A transient-state mathematical model for an ethanol basin solar still based on Spalding's work was developed. Driving force B was defined based on the mass balance between the evaporating (S) and condensing (G) surfaces. Mass transfer conductance (g) was obtained from an indoor experiment. Then productivity could be calculated. In order to validate the model an ethanol basin solar still was tested under outdoor conditions. The model had RMSEs of 4% and 23% of the measured mean temperature and productivity. The mean productivity was 0.33 kg/h when the mean solar radiation input was 1.95 MJ/m(2)/h. The simulated distillate concentrations were 74, 59 and 24%v/v for ethanol solution concentrations of 50, 30 and 10%v/v. The monthly means of the simulated daily productivity and total daily solar radiation were linearly correlated. An indoor experimental equipment of the same type as that used for the outdoor experiments was constructed. Ethanol solutions with concentrations of 10-100%v/v were distilled. The ethanol solution temperature varied between 40 and 70 degrees C. The experimental data from the still was then used to find the 9 used for the above mathematical model. The still height had a slight effect on the productivity. Increasing the ethanol solution concentration by not more than around 80% v/v could improve the still productivity. (c) 2007 Elsevier Ltd. All rights reserved.