Energetic,exergetic and thermoeconomic analysis of Bilkent combined cycle cogeneration plant

This paper is a case study of thermodynamics and economics related analyses applied to an existing gas/steam combined cycle cogeneration plant. Basic thermodynamic properties of the plant are determined by energy analysis utilizing main operation conditions. Exergy destructions within the plant and exergy losses to environment are investigated to determine thermodynamic inefficiencies and to assist for guiding future improvements in the plant. Cost balances and auxiliary equations are applied to several subsystems in the plant, hence, cost formation in the plant is observed. Additionally, cost rate of each product of the plant is calculated. Copyright © 2005 John Wiley & Sons, Ltd.     

S109E联合循环机组热电冷联产的热经济性分析

简要介绍了武昌热电公司利用天然气的改扩建工程;着重分析了S109E联合循环热电冷联产的热经济性,结果表明,这一联产形式实现了能源梯级利用,使能源转换效率高达70%.     

燃气热电联产系统的节能分析

热电联产是一种热能．电能同时生产的能源利用形式。它将高品位的热能用于发电,低品位的热能用于集中供热,既提高能源的利用效率,又减少了环境污染。燃气热电联产（CHP）系统则是利用燃气锅炉和供热汽轮机的热电联产供应系统。从能量的有效利用方面对CHP系统的各个环节进行了分析计算,并结合实例,将它与燃气热电分产系统进行比较。结果表明,CHP系统的可用能效率高,节能．经济,同时还可以减少环境污染。     

TAESS在煤多联产系统热经济分析中的应用

采用能量系统热经济分析软件(TAESS)对75t/h循环流化床煤多联产能源系统进行了热经济分析,得到了系统组元的产品单位炯成本,并分析了系统组元产品单位(火用)成本的分布形成过程.得出煤多联产系统(火用)效率为58.64%,锅炉、净化系统和汽轮发电机组等组元是挖掘提高运行效率潜力的主要部件.产品成本分析对于系统运行状况评价、终端产品定价、优化设计以及故障诊断将提供重要参考.     

Exergetic evaluation of methods for improving power generation efficiency of a gas turbine cogeneration system

A cogeneration system generating both heat and power for district heating and cooling is required to be more efficient to improve its economy. In this paper, three typical methods for improving the power generation efficiency of a gas turbine cogeneration system are evaluated by examining exergy flow at various points of the system. The three methods investigated are: (a) to raise turbine inlet temperature, (b) to incorporate a regenerative cycle, and (c) to introduce a dual-fluid cycle. Exergy flows at various points of each cogeneration system have been evaluated. It has been shown through quantitve analyses of exergy flows (1) what kind of energy loss of the system can be reduced by introducing each efficiency-improving method, (2) that the method of incorporating a regenerative cycle is highly useful in improving exergy efficiency of the cogeneration system. © 1997 by John Wiley & Sons, Ltd.     

Malfunction diagnosis method for the thermal system of a power plant based on thermoeconomic analysis

It is difficult to accurately diagnose and locate faults in the thermal system of power plants due to the coupling of multiple components. The goal of the current study is to develop a model that predicts how the thermodynamic parameters–performance curve is changed when one component exhibits anomalies. This model uses the concept of irreversibility in thermoeconomic structure theory as a means of quantitatively measuring changes in the performance of power plant thermal systems. This is achieved by initially filtering out the effect of anomalies on the control regulation system and subsequently comparing the change in performance to reference values, enabling qualitative analysis to decouple component interactions. Following model construction, advanced process simulation is applied to simulate several typical fault conditions in a 330-MW power plant, and the proposed model is used to diagnose the cause of malfunction based on thermoeconomic analysis. The results indicate that the method has satisfactory feasibility for malfunction diagnosis in a complex energy system.     

Exergy and thermoeconomic analysis of a turbofan engine during a typical commercial flight

In an energy perspective of cost-reduction and configuration-optimization, it becomes necessary to develop and use advanced tools for the analysis, design and improvement of energy conversion systems. In the aeronautical industry, such trend is fundamental since this industry has evolved to design extremely complex aircrafts, with highly integrated systems, requiring more information in order to evaluate the whole system. The aim of this paper is to present an exergy-based analysis as to evaluate the global performance of a typical turbofan engine and its components. The study presents values for exergy efficiency over the whole flight cycle, critical equipment and flight phases considering exergy destruction and estimating internal and exhaust flow costs.     

Performance analysis and optimization of heat exchangers: a new thermoeconomic approach

A thermoeconomic performance optimization has been carried out for a single pass counter-flow heat exchanger model. In the considered model, the irreversibilities due to heat transfer between the hot and cold stream are taken into account and other irreversibilities such as pressure drops and flow imbalance are ignored. The objective function is defined as the actual heat transfer rate per unit total cost considering lost exergy and investment costs. The optimal performance and design parameters which maximize the objective function have been investigated. The effects of the technical and economical parameters on the general and optimal thermoeconomical performances have been also discussed.     

Study of a fuel cell network with water electrolysis for improving partial load efficiency of a residential cogeneration system

A fuel cell energy network which connects hydrogen and oxygen gas pipes, electric power lines and exhaust heat output lines of the fuel cell cogeneration for individual houses, respectively, is analysed. As an analysis case, the energy demand patterns of individual houses in Tokyo are used, and the analysis method for minimization of the operational cost using a genetic algorithm is described. The fuel cell network system of an analysis example assumed connecting the fuel cell cogeneration of five houses. If energy is supplied to the five houses using the fuel cell energy network proposed in this paper, 9% of city gas consumption will be reduced by the maximum from the results of analysis. Two per cent included with 9% is an effect of introducing water electrolysis operation of the fuel cells, corresponding to partial load operation of fuel cell cogeneration. Copyright © 2005 John Wiley & Sons, Ltd.     

Multiobjective optimization for exergoeconomic analysis of an integrated cogeneration system

In this paper, a novel cogeneration system integrating Kalina cycle, CO₂ chemical absorption, process, and flash‐binary cycle is proposed to remove acid gases in the exhaust gas of solid oxide fuel cell (SOFC) system, improve the waste heat utilization, and reduce the cold energy consumed during CO₂ capture. In the CO₂ chemical absorption process, the methyldiethanolamine (MDEA) aqueous solution is utilized as a solvent, and feed temperature and absorber pressure are optimized via Aspen Plus software. The single‐objective and multiobjective optimization are carried out for the flash‐binary cycle subsystem. Results show that when the multiobjective optimization is applied to identify the exergoeconomic condition, the cogeneration system can simultaneously satisfy the high thermodynamic cycle efficiency and also the low product unit cost. The optimal results of the exergy efficiency, product unit cost, and normalized CO₂ emissions obtained by Pareto chart were 75.84%, 3.248 $/GJ, and 13.14 kg/MWhr, respectively.     

Experimental study of a domestic thermoelectric cogeneration system

Thermoelectric application for power generation does not appear to be appealing due to the low conversion efficiency given by the current commercially available thermoelectric module. This drawback inhibits its wide application because of the overall low thermal efficiency delivered by typical thermoelectric applications. This paper presents an innovative domestic thermoelectric cogeneration system (TCS) which overcomes this barrier by using available heat sources in domestic environment to generate electricity and produce preheated water for home use. This system design integrates the thermoelectric cogeneration to the existing domestic boiler using a thermal cycle and enables the system to utilise the unconverted heat, which represents over 95% of the total absorbed heat, to preheat feed water for domestic boiler. The experimental study, based on a model scale prototype which consists of oriented designs of heat exchangers and system construction configurations. An introduction to the design and performance of heat exchangers has been given. A theoretical modelling for analysing the system performance has been established for a good understanding of the system performance at both the practical and theoretical level. Insight has also been shed onto the measurements of the parameters that characterise the system performance under steady heat input. Finally, the system performance including electric performance, thermal energy performance, hydraulic performance and dynamic thermal response are introduced.     

A thermoeconomic analysis of biomass energy for trigeneration

The principal objective of this study is to formulate a calculation process, based on the second law of exergy, for evaluating the thermoeconomic potential of a steam-turbine plant for trigeneration. The plant employs biomass, namely, waste wood as its energy source. Four different plant configurations are presented and assessed. ‘Their cost effectiveness is evaluated with varying economic and operating parameters’, because only the fuel price and electricity price are varied. In case 1, high pressure superheated steam generated is supplied to meet the demand for process heat as well as chilled water production in an absorption chiller. In cases 2 and 3, steam is extracted at appropriate stages of the turbine and supplied to meet the demand for process heat and chilled water production in an absorption chiller. Steam generated in case 2 produces sufficient power to meet internal demands while case 3 generates excess electricity for sale back to the utility. In case 4, low pressure saturated steam is generated to meet the demand for process heat and electricity is bought from the utilities, including those used to power an electric vapour-compression chiller. For all cases, it was found that exergy destruction is most extensive in the furnace, amounting to nearly 60%. Exergy destruction in the steam drum is the next most extensive ranging from 11% to 16%. It was also observed that the overall production cost decreases with steam pressure and increases with steam temperature.     

Second law analysis of a natural gas‐fired gas turbine cogeneration system

The influence of operating conditions such as reheat, intercooling, ambient temperature and pressure ratio are analyzed from a second law perspective on the performance of a natural gas‐fired gas turbine cogeneration system. The effect of these operating parameters on carbon dioxide emissions is also discussed. The second law efficiency of gas turbine cogeneration system increases markedly with reheat option. Higher pressure ratios lead to decreased second law cogeneration efficiency but this effect can be reduced with a higher level of reheat option. The effect of intercooling on second law efficiency is strongly related to pressure ratio with higher pressure ratios significantly decreasing efficiency. The second law efficiency is not so sensitive to the environment temperature for levels of reheat or intercooling greater than 50%. Copyright © 2009 John Wiley & Sons, Ltd.     

Optimization of a finned heat sink array based on thermoeconomic analysis

The design and specification of heat sinks for electronic systems is not easily accomplished through the use of standard thermal design and analysis tools since geometric and boundary conditions are not typically known in advance. A second-law based thermoeconomic optimization procedure is presented for a finned heat sink array. This involves including costs associated with material, and irreversible losses due to heat transfer and pressure drop. The influence of important physical, geometrical and unit cost parameters on the overall finned array are optimized for some typical operating conditions that are representative of electronic cooling applications. The optimized cost results are presented in terms of Re_D, Re_L, λ_P / λ_H, and q for a finned system in a graphical form. In addition the methodology of obtaining optimum parameters for a finned heat sink system which will result in minimum operating cost is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaluation of the performance of a micro gas turbine cogeneration system in a sewage treatment facility: Optimized configuration of a cogeneration system

In this study, efficient configuration of a biogas‐fuelled cogeneration system (CGS) in a sewage treatment facility was investigated. The efficient configuration of the CGS was clarified on the basis of the relationship between exhaust heat recovery efficiency (η_ehr) of the CGS and the ratio of yearly average heat demand to yearly average biogas production of the facility (Q_h.d/Q_b.p). The CGS was assumed to be used under Q_h.d/Q_b.p<η_ehr,Q_h.d/Q_b.p≈η_ehr, and Q_h.d/Q_b.p>η_ehr conditions. It was found that although the CGS was able to cover total heat demand of the facility by only consuming biogas produced, from the point of view of energy utilization, reduction of unutilized biogas and reduction of electricity demand efficiencies, the most efficient CGS was obtained under the Q_h.d/Q_b.p≈η_ehr condition. Under the Q_h.d/Q_b.p≈η_ehr condition, energy utilization, reduction of unutilized biogas, and reduction of electrical demand efficiencies were 0.64, 0.99, and 0.32, respectively, whereas under the Q_h.d/Q_b.p<η_ehr and Q_h.d/Q_b.p>η_ehr conditions, energy utilization, reduction of unutilized biogas, and reduction of electrical demand efficiencies were in ranges of 0.56–0.64, 0.43–0.99, and 0.16–0.20, respectively. A more efficient system can be obtained if a CGS with lower η_ehr such as a fuel cell is used under the Q_h.d/Q_b.p<η_ehr condition and if a CGS with higher η_ehr such as a steam turbine is used under the Q_h.d/Q_b.p>η_ehr condition. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20389     

Performance analysis of two stage combined heat pump system based on thermoeconomic optimization criterion

A thermoeconomic performance analysis based on a new kind of optimization criterion has been performed for a two stage endoreversible combined heat pump cycle model. The optimal performances and design parameters that maximize the objective function (heating load per unit total cost) are investigated. The optimal temperatures of the working fluids, the optimum performance coefficient, the optimum specific heating load and the optimal distribution of the heat exchanger areas are determined in terms of technical and economical parameters. The effects of the economical parameter on the global and optimal performances have been discussed.     

Application of a chemical heat pump to a cogeneration system

The feasibility of a proposed system that combines a magnesium oxide/water chemical heat pump and a diesel engine as a cogeneration system is discussed based on experimental results. The combined system is intended to utilize the waste heat discharge from the engine by means of the chemical heat pump and to level the heat supply load of the engine, allowing enhanced energy utilization. The thermal performance of the chemical heat pump in the cogeneration system is estimated based on the results of a packed‐bed experiment. The estimation indicates that by storing the waste heat from the engine during low demand periods, the cogeneration system can produce more than several times the standard thermal output of the diesel engine during peak demand periods. Copyright © 2001 John Wiley & Sons, Ltd.     

Parametric study of exergetic efficiency of a small-scale cogeneration plant incorporating a heat pump

A comparative parametric analysis is carried out of a small-scale combined heat and power plant incorporating a heat pump and the conventional system in which heat is produced in a hot water boiler and electrical energy is drawn from the power grid. Relative exergetic efficiency is defined as the quotient of exergetic (rational) efficiencies of the cogeneration plant and the related conventional system. Dependence of this efficiency on the power-to-heat ratio for chosen values of parameters characterizing the compared systems is calculated and shown pictorially.