A solar chimney power plant (SCPP), also known as a “solar chimney” or simply a “solar tower,” is a renewable energy power plant that converts solar energy into electricity. Due to growing pollution concerns, this study supports international agreements and national energy action plans to increase the use of renewable energy and to reuse a rejected heat energy potential from geothermal power plants. In this study, a numerical solution method is used to solve the governing equations’ differential equations using a finite difference discretization method. In the Aluto Langano geothermal power plant, this article examines plant performance and combines it with a novel heat source from geothermal plant with mass flow rate 62 kg/s and 90 °C powered continuously that makes the solar chimney operating day and night. Thus, the collector temperature increases from 316 K to 323 K with combined effect of geothermal water and solar radiation. Additionally, this analysis makes use of plant dimensions built in Manzanares, Spain: chimney height = 194.6 m, collector diameter = 244 m, and chimney diameter = 10.16 m. The obtained results show a 7 °C rise in collector temperature, a pressure potential of 182.82 Pa, a pressure drop of 121.88 Pa on the turbine, a pressure loss of 60.94 Pa, and a power production of 123.59 kW. As a result of the integration, plant efficiency goes up to 0.242%, collector efficiency rises to 43.58.