Desalination plants play a fundamental role in the fight against fresh water shortage in places with seawater availability. On the other hand, optimization of industrial processes is an important goal in order to increase operation efficiency and to minimize costs. This paper deals with an experimental hybrid solar-gas desalination system designed, built, and operated at the Plataforma Solar de Almería (Spain) under the framework of a European R&D project. This desalination system, based on a multieffect distillation process, is partially powered by a low temperature static solar collector field of a compound parabolic concentrator type. With the aim of performing an optimal operation of the plant working with the solar resource, process dynamics have to be studied and modeled. This paper shows control-oriented low complexity models for the solar field and thermal storage subsystems as well as a model of the distillate production rate depending on process temperature. These models are validated with real data with the objective of being useful in the evaluation of optimal operating points, the design of operational procedures, and the establishment of adequate control references to maximize the use of the solar resource and to improve process efficiency.