Physical Transformation AtlasPTA
Disequilibrium · disequilibrium:salinity-gradient

Salinity gradient

Fresh water meeting seawater, recorded as a chemical disequilibrium with positive exergy. The recorded mixing-free-energy bound is about 0.8 kWh per cubic metre of fresh water mixed into the sea under the stated reference conditions.

symbol ΔSElectrochemistryenergy form chemicalexergy positivealso: salinity difference, blue energy, river–sea mixing, osmotic power, salinity-gradient power

Atlas record: 3 claims reference this disequilibrium — 2 established and 1 demonstrated.

Explorerelations · matrix context · routes · sources · cite

conditions: aqueous medium required · liquid
3claims5enumerated routes3routes with complete-composition evidence0candidate routes not searched5cited sources

Relations

drives · 3
Salinity gradient—drives→Reverse electrodialysisestablished
  • alternating cation- and anion-exchange membranes with sea and river water in alternate compartments
Salinity gradient—drives→Pressure-retarded osmosisestablished
  • a semipermeable membrane with fresh water on one side and seawater pressurised below its osmotic pressure on the other
Salinity gradient—drives→Capacitive mixingdemonstrated
  • porous carbon electrodes charged in salt water and discharged in fresh water in a four-step cycle
One primary experiment on record in this atlas; later replications exist in the literature but are not yet recorded here.

Matrix context

D = disequilibrium row · C = coupling family column. A cell reads the state of the atlas for that pair.

C.01 ThermoelectricC.02 ThermionicC.03 ThermoacousticC.04 PyroelectricC.05 ThermogalvanicC.06 ThermomagneticC.07 ThermophotovoltaicC.08 Heat engine (thermomechanical)C.09 Caloric (magneto/electro/elasto)C.10 PiezoelectricC.11 FlexoelectricC.12 TriboelectricC.13 Electrostatic (variable capacitance)C.14 Electromagnetic inductionC.15 MagnetostrictiveC.16 MagnetoelectricC.17 Spin caloritronicC.18 PhotovoltaicC.19 PhotoelectrochemicalC.20 PhotothermalC.21 ElectrochemicalC.22 Osmotic / salinity-gradientC.23 ElectrokineticC.24 TurbomachineryC.25 MagnetohydrodynamicC.26 RadiovoltaicC.27 Nuclear heatC.28 RectennaC.29 ThermochemicalC.30 BiologicalC.31 Fluctuation / information-drivenC.32 Photon momentumC.33 ThermodiffusiveC.34 MarangoniC.35 AcoustoelectricC.36 PhotodiffusiveC.37 Thermo-osmoticC.38 ElectrohydrodynamicC.39 RadioluminescentC.40 Thermopolarization

Enumerated routes through this · 5

Cited sources · 5

  1. [1]
    R. E. Pattle. Production of electric power by mixing fresh and salt water in the hydroelectric pile (1954)
    Nature 174, 660 · doi:10.1038/174660a0 · crossref ✓ 2026-09-19 · record
  2. [2]
    J. W. Post, et al.. Salinity-gradient power: Evaluation of pressure-retarded osmosis and reverse electrodialysis (2007)
    Journal of Membrane Science 288, 218–230 · doi:10.1016/j.memsci.2006.11.018 · crossref ✓ 2026-09-19 · record
  3. [3]
    B. E. Logan, M. Elimelech. Membrane-based processes for sustainable power generation using water (2012)
    Nature 488, 313–319 · doi:10.1038/nature11477 · crossref ✓ 2026-09-19 · record
  4. [4]
    S. Loeb. Osmotic power plants (1975)
    Science 189, 654–655 · doi:10.1126/science.189.4203.654 · crossref ✓ 2026-09-19 · record
  5. [5]
    D. Brogioli. Extracting renewable energy from a salinity difference using a capacitor (2009)
    Physical Review Letters 103, 058501 · doi:10.1103/PhysRevLett.103.058501 · crossref ✓ 2026-09-19 · record

Cite this entity

Physical Transformation Atlas (2026). entity disequilibrium:salinity-gradient: Salinity gradient. Dataset revision rbfbfcbb70e57 (hash of the canonical data). https://physical-transformation-atlas.wldud5192.workers.dev/e/disequilibrium/salinity-gradient

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