New procedure for optimal solar repowering of thermal power plants and integration with MSF desalination based on environmental friendliness and economic benefit

Highlights: • New algorithm for Optimal Solar Repowering based on Environmental Friendliness and Economic Benefit. • Integration of solar collector and MSF desalination with Bandar Abbas thermal power plant. • Transient energy, exergy, economic, and environmental analyzes. • Conventional and advanced exergy, exergoeconomic and exergoenvironmental analysis. Using solar collectors to repower steam power plants is one of the cheapest methods to improve these power generation sites' technical, economic, and environmental performance. In this paper, using a comprehensive method based on economic benefits and environmental friendliness, solar collectors are designed to parallel with the feedwater heaters to repower the steam power plant. Also, an MSF desalination unit has been used to simultaneously generate power, heat, and freshwater in the repowered cycle due to the proximity of the studied steam power plant to the sea. Transient thermodynamic, exergy, economic, and environmental analyzes have been used to demonstrate performance improvements due to solar repowering. Results show that due to proper solar radiation at the site of the steam power plant, more use of solar collectors or solar factors equal to one lead to the highest economic benefits and the highest reduction in environmental impact. The solar collectors are also designed based on solar factors equal to one. The first scenario of repowering generates between 330 and 400 MW of power during the year. But in the second scenario, due to the consumption of the part of the cycle steam in the MSF unit, the amount of power generation in most months is about 310 MW. In the first and second scenarios of repowering compared to the base steam power plant, the total cost is reduced by an average of 50% and 41%, respectively. The total environmental impacts in the first and second scenarios of the repowering have been reduced by 30% and 22%, respectively, about the steam cycle. The mass flow of freshwater produced in this unit will be 115.4 kg/s. The performance ratio of the MSF unit will be 8.8, and the gain output ratio will be 9.62. The price of freshwater produced in this unit will be $0.21 per cubic meter of desalinated water.