Solar repowering existing steam cycle power plants

Currently concentrating solar power technologies are increasingly being researched. Using solar energy for replacement of regenerative feed water heaters and partial replacement of economizer and evaporating heating surfaces of the existing steam generator are studied in this paper. The solar-to-electric efficiency equation for the solar-fossil hybrid power plants, created through solar repowering existing steam cycle power plants, is proposed. 155 MW steam turbine of Tashkent power plant is analyzed for solar repowering according to the mentioned schemes. Several values of parabolic trough concentrators’ aperture area are analyzed to realize. Simulation results show, the higher the temperature of entering solar heat into the cycle, the higher the solar-to-electric efficiency ηesol: ηesol=0.078 for solar replacement of low pressure feed water heater #1 and ηesol=0.270 for solar replacement of high pressure feed water heater #6. As well as the higher the temperature of solar heat input into the cycle, the higher a reduction of fossil fuel heat input in steam generator: each unit of the solar heat input leads to decrease a fuel heat input in steam generator by 0.22 unit while solar replacement of low pressure feed water heater #1, by 0.77 unit while solar replacement of high pressure feed water heater #6 and by 1.12 unit while partial replacement of economizer and evaporating heating surfaces of existing fuel steam generator. Highest solar-to-electric efficiency ηesol=0.344 is attainable according to the scheme of partial replacement of economizer and evaporating heating surfaces of the existing fuel steam generator with a solar steam generator. © 2023 The Authors