Optimal turbine pressure drop for solar chimney-aided dry cooling system in coal-fired power plants

Highlights: • An analytical model of hybrid system is proposed. • A fitting equation of optimal turbine pressure drop for hybrid system is derived. • The optimal turbine pressure drop positively correlates to solar collector radius and solar radiation. • Critical solar collector radius and critical solar radiation exist for the optimal turbine pressure drop. - Abstract: In solar chimney-aided dry cooling systems, the low-grade waste heat released by condensers in coal-fired power plants heats the inlet air of solar collectors, thus improves the power output and decreases the power consumption of fans. An analytical model of this hybrid system is proposed to study the characteristics of heat transfer and fluid flow in the water-air heat transfer, solar collector, heat storage layer, draft tower, and turbines. The fitting equation of the optimal turbine pressure drop for the hybrid system is derived, and the effects of the solar collector radius and solar radiation on power outputs are discussed. Results show that the optimal turbine pressure drop is positively correlated to the solar collector radius and solar radiation. However, a critical collector radius and a critical solar radiation for the turbine configuration exist. The performance of a hybrid system integrated with a 660 MW supercritical coal-fired power unit reveals that the optimization scheme proposed in this study outperforms the two schemes provided in the references.