This thesis investigates membrane distillation (MD) as a route to produce ultrapure water from saline/brackish feeds and analyses its thermal integration with a photovoltaic (PV) module and an electrolyser for co-production of freshwater and green hydrogen. A dual modelling framework is developed: a 0D physics-based analytical model and a 2D Simulink model that closes the thermal balance between PV rear side losses and the MD feed channel, linking distillate flow to the electrolyser’s water demand. The work also offers a critical review and operating guidelines for pre/post-treatment and membrane cleaning across diverse industrial effluents. Simulations considering a flat sheet DCMD module show that the axial temperature field governs the vapor pressure gradient and thus flux: at 40 °C and 60 °C with a feed velocity of 0.1 m/s, fluxes of 3.1 and 9.2 kg h-1m-2 are obtained, with a peak near the feed inlet.