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New membrane unlocks energy from chemical difference between fresh and saltwater
- kitsuac 7y agoIt sounds like a non-renewable energy source which changes the natural flow of the water permanently. Isn't there bound to be negative environmental effects?
- aedron 7y agoI dunno, the article said that one square meter of the membrane could power 400 homes. And they believe the material can be made even more effective with a proper manfucaturing process. That would not seem to disrupt waterflow. I personally think this sounds incredibly promising.
- orbifold 7y agoIf you use a small membrane there will be basically no way that a sufficiently large gradient between the two sides exist to produce meaningful amounts of electricity. This article is total bullshit even if the material science is nice.
- bradyd 7y ago> the article said that one square meter of the membrane could power 400 homes The article was updated to correct this number, it was actually 3 instead of 400.
- vanderZwan 7y ago> a non-renewable energy source The sea will remain salt and as long as rivers will flow the ion potential will exist along the coastline. Are you referring to other parts of the method?
- jandrese 7y agoReally this is a roundabout way of harnessing the power of the Sun. In this case the energy used to liberate water vapor from the ocean. When you think about it this way, all of our energy sources are just repackaged solar except for nuclear.
- nkrisc 7y agoNon-renewable? All that salt in the ocean isn't going anywhere and we'll have fresh water as long as the water cycle continues. You could even use grey water waste from fresh water that was originally desalinized for human use. I mean, you could say solar is non-renewable because the sun die one day. After all, there is a finite supply of solar energy.
- tathougies 7y agoThis is actually a form of solar energy anyway because it is the sun that provides the initial energy to separate the water, and move the water into the atmosphere against gravity.
- nkrisc 7y agoHah, great point. I guess you could take the unnecessarily further and state that all energy potential on Earth ultimately derives from the sun. We're 100% solar already!
- ouaiueoaieaeoiu 7y agoI'd say most of the chemical energy on the surface of the planet is derived from solar power, in contrast to nuclear (fusion or fission) power. Of course, solar is nuclear too. So we're actually 100% nuclear powered.
- benibela 7y agoNot nuclear or geothermal power
- quasimodem 7y agoWe could have never developed nuclear without the sun getting us started though...
- tathougies 7y agoWell, no not all. Batteries (non-rechargeable) and nuclear are given energy by previous supernovae, I would assume.
- munk-a 7y agoThis doesn't sound terrible but it will have effects on the ecosystem similar to hydro at least - blocking fish migration paths, reducing river flow rate and potentially causing algae blooms, fish die-offs or water toxicity increases as sediments are disturbed in fun new ways. All that said, it's certainly miles above either coal or natural gas.
- vanderZwan 7y ago> If researchers can scale up the postage stamp–size membrane in an affordable fashion Not to be a downer, but this feels like it is in the "possibly long-term solution" department. Which is definitely important to investigate, don't get me wrong!
- cagenut 7y agoat a meta level, these types of articles with a ridiculous headline and without any meaningful pictures or diagrams are infuriating. w/r/t the actual scientific discovery, i'm fascinated by how much of solving the overall energy/carbon problem is coming down to 'nano' scale material science and engineering. does anyone know of a better media venue for materials science developments that isn't just some loud guy reading wiki articles to a webcam?
- rkangel 7y agoWhat I find infuriating is units like '30 megawatt hours per year'. Why not just tell us how many megawatts?
- cbmuser 7y agoBecause you can just divide 30 by 365*24 to get the actual power which would be 3 Kilowatts or 0.003 Megawatts.
- dienciebsiwbsi 7y agoIt's 3.4 kW, enough for two toasters. So not nearly enough for 400 homes; their math is wrong.
- yetihehe 7y agoBut do people run their toasters continuously 24h/365 days a year? THAT's why they used yearly average.
- jandrese 7y agoNo, but running 400 homes on that level of power only works if every home is only intermittently using a single high efficiency lightbulb or something. A few refrigerators or electric ranges or electric heat pumps will blow that power budget right out the window.
- marshray 7y ago
- aedron 7y agoSo many jaded comments! This is incredibly cool. The 'breakthrough' (if you can talk about that at such an early stage) is a few simple materials engineering hacks: The nanotubes were easy. Cetindag says the lab just buys them from a chemical supply company. The scientists then add these to a polymer precursor that’s spread into a 6.5-micrometer-thick film. To orient the randomly aligned tubes, the researchers wanted to use a magnetic field. The problem: BNNTs aren’t magnetic. So Cetindag painted the negatively charged tubes with a positively charged coating; the molecules that made it up were too large to fit inside the BNNTs and thus left their channels open. Cetindag then added negatively charged magnetic iron oxide particles to the mix, which affixed to the positively charged coatings. When the researchers applied a magnetic field, they could maneuver the tubes so that most aligned across the polymer film. They then applied ultraviolet light to cure the polymer, locking everything in place. Finally, the team used a plasma beam to etch away some of the material on the top and bottom surfaces of the membrane, ensuring the tubes were open to either side. The final membrane contained some 10 million BNNTs per cubic centimeter. When the researchers placed their membrane in a small vessel separating salt- and freshwater, it produced 8000 times more power per area than the previous French team’s BNNT experiment.
- zozbot234 7y ago> So many jaded comments! This is incredibly cool. I agree. You could use the process to power a desalination plant, and make even more freshwater!
- marcosdumay 7y agoYou need a membrane permeable to negative ions too for that. In fact, I think you'll need that membrane for electricity generation too. Otherwise you will only get to make a single layer of it, what is underwhelming. But it is a large breakthrough.
- chongli 7y agoI think the GP was making a joke. What they suggested strongly implies the existence of perpetual motion machines, contradicting the laws of thermodynamics.
- aazaa 7y agoThe article unfortunately does not use the more common term for the "blue energy" principle: "osmotic power." The Wikipedia article on osmotic power explains the physical principles better: https://en.wikipedia.org/wiki/Osmotic_power https://en.wikipedia.org/wiki/Osmotic_power The Science article didn't explain very well why an estuary is required. The idea is apparently to have two bodies of water - with differing salinities - in close proximity. This happens near estuaries. The ocean provides water with high salt content. The outbound river provides water with low salt content. Those two sources of water in close proximity can either be used where they are or pumped into even closer proximity. Place a membrane (like the carbon boron nanotube devices discussed in the article) between the two pools of water with different salt content. They may be housed inside a power plant or outside. Then capture the energy released from the movement of ions through the membrane. There appear to be different approaches for that last part. In other words, the saltwater and freshwater sides of an estuary provide the two charge compartments of a very large battery. The breakthrough here is a way to manufacture the high-performance membranes needed provide a path for the ions through this system.
- asdfman123 7y agoDo you need an estuary? Can't you just divert river water, put it next to salt water, and then you can produce power? In fact, the only place "estuary" is used in the article is in the image caption, and I assume they used it because it's tangentially related and it's a pretty picture. Really you just need a pool of salt water and a pool of freshwater, and those two things are easy to get where rivers flow to the sea.
- aaronblohowiak 7y ago> those two things are easy to get where rivers flow to the sea. Isn’t that an estuary?
- asdfman123 7y ago"An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea" I think of an estuary as that partially enclosed area, which is neither the river or the sea. But really all you need are those two things: the freshwater river, and the saltwater sea.
- aljungberg 7y agoOne wonders how quickly these pores will become clogged over time. If the membrane deteriorates fast, the energy cost of producing more membranes continuously needs to be factored in. The article headline is pretty weird, by the way. So this technology can generate “thousands of nuclear power plants worth of energy”? But then in the third paragraph it sounds like they mean to say if you installed this membrane in every estuary in the world, then it’d beat 2000 nuclear plants. It’s like saying there’s more water in a cup than in a bathtub, as long as the cup is the size of a car.
- aedron 7y agothe researchers estimated a single square meter of the membrane [...] could [...] power more than 400 homes.
- aljungberg 7y agoEven the smallest nuclear power plant in the states generates 582 MW — enough for 95 000 homes. I’m not saying this isn’t a cool membrane. I’m making the point here that the comparison to 2000 nuclear power plants seems arbitrary.
- pjc50 7y ago.. or in real units, 30MWH/year = 3.425 kW. Which is quite a lot. That's what I get from about 10 square meters of solar panels, or one electric kettle running continuously. Seems implausibly high, I would move the decimal point over by one and naively guess it has the same energy density as solar panels.
- raisedbyninjas 7y agoThat is really high. However I think you could run a few kettles off this. In the US most tea kettles are 1-1.5kW, as are other high power appliances like microwaves, hair dryers, vacuum cleaners etc. 15A circuit breakers are common for general purpose home power outlets which max out at 1.6kW. I think the NEC recommends 2 20A circuits to supply kitchen's non-dedicated power outlets.
- martimarkov 7y agoCan anyone explain why the fresh water is needed? The article mentions that the ions in water are not bound to one another so why can’t we just use salt water entirely?
- mnw21cam 7y agoThere has to be a difference in the water on either side of the membrane. The energy is being extracted from the entropy of the system. Currently, fresh water flows into the ocean, where it mixes with salty water, and goes from a highly ordered system (separate fresh and salty) to a disordered system. We generate energy from heat the same way. It is no good to just have heat. To generate electricity or motion, you also need cold. It is the transfer of heat from hot to cold, making the hot cooler and the cold warmer, that allows us to make use of it. Practically speaking, this membrane lets positive ions through, but not negative ones. So, you put fresh water on one side, which has few ions, and salty water on the other side, which has plenty of both. Then, the positive ions flow through, and you end up with water full of positive ions on one side and water full of negative ions on the other side. That is electricity that can be directly tapped.
- marcan_42 7y agoWhere does the energy go when it is not being extracted with this method? I understand that the energy is extracted from the movement of ions between reservoirs of different salinity. If you're just letting the two sides mix, as they do naturally, where does the energy go instead? Is it released as heat?
- marcosdumay 7y agoIt converts thermal energy into usable electricity (that is, the water gets cooler), at the cost of the increased entropy in the mixing of fresh and saline water.
- Accujack 7y agoAlso, the environmental cost of keeping river estuaries blocked by impermeable membranes so you can maintain the gradient of salt/fresh water.
- sigmaprimus 7y agoAlso why bother with a membrane, the fact is river water for the majority of the year is either warmer or cooler than the typically constant ocean temperature. Two bodies of water at different temperatures plus a heat pump can be quite effective at producing energy, no?
- semi-extrinsic 7y agoUnfortunately heat pumps are not very good at producing power from small heat differences. In industrial plants, any waste heat stream that's below 100C is considered "low grade" and mostly used for heating office buildings etc.
- sigmaprimus 7y agoAhh, I did not know that. My experience is through my HVAC course where it only covered heating applications not power generation. Still the way a heat pump in a HVAC system works you turn a small temperature difference into larger difference through the "A" coil, essentially compressing the warm air to make it hot, but I guess this does not scale well.
- dwiel 7y agoI wonder if this could work in places with no ocean nearby just using rain water and rain water with added salt. Would you need an obscene amount of new salt/rain water?
- jandrese 7y agoThe energy cost of acquiring the salt would probably make it uneconomical. Plus you have to get rid of massive quantities of brackish water without a convenient ocean nearby. Maybe it could be used at the Great Salt Lake, but otherwise the options are limited.
- asdfman123 7y agoOne potential problem: you derive energy from converting freshwater to salt water. What do you do with all that salt water? You could cook it in the sun to evaporate out the water and start the process over again, but you've basically made a solar energy plant. The cool thing about using membranes near rivers and the ocean is it uses the ocean as your solar energy plant. You could also place this device near natural dead seas to produce power... but that's basically what the article is proposing.
- hockeybias 7y agoWhat sort of impact might such plants have on the various Pacific Rim Salmon species that need to return from the saltwater to their natal freshwater streams to spawn?
- driverdan 7y ago> If researchers can scale up the postage stamp–size membrane in an affordable fashion That's a huge "if." This type of development happens all the time and usually that "if" never comes true.
- logfromblammo 7y agoImagine how much power could be generated at the place where the Colorado River empties into the Gulf of California! -- If you didn't understand the implication, I think that in the future we will need the fresh water more than we will need to get power from making it more salty. The Colorado River has only rarely reached the ocean since 1960. It's like the Aral Sea. Human activity uses the entire river.
- TheSoftwareGuy 7y agoThis is exactly what I was thinking. There are those who believe that the next world wars will be fought over access to fresh water. This technology seems to make that future even more likely
- amluto 7y agoIt might make sense to use a technology like this to extract power at a sewage treatment plant.
- alistproducer2 7y agoCan anyone provide a link to the paper? I've googled and haven't been able to find anything.
- Teknoman117 7y ago2.6 TW/h with 100% global resource utilization, which amounts to 1/60th of the world's energy usage in 2013...
- bcatanzaro 7y agoIndustrializing our most environmentally sensitive areas by controlling all the water flow in wetlands... What could possibly go wrong?
- 8bitsrule 7y agoFollowing are original paper and phys.org article about (a similar project?) at EPFL in 2016. They use a molybdenum disulfide membrane. 'Single-layer MoS2 nanopores as nanopower generators' https://www.nature.com/articles/nature18593 https://www.nature.com/articles/nature18593 'Electricity generated with water, salt and a three-atoms-thick membrane' https://phys.org/news/2016-07-electricity-salt-three-atoms-thick-membrane.html https://phys.org/news/2016-07-electricity-salt-three-atoms-t...