[en] The combined cycle power plants characteristics are better than one course open to a closed loop presenting an electrical efficiency close to 60% do not reach for gas turbine engines for power plants and conventional steam engines.

[en] Highlights: • The ranking of different types of power plants with different super efficiency methods are the same. • Combined cycle power plants are more efficient than steam and gas power plants. • Gas power plants are less efficient than steam and gas power plants. • The efficiency of combined cycle power plants has improved over time. • The efficiency of gas and steam power plants decreases or remains constant over time. Nowadays, with the ever-increasing development of the communities, the demand for different forms of energy like electricity has drastically increased. Hence, attention to energy efficiency, especially electricity, seems necessary. Different approaches exist for calculating the efficiency and ranking decision-making units (DMUs), among which data envelopment analysis (DEA) and particularly super-efficiency (SE) method is of the most important ones. In this study, the efficiency of various types of thermal power plants (steam, gas and combined-cycle) has been measured in Iran from 2011 to 2019 using three SE models which are introduced by Anderson-Peterson [1]; Lin-Chen [2] and Li, Jahanshahloo and Khodabakhshi [3]. The efficiency ranking of different types of power plants in three different super-efficiency methods is almost similar. Comparison of the efficiency of combined cycle, steam and gas power plants shows that combined cycle power plants are more efficient than other power plants and gas power plants have the lowest efficiency. An examination of the efficiency score of power plants over time shows that the efficiency of combined cycle power plants has improved over time, while in other power plants this has not happened and some have experienced a reduction in efficiency.

[en] This paper assesses two patterns in transition processes for using them as strategies towards a sustainable energy system, i.e., niche accumulation and hybridisation. Both play important but different roles in transitions. The expected success of these strategies depends on the innovation's history and the innovation context. The different strategies are illustrated with several examples from the energy domain

[en] Integrated gasification combined-cycle plants are considered as one of the promising directions for the development of thermal power plants using fossil fuel. Interest in this area is explained by large natural reserves of coal and minimal harmful emissions into the atmosphere during the process of generator gas combustion. The aim of the study is to make the relationship between the specific investment and the efficiency of integrated gasification combined-cycle plant and to perform the optimization researches according to the criterions of minimum electricity price. (paper)

[en] This study investigates the possibility of achieving 65 % efficiency in a gas turbine combined cycle. Several options to realize it were compared. A sensitivity analysis was performed for the latest H-class gas turbine in a simple cycle to quickly and easily predict the performance variation due to changes in each design parameter. When each design parameter was improved by the same percentage, the combined cycle efficiency was maximized by the improvement in turbine efficiency. The degree of increase in the combined cycle power was the largest when improving the turbine inlet temperature (TIT). To realize the turbine industry’s goal of 65 % efficiency in the combined cycle, the efficiency of the compressor and the turbine should be improved by 2 %, the TIT should be increased by 100 °C, and the pressure ratio should be increased from 23 to 32 in comparison to current H-class gas turbines. The possibility of improving the cycle performance was also investigated through modifications of the gas turbine cycle, such as reheating, inter-cooling, and recuperation. When reheating and recuperation were adopted simultaneously, a cycle efficiency of 65 % was possible with an increase of 1 % in both the compressor and turbine efficiencies, which is a moderate and practical improvement.

[en] The thermal efficiency of LWR type reactors can be increased making use of the Tsikl-Durst cycle, where the gas turbine is combined with the nuclear reactor using a steam mixer. The principle of this combined cycle is outlined. It is envisaged that the overall thermal efficiency of the power plant can be increased to 41 - 44%. The total output would be two to three times higher. With advanced light-water reactors (ABWR, AP-600) and advanced gas turbines in combination with the one-way steam generator as developed by Solar Turbines Inc., producing steam at 650 degC to 750 degC, it is feasible to attain a total thermal efficiency of 55%. The combination of two kinds of fuel (nuclear fuel and natural gas) improves operating flexibility of the cycle in various regimes so as to respond to natural gas prices and electricity demands. The gas turbine adds to the nuclear power plant an independent source of power, so that standby dieselgenerators are no more necessary. (P.A.). 1 tab., 2 figs

[en] Highlights: • A combined cycle power plant for bidirectional peak shaving is proposed. • Waste heat and cold energy are used by cascade in the liquid air energy storage. • Thermo-economic sensitivity and comparative analysis are performed. • The power conversion efficiency of the integrated system can reach 99.39%. Natural gas peak shaving power station with gas-steam combined cycle is widely used to meet the demand of peak load regulation of the power grid. However, the exhaust heat of the system and the high-grade cold energy from the nearby liquified natural gas terminal are not fully utilized. Liquid air energy storage is a load leveling method suitable for grid scale but the system efficiency needs to be further improved. Therefore, a system that flexibly integrates the combined cycle power plant and liquid air energy storage to maximize the recovery of the wasted heat and cold energy is proposed, achieving the bidirectional peak shaving. The system realizes the cryogenic compression during the charging process and adequate exploitation of the exhaust heat from the power station during the discharging process. The effects of compressor and air turbine inlet temperatures, ambient temperature and natural gas pressure on the system are investigated by the thermodynamic analysis. The highest system efficiency can reach 99.39%. Also, it is demonstrated that the integrated system is economically preferable. Moreover, within the inlet temperature ranges of the compressor and air turbine studied, the systemic economics performance deteriorates as the temperature increases.

[en] Highlights: • The accuracy of power generation prediction in CCPP is improved by an ensemble model. • A stacking prediction model based on a multi-model ensemble is proposed. • The power prediction model based on stacking under environmental variables is realized. • The hyperparameters of the sub-model are optimized by the grid-search algorithm. • The proposed method provides more accurate predictions than other methods. Electric power makes a significant contribution to society. Predicting power generation is becoming increasingly important for electric power planning and energy utilization. A reliable forecasting model is necessary for accurate planning of electricity generation. The main goal of this study is to develop effective and realistic solutions for the full-load power generation prediction of combined cycle power plants. According to 9568 items of data pertaining to a combined cycle power plant in six years of its full-load operation, a prediction method based on stacking ensemble hyperparameter optimization is established. The results demonstrate that this method provides high prediction accuracy for the power plant under multiple complex environmental variables. Besides, the predictions generated using this method are compared with those of traditional machine learning methods, random forest, and other ensemble methods, as well as those cited in the literature using the same dataset. The predictions show that the proposed method offers more accurate predictions of the power generation from a combined cycle plant, which opens up a new idea for power planning and energy utilization.

[en] Highlights: • Develop a comprehensive model for a very advanced cogeneration plant using real data. • Evaluate ME-TVC-MED unit using the latest thermodynamic properties of seawater. • Evaluate the desalination unit contribution to the overall efficiency. • Evaluate the stage exergetic efficiency in the ME-TVC-MED unit. • Numerous possibilities have been suggested to improve the proposed system. - Abstract: A comprehensive model of cogeneration plant for electrical power and water desalination has been developed based on energetic and exergetic analyses using real operational data. The power side is a combined cycle power plant (CCPP), while the desalination side is a multi-effect thermal vapour compression plant coupled with a conventional multi-effect plant (ME-TVC-MED). IPSEpro software was utilized to model the process, which shows good agreement with the manufacturer's data and published research. The thermodynamic properties of saline water were obtained from the latest published data in the literature. The performance of the cogeneration plant was examined for different ambient temperatures, pressure ratios, loads, feed water temperatures, number of effects and entrainment ratios. The results show that gas turbine engines produce the highest level of useful work in the system at around 34% of the total fuel input. At the same time, they constitute a major source of irreversibility, which accounts for 84% of the total exergy destruction in the plant, while the lowest source of irreversibility is in the steam turbine of 3.3% due to the type of working fluid and reheating system. In the ME-TVC-MED desalination unit, the highest source of irreversibilities occurs in the effects and in the thermo-compressor. The first two effects in the ME-TVC parallel section were responsible for about 40.6% of the total effect exergy destruction, which constitutes the highest value among all the effects. Operating the system at full load while reducing ambient temperature, and increasing pressure ratio and feed water temperature, were strongly recommended in order to improve the plant's performance; while increasing the number of effects is always preferable with low entrainment ratio for high cogeneration plant performance and capacity.

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