Development of robust control strategy is critical for solar thermal receivers to minimize the problems associated with intermittent nature of solar radiation. Adjustment of aperture size is a promising option to control the temperature inside a solar receiver by regulating the light entry. However, effect of aperture size on process dynamics is highly non-linear and the process gain changes because of moving to different operating points due to the unsteady character of the process which requires the controller parameters move adversely. To address this issue, an optimal control strategy for aperture size adjustment was developed in order to control the temperature in a solar receiver. To design this controller, a transient one dimensional model was formulated by taking the most important processes in the system including absorption of solar heat flux entering through the aperture, radiation and conduction heat transfer between internal surfaces of the cavity, convection between gas and inner cavity walls and heat losses due to re-radiation. The model was validated by comparing the estimated and experimentally measured temperatures at different points of the solar receiver and average deviation was lower than 7%. Simulations results of this dynamic model were used to design predictive control algorithm for temperature regulation. Closed loop simulations indicated that the predictive controller outperforms a conventional proportional integral (PI) controller with regards to tracking desired set points and compensating the effect of disturbances in the process.