Efficiency Entitlement for Bottoming Cycles

2006 ◽  
Author(s):  
Douglas C. Hofer ◽  
S. Can Gulen
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
New Method ◽  
Working Fluid ◽  
Generating Capacity ◽  
Topping Cycle ◽  
Cycle Efficiency ◽  
Steam Cycle

A significant portion of the new electrical generating capacity installed in the past decade has employed heavy-duty gas turbines operating in a combined cycle configuration with a steam turbine bottoming cycle. In these power plants approximately 1/3 of the power is generated by the bottoming cycle. To ensure that the highest possible combined cycle efficiency is realized it is important to optimize the bottoming cycle efficiency and doing so requires a solid understanding of the efficiency entitlement. This paper describes a new technique for calculating the theoretical efficiency entitlement for a bottoming cycle that corresponds to the maximum possible bottoming cycle work and maximized combined cycle work and efficiency. This new method accounts for the decrease in ideal efficiency as the gas turbine exhaust is cooled as it transfers heat energy to the working fluid in the bottoming cycle. The new definition is compared to conventional definitions, including that of Carnot and an Exergy based second law efficiency, and shown to provide a simple and accurate analytical expression for the entitlement efficiency in a bottoming cycle. For representative cycle conditions, the entitlement efficiency for the bottoming cycle is calculated to be ∼45% compared to the Carnot efficiency for the same conditions of ∼67%. Although the new method is applicable to any power cycle obtaining its heat input from the exhaust stream of a topping cycle, special attention is given to the steam bottoming cycle traditionally used in modern gas turbine combined cycle power plants. Comparisons are made between the ideal bottoming cycle and variants of a steam cycle including a single pressure non-reheat and a three pressure reheat cycle. These comparisons explore the unavoidable loss in efficiency associated with constant temperature heat addition that occurs in the steam cycle.

Effect of Bottoming Cycle Alternatives on the Performance of Combined Cycle

2003 ◽  
Author(s):  
R. Yadav
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Positive Influence ◽  
Combined Cycle ◽  
Exhaust Temperature ◽  
Compressor Pressure Ratio ◽  
Topping Cycle ◽  
Steam Parameters ◽  
Cycle Efficiency ◽  
Steam Cycle

The increase in efficiency of combined cycle has mainly been caused by the improvements in gas turbine cycle efficiency. With the increase in firing temperature the exhaust temperature is substantially high around 873 K for moderate compressor pressure ratio, which has positive influence on steam cycle efficiency. Minimizing the irreversibility within the heat recovery steam generator HRSG and choosing proper steam cycle configuration with optimized steam parameters improve the steam cycle efficiency and thus in turn the combined cycle efficiency. In this paper, LM9001H gas turbine, a state of art technology turbine with modified compressor pressure ratio has been chosen as a topping cycle. Various bottoming cycles alternatives (sub-critical) coupled with LM9001H topping cycle with and without recuperation such as dual and triple pressure steam cycles with and without reheat have been chosen to predict the performance of combined cycle.

scholarly journals Repowering Fossil Steam Power Plants With Combustion Turbine-Based Technologies

1996 ◽  
Author(s):  
Stanley Pace ◽  
Arden Walters
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Environmental Benefits ◽  
Technology Selection ◽  
Original Plant ◽  
Generation Capacity ◽  
Gas Turbine Exhaust ◽  
Topping Cycle

Increased competition fostered by changes in legislation governing power generation entities has engendered a need to closely assess the economics of operating older-electric generating units. Decisions must be made as to whether these units should be retired and replaced with new, greenfield generation capacity, whether capacity should be purchased from other generation companies, or whether such units should be repowered in some way. The repowering alternative has merit when economic factors and environmental considerations show it to project the least cost of electricity over other choices. The chief advantages of repowering, include use of existing real estate and infrastructure, existing transmission facilities and staffing. Since the repowered plant usually emits less stack gas pollutants per unit of energy generated then the original plant, environmental benefits can also accrue. Various types of gas turbine based repowering options for steam electric plants are presented. All the approaches discussed involve the addition of gas turbines to the cycle and the consequent benefit of some form of combined cycle operation. This option includes boiler retirement (and replacement with combined cycle), hot or warm windbox repowering (the boiler is retained and a gas turbine topping cycle is added), feedwater heating repowering (the gas turbine exhaust heats feedwater), and site repowering (only the site infrastructure is re-used as the site for a combined cycle). Business considerations are discussed in terms of their impact on the decision to repower and technology selection. An example involving feedwater heater repowering is used to illustrate the interaction between the business and technical aspects of repowering.

Evaluation for Scalability of a Combined Cycle Using Gas and Bottoming SCO2 Turbines

2015 ◽  
Author(s):  
Leonid Moroz ◽  
Petr Pagur ◽  
Oleksii Rudenko ◽  
Maksym Burlaka ◽  
Clement Joly
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Combined Cycle ◽  
Electricity Production ◽  
Working Fluid ◽  
Gas Temperature ◽  
Cycle System ◽  
Gas Turbine Exhaust

Bottoming cycles are drawing a real interest in a world where resources are becoming scarcer and the environmental footprint of power plants is becoming more controlled. Reduction of flue gas temperature, power generation boost without burning more fuel and even production of heat for cogeneration applications are very attractive and it becomes necessary to quantify how much can really be extracted from a simple cycle to be converted to a combined configuration. As supercritical CO2 is becoming an emerging working fluid [2, 3, 5, 7 and 8] due not only to the fact that turbomachines are being designed significantly more compact, but also because of the fluid’s high thermal efficiency in cycles, it raises an increased interest in its various applications. Evaluating the option of combined gas and supercritical CO2 cycles for different gas turbine sizes, gas turbine exhaust gas temperatures and configurations of bottoming cycle type becomes an essential step toward creating guidelines for the question, “how much more can I get with what I have?”. Using conceptual design tools for the cycle system generates fast and reliable results to draw this type of conclusion. This paper presents both the qualitative and quantitative advantages of combined cycles for scalability using machines ranging from small to several hundred MW gas turbines to determine which configurations of S-CO2 bottoming cycles are best for pure electricity production.

Aerodynamic Turbine Design for an Oxy-Fuel Combined Cycle

2016 ◽  
Author(s):  
Adrian Dahlquist ◽  
Magnus Genrup
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Power ◽  
Design Methods ◽  
Combined Cycle ◽  
Working Fluid ◽  
3D Analysis ◽  
Conventional Design ◽  
Turbine Design

The oxy-fuel combined cycle (OCC) is one of several carbon capture and sequestration (CCS) technologies being developed to reduce CO2 emissions from thermal power plants. The OCC consists of a semi-closed topping Bryton cycle, and a traditional bottoming Rankine cycle. The topping cycle operates with a working medium mixture of mainly CO2 and H2O. This CO2-rich working fluid has significantly different gas properties compared to a conventional open gas turbine cycle, which thereby affects the aerodynamic turbine design for the gas turbine units. The aerodynamic turbine design for oxy-fuel gas turbines is an unexplored research field. The topic of this study was therefore to investigate the aerodynamic turbine design of turbines operating with a CO2-rich working fluid. The investigation was performed through a typical turbine aero-design loop, which covered the 1D mid-span, 2D through-flow, 3D blade profiling design and the steady-state 3D analysis. The design was performed through the use of conventional design methods and criteria in order to investigate if any significant departures from conventional turbine design methods were required. The survey revealed some minor deviations in design considerations, yet it showed that the design is feasible with today’s state-of-the-art technology by using conventional design practice and methods. The performance of the oxy-fuel combined cycle was revised based on the performance figures from the components design. The expected total performance figures for the oxy-fuel combined cycle were calculated to be a net electrical power of 119.9 MW and a net thermal efficiency of 48.2%. These figures include the parasitic consumption for the oxygen production required for the combustion and the CO2 compression of the CO2 bleed stream.

Analysis of a Combined Cycle Plant Using a Small Particle Receiver to Drive a Primary Brayton Cycle

2015 ◽  
Author(s):  
Matthew Miguel Virgen ◽  
Fletcher Miller
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Small Particle ◽  
Power Plants ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Efficiency Gains ◽  
Steam Cycle

All current commercial CSP plants operate at relatively low thermodynamic efficiency due to lower temperatures than similar conventional plants and due to the fact that they all employ Rankine conversion cycles. We present here an investigation on the effects of adding a bottoming steam power cycle to a hybrid CSP plant based on a Small Particle Heat Exchange Receiver (SPHER) driving a gas turbine as the primary cycle. Due to the high operating temperature of the SPHER being considered (over 1000 Celsius), the exhaust air from the primary Brayton cycle still contains a tremendous amount of exergy. While in the previous analysis this fluid was only used in a recuperator to preheat the Brayton working fluid, the current analysis explores the potential power and efficiency gains from instead directing the exhaust fluid through a heat exchanger to power a Rankine steam cycle. Not only do we expect the efficiency of this model to be competitive with conventional power plants, but the water consumption per kilowatt-hour will also be reduced by nearly two thirds as compared to most existing concentrating solar thermal power plants as a benefit of having air as the primary working fluid, which eliminates the condensation step present in Rankine-cycle systems. Coupling a new steam cycle model with the gas-turbine CSP model previously developed at SDSU, a wide range of cases were run to explore options for maximizing both power and efficiency from the proposed CSP combined cycle gas turbine (CCGT) plant. Due to the generalized nature of the bottoming cycle modeling, and the varying nature of solar power, special consideration had to be given to the behavior of the heat exchanger and Rankine cycle in off-design scenarios. The trade-offs of removing the recuperator for preheating the primary fluid are compared to potential overall power and efficiency gains in the combined cycle case.

Increasing the Efficiency of a Gas Turbine Power Plant by Waste Heat Recovery

2009 ◽  
Author(s):  
P. Shukla ◽  
M. Izadi ◽  
P. Marzocca ◽  
D. K. Aidun
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Waste Heat ◽  
Current System ◽  
Temperature Drop ◽  
Combined Cycle ◽  
Gas Turbine Power Plant ◽  
Steam Cycle

The objective of this paper is to evaluate methods to increase the efficiency of a gas turbine power plant. Advanced intercooled gas turbine power plants are quite efficient, efficiency reaching about 47%. The efficiency could be further increased by recovering wasted heat. The system under consideration includes an intercooled gas turbine. The heat is being wasted in the intercooler and a temperature drop happens at the exhaust. For the current system it will be shown that combining the gas cycle with steam cycle and removing the intercooler will increase the efficiency of the combined cycle power plant up to 60%. In combined cycles the efficiency depends greatly on the exhaust temperature of the gas turbine and the higher gas temperature leads to the higher efficiency of the steam cycle. The analysis shows that the latest gas turbines with the intercooler can be employed more efficiently in a combined cycle power application if the intercooler is removed from the system.

Novel High-Performing Single-Pressure Combined Cycle With CO2 Capture

2010 ◽  
Vol 133 (4) ◽  
Author(s):  
Nikolett Sipöcz ◽  
Klas Jonshagen ◽  
Mohsen Assadi ◽  
Magnus Genrup
Keyword(s):  
Natural Gas ◽  
Electric Power ◽  
Gas Turbine ◽  
Co2 Capture ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Working Fluid ◽  
Market Demand ◽  
Combined Cycles

The European electric power industry has undergone considerable changes over the past two decades as a result of more stringent laws concerning environmental protection along with the deregulation and liberalization of the electric power market. However, the pressure to deliver solutions in regard to the issue of climate change has increased dramatically in the last few years and has given rise to the possibility that future natural gas-fired combined cycle (NGCC) plants will also be subject to CO2 capture requirements. At the same time, the interest in combined cycles with their high efficiency, low capital costs, and complexity has grown as a consequence of addressing new challenges posed by the need to operate according to market demand in order to be economically viable. Considering that these challenges will also be imposed on new natural gas-fired power plants in the foreseeable future, this study presents a new process concept for natural gas combined cycle power plants with CO2 capture. The simulation tool IPSEpro is used to model a 400 MW single-pressure NGCC with post-combustion CO2 capture using an amine-based absorption process with monoethanolamine. To improve the costs of capture, the gas turbine GE 109FB is utilizing exhaust gas recirculation, thereby, increasing the CO2 content in the gas turbine working fluid to almost double that of conventional operating gas turbines. In addition, the concept advantageously uses approximately 20% less steam for solvent regeneration by utilizing preheated water extracted from heat recovery steam generator. The further recovery of heat from exhaust gases for water preheating by use of an increased economizer flow results in an outlet stack temperature comparable to those achieved in combined cycle plants with multiple-pressure levels. As a result, overall power plant efficiency as high as that achieved for a triple-pressure reheated NGCC with corresponding CO2 removal facility is attained. The concept, thus, provides a more cost-efficient option to triple-pressure combined cycles since the number of heat exchangers, boilers, etc., is reduced considerably.

Advancements in H Class Gas Turbines and Combined Cycle Power Plants

2018 ◽  
Author(s):  
Christian Vandervort
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Operating Experience ◽  
Combined Cycle ◽  
Test Facility ◽  
Air Cooling ◽  
Operational Flexibility ◽  
Cycle Efficiency

The power generation industry is facing unprecedented challenges. High fuel costs combined with an increased penetration of renewable power has resulted in greater demand for high efficiency and operational flexibility. Imperative for a reduced carbon footprint places an even higher premium on efficiency. Power producers are seeking highly efficient, reliable, and operationally flexible solutions that provide long-term profitability in a volatile environment. New generation must also be cost-effective to ensure affordability for both domestic and industrial consumers. Gas turbine combined cycle power plants provide reliable, dispatch-able generation with low cost of electricity, reduced environmental impact, and improved flexibility. GE’s air-cooled, H-class gas turbines (7/9HA) are engineered to achieve greater than 63% net, combined cycle efficiency while delivering operational flexibility through deep, emission-compliant turndown and high ramp rates. The largest of these gas turbines, the 9HA.02, exceeds 64% combined cycle efficiency (net, ISO) in a 1 × 1, single-shaft configuration. In parallel, the power plant has been configured for rapid construction and commissioning enabling timely revenue generation for power plant developers and owners. The HA platform is enabled by 1) use of a simple air-cooling system for the turbine section that does not require external heat exchange and the associated cost and complexity, and 2) use of well-known materials and coatings with substantial operating experience at high firing temperatures. Key technology improvements for the HA’s include advanced cooling and sealing, utilization of unsteady aerodynamic methodologies, axially staged combustion and next generation thermal barrier coating (TBC). Validation of the architecture and technology insertion is performed in a dedicated test facility over the full operating range. As of February 2018, a total of 18 HA power plants have achieved COD (Commercial Operation). This paper will address three topics relating to the HA platform: 1) gas turbine product technology, 2) gas turbine validation and 3) integrated power plant commissioning and operating experience.

Commercialization and Fleet Experience of the 7/9HA Gas Turbine Combined Cycle

2019 ◽  
Author(s):  
Christian Vandervort ◽  
David Leach ◽  
David Walker ◽  
Jerry Sasser
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
High Efficiency ◽  
Operating Experience ◽  
Combined Cycle ◽  
Lessons Learned ◽  
Operational Flexibility ◽  
Industrial Gas Turbine ◽  
Cycle Efficiency

Abstract The power generation industry is facing unprecedented challenges. High fuel costs and increased penetration of renewable power have resulted in greater demand for high efficiency and operational flexibility. Imperatives to reduce carbon footprint place an even higher premium on efficiency. Power producers are seeking highly efficient, reliable, and operationally flexible solutions that provide long-term profitability in a volatile environment. New generation must also be cost-effective to ensure affordability for both domestic and industrial consumers. Gas turbine combined cycle power plants meet these requirements by providing reliable, dispatchable generation with a low cost of electricity, reduced environmental impact, and broad operational flexibility. Start times for large, industrial gas turbine combined cycles are less than 30 minutes from turning gear to full load, with ramp rates from 60 to 88 MW/minute. GE introduced the 7/9HA industrial gas turbine product portfolio in 2014 in response to these demands. These air-cooled, H-class gas turbines (7/9HA) are engineered to achieve greater than 63% net combined cycle efficiency while delivering operational flexibility through deep, emission-compliant turndown and high ramp rates. The largest of these gas turbines, the 9HA.02, is designed to exceed 64% combined cycle efficiency (net, ISO) in a 1×1, single-shaft (SS) configuration. As of December 2018, a total of 32 7/9HA power plants have achieved COD (Commercial Operation Date) while accumulating over 220,000 hours of operation. These plants operate across a variety of demand profiles including base load and load following (intermediate) service. Fleet leaders for both the 7HA and 9HA have exceeded 12,000 hours of operation, with multiple units over 8,000 hours. This paper will address four topics relating to the HA platform: 1) gas turbine product technology, 2) gas turbine validation, 3) integrated power plant commissioning and operating experience, and 4) lessons learned and fleet reliability.

Performance Charateristics of Advanced Gas Turbine Cogeneration Power Plants

2005 ◽  
Author(s):  
Meherwan P. Boyce
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Firing Temperature ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Air Filter ◽  
Cycle Efficiency

The performance analysis of the new generation of Gas Turbines in combined cycle operation is complex and presents new problems, which have to be addressed. The new units operate at very high turbine firing temperatures. Thus variation in this firing temperature significantly affects the performance and life of the components in the hot section of the turbine. The compressor pressure ratio is high which leads to a very narrow operation margin, thus making the turbine very susceptible to compressor fouling. The turbines are also very sensitive to backpressure exerted on them by the heat recovery steam generators. The pressure drop through the air filter also results in major deterioration of the performance of the turbine. The performance of the combined cycle is also dependent on the steam turbine performance. The steam turbine is dependent on the pressure, temperature, and flow generated in the heat recovery steam generator, which in turn is dependent on the turbine firing temperature, and the air mass flow through the gas turbine. It is obvious that the entire system is very intertwined and that deterioration of one component will lead to off-design operation of other components, which in most cases leads to overall drop in cycle efficiency. Thus, determining component performance and efficiency is the key to determining overall cycle efficiency. Thermodynamic modeling of the plant with individual component analysis is not only extremely important in optimizing the overall performance of the plant but in also determining life cycle considerations.

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