle system (ISCCS) and a combined cycle gas turbine system (CCGTS) show that ISCCS provides the best solution with the highest efficiency of heat to electricity among them. The results reflected by theoretical calculation also reveal that ISCCS is beneficial to energy saving and emission reduction. Due to the great advantages of ISCC, comprehensive analysis on the basic conditions for building ISCC power plants is analyzed in detail.

Model Predictive Control for Power and Thermal Management of an Integrated Solid Oxide Fuel Cell and Turbocharger System

This paper identifies and addresses the control challenges associated with simultaneous power and thermal management of a 5-kW-class solid oxide fuel cell and gas turbine combined cycle system. A model predictive controller (MPC) is developed to achieve improved system performance subject to input and state constraints. The subsystem dynamic couplings and control authority limitations under thermal constraints are investigated by both static and dynamic analysis. Through judicious allocation of penalty parameters in the cost function associated with the fuel cell current, anode fuel flow rate, and generator load, several different MPC implementations are derived to explore different control design degree of freedom and their performance is evaluated. Simulation results show the efficacy of the MPC design by demonstrating the fast load transition while maintaining the stack temperature within the allowable operation limits.

Thermodynamic and Experimental Analysis of a Biomass Steam Power Plant: Critical Issues and their Possible Solutions with CCGT Systems

This paper shows the experimental and numerical analysis of a biomass steam power plant from maximum power of 2.3 MW with a maximum pressure of 48bar and a turbine inlet temperature of about 430°C at the design point. The analysis has been conducted using experimental data, collected directly on the power plant, at the design point, and they have been afterwards used to validate a thermodynamic model. The analysis of the biomass power plant pointed out some critical issues that can be summarized in three points: low plant efficiency due to the small size, biomass supply range and continuous variation of the operating point. In order to solve this problem, different plant configurations were numerically evaluated. The first solution to these problems consists of a 100 kWe micro gas turbine (MGT) fueled by natural gas, whose exhaust gas were sent to the steam generator of the biomass power plant in order to evaluate the benefits on the power fluctuations and on global electric efficiency. A thermodynamic model of the MGT has been developed and validated with experimental data from technical literature, creating a CCGT (Combined Cycle Gas Turbine) system. The analysis of the results of this system showed improvement in terms of efficiency and operational stability. The second option was to fuel the previously validated method of MGT with four different alternative fuels and to evaluate the integration with the biomass plant for all of them. Furthermore, to emphasize the benefits of this integration, the power of the micro turbine has been increased assuming the use of more MGT at the same time. These analyses show an increase of the system efficiency, it could been also used the biomass, not suitable for direct combustion (high humidity), to produce biogas that fuels the MGT, reducing the range of biomass supply.

An Assessment of Wet Compression Process in Gas Turbine Systems with an Analytical Modeling

Recently humidified gas turbine systems in which water or steam is injected have attracted much attention, since they can offer a high efficiency and a high specific power with a relatively low cost compared to combined-cycle gas turbine systems, and therefore they have a potential for future power generation. In this study, performance analysis of the wet compression process is carried out with an analytical modeling which was developed from heat and mass transfer, and thermodynamic analyses based on droplet evaporation. Wet compression variables such as temperature-averaged polytropic coefficient, compressor outlet temperature, and compression work are estimated. Parametric studies show the effect of system parameters such as droplet size, water injection ratio or compression ratio on transient behavior.

Central power generation versus distributed generation – An air quality assessment in the South Coast Air Basin of California

This study assesses the air quality impacts of central power generation and compares them with the impacts of distributed generation (DG). The central power plant emissions factors used are from a newly installed combined cycle gas turbine system. Because location of power plants is a key parameter affecting air quality impacts, this study considers three potential locations for the installation of central power plants. Air quality impacts are evaluated for the South Coast Air Basin of California, in the year 2010, using a three-dimensional air quality model. Results are compared to air quality impacts from two potential DG scenarios to meet the same power demand as that of the central power plant case. Even though emissions from central generation are lower than emissions from the DG technology mix considered herein, central generation concentrates emissions in a small area, whereas DG spreads emissions throughout a larger cross-section of the air basin. As a result, air quality impacts from central generation are more significant than those from DG. The study also shows that assessment of air quality impacts from distributed and central generation should not only consider emissions levels, but also the spatial and temporal distribution of emissions and the air quality that results from atmospheric chemistry and transport – highly non-linear processes. Finally, analysis of population exposure to ozone and PM 2.5 shows that central generation located in coastal areas upwind from populated areas would cause the highest population exposure and even though emissions from central generation are considerably lower than DG emissions spread throughout the basin, results show that central generation causes a higher pollutant exposure than DG.