Dear Colleagues,

When river water flows into a sea, a substantial amount of energy is released from the mixing of the two waters. Salinity gradient power (SGP), as its name suggests, is a form of chemical potential energy arising from the salinity difference. It is also commonly called “osmotic energy.” With an osmotic pressure difference of approximately 2.7 MPa between fresh water and seawater (equivalent to the potential energy from a waterfall with a 270 m elevation difference), an osmotic energy of up to 0.75 kWh/m3 can be extracted. The total amount of osmotic energy that can be potentially extracted from mixing fresh water and seawater is estimated to be around 1 terawatts—an amount that is on par with global hydroelectric power generation [1,2]. Aside from the mixing of fresh water and seawater, researchers are also exploring many other possibilities, such as the beneficial use of saline brine and wastewater for energy production. A wide range of different osmotic power extraction technologies (e.g., pressure retarded osmosis, reverse electrodialysis, and capacitive mixing) and their derivatives (e.g., the hybrid of pressure retarded osmosis with the desalination process) have been actively pursued in recent years.

This Special Issue of Energies welcomes works related to the topic of extracting and  beneficially using osmotic pressure. Both original contributions and reviews concerning recent advances in theory, materials, and processes development, operational issues, and novel applications are greatly welcome.

[1] Skilhagen, S.E.; Dugstad, J.E.; Aaberg, R.J. Desalination 2008, 220, 476–482.
[2] Logan, B.E.; Elimelech, M. Nature 2012, 488, 313–319.

Prof. Dr. Chuyang Y. Tang
Guest Editor

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• clean energy
• osmotic energy
• salinity gradient power
• pressure retarded osmosis
• reverse electrodialysis
• capacitive mixing