Sharif Digital Repository

Energy crisis has directed scientific efforts to increase the efficiency of power generation systems. Thermodynamic optimization of MHD (Magneto Hydrodynamic) generator based combined cycles due to their high operating temperatures may seriously reduce exergy destruction and improve the second law efficiency. In this research a combined cycle, comprising of MHD cycle as topping and gas turbine cycle as bottoming cycle has been simulated and analyzed and its pros and cons have been exposed. The first and second law efficiencies have been estimated from the operating pressures and temperatures of the system. To calculate the second law efficiency, the entropy generation of all components of... 

Combined cycles, at present, have a prominent role in the power generation and advanced combined cycles efficiencies have now reached to 60 percent. Examination of thermodynamic behavior of these cycles is still carried out to determine optimum configuration and optimum design conditions for any cycle arrangement. Actually the performance parameters of these cycles are under the influence of various parameters and therefore the recognition of the optimum conditions is quiet complicated. In this research an extensive thermodynamic model was developed for analyzing major parameters variations on gas turbine performance and different configurations of advanced steam cycles: dual and triple... 

This paper shows a new possible way with particle swarm optimisation (PSO) to achieve an exergoeconomic optimisation of combinedcycle power plants. The optimisation has been done using a classic exergoeconomic and genetic algorithm, and the effects of using three methods are investigated and compared. The design data of an existing plant is used for the present analysis. Two different objective functions are proposed: One minimises the total cost of production per unit of output, and maximises the total exergetic efficiency. The analysis shows that the total cost of production per unit of output is 2%, 3%and 5% lower and exergy efficiency is 4%, 8% and 6% higher with respect to the base case... 

In this paper, the effect of different parameters of power plants, such as height above sea level, performance, ambient temperature, fuel type on emissions in Iran's power plants is investigated. Based on that, a general strategy for selecting the type of power plant, fuel that fit with the geographical situation in the Middle East is presented. Results taken from this scientific study shows that using natural gas to generate power in the region should be a priority. As well as expected, the value of various emission factors decrease by increasing power produce. Also the emission factors of combined cycle power plants are the lowest as compared to other types of power plants  

Power plant successful operation is always a function of its constituent sub-systems and components. Due to the current financial constraints in power industry, power plant operators are continuously facing a wide range of challenges when dealing with maintenance scheduling and asset management practices of the plant sub-systems. Knowledge on the roles and criticality of the constituent components on the plant overall performance will help in establishing the plans for its smooth, safe, and economic operation. To ensure making the techno-economical decisions on the maintenance of power plant equipment, this paper focuses on the reliability modeling of the combined cycle power plants (CCPP).... 

The supplementary firing is one of the techniques which are used to increase the output power of the combined cycle power plants (CCPP). The low construction cost per generated power encourages designers to consider it in the new CCPP. In this paper the thermal and exergy analyses of HRSG for various operating conditions in variation of loads and variation of ambient temperature carried out. They are based on the performance test data at different operating conditions. The objective of these analyses is to present the effects of supplementary firing on gross power output, combined cycle efficiency and the exergy loss in Heat Recovery Steam Generator (HRSG) devices at different ambient... 

This article addresses a combined approach of sliding mode control (SMC) with generalized predictive control (GPC) to achieve fluid temperature control in the evaporator of a heat recovery steam generator. The evaporator is modelled as a first-order plus dead time process. The model is developed using the experimental data obtained at an actual power plant. An output error identification algorithm is used to minimize the error between the model and the experiments in different operating conditions. A GPC method is exploited to optimize the sliding surface and the coefficients of the switching functions used in SMC. The proposed control schemes are evaluated by thorough simulation for... 

In this paper, a systematic investigation and modeling of all available technologies (such as NGL, injection in pipelines, LNG, GTL, NGH, and CNG plants, EOR, electricity production by thermal power plants, and water generation by MED technologies) for flare gas recovery has been developed. An optimal combination of the technologies has been proposed for flare gas recovery of five oil wells in the south of Iran with different specifications as case studies. The optimal combinations of all the technologies have been investigated with minimizing the payback period of capital costs (economical) and maximizing CO2 pollutant reduction (environmental) objective functions by using the genetic... 

In this study, failure of a high pressure economizer tube of a boiler used in gas-Mazut combined cycle power plants was studied. Failure analysis of the tube was accomplished by taking into account visual inspection, thickness measurement, and hardness testing as well as microstructural observations using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Optical microscopy images indicate that there is no phase transformation during service, and ferrite-pearlite remained. The results of XRD also revealed Iron sulfate (FeSO4) and Iron hydroxide sulfate (FeOH(SO4)) phases formed on the steel surface. A considerable amount of Sulfur was also... 

Combined cycle power plants (CCPPs) play an important role in electricity production throughout the world. Their energy efficiency is relatively high and their production rates of greenhouse gases are considerably low. In a country like Iran with huge oil and gas resources, most CCPP's use natural gas as primary fuel and diesel as secondary fuel. In this study, effect of using diesel instead of natural gas for a selected power plant will be investigated in terms of exergy, economic and environmental impacts. The environmental evaluation is performed using life cycle assessment (LCA). In the second step, the operation of the plant will be optimized using exergy and economic objective... 

In order to generate adequate electricity energy, conventional power plants utilize dramatic volume of water resources. Different methods such as replacing cutting-edge technologies of facilities have been proposed to diminish water consumption in this industry. Most of the approaches are considered as medium or long-term solution which requires substantial investment costs. Meanwhile, because of the process and technology, natural gas-fired power plants need less water among conventional power plants. Therefore, shifting unit commitment planning toward these power plants would aid to save water consumption. Nevertheless, overlooking combined cycle power plants can perform negative impact on... 

In advanced combined-cycle power plants, significant improvements in the thermodynamic performance are mainly achieved by the development of more efficient gas-turbine systems. This paper evaluates the effect of selected decision variables in the steam system for optimization of Thermal Combined Cycle Gas Turbine (TCCGT) power plant using an iterative exergoeconomic. The design variables were the thermodynamic parameters that establish the configuration both of the steam and gas systems. The design data of an existing plant (Damavand power plant in Tehran-Iran) is used. Two different objective functions are proposed: one minimizes the total cost of production per unit of output, and the... 

The heat recovery steam generator (HRSG) is one of the few equipments that are custom made for combined cycle power plants, and any change in its design affects all performance parameters of a steam cycle directly. Thus providing an optimization tool to optimize its design parameters and the layout of its heat exchangers is of great importance. A new method is introduced for modeling a steam cycle in advanced combined cycles by organizing non-linear equations and their simultaneous solutions by use of the hybrid Newton methods in this article. Thereafter, optimal thermodynamic performance conditions for HRSGs are calculated with the help of the genetic algorithm. In the conclusion, the... 

This study presents a comprehensive framework for evaluating renewable and non-renewable power plants' performance using the Life Cycle Analysis (LCA) and emergy analysis. The emergy analysis is used to consider the free ecosystem services in the sustainability of the systems as a supplement to the LCA. The results indicate that the wind and photovoltaic power plants have the best performance in terms of the LCA analysis, while the wind and combined cycle power plants have the highest emergy sustainability index. The best scenario is chosen under a two-objective optimization problem, including the single score and emergy sustainability as objective functions. Here, the wind power plant is... 

This study presents a comprehensive framework for evaluating renewable and non-renewable power plants' performance using the Life Cycle Analysis (LCA) and emergy analysis. The emergy analysis is used to consider the free ecosystem services in the sustainability of the systems as a supplement to the LCA. The results indicate that the wind and photovoltaic power plants have the best performance in terms of the LCA analysis, while the wind and combined cycle power plants have the highest emergy sustainability index. The best scenario is chosen under a two-objective optimization problem, including the single score and emergy sustainability as objective functions. Here, the wind power plant is...