Neither Statkraft nor Wetsus expects to crank out more than just a few kilowatts—enough to boil water—with their initial experiments. Instead, they plan to demonstrate what could be scalable, commercially viable energy production as well as determine if salt power endangers the health of source-water estuaries. Statkraft estimates salt power's worldwide electricity-generating potential at up to 1,700 terawatt-hours, or about 10 percent of global demand.
Salt power is attractive for several reasons: For one, unlike renewable energy technologies for harvesting solar or wind power, salt systems are not dependent on the weather and could provide baseload (constant, predictable) electricity like that supplied by coal, natural gas and nuclear energy. "The river water is flowing into the sea 24/7, so you have a constantly available source of energy," Skilhagen says. He also points out there are no emissions besides brackish water, which swirls in the river's mouth anyway.
Unlike conventional hydropower, a saline power plant does not require damming off a waterway, and it may require less infrastructure than, say, riverbed-mounted turbines or floating fleets of generators for equivalent tidal and wave power. A salt power plant, including its membrane stacks, turbines, cleaning facilities and offices, could actually be located in a riverside industrial complex's basement, for example, or constructed underground within a riverbank with pipes extending into the waterway, Statkraft's Skilhagen says—a big advantage for incorporating such facilities into already-developed, populated coastal areas.
Membrane design and performance remain the biggest hurdles for both Statkraft's and Wetsus's approaches. The membranes must be made more efficient, durable and resistant to microbial buildup, or so-called biofouling. Pretreating the pumped-in water by filtering out organic matter and river-borne debris helps, but this critical step consumes energy and is expected to be expensive, Skilhagen says, adding that it is too early to know just how expensive.
Accordingly, experts remain cautious about salt power's prospects. "Both these methods are promising and certainly worth researching," says Ari Seppala, a mechanical engineer and thermodynamicist at the Helsinki University of Technology in Finland, "but both may still need a breakthrough innovation before commercialization." Seppala sees no physical or chemical showstoppers standing in the way of producing much-improved membranes, although he also points out that a better, membrane-free method could yet be found for exploiting salinity differences to yield electricity.
Another key uncertainty: a salt-power plant's effect on the local aquatic environment. "This is a completely new process that has not been tested on this scale," says Menachem Elimelech, a professor of chemical and environmental engineering at Yale University. "I doubt there will be no [environmental] impact at all." If the ecological footprint is minimal and the membrane technology advances, however, he adds that salt power could be a "significant renewable energy option."
Subscription Center
See what we're tweeting about
10 Comments
Add CommentI love the idea, but for one concern.
Reply | Report Abuse | Link to thisThese areas where rivers meet the sea are some of the most sensitive areas, ecologically speaking. I'm not much of an environmentalist and I don't usually find myself on the side of the nay sayers when it comes to building things, but this case sounds particularly full of potential to disrupt the way these natural systems works.
You'd pretty much have to do this "in situ" for the volume of water to be enough for full scale use. You can't pump the sea water or the fresh water all that far or you'll loose the energy gain. You also can't do it by just adding salt to regular water in less sensitive locations because you end up creating a lot of salt water which you then have to either desalinate or change the ratio of fresh to salt water in the area.
If you do this work at the place where these rivers meet the ocean, you have to take water out of the river upstream, let it flow through to where your plant is -- presumably at the coast itself, and let it run through your plant then back out into the ocean. Doing that will change the location where the mixing happens. Do that at a large enough scale, and maybe you risk changing the entire local ecosystem.
Can the same principles be applied to other kinds of reactions? Maybe some where the outcome product is beneficial in some other ways?
AJP's got some good points, although the ideas seem attractive under the surface ;-)
Reply | Report Abuse | Link to thisWhat I'd like to see is a use of these principles in conjunction with desalination. If research resources are to be devoted this process, then it shouldn't be too hard to direct them to a combined operation at this early stage.
5 watts per square meter?!? Sheesh. Even the most horribly inefficient solar cells can get 10 times that much.
Reply | Report Abuse | Link to thisfrgough - yes its low at 5 watts/sq. m, but these membranes are usually cylindrical, so their footprint for a given area is much smaller.
Reply | Report Abuse | Link to thisRegardless, 10 times the power is useless if it isn't consistent. As the article noted, this tech has the benefit of easily meeting baseload demnads. Plus, infrastructure costs may be low compared to making and installing solar cells (not to mention the land requirements).
The importance is on the fact that humanity needs more and more energy. So go ahead!
Reply | Report Abuse | Link to thisThe importance is on the fact that humanity needs more and more energy. So go ahead!
Reply | Report Abuse | Link to this"Statkraft estimates salt power's worldwide electricity-generating potential at up to 1,700 terawatt-hours, or about 10 percent of global demand."
Reply | Report Abuse | Link to thisYet again editors that should know better are confusing the public, already confused about the difference between power and energy. The phrasing should be:
"Statkraft estimates salt power's worldwide electricity-generating potential at up to 1,700 terawatt-hours per year, or about 10 percent of global demand."
Or, just use average power:
"Statkraft estimates salt power's worldwide electricity-generating potential at up to 200 gigawatts, or about 10 percent of global demand."
http://en.wikipedia.org/wiki/Watt#Confusion_of_watts_and_watt-hours
In reply to commenters who pooh-pooh all difficult innovations as pie-in-the-sky: this is Scientific American, not Popular Mechanics, yet even most Popular Mechanics readers enjoy far-out technologies. Thanks SciAm for reporting broadly on this research, but maybe take a hint from the nay-sayers and avoid publishing too much wishful prophecy, even if you do balance it with concerns.
It's gonna take all these imperfect methods combined to replace our dismal array of fossil fuels. The answer is not "this thing or that thing now makes all our power instead of the old way", it's "what do we have here, some geothermal, sure we can use that, solar over there, aquatic turbulence here, windy over there, micro-hydro up the mountain, we can use it all."
Reply | Report Abuse | Link to thisEventually, all those small percentages add up to a big number, and before you know, we have many companies, in many sub-industries, with specialists, engineers, designers, equipment mfg, distribution, maintenance... innovation, competition... sound familiar? Look at all these new things for people to do, instead of just sell saudi gas on the corner for minimum wage.
Hey Adam, cool article. I wrote about this for Science Illustrated during my internship at popsci two summers ago. Unfortunately, it doesn't seem like much (or any) progress has been made in the subsequent year and a half. But I like the basic salt-power idea, so I'm keeping my eyes open for new developments.
Reply | Report Abuse | Link to thisI will follow closely the development. The whole science is known, there is no special pressure or higher temperatur involved. The whole apparatus can be made from simple plastic tubing and valves.No corrosion, wich means long trouble free life. I would talk with people that use reverse osmosis about their experience with
Reply | Report Abuse | Link to thisthe maintenance problems. Good luck. Dr.Kamlander@aon.at