Rising energy demands, the depletion of fossil fuels, and their environmental impact necessitate a shift towards sustainable power generation. Concentrating solar power (CSP) offers a promising solution. This study examines a hybridization of a combined cycle power plant (CCPP) based on solar energy with fossil fuel and energy storage in rock layers to increase Saudi Arabia’s electricity production from renewable energy. The fuel is used to keep the temperature at the inlet of the gas turbine at 1000 °C, ensuring the power produced by the Rankine cycle remains constant. During the summer, the sun is the main source of power generation, whereas in the winter, reliance on fuel increases significantly. The Brayton cycle operates for 10 h during peak solar radiation periods, storing exhaust heat in rock beds. For the remaining 14 h of the day, this stored heat is discharged to operate the Rankine steam cycle. Simulations and optimizations are performed, and the system is evaluated using a comprehensive 4E analysis (energy, exergy, exergoconomic, and environmental) alongside a sustainability assessment. A parametric evaluation examines the effect of key factors on system performance. The rock bed storage system compensates for solar intermittency, enabling power generation even without sunlight. The study reveals that the system generated 12.334 MW in June, achieving an energy efficiency of 37% and an exergy efficiency of 40.35%. The average electricity cost during this period was 0.0303 USD/kWh, and the carbon footprint was 0.108 kg CO2/kWh. In contrast, during January, the system produced 13.276 MW with an energy efficiency of 37.91% and an exergy efficiency of 44.16%. The average electricity cost in January was 0.045 USD/kWh, and the carbon footprint was 0.1 kg CO2/kWh. Interestingly, solar energy played a significant role: it contributed 81.42% of the heat in June, while in January, it accounted for 46.77%. The reduced electricity costs during June are primarily attributed to the abundant sunshine, which significantly powered the system.
