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Ocean gradient energy: OTEC, DOWA and osmotic power
Published in John Twidell, Renewable Energy Resources, 2021
Osmotic power is the extraction of useful energy from the difference in salt concentration between the ocean and a nearby source of fresh water (e.g. a river). The technique uses the osmotic pressure that is apparent when two volumes of a solvent (e.g. water) having different concentrations of solute (e.g. salt) are separated by a semi-permeable membrane, as shown in Fig. 13.7. Microscopically the molecules of the solvent are able to diffuse back and forth through the membrane, but the larger molecules of the solute cannot do this. Consequently, the more concentrated solution becomes less concentrated because more solvent passes one way than the other. This causes a macroscopic pressure difference across the membrane. Eventually equilibrium is reached, for which the static pressure difference across the membrane is termed the osmotic pressure. Osmotic pressures are very large (e.g. 30 atmospheres between fresh water and sea water, for further detail see textbooks on physical chemistry). Osmotic pressure differences and movement of solvents is an essential process in life systems (e.g. kidney function and water movement through semi-permeable cell walls).
Nanofiber Membranes for Energy Applications
Published in Ahmad Fauzi Ismail, Nidal Hilal, Juhana Jaafar, Chris J. Wright, Nanofiber Membranes for Medical, Environmental, and Energy Applications, 2019
Mehmet Emin Pasaoglu, Ismail Koyuncu, Reyhan Sengur-Tasdemir
Salinity gradient energy naturally occurs when freshwater encounter saline water all over the world. Osmosis process can be used for capturing the energy of mixing fresh and saline waters, which is ultimately lost when freshwater dilutes saline water. Estimated of all salinity gradients in the world is 1.4–2.6 TW from which approximately 980 GW (Ramon et al., 2011; Logan and Elimelech, 2012) can be effectively harnessed with an appropriate designed system (Bui and McCutcheon, 2014). An osmotic pressure difference occurs between two solutions from a dilute solution across a semipermeable membrane to a more concentrated draw solution. Hydrostatic pressure applied by the draw side, which is less than osmotic pressure, the osmotic flow is retarded. The Norwegian power company Statkraft estimates that osmotic power generation may be developed to be competitive with other energy sources without the drawbacks (Bui and McCutcheon, 2014).
Traditional and Alternative Energy Sources
Published in J.K. Yates, Daniel Castro-Lacouture, Sustainability in Engineering Design and Construction, 2018
J.K. Yates, Daniel Castro-Lacouture
The generation of osmotic energy and the desalinization of water are being explored in Norway, Japan. and Canada as methods for generating carbon-free renewable energy. Osmotic power is also called salinity-gradient power because it takes advantage of the lower concentration of water in saltwater that attracts freshwater. The freshwater is separated from the saltwater by a thin, permeable membrane, and the freshwater attempts to force its way through the membrane into the saltwater and as it does this pressure builds up and pushes the water through a pipe used to drive a turbine. This process will become more viable as soon as additional membrane manufacturers enter the market. Currently, only small amounts of electricity are being generated by osmotic processes (Halper 2010).
Modelling and economic evaluation of pressure-retarded osmosis power plant case study: Iran
Published in International Journal of Ambient Energy, 2019
Abolfazl Ansari, Majid Abbaspour
Osmotic power can be produced by a continuous inflow of fresh and salt water into the osmotic power plant, and by a continuous discharge of the brackish water. The larger the fresh water availability and salinity gradient, the larger the amount of produced energy will be. According to the research of Kleiterp (2012), a continuous flow of 1 m3/s river water mixed with sea water represents a gross capacity of approximately 1 MW.