The growth of the electrical energy consumption form one side and the bounded available fossil fuel and other limitations from the other side, makes the thermal power plants upgrading as a main demand in the world. Decreasing the internal energy consumption, increasing the performance and the output power with the minimum costs are the important targets of the power plants retrofitting. Nowadays power plant repowering with the help of gas turbine that includes two manners (Full Repowering and Para-Repowering) is one of the best methods for the power plants progress. Different repowering methods according to their costs, amount of the output power increase and the power plant situation could be various solutions for the retrofitting. Choosing each of these methods can be done just by analyzing the related parameters. Technical and economic comparisons between different repowering methods needs an investigation of several technical and economic parameters and the characteristics of the electrical networks development as well. Combined cycling/cycles as a repowering method usually is used for low capacity units and for the bigger units para repowering could be more suitable. Feasibility study for repowering a power plant and choosing the best method should be done through a case study for that specific power plant. In this paper using different para repowering methods has been studied for the Low shan power plant. The results show that feed water heating repowering is the best method based on the cost of electrical energy generation in this case.

Making targeted subsidies and the process of releasing energy market and specified criteria for quality of delivered energy to consumers shows the necessity in explanation of producing energy in Iran. In the meantime, Thermal power plants produce about 85% of electricity generation in Iran. Steam and gas turbine power plants have created the vast capacity of thermal plants power generation but the significant portion of this generated power is not in the sense of new energy policy. Therefore the reconstructing and improvement of thermal power plants has undeniable importance. In this paper, considering two major methods in reconstructing of the thermal power plants, eligible power plants have been presented. Results are being discussed according to the important economic parameters like electricity generation costs, capital return rate, cost benefit, annual interest and etc. In the meantime, estimation of changes in target plants in terms of technical and economical characteristics will have an effective role in our decisions it means the changes have been effected by considering features of current plants and their potentials. The efficacy of reconstructing on average efficiency, capacity and electricity generation cost can be effective parameters in future management decisions.

This study investigates the feed water heating repowering of Isfahan Montazeri Steam Power Plant is. To do this, three designs have been suggested; low pressure heat exchangers, high pressure heat exchangers and both of heat exchangers respectively are replaced by the new heat recovery heat exchangers. Energy and exergy efficiencies are used as goal functions. Cycle-tempo software is used to simulate. As it shown in results, in the method of replacing all heat exchangers with two heat recovery heat exchangers, the maximum exergy efficienciy is reached. In this case, The gas turbine westinghause-401 is the best choice that energy and egergy grass efficiencies and power production of the cycle increase 12.8, 13.1 and 42 percents, respectively.

Repowering means addition of gas turbine unit (s) to a steam power plant in order to make use of the exhaust gas heat and to increase efficiency of the new combined cycle. There are two groups of repowering methods: partial repowering and full repowering. Full repowering is more common and is used in power plants with nearly ended useful lifetime. In this case the capital investment is considerably reduced compared with the case of making a similar combined cycle. Objective functions are per kWh electricity cost and exergy efficiency. These functions are based on important independent variables of heat recovery boiler, steam turbines, gas turbine. Finally, considering the introduced objective functions, it is tried to achieve the most optimized techno-economic characteristics for Be’sat power plant repowering cycle, using genetic algorithm optimization method with two scenarios of single and multi objective.

Adding gas turbine units to steam power plants for enhancing steam cycle’s properties and regenerating heat from adjunct cycle (s) have been known as repowering. Repowering methods are divided into two main categories, partial and full repowering. One of the latest methods of partial repowering is parallel feed water heating repowering. In this paper the mentioned method has been applied to Shahid Rajaee power plant. Cost functions of generated-electricity and exergy efficiency are defined as objective functions in one and two objective optimizations. Finally, the most suitable scenario has been chosen to apply this method on, considering desirable technical and economic parameters for partial and nominal load. The results of the chosen design are: 3.4% and % 27 increases in exergy efficiency and steam power plant capacity, respectively.

In this study, Given the importance of Bandar Abbas steam power plant in terms of Location and its electricity generating, it has been considered for applying the repowering method. After reference cycle modeling and assessing results accuracy, the applied repowering method has been implemented and it’s results reported in four main scenarios. Exergy efficiency and electricity generation cost (per kWh) have been considered as objective functions. Based on the six independent variables and four different scenario multi objective optimization has been done. The final reported results can be implemented by the energy managements for making the best decision and choosing the adequate option. Multi objective optimization of proposed combined cycles with single and double pressure heat recovery boilers indicate that the exergy efficiency upgrades up to 46%.