Thermoeconomic optimization of combined cycle gas turbine power plants using genetic algorithms

This paper shows a possible way to achieve a thermoeconomic optimization of combined cycle gas turbine (CCGT) power plants. The optimization has been done using a genetic algorithm, which has been tuned applying it to a single pressure CCGT power plant. Once tuned, the optimization algorithm has been used to evaluate more complex plants, with two and three pressure levels in the heat recovery steam generator (HRSG).The variables considered for the optimization were the thermodynamic parameters that establish the configuration of the HRSG.Two different objective functions are proposed: one minimizes the cost of production per unit of output and the other maximizes the annual cash flow. The results obtained with both functions are compared in order to find the better optimization strategy.The results show that it is possible to find an optimum for every design parameter. This optimum depends on the selected optimization strategy.     

Energetic and exergetic analysis of a hybrid combined‐nuclear power plant

Combined‐cycle power plants are currently preferred for new power generation plants worldwide. The performance of gas‐turbine engines can be enhanced at constant turbine inlet temperatures with the addition of a bottoming waste‐heat recovery cycle. This paper presents a study on the energy and exergy analysis of a novel hybrid Combined‐Nuclear Power Plant (HCNPP). It is thus interesting to evaluate the possibility of integrating the gas turbine with nuclear power plant of such a system, utilizing virtually free heat. The integration arrangement of the AP600 NPP steam cycle with gas turbines from basic thermodynamic considerations will be described. The AP600 steam cycle modifications to combine with the gas turbines can be applied to other types of NPP. A simple modeling of Alstom gas turbines cycle, one of the major combined‐cycle steam turbines manufacturers, hybridized with a nuclear power plant from energetic and exergetic viewpoint is provided. The Heat Recovery Steam Generator (HRSG) has single steam pressure without reheat, one superheater and one economizer. The thermodynamic parameters of the working fluids of both the gas and the steam turbines cycles are analyzed by modeling the thermodynamic cycle using the Engineering Equation Solver (EES) software. In case of hybridizing, the existing Alstom gas turbine with a pressurized water nuclear power plants using the newly proposed novel solution, we can increase the electricity output and efficiency significantly. If we convert a traditional combined cycle to HCNPP unit, we can achieve about 20% increase in electricity output. This figure emphasizes the significance of restructuring our power plant technology and exploring a wider variety of HCNPP solutions. Copyright © 2011 John Wiley & Sons, Ltd.     

Distribution of size in steam turbine power plants

This paper shows that the mass inventory for steam turbines can be distributed between high‐pressure (HP) and low‐pressure (LP) turbines such that the global performance of the power plant is maximal. This is demonstrated for two design classes. For an HP turbine in series with an LP turbine, the optimal intermediate pressure (IP) is a geometric average of HP and LP. The total mass is distributed in a balanced way based on the total mass of turbines. For a train consisting of many turbines expanding the steam at nearly constant temperature, the pressure ratio between consecutive IP should be constant, and more mass should be distributed at HPs. This approach to discovering the configuration of the power plant should be used in conjunction with classical approaches that account for vibration, centrifugal force and blade length. Copyright © 2009 John Wiley & Sons, Ltd.     

Engineering design and exergy analyses for combustion gas turbine based power generation system

This paper presents the engineering design and theoretical exergetic analyses of the plant for combustion gas turbine based power generation systems. Exergy analysis is performed based on the first and second laws of thermodynamics for power generation systems. The results show the exergy analyses for a steam cycle system predict the plant efficiency more precisely. The plant efficiency for partial load operation is lower than full load operation. Increasing the pinch points will decrease the combined cycle plant efficiency. The engineering design is based on inlet air-cooling and natural gas preheating for increasing the net power output and efficiency. To evaluate the energy utilization, one combined cycle unit and one cogeneration system, consisting of gas turbine generators, heat recovery steam generators, one steam turbine generator with steam extracted for process have been analyzed. The analytical results are used for engineering design and component selection.     

燃机电厂9F型机组热电负荷优化分配研究

电厂热电负荷优化分配是指在全厂总调度负荷下,根据各机组的热力性能确定各机组应承担的热电负荷,使得全厂效益最大或能耗最小的一种最优化问题.不同于燃煤热电厂,燃机电厂9F型机组由于设计为燃气轮机加蒸汽轮机的组合方式运行,因此在联合循环热力性能模型建立上较为复杂.提出了将余热锅炉新蒸汽参数作为中间变量,建立了机组天然气燃料消耗与电负荷、热负荷之间的关系模型,确定了优化计算的目标函数和边界约束条件,并采用非线性规划方法求解.模拟与实际运行结果均表明,该优化分配方法能有效降低燃机电厂燃料消耗水平,可以为同类型燃机电厂热电负荷优化分配提供参考.     

Power generation with gas turbine systems and combined heat and power

This article gives an overview of power generation with gas turbine and combined heat and power (CHP) systems. It also presents the European Union strategy for developing gas turbines and CHP systems. Ways to improve the performance of the several types of gas turbine cycle will be a major objective in the coming years. The targets are combined cycle efficiencies above 60% industrial gas turbine system efficiencies of at least 50% and small gas turbines efficiencies above 35% and designs for the use of fuels with less than 25% heating value of that of natural gas. The main CHP targets are the reduction of the overall costs and the development of above 40 kW biomass-fired systems.     

电站汽轮机研制与生产的可靠性技术研究

给出了电站汽轮机的10个可靠性特征量的计算公式或术语以及汽轮机强度与振动的17个设计判据。介绍了电站汽轮机关键部件寿命评定技术研究的新进展和汽轮机关键部件寿命设计技术规程。分析了超临界汽轮机、超超临界汽轮机、空冷汽轮机、燃气轮机联合循环汽轮机和核电汽轮机结构可靠性设计的技术特点。介绍了电站汽轮机研制和生产过程的可靠性通用大纲,内容包括可靠性工作的5项总要求和18项详细要求。参14     

轻型燃气轮机长寿命动力涡轮的结构设计

本文介绍一种长寿命动力涡轮结构的设计方法和研制结果。这种结构代替了原设计,生产制造了两台,并进行了１５０小时运行考核。测得的主要部件温度,应力数值与设计计算值基本一致,运行参数和拆检结果都表明产品达到了设计要求。该结构适用于各种固定式和移动式燃气轮机,特别是航空发动机改装的动力涡轮设计。     

A modern injected steam gas turbine cogeneration system based on exergy concept

Factors such as low capital cost, good match of power and heat requirements and proven reliability can sometimes lead an end user into purchasing gas turbines for use in a modern cogeneration plant. The steam‐injected gas turbine is an attractive electrical generating technology for mitigating the impacts of rising energy prices. According to such mentioned above this paper is to provide results of an optimization study on cogeneration power cycle, which works by gas turbine with recuperator and injection steam added to the combustor of the gas turbine. The performance characteristics of the cycle based on energy and exergy concepts and based upon practical performance constraints were investigated. The effect of the recuperator on the cycle was greatly clarified. Results also show that the output power of a gas turbine increases when steam is injected. When extra steam has to be generated in order to be able to inject steam and at the same time to provide for a given heat demand, power generating efficiency increases but cogeneration efficiency decreases with the increasing of injected steam. Copyright © 2004 John Wiley & Sons, Ltd.     

The impact of the new investments in combined cycle gas turbine power plants on the Italian electricity price

The paper measures the variation of the electricity price in Italy within the next 10 years due to the recent investment flow in combined cycle gas turbine (CCGT) power plants. It starts by investigating the possibility of decoupling gas and oil prices on the basis of hypotheses about the amount of existing resources and plausible technical substitutability assumptions of the latter with the former. In particular, it is supposed that, in the Italian market, natural gas will play a crucial role which oil has had in power generation. The price of electricity stemming from natural gas is then calculated taking into account the role of the power mix restructuring that derives from the CCGT power plants investments. Under reasonable assumptions, it is shown that a net reduction of at least 17% on the electric price is likely to be expected.     

Improvement of part load efficiency of a combined cycle power plant provisioning ancillary services

According to the type of ancillary service provisioned, operation mode of a power plant may change to part load operation. In this contribution, part load operation is understood as delivering a lower power output than possible at given ambient temperature because of gas turbine power output control. If it is economically justified, a power plant may operate in the part load mode for longer time. Part load performance of a newly built 80 MW combined cycle in Slovakia was studied in order to assess the possibilities for fuel savings. Based on online monitoring data three possibilities were identified: condensate preheating by activation of the currently idle hot water section; change in steam condensing pressure regulation strategy; and the most important gas turbine inlet air preheating. It may seem to be in contradiction with the well proven concept of gas turbine inlet air cooling, which has however been developed for boosting the gas turbine cycles in full load operation. On the contrary, in a combined cycle in the part load operation mode, elevated inlet air temperature does not affect the part load operation of gas turbines but it causes more high pressure steam to be raised in HRSG, which leads to higher steam turbine power output. As a result, less fuel needs to be combusted in gas turbines in order to achieve the requested combined cycle’s power output. By simultaneous application of all three proposals, more than a 2% decrease in the power plant’s natural gas consumption can be achieved with only minor capital expenses needed.     

Comparison of the efficiency of the variants of a primary gas turbine supplementing a coal-fired power plant

Thermodynamic effects of four variants of the installation of a primary gas turbine supplementing a coal-fired power plant have been determined. The variants differ in the utilization mode of the heat recovery boiler of the gas turbine, which may be used to preheat the feed water of the steam power plant, but also for a secondary superheating of the steam. The introduction of an additional gas turbine expanding the working fluid down to a pressure lower than the ambient one with an additional compressor installed after the heat recovery boiler has been considered too. The reduction of exergy losses in the heat recovery boiler has been accepted as the main purpose of changing the scheme of the system. The new variants have been compared by means of the incremental energy efficiency of the gas turbine, characterizing the utilization degree of natural gas in the complex system.     

A TEST RIG FOR THE REALIZATION OF WATER RECOVERY IN A STEAM-INJECTED GAS TURBINE

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Design of a wind turbine pitch angle controller for power system stabilisation

The design of a PID pitch angle controller for a fixed speed active-stall wind turbine, using the root locus method is described in this paper. The purpose of this controller is to enable an active-stall wind turbine to perform power system stabilisation. For the purpose of controller design, the transfer function of the wind turbine is derived from the wind turbine's step response. The performance of this controller is tested by simulation, where the wind turbine model with its pitch angle controller is connected to a power system model. The power system model employed here is a realistic model of the North European power system. A short circuit fault on a busbar close to the wind turbine generator is simulated, and the dynamic responses of the system with and without the power system stabilisation of the wind turbines are presented. Simulations show that in most operating points the pitch controller can effectively contribute to power system stabilisation.     

Gas turbine cogeneration systems: a review of some novel cycles

The gas turbine engine is known to have a number of attractive features, principally: low capital cost, compact size, short delivery, high flexibility and reliability, fast starting and loading, lower manpower operating needs and better environmental performance, in relation to other prime movers, especially the steam turbine plant, with which it competes. However, it suffers from limited efficiency, especially at part load. Cogeneration, on the other hand, is a simultaneous production of power and thermal energy when the otherwise wasted energy in the exhaust gases is utilised. Hence, cogeneration with gas turbines utilises the engine’s relative merits and boosts its thermal efficiency. Thereby, the worldwide concern about the cost and efficient use of energy is going to provide continuing opportunities, for gas turbine cogeneration systems, in power and industry.In this work, ten research investigations carried out by the author and associates during the last ten years in the field of gas turbine cogeneration in power and industry are reviewed briefly.     

Integration of steam turbine controls into power plant systems

The unique control and protection requirements of steam turbines are described, and the concept of a unit control system, which by itself is capable of starting, loading, and unloading, as well as protecting, a steam turbine through all operational phases, is introduced. The unit control then interfaces to the plant control at a level where the speed of response and degree of security of a plantwide network is acceptable for the turbine. Examples of unit controls for different types of turbines are given, together with methods for interfacing to plant control systems     

Co-located gas turbine/solar thermal hybrid designs for power production

This paper describes gas turbine/solar trough hybrid designs that achieve a solar contribution greater than 50% and increase the solar-to-electric efficiency while reducing gas heat rate. Two conceptual designs are explored: (1) integrating gas turbines with conventional oil heat-transfer-fluid (HTF) troughs running at 390 °C, and (2) integrating gas turbines with salt-HTF troughs running at 450 °C and including thermal energy storage (TES). The latter system is also representative of molten-salt power towers, although the power towers run at temperatures near 565 °C and would require selection of an appropriate gas turbine to provide waste heat at those temperatures. Using gas turbine waste heat to supplement the TES system provides operating flexibility while enhancing the efficiency of gas utilization. The analysis indicates that the hybrid plant designs produce solar-derived electricity and gas-derived electricity at lower costs than either system operating alone.     

Development of a gas turbine performance analysis program and its application

A general-purpose performance prediction program, which can simulate various types of gas turbine such as simple, recuperative, and reheat cycle engines, has been developed. A stage-stacking method has been adopted for the compressor, and a stage-by-stage model including blade cooling has been used for the turbine. The combustor model has the capability of dealing with various types of gaseous fuels. The program has been validated through simulation of various commercial gas turbines. The simulated design performance has been in good agreement with reference data for all of the gas turbines. The average deviations of the predicted performance parameters (power output, thermal efficiency, and turbine exhaust temperature) were less than 0.5% in the design simulations. The accuracy of the simulation of off-design operation was also good. The maximum root mean square deviations of the predicted off-design performance parameters from the reference data were 0.22% and 0.44% for the two simple cycle engines, 0.22% for the recuperative cycle engine, and 0.21% for the reheat cycle engine. Both the design and off-design simulations confirmed that the component models and the program structure are quite reliable for the performance prediction of various types of gas turbine cycle over a wide range of operations.     

Steam-gas power stations with multi-stage residual-oil combustion

This paper describes a method for the multi-stage combustion of high-sulphur residual fuel oils in thermal power stations which ensures minimum contamination of the atmosphere. In the first stage of combustion, high-pressure steam and fuel gas are produced. The latter is cooled and freed of ash and sulphur compounds. The steam and the purified gas are then used for power generation. The method gives a high rate of sulphur removal and considerable reduction of nitrogen oxide emission. This new power station concept employs gas turbines and steam/gas turbines to achieve the optimal use of energy. A discussion of technical and economic aspects concludes the paper.     

Current status of Japanese thermal power plants and life assessments of high temperature steam and gas turbine components

More than 80% of prime energy is now supplied by thermal power plants in Japan since the Great East Earthquake of 2011 and more than two thirds of them were operated for over 30 years. Evaluation of the residual life of those aged plants are, therefore, required to maintain reliability and also to avoid premature retirement. Several kinds of life assessment technologies for the high temperature components of aged steam and gas turbines have already been developed and applied to actual components. Further developments for the advanced ones are now still being conducted. The current status of Japanese thermal power plants is briefly overviewed and the life assessment technologies developed for evaluating the material degradation and component damage conditions and life extension capabilities of steam and gas turbines are explained with some examples of the applications. The differences between the development concepts and the methods developed for both turbines are also explained along with those of the design specifications.