Membrane distillation is an attractive technology for extracting fresh water from seawater. Newly developed modules have been used in pilot tests and bench scale tests to demonstrate the potential of producing excellent product water quality in a single step, little need for water pretreatment and a thermal energy requirement of approximately 520 MJ/m(3) water. Evaluations for large scale applications in the future, using low cost waste heat and assuming an energy requirement of 140-230 MJ/m(3), are indicating operational costs competitive to conventional desalination techniques, such as reversed osmosis and multi-effect distillation. (C) 2012 Elsevier B.V. All rights reserved.