As is known, efficient renewable energy plant designs should incorporate features that make maximum use of solar energy. In addition to the need of further development and experimental performance evaluation of the solar plant＇s energy, there is also the need to develop mathematical models for accurate prediction and control of the solar plant＇s thermal environment. These models can also be used as a design tool and in economic feasibility studies. In this paper, a dynamic mathematical model for predicting the thermal performance of a low temperature solar plant was developed. Consequently, the model gives the optimal control mode that offers maximum thermal efficiency to the plant. Validation of the model was performed for both the calculation of daily and long term performances (monthly and yearly) considering a large sized solar plant installed in the north of Tunisia. The result showed good reproduction of thermal performance. Furthermore, comparison of the plant measured variables with model predictions showed a high degree of correlation.