Reader TTS

Access through your institution Buy or subscribe In the end, life comes down to electrochemical gradients. But we haven't yet found very effective ways of making what works for the cell

work for society: harnessing the energy released by the equalization of solute concentrations. The power that could be tapped from the entropy of mixing of saline and fresh water, as rivers

reach the sea, might seem tiny locally, but like everything else associated with the oceans, becomes vast on the global scale: of the order of a few terawatts, which would provide a

significant fraction of current world energy demand. Highlighting this overlooked energy source in 1954, the engineer R. E. Pattle estimated that the energy released in a river estuary is

equivalent to that available if the river were plunging over a 680-foot waterfall1. Of course, energy production from salinity gradients suffers the curse of all renewables: global sums

sound appealing, but the energy is so dispersed that capturing even a small part of it is immensely challenging, technologically and economically. That hasn't prevented attempts since

Pattle first proposed his 'hydroelectric pile'. Most notably, in the 1970s Sidney Loeb imagined harnessing the pressure generated as fresh water is drawn through a salt-obstructing

membrane — a method called pressure-retarded osmosis, now being developed by the Norwegian-based renewable energy company Statkraft, which aims to have a commercial generator by 2015. This

is a preview of subscription content, access via your institution ACCESS OPTIONS Access through your institution Subscribe to this journal Receive 12 print issues and online access $259.00

per year only $21.58 per issue Learn more Buy this article * Purchase on SpringerLink * Instant access to full article PDF Buy now Prices may be subject to local taxes which are calculated

during checkout ADDITIONAL ACCESS OPTIONS: * Log in * Learn about institutional subscriptions * Read our FAQs * Contact customer support REFERENCES * Pattle, R. E. _Nature_ 174, 660 (1954).

Article  CAS  Google Scholar  * Brogioli, D. _Phys. Rev. Lett._ 103, 058501 (2009). Article  Google Scholar  * La Mantia, F., Pasta, M., Deshazer, H. D., Logan, B. E. & Cui, Y. _Nano

Lett._ doi:10.1021/nl200500s (2011). Download references Authors * Philip Ball View author publications You can also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS

Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Ball, P. A pinch of salt. _Nature Mater_ 10, 344 (2011). https://doi.org/10.1038/nmat3018 Download citation * Published: 20

April 2011 * Issue Date: May 2011 * DOI: https://doi.org/10.1038/nmat3018 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link

Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative