The salinity gradient when fresh and brine meet has been harvested for a new class of renewable energy , albeit on a flyspeck scale . This could become a clean electricity source that is far more stable than those drug-addicted on the wind and Sun , potentially offer a reliable reservoir of free energy in coastal locations .
Dr Kristian Dubrawskiof Stanford University is attempting to harness the electric potentiality of meld saltiness and freshwater and use it to power coastal wastewater intervention plants . He build up a prototype savings bank of batteries with Prussian Blue and polypyrrole electrodes and alternately bathed them in table salt and freshwater for an hr at a fourth dimension . To ensure the test was naturalistic , Dubrawski used brine gather from Half Moon Bay , California , and the nearly fresh outpouring from the Palo Alto Regional Water Quality Control Plant .
InACS Omega , Dubrawski describe how sodium and chloride ions passed into the stamp battery ’s electrodes during the saltwater stage , carrying charge with them . When the wastewater exchange the salt , the ion left the electrode , acquit charge in the opposite direction .
away from gates switching which urine would flow over the barrage , no remark energy was postulate . Electricity was bring forth throughout the physical process , although the power available for international exercise was high-pitched at the jump of the brine form .
The heading of Dubrawski ’s Lab , Professor Craig Criddle , sees the engineering as an opportunity to render water discussion plants with a reliable source of clean ability , freeing them from the danger personate if grid king is cut off , such as happened during California ’s wildfires .
Theoretically , it could be scaled up to habituate the vast outflows from major rivers . Aprevious studyestimated global estuarine potential as 2 Terrawatts , not far below world electrical energy consumption , although it is unlikely we will ever intercept more than a tiny proportion of this . The production of the world ’s wastefulness treatment plant life alone could theoretically power Argentina .
With perfect efficiency , it is potential to produce 650 watt hours from a three-dimensional metre ( 220 congius ) each of fresh and seawater – a half - fresh / half - salty backyard swimming pool could power an middling American house for a twenty-four hours . Dubrawski ’s test manakin achieved two - third efficiency , although he acknowledges this may not hold at larger scales .
Others have noticed the potential available from the coming together of new and piquant water , and many prototype have been built to capture it . However , these have used prohibitively expensive technologies like membrane or hydrogels that expand or contract depending on their environment .
" Our battery is a major step toward much capturing that energy without membrane , travel parts or energy input , ” Dubrawski read in astatement . Unlike previous effort , the ingredient are all made from tawdry and wide available materials .
