In this research, the effect of using the exhausted smoke of a cogeneration power plant as the working fluid of a solar chimney to increase power generation is studied by numerical methods. First, the cogeneration power plant is modeled using ASPEN HYSYS; then, the properties of the exhausted smoke including temperature, mass flow rate and etc. are entered to the model of solar chimney power plant, developed in ANSYS FLUENT. Using this hybrid model, the effect of solar radiation on power generation is compared for both air and smoke as working fluids. Furthermore, the effect of inlet temperature on power generation is also studied. The results showed that the power generation increases on average 4 times using smoke instead of air. It is also found that the optimum chimney height is 500 m using air and 600 m using the exhausted smoke of cogeneration power plant.