* scientific american * * register + Newsletters + SA Community + SA Digital + Print Subscriber Services * online sections + News + Features + Mind Matters + In-Depth Reports + Fact or Fiction + Extreme Tech + Ask the Experts + Edit This + Slide Shows + Image Gallery + Videos + 60-Second Science Podcast + 60-Second Earth Podcast + 60-Second Psych Podcast + Science Talk Podcast + Content Partners * blogs + Scientific American Observations + Bering in Mind + Extinction Countdown + Solar at Home + Expeditions * scientific american magazine + Subscribe + INSIDE THIS ISSUE + Features + News Scan + 50, 100 & 150 Years Ago + Antigravity + Skeptic + Critical Mass + Scientific American Perspectives + Sustainable Developments + Ask the Experts + Recommendations + Letters + From the Editor + Special Editions + * scientific american mind magazine + Subscribe + INSIDE THIS ISSUE + Features + Head Lines + Perspectives + Ask the Brains + We're Only Human + Illusions + Facts and Fictions in Mental Health + Reviews and Recommendations + Consciousness Redux + Mind in Pictures + From the Editor + Letters + Calendar + * science jobs * subscribe * Basic Science + Biology + Chemistry + History of Science + Math + Physics + Society & Policy + Everyday Science + Science Education * Space + Astrophysics + Extraterrestrial Life + Galaxies + Space Exploration + Cosmology * Evolution + Archaeology & Paleontology + Dinosaurs + Evolutionary Biology + Language & Linguistics * Energy & Sustainability + Alternative Energy Technology + Clean Air Policy + Climate + Ecology + Energy Technology + Environment + Green Living * Mind & Brain + Addiction & Recovery + Language & Linguistics + Neurological Disorders + Neuroscience + Psychiatry + Psychology + Thought & Cognition * Health & Medicine + Biotechnology + Ethics + Infectious Diseases + Medical Technology + Pharmaceuticals * Technology + Alternative Energy Technology + Automotive Technology + Biotechnology + Communications + Computing + Consumer Electronics + Energy Technology ____________________ submit Rss RSS Feeds Newsletter Signup Newsletters Bookmark Bookmark ScientificAmerican.com > News > Energy & Sustainability > Water October 19, 2009 | 9 comments Energy Out of the Blue: Generating Electric Power from the Clash of River and Sea Water Two pilot projects are testing the potential of "salt power," a renewable energy that relies on the differing salinities at river mouths to make watts By Adam Hadhazy Freshwater, Saltwater, Salt Power 1. 2. Back 3. IMAGE 1 of 3 4. Next ELECTRIC BLUE: New projects aim to generate energy by harnessing the salinity-balancing effects where freshwater rivers flow into salty seas. © NASA/ROBERT SIMMON e-mail print comment In the hunt for alternatives to polluting and climate-warming fossil fuels, attention has turned to where rivers meet the sea. Here, freshwater and saltwater naturally settle their salinity difference, a phenomenon that two pioneering projects in Europe will try to harness to generate clean energy. This concept of "salt power"—also known as osmotic, or salinity-gradient, power—has been kicked around for decades, and now, proponents hope, technology has advanced enough to make it economically competitive. On November 24, the world's first large-scale prototype facility for developing a form of salt power called pressure-retarded osmosis is expected to begin fully operating in Norway. "The big reason to build this thing is to answer important questions [about osmotic power], and while we've done a lot of theoretical studies, we need live experience," says Stein Erik Skilhagen, vice president of osmotic power at Statkraft, Norway's state-owned power utility that built the plant. The prototype will have no customers, although the very small amount of electricity it generates will technically be directed into the power grid. Statkraft's approximately $5-million prototype plant is a converted paper mill in the seaside village of Tofte, about 60 kilometers south of Oslo. The plant's pressure-retarded osmosis setup will place freshwater and brine on either side of a semipermeable membrane that prevents the passage of salt particles but allows water through. Water from the fresh side naturally flows into the salty side, generating pressure equivalent to a column of water 120 meters high. This pressurized water can be used to turn a turbine to make electricity. Statkraft's goal is to yield five watts per square meter of membrane, although current capacity is about three watts. If successful, the utility hopes to build a commercial salt power plant for paying customers around 2015 with a targeted cost ranging from seven to 14 cents per kilowatt-hour (pdf) (at current euro–dollar conversion rates), which at the low end would be competitive with coal and natural gas prices. To the south in the Netherlands, a Dutch research firm called Wetsus has fired up its own salt power experiment to evaluate what is essentially a saltwater–freshwater battery. Wetsus, with the collaboration of a spin-off company called Redstack, is pursuing a version of salt power dubbed "blue energy". A pilot-scale installation that is about two times the size of a big American refrigerator is up and running in Harlingen, by the Wadden Sea, says Gert Jan Euverink, Wetsus's deputy scientific director. The technology relies on reverse electrodialysis, wherein a series of fresh and saltwater streams are diverted via underground pipes to opposite sides of two kinds of membranes. These let sodium or chlorine ions—the constituent elements of salt—dissolved in the water to pass into separated freshwater streams. This builds an electrical potential across the membranes, like a battery, and this charge reacts with iron to form an electric current. Joost Veerman, a researcher at Wetsus, says the company aims to get five watts per square meter of membrane, the same result as Statkraft's process. Read Comments (9) | Post a comment 1 2 Next > Share Propeller Digg! Reddit delicious Fark Slashdot RT @sciam Energy Out of the Blue: Generating Electric Power from the Clash of River and Sea Water Twitter Review it on NewsTrust sharebar end You Might Also Like * [generic_50x50.gif] Turning the Tide on Harnessing the Ocean's Abundant Energy * [generic_50x50.gif] Turbine Rides Underwater Currents Like a Kite * [generic_50x50.gif] Facing the Freshwater Crisis * [generic_50x50.gif] First U.S. "Power Tower" Lights Up California * [generic_50x50.gif] Drink Up: Taking the Salt Out of Seawater * [generic_50x50.gif] Ask the Experts: Why don't we get our drinking water from the ocean by taking the salt out of seawater? * Plan B for Energy: 8 Revolutionary Energy Sources * World Changing Ideas: 20 Ways to Build a Cleaner, Healthier, Smarter World Discuss This Article Click here to submit your comment. VIEW: [Oldest to Newest] ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ 2,573 characters remaining [_] Email me when someone responds to this discussion. Submit risk free issue _________________________________________________________________ Sciam - cover Email: ____________________ Name: ____________________ Address: ____________________ Address 2: ____________________ City: ____________________ State: [..] ____________________ spacer _________________________________________________________________ Continue Subscription Center Scientific American - cover * Risk-Free Issue * Digital Subscriptions * Give A Gift * Customer Service Advertisement Editor's Pick * top-science-2009-ardi-LHC-hubble-epigenetics-stimulus-LCROSS-NIF-lasers-AIDS-vaccine-copenhagen-H1N1 The Top 10 Science Stories of 2009 [Slide Show]A hominid ancestor, swine flu, the world's biggest laser system and other highlights that defined this year in science Newsletter Energy & Sustainability Newsletter Get weekly coverage delivered to your inbox ____________________ submit Video * Microsoft Reveals Tricks Behind Controller-Free Natal for Xbox 360 Players Microsoft Reveals Tricks Behind Controller-Free Natal for Xbox 360 Players * Microsoft Reveals Tricks Behind Controller-Free Natal for Xbox 360 Players Microsoft Reveals Tricks Behind Controller-Free Natal for Xbox 360 Players * Base jump world record Base jump world record Podcasts * 60-Second Science RSS · iTunes Monkeys Are Canaries in Lead Mine click to enable Download * Science Talk RSS · iTunes Alan Alda's Human Spark, Part 2 click to enable Download Slideshows * grevy's zebra Could Re-Wilding Avert the 6th Great Extinction? [Slide Show] * top 10 decade science disappointment 10 Science Letdowns of the New Millennium [Slide Show] * Most Popular * Latest Stories Drive to the airport, get clearance, and take off in your flying... car? The Next 20 Years of Microchips: Pushing Performance Boundaries Could Re-Wilding Avert the 6th Great Extinction? [Slide Show] Easy Flyer: A Land/Air-Capable Motorcycle May Be in the Offing Where on Earth will we store all that captured CO2? Try the U.S. east coast A galaxy of new worlds: Dispatch from the American Astronomical Society meeting Heavy Brows, High Art?: Newly Unearthed Painted Shells Show Neandertals Were Homo sapiens's Mental Equals Turning Trash to Fuel and Reducing Battlefield Risks Mountaintop removal mining: EPA says yes, scientists say no Fallout Forensics: Carbon 14 test could help fight illegal ivory trade Advertisement VIEW ALLNews from Our Partners Reuters * Obama awards $2.3 billion clean energy tax credits * Obama awards $2.3 bln clean energy tax credits * Factbox: New U.S. clean energy manufacturing tax credits ESA * European Commission announces the award of major Galileo contracts * ESA Member States give green light to ExoMars Programme * Forests take centre stage at Copenhagen Nature News * Oceans release DDT from decades ago * Sea stars suck up carbon * Quivering ions pass quantum test ADVERTISEMENT Also on Scientific American Heavy Brows, High Art?: Newly Unearthed Painted Shells Show Neandertals Were Homo sapiens's Mental Equals Observations Record 232-digit number from cryptography challenge factored What Keeps Time Moving Forward? Blame It on the Big Bang Microsoft, Natal, Xbox, video game Binary Body Double: Microsoft Reveals the Science Behind Project Natal for Xbox 360 Another Reason to Save Coral? Reefs Are Responsible for Ocean Biodiversity Information * About Us * Advertising * Privacy Policy * Terms of Use * Special Ad Sections * Site Map * Contact Us * Products & Services * Partner Network Publications * Scientific American * Scientific American Mind * Scientific American Digital * Special Editions and Reports * International Editions Services * Subscribe * Renew * Subscriber Service * Gift Subscriptions * Order Back Issues Follow Us Via... * RSS Feeds RSS Feeds * E-mail Newsletters E-mail Newsletters * Blog Blog * Podcasts Podcasts * Mobile Mobile * Widgets Widgets © 2010 Scientific American, a division of Nature America, Inc. All Rights Reserved. ADVERTISEMENT Quantcast