Modern Combined Cycle Power Plants Research Articles

Hydrogen vs. methane: A comparative study of modern combined cycle power plants

This article compared modern hydrogen power plants over a wide range of total compression ratios while maintaining constant system output. In addition, the conventional modern new combined cycle power plant fueled by 100 % methane serves as a reference (comparative) variant representing the currently constructed generating units. Simulations were done using Ebsilon Professional software in the total compression ratio range of 20–50. Previous literature has mainly been based on comparing only the efficiency of GRAZ systems with a combined cycle power plant. The paper discusses a number of performance characteristics. Attention was drawn to the limitations of the currently used COT temperature and the temperature of the compressed medium. For the gas-steam power plant, hydrogen was traditionally burned in air, and in the Graz system, hydrogen was burned in pure oxygen. The structures of the analysed systems were presented and characterised, and their main computational assumptions were standardised in order to compare the systems. A common turbine cooling model was used for both systems. The methodologies for evaluating the performance of energy systems were discussed. Efficiencies, and levels of CO2 emissions per unit were compared for the studied systems. The calculations showed that for the currently used combustion outlet temperature (COT) of 1600 °C, the Graz system achived the best results. The system achieved a COT of 1600 °C for a total compression ratio of 82, which is much higher than that of the main analyses. It operated without CO2 emissions and had an efficiency of 56.21 %, considering the energy consumption of the air separation unit (ASU). For the modern new combined cycle power plant fueled by 100 % methane and for a hydrogen-fueled variant systems, the efficiencies were 53.86 % and 51.39 %, respectively. The modern gas-steam power plant had a high emission rate compared to other systems, reaching 325.17 kgCO2/MWh.

Energy saving technology in power plants industry by HFRW

This paper aims at investigating the use of high frequency resistance welding (HFRW) to deploy energy saving technology in power plants industry. The new approach of dissimilar welds A240TP409 finned and 2¼ Cr-1 Mo seamless tube under various conditions of high frequency resistance welding (HFRW) are found in power plant boilers and reducing energy costs is possible through the use of finned tubes. HFRW have accom-plished on samples by changing multiple parameters including current of welding, electric potential, travel speed and fin pitch. Microstructural evolution in weld bond, hardness and tensile strength tests revealed that metallurgical bonding more than 90 % was measured at the weld interface and the average of tensile strengths were more than 275MPa, with setting on appropriate welding parameters and optimum pressure. Since the pitch and fin thickness can be severely reduced, the output transfer surface treatment in final process can be dramatically diminished. Lastly, a well-engineered approach to the design of the best conditions of finned tube welding bond is discussed in modern combined cycle power plant (CCPP).

Feasibility analysis of solar photovoltaics for the feeding of cooling pump of a natural gas power plant

In the present work, the energy and exergy analysis of combined cycle power plant were carried out using the actual operating parameters to investigate the exergetic efficiency, exergy destruction/losses for the components. The energy and exergy efficiencies of the combined cycle power plant were found to be 48.4% and 47.2%, respectively. The results of the energy analysis show that the condenser is associated with the highest energy losses occurred in the system but according to the exergy analysis, the combustion chamber has the highest exergy destruction rate among the system components. The attention is focused on a solar photovoltaic (PV) system satisfying partly the energy demands of an cooling water pumps. An integrated solar Photovoltaic Combined Cycle System is proposed as a means of integrating a photo voltaic solar thermal plant with the modern combined cycle power plants. The 1 MW direct solar PV system which supply the electricity of the cooling water pump that uses electricity most in the system is proposed as a way to increase the efficiency of this plant. The electricity consumption of this pump is thus reduced by about 0.25% with the usage of the electricity directly supplied by the solar PV generator. Electricity from the solar PV system is partly used to operate a cooling pump to mitigate the electricity demands. The 29.2% of the electricity demanded by the cooling pump is provided by the photovoltaic production.

Comprehensive multivariable analysis of the possibility of an increase in the electrical efficiency of a modern combined cycle power plant with and without a CO2 capture and compression installations study

The main objective of the presentstudy is to determine whether the thermodynamic efficiency of a modern combined cycle power plant (CCPP) with steam reheating can be increased when using designs both with and without CO2 separation and compression installations. The relatively high costs of a steam cycle compared to a gas turbine (GT) have motivated the present direction of efficiency research in this area. Therefore, in all systems analyzed in this work, the same structure of heat recovery steam generator (HRSG) was assumed, producing fresh and secondary steam, with the parameters 600 °C/18 MPa and 600 °C/4 MPa, respectively, and a constant GT exhaust gas temperature of 630 °C. A methodology for modeling the operation of a GT within a wide range of compression ratios β (10 ≤ β ≤ 100) has been developed.Power plants that employ various types of open-air cooling (convective, film, or transpiration) in order to cool the air in a steam cycle (SC) were analyzed. These power plants were equipped with closed steam and closed air cooling, sequential combustion (reheat), and the ability to capture CO2from the flue gas.For all analyzed systems, a uniform methodology for determining the efficiency, the stream of coolant used in a GT, combustor outlet temperature (COT), and unitary CO2 emission was developed. These parameters were determined as a function of the pressure ratio, β.It is important to show the limitation of the efficiency increase that results from the COT, β level, the cooling method, and the structure of the CCPP. This paper shows that the power plant equipped with sequential combustion and steam cooling has the greatest potential for an increase in efficiency from ηel.n = 61.5% (β = 30) and ηel.n = 65.8% (β = 60) to ηel.n = 67.9% (β = 100), all at COT ≤ 1550 °C. Assuming COT = 1900 °C, the CCPP equipped with only closed-steam gas turbine cooling will reach the efficiency ηel.n = 65.5% at β = 76, and the system with film cooling will reach an efficiency ηel.n = 63.56% at β = 66. At β = 30, these CCPPs achieve efficiencies ηel.n = 61.7% (COT = 1550 °C) and ηel.n = 61.3% (COT = 1580 °C), respectively.

The thermodynamic and economic characteristics of the modern combined cycle power plant with gas turbine steam cooling

This paper presents a methodology to clearly identify energy benefits (in terms of power and efficiency) resulting from the use heat from gas turbine steam cooling and heat from cooling air. These potential benefits are evaluated in terms of the characteristics of combined cycle power plants in a wide range of pressure ratios β = 10 ÷ 100. Calculations were made for four variants (optimistic and conservative), differing in terms of the performance characteristics of the compressor and turbine isentropic efficiency as a function of β and the permissible temperature of the expander blades in the gas turbine. The steam part of the power plant in question is composed of a classical steam cycle with a triple-pressure subcritical heat recovery steam generator (HRSG) with reheating, to which gases from a gas turbine are fed at a constant temperature of 630 °C. The power plant also has an additional steam cycle utilizing the heat from cooling the air from the intercooler of the air compressor. The impact of using steam cooling on the electrical efficiency of the gas turbine as well as the entire power plant is presented. This was compared to classical open-air cooling, achieving a gas turbine electrical efficiency seven percentage points higher for high pressure ratios. Using steam and air heat, the combined cycle power plant achieves a net electrical efficiency of more than 65% for β ≥ 95. This paper presents the calculation algorithm of the break-even cost of electricity Celb-e (at the NPV = 0) and the cost of the components as a function of the pressure ratio β. In addition, the efficiency and power degradation of the power plant over time is presented. The lowest cost Celb-e = 64.85 €/MWh (at the fuel price 8.179 €/GJ) was obtained for the compression ratio β = 31. But, the range of compression ratios for which this is close to the optimum is wide and is within the range of β = 18 ÷ 53. Sensitivity analysis of the break-even cost of electricity to changes in microeconomic factors was performed for case O1 (characterized by the highest net electrical efficiency of the unit), such as: investment costs, gas fuel price, power plant operating time and CO2 emission allowance cost. This showed that a change in these factors has little effect on the change in the optimal gas turbine pressure ratio, while significantly affecting the profitability of the combined cycle power plant. Calculations show that the thermodynamic optimum (maximum efficiency) and economic optimum (minimum break-even cost of electricity) do not overlap.

Analysis of increasing efficiency of modern combined cycle power plant: A case study

The paper presents a comprehensive thermodynamic analysis of various gas turbine improvements in a modern combined cycle power plant designed to increase its electrical efficiency. The power plant was analyzed for use in: open air (convection, film and transpiration) cooling without and with cooling air cooler, closed air cooling, closed steam cooling and sequential combustion. The combined cycle power plant is equipped with a 200 MW gas turbine and a subcritical heat recovery steam generator with steam reheating. This article presents the effect of coolant cooling (air) and its use in the steam cycle of the combined cycle power plant. The influence of the higher permissible metal blade temperature in gas turbine on the electric efficiency of the gas turbine as well as the entire combined cycle power plant was also shown. It has also been proven that using industry - known solutions such as steam cooling and sequential combustion, the net electric efficiency of a combined cycle power plant can reach 0.63–0.65.

Повышение аэродинамической эффективности широкоугольных плоских диффузоров

In designing the transition pipes from the gas turbine output diffuser to the heat-recovery steam generator used in modern combined-cycle power plants, the compactness requirements are in some cases the governing ones. As a result, channels having non-optimal aerodynamics are used, including those in the form of wide-angle diffusers, the current in which may contain zones with flow separation and a sharply non-uniform field of outlet velocities. Such a flow pattern downstream of the transition pipe at the heat-recovery steam generator inlet significantly impairs the heat transfer in the steam generator’s tube bundles located first along the flow. Among the aerodynamic methods used to modify the flow pattern in diffusers, methods that allow their performance to be improved significantly without additional energy expenditures are of great interest. A flow separation delaying method involving the use of so-called vortex generators as received wide use. These vortex generators are made in the form of flat or profiled plates installed directly on the diffuser channel wall perpendicular to it. As the current flows over the plates, near-wall vortices are generated, which intensify turbulent heat transfer in the boundary layer and make this layer more resistant to separation. The article presents the results from an experimental study of the method for reducing energy losses and equalizing the field of outlet velocities in wide-angle diffuser channels by installing a short plate in the channel inlet section in parallel to the deflected wall. With such an arrangement, the plate is not only a generator of vortices that transfer additional energy to the boundary layer, but also transmits an additional momentum to the wall due to flow deflection. The investigations were carried out in an open-type wind tunnel with the dimensionless velocity values at the diffuser inlet not exceeding 0.3. The values of total energy loss coefficients were obtained in moving the plate both along and perpendicular to the diffuser channel deflecting wall. The plate optimal location in the channel inlet section in terms of the greatest reduction of energy losses has been determined. The velocity distribution patterns in the diffuser outlet section for regimes with and without flow separation have been obtained. It is shown that in the case of separation flow modes in the diffuser, the use of a plate installed in it can significantly reduce the total energy loss, increase the diffuser effect, and equalize the velocity field in the channel outlet section of due to partial or complete elimination of flow separation. During the experiments, static pressure pulsations on the deflected wall were measured in five sections along its length. It is shown that in case of separation flow modes, the plate installed in the inlet section decreases the intensity of the near-wall pulsating motion and, hence, the dynamic loads on the channel walls. The obtained results allow us to recommend the investigated flow control method in a wide-angle diffuser for being used in the transition pipes from the gas turbine to the combined cycle plant’s heat-recovery steam generator in the course of their modernizations and repairs to equalize the velocity field at the heat-recovery steam generator inlet, to decrease the energy losses, and to reduce the dynamic loads.

A high-temperature gas-and-steam turbine plant operating on combined fuel

A high-temperature gas–steam turbine plant (GSTP) for ultrasupercritical steam conditions is proposed based on an analysis of prospects for the development of power engineering around the world and in Russia up to 2040. The performance indicators of a GSTP using steam from a coal-fired boiler with a temperature of 560–620°C with its superheating to 1000–1500°C by firing natural gas with oxygen in a mixingtype steam superheater are analyzed. The thermal process circuit and design of a GSTP for a capacity of 25 MW with the high- and intermediate-pressure high-temperature parts with the total efficiency equal to 51.7% and the natural gas utilization efficiency equal to 64–68% are developed. The principles of designing and the design arrangement of a 300 MW GSTP are developed. The effect of economic parameters (the level and ratio of prices for solid fuel and gas, and capital investments) on the net cost of electric energy is determined. The net cost of electric energy produced by the GSTP is lower than that produced by modern combined-cycle power plants in a wide variation range of these parameters. The components of a high-temperature GSTP the development of which determines the main features of such installations are pointed out: a chamber for combusting natural gas and oxygen in a mixture with steam, a vacuum device for condensing steam with a high content of nondensables, and a control system. The possibility of using domestically available gas turbine technologies for developing the GSTP’s intermediate-pressure high-temperature part is pointed out. In regard of its environmental characteristics, the GSTP is more advantageous as compared with modern condensing power plants: it allows a flow of concentrated carbon dioxide to be obtained at its outlet, which can be reclaimed; in addition, this plant requires half as much consumption of fresh water.

Study on Neutronics and Thermalhydraulics Characteristics of 1200-MWel Pressure-Channel Supercritical Water-Cooled Reactor

Nuclear power becomes more and more important in many countries worldwide as a basis for current and future electrical energy generation. The largest group of operating nuclear power plants (NPPs) equipped with water-cooled reactors (96% of all NPPs) has gross thermal efficiencies ranging from 30–36%. Such relatively low values of thermal efficiencies are due to lower pressures/temperatures at the inlet to a turbine (4.5–7.8 MPa/257–293°C). However, modern combined-cycle power plants (Brayton gas-turbine cycle and subcritical-pressure steam Rankine cycle, fueled by natural gas) and supercritical-pressure coal-fired power plants have reached gross thermal efficiencies of 62% and 55%, respectively. Therefore, next generation or Generation IV NPPs with water-cooled reactors should have thermal efficiencies as close as possible to those of modern thermal power plants. A significant increase in thermal efficiencies of water-cooled NPPs can be possible only due to increasing turbine inlet parameters above the critical point of water, i.e., supercritical water-cooled reactors (SCWRs) have to be designed. This path of increasing thermal efficiency is considered as a conventional way that coal-fired power plants followed more than 50 years ago. Therefore, an objective of the current paper is a study on neutronics and thermalhydraulics characteristics of a generic 1200-MWel pressure-channel (PCh) SCWR. Standard neutronics codes DRAGON and DONJON have been coupled with a new thermalhydraulics code developed based on the latest empirical heat-transfer correlation, which allowed for more accurate estimation of basic characteristics of a PCh SCWR. In addition, the computational fluid dynamics (CFD) Fluent code has been used for better understanding of the specifics of heat transfer in supercritical water. Future studies will be dedicated to materials and fuels testing in an in-pile supercritical water loop and developing passive safety systems.

Gas Turbines and Natural Gas Synergism

This article presents a study on new electric power gas turbines and the advent of shale natural gas, which now are upending electrical energy markets. Energy Information Administration (EIA) results show that total electrical production cost for a conventional coal plant would be 9.8 cents/kWh, while a conventional natural gas fueled gas turbine combined cycle plant would be a much lower at 6.6 cents/kWh. Furthermore, EIA estimates that 70% of new US power plants will be fueled by natural gas. Gas turbines are the prime movers for the modern combined cycle power plant. On the natural gas side of the recently upended electrical energy markets, new shale gas production and the continued development of worldwide liquefied natural gas (LNG) facilities provide the other element of synergism. The US natural gas prices are now low enough to compete directly with coal. The study concludes that the natural gas fueled gas turbine will continue to be a growing part of the world’s electric power generation.

Exergy analysis of an integrated solar combined cycle system

Exergetic analysis has become an integral part of thermodynamic assessment of any power generation system. Energy and exergy studies for power plants optimum design and for combined chemical industries received much attention recently. An Integrated Solar Combined Cycle System (ISCCS) is proposed as a means of integrating a parabolic trough solar thermal plant with modern combined cycle power plants. In this study attempt will be made to analyze the Integrated Solar Combined Cycle in Yazd, Iran using design plant data. Energy and exergy analysis for the solar field and combined cycle is carried out to assess the plant performance and pinpoint sites of primary exergy destruction. Exergy destruction throughout the plant is quantified and illustrated using an exergy flow diagram, and compared to the energy flow diagram. The causes of exergy destruction in the plant include: losses in combustor, collector, heat exchangers, and pump & turbines which accounts for 29.62, 8.69, 9.11 and 8% of the total exergy input to the plant, respectively. Exergetic efficiencies of the major plant components are determined in an attempt to assess their individual performances.

Dynamic simulation of a supercritical once-through heat recovery steam generator during load changes and start-up procedures

This paper presents a static and dynamic simulation model of a supercritical once-through heat recovery steam generator (SC HRSG) and its application to investigate the load changes and start-up processes for next generation high efficiency combined cycles. The scale and complexity of the modern combined cycle power plants based on high pressure and temperature steam requirements are increasing. To design such a system, it is necessary to generate detailed computer models. This study describes the upgrading of a validated sub-critical heat recovery steam generator model to a supercritical once-through heat recovery steam generator up to 250 bars in the high pressure circuit. The SC HRSG model is built using commercial simulation software named Advanced Process Simulation Software (APROS). The model includes advanced control circuits to have a high level of accuracy, especially during start-up. The comparison between the simulation results and the designed data in steady state and different load changes are documented. The obtained results demonstrate that the simulation is very reliable to predict the start-up procedure for the SC HRSG. Through a comparative study, the differences in the thermal efficiency and the steam parameters between super/sub-critical heat recovery steam generators during warm start-up process are assessed.