High performance in power generation by pressure-retarded osmosis (Pro) from hypersalinity gradient: Case study of hypersaline lake of Urmia, Iran

Pressure-retarded osmosis (PRO) is a renewable energy that generates its energy from mixing freshwater streams with saline water. The limitation of this energy has been reported to be 0.192 kWh/m³ of the mixed solution when using seawater as the saline source, which could limit the potential of the technology. However, using hypersaline water sources allows for higher energy densities, and could be a way to make PRO viable. Lake Urmia in Iran is the second largest hypersaline lake in the world, and in this study, the PRO potential has been evaluated. An energy potential between 250 and 1,250 MW depending on the freshwater source was calculated by using a newly developed mixing model. The results of a new model were compared with previously reported energy potentials of Lake Urmia calculated with simplified models. Based on our analysis the Madsen’s model predicts approximately two times higher energy production over these models, showing that a hypersaline PRO plant at Lake Urmia could be a significant producer of renewable energy in the region. Finally, the sensitivity analysis for membrane revenue based on the fluctuation of the retail price of electricity has been carried out. The results of this investigation can be used as a reference to predict energy production from the other hypersaline lakes around the world.