A new combined power and desalination system is proposed. This system is driven by low grade heat sources such as solar energy, geothermal or waste heat. This system combines a supercritical organic Rankine cycle (SORC), an ejector and a multi-effect distillation (MED) desalination system, which could be used for seawater or concentrated brine such as frac flowback water produced during natural gas mining. A theoretical model is presented and partially validated based on experimental results from the literature. The thermal performance of the proposed system is analyzed using the model and a parametric sensitivity analysis is carried out to quantify the performance of this combined power and water system. The combined system has an overall exergy efficiency close to 40% for salt concentration of 35 g/kg using a low temperature heat source at 150 degrees C The proposed system could treat concentrated brine up to 55 g/kg salt concentration with no additional energy input except heat supplied to the power cycle. (c) 2012 Elsevier Ltd. All rights reserved.