This paper deals with the dynamical modelling of a solar evacuated tube collector under variable weather conditions. After describing the mathematical model, the paper presents elements of validation. In a first step, the theorical model is validated against the experimental results. Then a parametric sensitivity analysis is applied to the model. Such a study is very interesting for modellers in order to determine the relative importance and the nature of the effect of the parameters. It is important so as to improve the model by controlling this paramaters or accurately measuring it.