The shortage of drinking water is a major problem in the South East of Spain. In these areas, it is essential to make use of water from underground reservoirs, most of which are over exploited and suffer from saline contamination given their proximity to the sea. The desalination of brackish water is a means of obtaining low cost drinking water. The method of desalination designed in this paper uses an electrodialysis system fed by photovoltaic modules that is simple, reliable, and low cost because it does not include battery storage or a battery regulator. These systems are of particular interest for isolated zones with access to wells of brackish water where connection to the electric grid is not possible. In this paper, the feasibility of the desalination of brackish water using an electrodialysis system powered by photovoltaic energy and the influence of experimental parameters has been studied. Likewise, a mathematical simulation model that allows predicting and simulating the functioning of a system of these characteristics under different meteorological conditions has been developed. The model has been applied with satisfactory results to the desalination of a NaCl solution in different experimental conditions. Data given by the mathematical simulation model was contrasted with experimental results in order to compare the reliability of the model, and good agreement was obtained. The application of this model allows the design of an electrodialysis system powered by photovoltaic energy (electrodialyzer size and the number and configuration of the PV modules), for the desalination of brackish water, as well as the study of its behaviour in different geographical locations. (c) 2005 Elsevier B.V. All rights reserved.