This paper presents a simulation code for the solar drying of sludge. This code is using a model of the drying kinetics of wastewater sludge, and takes into account water transport in the product during drying. An application of the FAST method for the parametric sensitivity test of this code has been used in order to highlight influencial parameters on the solar collector model. Finally, it is shown that outputs of the model, could be approached by a regression polynomial called "metamodel" created from sensitivity analysis. Sensitivity analysis becomes an alternative in order to model a system, working under various weather conditions.