This paper describes the development, validation and use of a design and simulation tool for modeling the performance of a salinity gradient solar pond. An experimental solar pond pilot plant was constructed in central Catalonia (NE part of the Iberian Peninsula). The body of the pond is a cylindrical reinforced concrete tank, with 3 m height, 8 m diameter and total area of 50 m(2). The lateral tank wall has been insulated with 60 mm of rock wool. The gradient in the solar pond was settled and maintained since 30 September 2009 to date. The developed tool was validated by comparing simulation results to experimental data collected from the experimental solar pond from November 2009 until August 2011. The resulting first-order differential equations describing the overall energy balance in the pond were solved numerically using a finite-difference method. The temperature profiles of the pond were properly described, especially at lower subzones of the non-convective zone (NCZ) and the lower convective zone (LCZ). The higher errors between experimental and predicted values were found in the upper convective zone (UCZ). Once validated, successfully, the model was used to predict the thermal performance of pre-industrial solar pond to be constructed and operated in Granada, SW of Spain. The thermal profiles predicted temperature differences between surface and bottom of around 40 degrees C during summer time, with a maximum temperature of 75 degrees C. The energy efficiency of the LCZ was anticipated to range between 12% and 25% along one year operation, resulting in 16% of incoming radiation to be extractable for site application. (C) 2013 Elsevier Ltd. All rights reserved.