Combined Cycle Gas Turbine Plant Research Articles

The energy future of Saudi Arabia

In a recent publication, North European experts argue that “Saudi Arabia can achieve a 100% renewable energy power system by 2040 with a power sector dominated by PV single-axis tracking and battery storage”. They also say “Battery storage contributed up to 30% of the total electricity demand in 2040 and the contribution increases to 48% by 2050”. Based on considerations specific to the geography, climate conditions, and resources of Saudi Arabia, it is explained as batteries and photovoltaic solar panels are not the best choice for the country's energy sector. To cover all the total primary energy supply of Saudi Arabia by solar photovoltaic, plus battery storage to compensate for the sun's energy intermittency, unpredictability, and seasonal variability, is impracticable and inconvenient, for both the economy and the environment. Better environment and economy may be achieved by further valorizing the fossil fuel resources, through the construction of other high-efficiency plants such as the combined cycle gas turbine plants of Qurayyah, development of novel technologies for the production of clean fuels and clean electricity, including oxyfuel combustion and carbon capture and storage. Construction of nuclear power plants may also be more beneficial to the economy and the environment than photovoltaic and batteries. Regarding solar energy, enclosed trough solar thermal power systems developed along the coast have much better perspectives than solar photovoltaic, as embedded thermal energy storage is a better approach than battery storage. Further, a centralized power plant works better than distributed rooftop photovoltaic installations covered by dust and sand, rusted or cracked. Finally, pumped hydro energy storage along the coast may also have better perspectives than battery storage.

Comparative analysis of the Allam cycle and the cycle of compressorless combined cycle gas turbine unit

Nowadays, alternative thermodynamic cycles are actively studied. They allow to remove CO2, formed as a result of fuel combustion, from a cycle without significant energy costs. Calculations have shown that such cycles may meet or exceed the most advanced power plants in terms of heat efficiency. The Allam cycle is recognized as one of the best alternative cycles for the production of electricity. Nevertheless, a cycle of compressorless combined cycle gas turbine (CCGT) unit is seemed more promising for cogeneration of electricity and heat. A comparative analysis of the thermal efficiency of these two cycles was performed. Particular attention was paid to ensuring equal conditions for comparison. The cycle of compressorless CCGT unit was as close as possible to the Allam cycle due to the choice of parameters. The processes, in which the difference remained, were analysed. Thereafter, an analysis of how close the parameters, adopted for comparison, to optimal for the compressorless CCGT unit cycle was made. This analysis showed that these two cycles are quite close only for the production of electricity. The Allam cycle has some superiority but not indisputable. However, if cogeneration of electricity and heat is considered, the thermal efficiency of the cycle of compressorless CCGT unit will be significantly higher. Since it allows to independently regulate a number of parameters, on which the electric power, the ratio of electric and thermal power, the temperature of a working fluid at the turbine inlet depend. Thus, the optimal parameters of the thermodynamic cycle can be obtained in a wide range of operating modes of the unit with different ratios of thermal and eclectic powers. Therefore, the compressorless CCGT unit can significantly surpass the best steam turbine and combined cycle gas turbine plants in district heating system in terms of thermal efficiency.

Method of heat exchangers calculation for combined-cycle gas turbine plants in operation modes that differ from the nominal ones

We carried out a comparison of methods for calculating heat exchangers of combined-cycle gas turbine plants (CCGTP) in variable-load operation modes. It is shown that for calculations of waste heat boilers with complex thermal circuits and a large number of heat exchangers it is advisable to use approximate methods for calculations.

Combined-cycle gas turbine plant based on steam-turbine unit and a parallel superimposed gas-turbine plant with waste heat recovery boiler

We present a schematic diagram and the results of calculations of operating modes of the combined-cycle gas turbine plant (CCGTP) with a parallel superimposed gas-turbine plant (GTP). It is shown that at part-load operation in order to increase the efficiency of the unit, it is advisable to alter the steam turbine power while remaining the gas turbine power constant.

Techno-Economic Optimization of Electricity and Heat Production in a Gas-Fired Combined Heat and Power Plant With a Heat Accumulator

Abstract At present, power systems based on gas turbines are mainly used for electricity and heat generation. Gas turbines are used in industrial and institutional applications due to high-temperature exhaust, which can be used for heating, drying, or process steam production. The combined cycle gas turbine plants are a mature technology with high reliability and offering rapid response to changing demand for electricity and heat. The combination of a gas turbine with a heat recovery system and a heat accumulator makes the combined heat and power (CHP) plant a flexible unit. The paper presents the optimization tool for the planning process of electricity and heat production in the gas-fired CHP plant with a heat accumulator. The detailed mathematical model of the analyzed cogeneration plant was developed with the EBSILON®Professional and verified based on the results from on-site tests and warranty measurements. The implemented optimization algorithm is used to maximize the profits of the CHP plant operation. The presented solution is based on an evolutionary algorithm. The optimization algorithm is applied to the production determination for the day-ahead planning horizon, with 1-h time step. The obtained results show that the developed optimization model is a reliable and efficient tool for production planning in a CHP plant with gas turbines. The comparative exergy analysis for different technologies of heat recovery from gas turbine exhaust gases was performed to evaluate the quality of the energy conversion process in the CHP plant.

Deploying gas power with CCS: The role of operational flexibility, merit order and the future energy system

Combined cycle gas turbine (CCGT) power plants are an important part of many electricity systems. By fitting them with carbon capture their CO2 emissions could be virtually eliminated. We evaluate CCGT plants with different variations of post combustion capture using amine solvents, covering a range of options, including solvent storage, partial capture and shifting the energy penalty in time. The analysis is based on the UK electricity system in 2025. The behaviour of individual CCGT plants is governed by the plant’s place in the merit order and to a lesser extent by CO2 reduction targets for the electricity system. In the UK, CCGT plants built from 2016 onwards will emit ∼90% of the CO2 emissions of the whole CCGT fleet in 2025. The typical ‘base case’ CCGT plant with capture is designed to capture 90% of the CO2 emissions and to operate dynamically with the power plant. Downsizing the capture facility could be attractive for low-merit plants, i.e. plants with high short-run marginal costs. Solvent storage enables electricity generation to be decoupled in time from the energy penalty associated with carbon capture. Beyond a few minutes of solvent storage, substantial tanks would be needed. If solvent storage is to play an important role, it will require definitions of ‘capture ready’ to be expanded to ensure sufficient land is available.

A case study on combined cycle power plant integrated with solar energy in Trinidad and Tobago

Aim of the paper is to evaluate the benefit of a renewable energy initiative for Trinidad and Tobago. Trinidad and Tobago have abundant natural gas, a highly developed power generation system almost entirely based on combustion fuels, high solar irradiation, but skies often covered by clouds, a detrimental factor for concentrated solar power technologies. The simple, consolidated, parabolic trough technology, without the addition of thermal energy storage, has the potential to deliver better than solar photovoltaic capacity factors at a comparable cost when mass produced. Integration with natural gas combustion may permit to address the issues of clouds coverage. A computational analysis is proposed for an Integrated Solar Combined Cycle power plant comprising a reference combined cycle gas turbine plant, and a small solar field, located in Trinidad and Tobago. The simulations demonstrate the advantages, in terms of fuel conversion efficiency, of the small solar field addition. On average over the year, the plant operates over the morning and afternoon periods, of length about 8 h a day, at an efficiency of 57.34%, about 2.58% better, and over the mid-day periods, of length about 4 h a day, at an efficiency of 57.97%, about 3.16% better.

Simulation of a combined cycle gas turbine power plant in Aspen HYSYS

A detailed model is developed in Aspen HYSYS for simulating the operation of a triple-pressure reheat combined cycle gas turbine (CCGT) power plant. To our knowledge, this is the first such model in the literature. A comparison with an equivalent GateCycle model shows that the predictions of the two models (Aspen HYSYS and GateCycle) are comparable. The average relative deviations for the power outputs and thermal efficiencies of the gas turbine, steam cycle, and CCGT plant are less than 2.0%. The minor discrepancies are primarily from the differences in gas enthalpy correlations. On the other hand, Aspen HYSYS may have some advantages over GateCycle. First, its use of the well-proven real-gas Peng-Robinson fluid package may give more accurate predictions. Second, it allows easy integration with various energy systems such as CO2 capture, organic Rankine cycles, fuel cells, LNG terminals, air separation, absorption chillers, etc. Third, its model can be made dynamic for predicting the real-time behaviour of a CCGT plant.

Do unit commitment constraints affect generation expansion planning? A scalable stochastic model

Due to increasing penetration of stochastic renewable energy sources in electric power systems, the need for flexible resources especially from fast-start conventional generation units (e.g., combined cycle gas turbine plants) is growing. The fast-start conventional units are being operated more frequently in order to respond to the variability and uncertainty of stochastic generation. This raises two important technical questions: as it is common in the literature, is it still an appropriate simplification to ignore the operational unit commitment (UC) constraints of conventional units within the generation expansion planning optimization? And if not, which UC constraint impacts most the expansion planning outcomes? To answer these questions, this paper aims at measuring the planning inefficiency (i.e., the underestimation of need for new generation capacity) caused by ignoring each UC constraint. To this purpose, we develop a centralized network-constrained generation expansion planning model incorporating UC constraints. In particular, we model start-up and shut-down costs, minimum production level and hourly ramping limits of conventional units. Wind power production is considered as the only source of uncertainty, and is modeled through a set of scenarios. A two-stage stochastic programming tool is used, whose first stage determines the long-term expansion and short-term UC decisions over different hours of representative days, while the second stage models the real-time operation for accommodating imbalances arising from wind deviation under different scenarios. Since this problem is potentially hard to solve especially with a large number of representative days and scenarios, a multi-cut Benders’ decomposition algorithm is implemented. The well-functioning of the proposed model and the impact of each UC constraint on planning outcomes are evaluated using an extensive numerical study. In our case studies, the exclusion of ramping constraints from planning optimization causes large error and is the most distorting simplification.

Study of the work and efficiency improvement of combined-cycle gas turbine plants

The purpose of the paper is to study and analyze the possibility of increasing the power output of a combined-cycle gas turbine (CCGT) unit during the period of positive ambient temperatures. The first task is to analyze the operation of a 110 MW combined-cycle power unit at various ambient temperatures and to obtain alterations in the main CCGT characteristics when the ambient temperature changes. The other task is to study the usage of an absorption refrigeration machine in a CCGT cycle to increase its energy efficiency. Calculations of the thermal scheme of a gas turbine were carried out using mathematical modeling, the steam turbine was calculated based on guidelines. The conducted studies allow to conclude that the use of an absorption refrigeration machine in the cycle of a combined-cycle plant can improve the efficiency of the unit, increasing profits from power generation, and reducing penalties for non-compliance with the load schedule.

New operating strategy for a combined cycle gas turbine power plant

The highly dynamic nature of power demand forces a combined cycle gas turbine (CCGT) power plant to often run at less-efficient part-load conditions. A new operating strategy called EGR-IGVC is proposed in this work to improve the part-load performance of a CCGT plant. The strategy partially recycles the flue gas from the heat recovery steam generator and manipulates the inlet guide vanes to regulate part-load operation and boost plant efficiency. It allows the CCGT plant to set its own acceptable gas turbine temperature limits at any time and thus maximize the plant performance. Our previous CCGT flow diagram in Aspen HYSYS [Liu and Karimi (2018)] is modified to accommodate EGR for evaluating EGR-IGVC. Then, using a case study CCGT plant, EGR-IGVC is compared in detail with the conventional inlet guide vane control (IGVC). The results show that EGR-IGVC improves the plant part-load performance significantly. It increases the plant efficiency by up to 1.2% (actual) and reduces the CO2 emissions by up to 13.8 kg MW−1 h−1. By enabling an effective utilization of low-temperature waste heat and reducing the propensity for NOx formation, EGR-IGVC promises to be a better strategy for the part-load operation of CCGT plants.

Simulating combined cycle gas turbine power plants in Aspen HYSYS

Combined cycle gas turbine (CCGT) power plants are becoming increasingly important for electricity generation. Enhancing their thermal performance is essential for mitigating carbon emissions. This paper aims to present a methodology for simulating the off-design operation of a triple-pressure reheat CCGT plant in Aspen HYSYS. The modeling equations that rigorously capture the full off-design characteristics of various plant components (i.e. compressor, combustor, turbine, heat recovery steam generator, and steam turbines) are implemented in Aspen HYSYS, and a specially tailored procedure is proposed for solving them. The modeling strategy and solution procedure can be extended to simulate the off-design operation of any CCGT plants and are generically applicable to other process simulators (e.g. Aspen Plus, Unisim, and Pro II). To evaluate the model’s performance, its predictions are compared with those of an equivalent model from GateCycle. The results show the predictions of the two models (Aspen HYSYS and GateCycle) agree well. The average differences for the power outputs and thermal efficiencies of the gas turbine, steam cycle, and CCGT plant are less than 2.0%, 1.5%, and 0.6%, respectively. Besides, the differences arise primarily from the different gas enthalpy calculations. Since the model enables easy integration with various energy systems and can be made dynamic for predicting real-time behavior in Aspen HYSYS, it is very useful with wide applications.

Feasibility study of Combined Cycle Gas Turbine (CCGT) power plant integration with Adiabatic Compressed Air Energy Storage (ACAES)

The paper presents the research outcome on integration of an Adiabatic Compressed Air Energy Storage system with a Combined Cycle Gas Turbine power plant to increase its operation flexibility. The study demonstrates the novel hybrid CCGT-ACAES plant including an extended operational load level range and increased operation flexibility which supports the power grid to allow more power generation from connected intermittent renewable energy sources. It is also shown that this new hybrid power plant will avoid the Combined Cycle plant gas turbine operating under the low load level. Lowering the minimum hybrid plant operational load level during air and Thermal Energy Storage charging process to the required minimum Heat Recovery Steam Generator load level eliminates the need for Combined Cycle Gas Turbine plant cycling operation increasing the lifetime of the plant components. Adiabatic Compressed Air Energy Storage plant concept is based on proved and well established direct two-tank Thermal Energy Storage technology used in Concentrated Solar Power plants. Improved hybrid plant flexibility is occupied by slight decrease (2%) in the plant efficiency. Further investigation into alternative advanced Thermal Energy Storage systems based on latent heat and chemical reaction heat would offer better hybrid plant round-trip efficiency across operational plant load level range.

CO2 mitigation costs of catalytic methane decomposition

Catalytic methane decomposition (CMD) is promising for producing hydrogen without direct CO2 emissions. We estimate the CO2 mitigation costs associated with CMD for hydrogen production and subsequent power generation in a fuel cell. The overall CO2 emissions and economic viability are evaluated based on four scenarios: whether the by-product carbon can be sold or must be discarded into landfill; whether the catalyst can be recycled or not. CO2 emission savings and the associated costs of CMD concept are compared to the combined-cycle gas turbine (CCGT) power plant with and without carbon capture and storage (CCS). The results illustrate that the profitability of the concept as well as the ensuing CO2 abatement costs strongly depend on the ability to separate the catalysts from the carbon generated during the CMD. The life-cycle CO2 emissions per unit of electricity output of a CCGT plant with CCS are marginally higher than those generated in the CMD with perfect separation and regeneration of the catalysts. The levelized costs of electricity generation (LCOE) of CMD without selling the by-product are also higher than for CCGT with CCS. In contrast, the CMD can be highly profitable assuming selling the by-product carbon at current prices.

Increasing the Energy Efficiency of the Power Supply System on Liquefied Natural Gas through the Use of a Combined Cycle Gas Turbine Plant

The use of LNG for the production of additional energy is topical today. Very often LNG is used for gasification of settlements and industrial enterprises. LNG makes it possible to gasify objects remote from main pipelines for long distances by creating an LNG reserve directly from the consumer, avoiding the construction of expensive piping systems. However, in this case, there are large losses of cryoproduct and its low-potential heat. In this article, we propose a technical solution for compensating for the loss of cryoproducts during storage using an installation consisting of two circuits, one of which is a loss compensation loop and the other is a circuit for generating additional energy. The conducted researches showed that the use of this system allowed to return the previously used for liquefying electric power in the amount of 24%.

Simulation and optimization of a combined cycle gas turbine power plant for part-load operation

Combined cycle gas turbine (CCGT) power plants must often run at part-load conditions, as the electricity demand varies constantly. We present a method and necessary correlations for simulating the part-load operation of a typical CCGT plant in a commercial simulator (e.g. GateCycle). We show that assuming constant values for some equipment parameters (e.g. efficiencies) and ignoring the operating maps of key equipment can overestimate plant performance significantly at part-loads. Furthermore, a rise in the ambient temperature lowers the plant capacity, but increases the plant efficiency. Then, we propose a simulation-based optimization approach that yields an optimal operating strategy to maximize the overall plant efficiency for any part-load. Our strategy forms a basis for evaluating the two widely used operating policies (fuel flow control or FFC and inlet guide vane control or IGVC). Our proposed strategy increases the plant efficiency by as much as 2.63% (absolute) over FFC and 0.93% over IGVC. This work highlights the need for integrating the two cycles (gas turbine and steam) to optimize the plant performance. We find that FFC seems to prioritize the gas turbine and IGVC tends to prioritize the steam cycle, while our proposed strategy strikes an optimal balance between the two.

ИССЛЕДОВАНИЕ ВОЗМОЖНОСТИ ПРИМЕНЕНИЯ ПАРОГАЗОВЫХ УСТАНОВОК НА СУДАХ РОССИЙСКОГО ФЛОТА

The article studies the possibility of application combined-cycle gas turbine plants (CCGT) in the Russian Navy. A review of numerous publications allows to infer that the essential increase of ship power plant (SPP) efficiency (10-15%) can be reached by using combine-cycle gas turbine plants. It should be noted that the greatest effect on CCGT performance makes the level of technological sophistication of gas-turbine units (GTU), in particular, the gas temperature achieved before the turbine. The possibility of creating marine CCGT in Russia is being explored. The article contains examples of the use of GTUs on board foreign ships. Close attention is drawn to the advanced techniques used to increase CCGT efficiency. There have been presented calculations of the approved scheme of CCGT, which demonstrate the advantages of using CCGTs.

Thermal and nuclear power plants: Competitiveness in the new economic conditions

In recent years, the conditions of development and functionality of power generating assets have notably changed. Considering the decline in the price of hydrocarbon fuel on the global market, the efficiency of combined-cycle gas-turbine plants in the European part of Russia is growing in comparison with nuclear power plants. Capital investments in the construction of nuclear power plants have also increased as a result of stiffening the safety requirements. In view of this, there has been an increasing interest in exploration of effective lines of development of generating assets in the European part of Russia, taking consideration of the conditions that may arise in the nearest long-term perspective. In particular, the assessment of comparative efficiency of developing combined-cycle gas-turbine plants (operating on natural gas) in the European part of Russia and nuclear power plants is of academic and practical interest. In this article, we analyze the trends of changes in the regional price of hydrocarbon fuel. Using the prognosis of net-weighted import prices of natural gas in Western European countries—prepared by the International Energy Agency (IEA) and the Energy Research Institute of the Russian Academy of Sciences (ERIRAS)—the prices of natural gas in the European part of Russia equilibrated with import prices of this heat carrier in Western Europe were determined. The methodology of determining the comparative efficiency of combined-cycle gas turbine plants (CCGT) and nuclear power plants (NPP) were described; based on this, the possible development of basic CCGTs and NPPs with regard to the European part of Russia for various scenarios in the prognosis of prices of gaseous fuel in a broad range of change of specific investments in the given generating sources were assessed, and the extents of their comparative efficiency were shown. It was proven that, at specific investments in the construction of new NPPs in the amount of 5000 dollars/kW, nuclear power plants in the European part of Russia become less efficient as compared to CCGTs operating on natural gas.

Transient simulation and fatigue evaluation of fast gas turbine startups and shutdowns in a combined cycle plant with an innovative thermal buffer storage

In this paper a novel buffer storage for the thermal decoupling of gas turbine (GT) and heat recovery steam generator (HRSG) during startups and shutdowns is presented to the scientific public. The storage consists of a matrix of metal plates, placed in the flue gas channel between GT and HRSG, which is heated up during startup and cooled down during shutdown thus reducing the thermal gradients in the actual HRSG. The limitation to fast startups in combined cycle gas turbine (CCGT) plants is usually fatigue induced damage in critical components in the HRSG. To investigate the influence of the storage on the fatigue damage, a transient modeling strategy of both, storage and HRSG, is developed. It is found, that in the investigated plant such a storage is capable of reducing the cycling fatigue damage in the most critical part of the HRSG by up to 90% and therefore enables to act the GT as flexible as if no HRSG was connected to it.

Innovative configuration of a hybrid nuclear-solar tower power plant

This paper proposes a combination of a nuclear and a CSP plant and performs a thermodynamic analysis of the potential benefit. Most of today's operating nuclear reactor systems are producing saturated steam at relatively low pressure. This, in turn, limits their thermodynamic efficiency. Superheating of nuclear steam with solar thermal energy has the potential to overcome this drawback. Accordingly, an innovative configuration of a hybrid nuclear-CSP plant is assembled and simulated. It brings together pressurized water reactor and solar tower. The solar heat is transferred to nuclear steam to raise its temperature. Continuous superheating is provided through thermal energy storage. The results from design point calculations show that solar superheating has the potential to increase nuclear plant electric efficiency significantly, pushing it to around 37.5%. Solar heat to electricity conversion efficiency reaches unprecedented rates of 56.2%, approaching the effectiveness of the modern combined cycle gas turbine plants. Off-design model was used to simulate 24-h operation for one year by simulating 8760 cases. Due to implementation of thermal energy storage non-stop operation is manageable. The increased efficiency leads to solar tower island installed cost reductions of up to 25% compared to the standalone CSP plant, particularly driven by the smaller solar field.