LAUSR

Abstract The repowering of steam power plants is one of the ways to increase their efficiency and power capacity after the loss of efficiency resulting from the expiry of their useful lifetime. This paper presents an economical method for designing a parallel solar collector with feedwater heaters for the repowering of steam power plants. The dynamic energy, exergy, economic, environmental, and advanced analyzes have been developed to compare the performance of the base steam power plant and repowering scenarios. The higher benefit is the basis for designing solar collectors for the steam cycle repowering. Results show that the highest benefit is achieved when Solar Factor (SF) is equal to 1 in both solar collectors. According to the considerable amount of solar radiation in Iran, the costs associated with the solar collector, and the excess power generation in the repowered cycle, the greater use of solar collectors in this steam cycle would be more appropriate. The thirty-year benefit, assuming SF equals one, will be over $90 million. The power generation capacity is maximized in 6 months, such as January, February, March, October, November, and December and increased approximately 80 MW compared to the base steam power plant. Also, results show that in both repowering scenarios, the exergoeconomic and exergoenvironmental factor for most equipment exceeds 60 percent. The results show that at different months of the year, the rate of avoidable exergy destruction is about 10 percent of the total exergy destruction, and also, the exogenous rate of exergy destruction is 15 percent, which is very low, indicating that the design of the repowering cycle is appropriate.