In order to evaluate the performance of the AGMD modules, distillate production of each module was measured as a function of both hot and cold inlet flows and temperatures. Due to the transient nature of solar energy, it was not possible to control feed temperatures (hot temperature increased during a working day from 60 °C to 95 °C while cold temperature varies from 20 °C to 70 °C, approximately). Inlet flows were varied accordingly to a body centred multivariate experimental design (i. e., 5, 12.5 and 20 l/min).

Leakage was found at the very beginning of the experimental campaign (around 10-30% of leakage) depending on the hot inlet temperature and thus on the distillate production, leading to a distillate conductivity between 200-600 pS/cm, for that reason the amount of leakage was extracted from the distillate production in order to obtain a model to describe the performance of the system. Two months of experiments were carried out to obtain a single polynomial expression based on multiple linear regression, used to fit experimental data at 95% coefficients confidence interval level. The performance of individual AGMD module production, based on the polynomial expression, is depicted

in fig. 2 (correlation between predicted and observed values is acceptable at 95% confidence level). Leakage problems were solved by reassembling the modules. After that, the conductivity (although depending on hot inlet temperature) once achieved the stationary stage, was always around 2-3 pS/cm. No membrane scaling neither sings of membrane wetting was found during modules’ reassembling.