A membrane distillation process wherein distillate is generated from a feed by means of evaporation to vapour in a first liquid channel, which vapour is removed through a membrane and subsequently condensed in a vapour channel, wherein heat transfer occurs from the vapour channel to any subsequent liquid channel, and wherein the evaporation of feed in the first liquid channel occurs upon heat transfer from a heating channel in which a vapour flow condenses, wherein the generation of the distillate comprises steps of: - applying a system underpressure to at least one of the modules of the system, which system underpressure is forwarded to other modules (14, 16, 14, 116) through pressure communication; - transferring heat into the heating channel, that is separated by a wall from an adjacent liquid channel of a first membrane distillation module; - providing feed to a fluid entry of the first membrane distillation module, said feed entering the liquid channel and being heated by means of the transferred heat transmitted from the heating channel so as to evaporate feed liquid to vapour that may pass through a substantially fluid-impermeable, vapor permeable membrane into a vapor space coupled to a subsequent vapour channel; - generating distillate and transferring heat to an adjacent liquid channel by means of condensation of the vapour passed into the subsequent vapour channel; - repeatedly, in dependence of the number of distillation modules (14, 16, 114, 116) in use, transferring non-evaporated feed of the preceding membrane distillation module (14, 16, 114) to a subsequent membrane distillation module (16, 114, 116), and generating distillate from vapour passed into a subsequent vapour channel, therewith transferring heat to a adjacent liquid channel, wherein the distillate of the last membrane distillation module is generated in a vapour channel of a condenser module against a cooling fluid running in a cooling channel of the condenser module, wherein an underpressure is applied to an outlet of the cooling channel, so that the cooling liquid is sucked through the condenser module by means of a pressure difference between an inlet and the outlet of the cooling channel of the condenser module, and wherein the non-evaporated and concentrated feed flowing from the last membrane distillation module is diluted with at least part of the cooling liquid that has passed the condenser module, and is then pumped away. - applying a system underpressure to at least one of the modules of the system, which system underpressure is forwarded to other modules (14, 16, 14, 116) through pressure communication; - transferring heat into the heating channel, that is separated by a wall from an adjacent liquid channel of a first membrane distillation module; - providing feed to a fluid entry of the first membrane distillation module, said feed entering the liquid channel and being heated by means of the transferred heat transmitted from the heating channel so as to evaporate feed liquid to vapour that may pass through a substantially fluid-impermeable, vapor permeable membrane into a vapor space coupled to a subsequent vapour channel; - generating distillate and transferring heat to an adjacent liquid channel by means of condensation of the vapour passed into the subsequent vapour channel; - repeatedly, in dependence of the number of distillation modules (14, 16, 114, 116) in use, transferring non-evaporated feed of the preceding membrane distillation module (14, 16, 114) to a subsequent membrane distillation module (16, 114, 116), and generating distillate from vapour passed into a subsequent vapour channel, therewith transferring heat to a adjacent liquid channel, wherein the distillate of the last membrane distillation module is generated in a vapour channel of a condenser module against a cooling fluid running in a cooling channel of the condenser module,