Solar thermal power is a promising and rapidly expanding source of carbon-free energy. Analysis and design techniques for solar thermal power generation for the Solar Power Tower (SPT) systems are currently mathematically difficult. We simulated a model of a SPT that advances the simulation of SPT performance by modelling them in Thermolib software. The model in this study simulates SPT with a direct steam generation system with design variables of 0.04 kg/s heat transfer fluid (HTF) flow rate at 6 bar operating pressure using water as HTF. The reaction to varied operating pressure, fluid flow rates, and insolation input has been analysed. The simulation results show that steam will be produced at 1�3 bar with maximum steam quality of 0.06, 0.02 and 0.0015, respectively. Lowering the HTF flow rates to 0.02 and 0.03 kg/s will produce steam with maximum quality of 0.15 and 0.028, respectively. Increasing the amount of heliostat from 15 to 20 in staggered formation results in a 14.5 increase in power received by the receiver, resulting in a maximum steam quality produced of 0.029. The analysis shows that high quality of steam can be achieved with a lower HTF flow rate and pressure, but it compromises the useful energy generated by turbine. © Institute of Technology PETRONAS Sdn Bhd (Universiti Teknologi PETRONAS) 2024.