Power Production From the Salt/Fresh Water Barrier

Maybe, but I'm a bit skeptical...

."The charge imbalance between the two sides was so strong that the researchers estimated a single square meter of the membrane—packed with millions of pores per square centimeter—could generate about 30 megawatt hours per year. That’s enough to power more than 400 homes."...

If my calculations are right, there are 365.25 x 24 = 8766 hours in a year. 30 MWhr/yr x 1yr/8766 hr = 3422 Watts. That's not going to power 400 homes.

sure it will. 3422 Watts/ 400 homes = 8.6 Watts/home. That is about what will be allowed Under the GND.

The average US home uses around 30kWh per day, or around 11MWh's a year.....so no

..."A megawatt hour (MWh) is equal to 1,000 Kilowatt hours (kWh). It is equal to 1,000 kilowatts of electricity used continuously for one hour. It is about equivalent to the amount of electricity used by about 330 homes during one hour."...

So if we had 30MWh for 400 homes , we would use that in about 1 day...

So, "for a day" should be added to the end of that quote...

"The charge imbalance between the two sides was so strong that the researchers estimated a single square meter of the membrane—packed with millions of pores per square centimeter—could generate about 30 megawatt hours per year. That’s enough to power more than 400 homes.( for a day)"

"The charge imbalance between the two sides was so strong that the researchers estimated a single square meter of the membrane—packed with millions of pores per square centimeter—could generate about 30 megawatt hours per year. That’s enough to power more than 400 homes.( for a day)"

Or roughly, one square meter for one home continuously, on the order of kilowatts per square meter.

3400 W/m² is pretty impressive. I've seen numbers for Reverse Electrodialysis (RED) on the order of 1 W/m². I wonder if BNNT (Boron Nitride Nanotubes) make that much difference.

http://www.msrjournal.com/article_22128_55a08d0ea436351ac9fbe6f7c2b8cd8a.pdf

Well I think that is the estimated potential energy available, they are still working on improving the efficiency of the membrane conversion, a sort of breakthrough is what prompted this article it seems....

...."That gave the Rutgers team the lever it was looking for. 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. That power boost, Shan says, is likely because the BNNTs they used are narrower, and thus do a better job of excluding negatively charged chloride ions.

And they suspect they can do even better. “We’re not exploiting the full potential of the membranes,” Cetindag says. That’s because only 2% of the BNNTS were actually open on both sides of the membrane after the plasma treatment. Now, the researchers are trying to increase number of open pores in their films—which could one day give a long-sought boost to advocates of blue energy."...

https://www.electrochem.org/what-is-blue-energy

This is what osmotic energy has been up till now....this from 2016

https://www.marketwatch.com/story/this-breakthrough-in-blue-energy-could-change-the-world-2016-08-04

A figure of <...3400 W/m²...> is over twice the rate of insolation. Couldn't one use sunshine, first, and save all the technicalities of the <...Salt/Fresh Water Barrier...>?

This tech will probably be used in conjunction with other technologies as part of a system...When the sun don't shine the water still flows...

A figure of <...3400 W/m²...> is over twice the rate of insolation.

I don't see how these are connected. One is the amount of sunshine per square meter and the other is the estimated amount of power (ion current x voltage) per square meter of the BNNT membrane that can be obtained. It's a measure of the quality of the membrane.

The energy obtained from osmotic power does obtain from used sunshine (as do many other sources). Part of the sunlight's energy separates water vapor from the salty ocean, a decrease in entropy. This energy is reclaimed by the increase of entropy in a reverse electrodialysis unit. The ion flow between saltwater and freshwater is captured and converted to electricity, similar to what happens in a battery.

You might fill ponds (salinas) with seawater and let the sun evaporate some of the water, increasing the salinity before feeding it into a reverse electrodialysis plant with river water, increasing power production with the energy provided by the sunlight. (Is this what you were driving at? )

It's about the use area and the technology needed to make use of the area. These days, solar capture is relatively simple in comparison with that being advocated. The W/m² criterion can be seen as an empirical correlation between the two, nothing more.

You're right, solar is a mature technology, while "Blue Energy" is far from economical. I recall seeing the figure 30x the price of an equivalent conventional power plant.

The good news is that there is a large amount of energy available and big room for improvement of the membranes. There is a lot of engineering work to be done, but if it can be made economical, it will be there 24 hours/day regardless of whether the sun is shining or the wind is blowing, and it will never run out.

I think it's a dark horse worth pursuing.

Add "maybe" to your footnote SE. I am always skeptical when these silly claims are made. The power consumption of one home is purely location dependent so is an irrelevant measure in these blogs.

Sort of reverse osmosis in reverse which would make it osmosis but no mention is made of the pressure and temperature required to generate and as we know reverse osmosis takes a lot of energy in pumping to make pure water.

A bit like the claims of off grid people around here that they run their whole home on solar! "One appliance at a time".

Well this research is still in its very early stages it doesn't hurt to follow along and I'm sure nobody here thinks this is going to replace solar or wind efforts any time soon....but we all do like to keep up with what's happening out there and I think everybody here realizes how difficult it is to bring forth a new technology like this, the methods used are interesting and might apply to other product development efforts, you never know....coating nano tubes and using magnetic fields to align them in certain formations, plasma scraping, might apply to other technologies as well....

"The charge imbalance between the two sides was so strong that the researchers estimated a single square meter of the membrane—packed with millions of pores per square centimeter—could generate about 30 megawatt hours per year. That’s enough to power three homes."

"*Correction, 6 December, 11:30 a.m.: This article has been corrected to accurately reflect how many homes a blue membrane could power and how much energy per area it produces"

https://www.sciencemag.org/news/2019/12/rivers-could-generate-thousands-nuclear-power-plants-worth-energy-thanks-new-blue

Sounds interesting.............what's the downside? I remember hearing the phrase "electricity too cheap to meter". Never experienced it though after I started paying my own electric bill.

Years ago I read where the Salton Sea was becoming extremely toxic because of lithium from drainage from irrigation runoff.

With lithium in such high demand,why hasn't someone started mining it from the Salton Sea?

Very good point! And it might be that doing so would even provide a means of cleaning up that area as far as toxic wastes go. The Salton Sea if I remember correctly from when I lived in California was primarily caused by Inland salt not having any way to leave, so that it just gradually evaporated and then we wound up with a salt toxic mess. But the lithium is a new thing, as far as I understand. But with the Advent of lithium ion batteries and the lithium Polymer batteries, lithium obviously is becoming a much more important element than it used to be. Whether it will stay that way or not remains to be seen because battery technology and chemistry keeps changing. But it will be interesting to watch weather someone with the money and the know how gets busy mining that, and finds enough of it to be worth doing. And wouldn't it be nice, even the double benefit, if power production using the membranes, turned out to be part of the process of recovery of the lithium?

..."Companies have tried for decades to extract lithium from the super-heated underground fluid used for energy generation at the southern end of the Salton Sea, home to one of the world's most powerful natural geothermal hot spots.Oct 14, 2019"...

Another thought comes to me about thermal inversion that occurs in some salt water environs,where the heat sinks to the bottom,and the cold stays on top.

Normally,the heat would rise to the top,but when the salinity reaches a certain percentage,the weight of the hot high salinity water carries it to the bottom.

This Heat accumulates in some conditions to near boiling,but the pressure and saline solution suppresses the boiling point

Seems like it would be a good source of heat for boiling ammonia or other condensables to produce energy.

Any thoughts on this?

Finding such a source close to demand is the trick....Maybe volcanic vents could be used to power floating cities sometime in the future...Just need to be able to go underwater far enough to avoid the storms....

..."Project permitting, engineering, financing, and implementation are underway. Next steps include securing over $350 million in funding for project development and construction.

When in full operation, estimated to be early 2023, Project ATLiS is expected to generate over $25 million per year in direct economic benefits to the local community including employee salaries, royalties, utilities, and taxes. In addition with much of the materials, supplies and services being sourced locally, the annual maintenance program will infuse $60 million each year.

According to the U.S. Department of Transportation, over half of the cars on the roads are projected to be electric by 2040. The lithium industry will need to grow by an order of magnitude in production volume to support this growth. "...

http://www.thinkgeoenergy.com/minerals-arm-of-energysource-successful-in-lithium-extraction-from-geothermal/

Here is a plot that shows how much energy is theoretically available in MJ between 1m³ of concentrated NaCl solution (horizontal axis) and 1m³ dilute solution (vertical axis).

"According to the Gibbs free energy of mixing [3] the amount of the energy that theoretically can be generated mixing 1 m³ of river water with the identical sea water volume is 1.7 MJ or even 2.5 MJ when mixed with a large surplus of sea water [4] and it is possible to convert this potential energy into useful electricity with an 85% efficiency [5] (Figure 1.2)."

"Figure 1.2 Theoretically available amount of energy (MJ) from mixing 1m³ of a diluted and 1m³ of a concentrated sodium chloride solution (T = 293 K) [3]."

https://core.ac.uk/download/pdf/53303122.pdf

So maybe .5 kWh per cu meter...that's not bad...not much compared to a hydroelectric dam...

Freshwater from rivers don't readily mix with seawater but float on top. Here is an interesting picture I ran across, showing a reflection on the interface between fresh and saltwater.

"That top section isn’t the surface. It’s fresh water. It looks magical and is undoubtedly one of the most amazing natural wonders on Earth. It’s phenomenal."

https://www.quora.com/What-happens-where-fresh-water-and-salt-water-meet

I wonder if you might check your units again. The power function in the calculator seems to be in cu m per second, so to get kWh would need to run for 3600 seconds.

I'm a little jealous though at the moment. Some of our large rivers over here are running at less than a fire hose. Manning River at Killawarra bridge currently running less than 1ML per day for instance.

The amount of power available from temperature differential is fairly large.I wonder how much water depth is required to get a thermal inversion with saturated salt water?

Could it be done on a small scale with a swimming pool with a bubble-wrap type cover with a volume of say 30,000 gallons?

Just wondering.

https://engineering.stackexchange.com/questions/3195/how-do-i-calculate-the-density-of-seawater-at-different-temperatures

http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/seawater.html

https://www.open.edu/openlearn/science-maths-technology/the-oceans/content-section-3.2

Saw papers on similar some years ago. The concept was to place the constructed "generation units" near the ocean boundaries of rivers and such, close to the intertidal zone.

Conceptually, the "fresh" river water was already destined to mix into the ocean, so they intended to use the potential to create pressure from essentially osmosis to create power.

It's pleasing to see this still advancing. Heck, if they get the energy density sorted, it might even become the "battery" of the future with RO "banking" energy and FO recovering it.

I seem to remember that previous paper discussing FORO where non-potable water through FO provided the power to achieve RO yield of potable water and the intermediate concentrate was returned to the FO membrane in a closed cycle. Dealing with contaminants in the primary solution that were essentially poisonous. They were examining yield where the FO membrane was extremely fine but the intermediate "salt" was atomically large and so the RO membrane could have larger pore sizes and thus lower extraction energy.

It looks like the Dutch have been operating a pilot "Blue Energy" power plant for about 5 years now.

"Dutch King Willem-Alexander put the world's first blue-energy RED power plant to use on 26 November.

The plant is located on the closure dam Afsluitdijk, the Netherlands, and produces electricity directly from the difference in salt concentration in the surface water on each side of the dam.

The pilot plant is operated by RedStack, the company that developed the technology based on reverse electro dialysis (RED), using special designed membranes.

Blue Energy is a joint development of Redstack, FujiFilm and water technology knowledge institute Wetsus.

The Blue energy pilot plant mixes fresh and salt surface water.

Technical feasibility
Theoretically, with 1m3/s river water and an equal amount of sea water approximately 1 MW of renewable electricity can be recovered.

The pilot plant on the Afsluitdijk is to produce 50 kW blue-energy per hour and will show the technical feasibility in real life conditions using fresh IJsselmeer water and salt water from the Wadden Sea."

more...

https://web.archive.org/web/20160416092205/http://www.dutchwatersector.com/news-events/news/12388-dutch-king-opens-world-s-first-red-power-plant-driven-on-fresh-salt-water-mixing.html

So if I'm reading this correctly that would be 50 kWh from 3600 cubic meters or about 14 watts per cubic meter compared with potentially 500 watts with the new tech....quite a leap forward...

The numbers are confusing on this topic, which makes it difficult to make comparisons.

The amount of theoretical energy is in megaJoules per cubic meter (MJ/m³), depending on the salinity difference. The amount of theoretical power is in MW, obtained by multiplying by the flow rate (m³/sec).

One of the "bottlenecks", of course, is the membrane, which is rated in power/area, with the BNNT membrane about 3400 W/m². The ion current density would be this power density divided by the cell voltage (not specified).

The Dutch power plant produces 50KW with a flow rate of 1 m³/s (if I read it right), but we don't know the area of the membranes and so cannot compare with the BNNT membrane. The number quoted in the article was "theoretically 1MW" with a 1 m³/s flow rate (1 MJ/m³ energy density), which would indicate that 5% of the available energy is captured with whatever area of membranes they are using.

https://web.archive.org/web/20160416092205/http://www.dutchwatersector.com/news-events/news/12388-dutch-king-opens-world-s-first-red-power-plant-driven-on-fresh-salt-water-mixing.html

I guess we just wait for it to play out, but can reasonably assume that there is some potential there worth pursuing.....certainly the cost would have to be fairly low, and that's an open question....but the possibility of other applications might prove the most practical application...

..."

Iontronics and medical applications

“We need a way to approach the human body with electrochemistry, and I think iontronics could be that way,” Chung says. “This allows us to interface between our nervous system and a computer or artificial system through a seamless device.”

Iontronics also draw many similarities to electronics, but instead of being driven by electrons, iontronics are driven by ions. However, the power tends to be much lower than that of conventional electronics, which makes them impractical for devices such as smartphones and computers. Because iontronics function on the same principals as the human nervous system and are able to emit low-powered electrical fields, Chung believes the real potential for this technology lies in patch-based drug delivery systems.

While these medical patches for drug delivery are not new, applying the iontronic technology would significantly reduce the delivery speed as well as make the overall experience safer for patients.

“By using the iontronics and the salt gradient, the power generated is very low but enough so that we can efficiently enhance drug delivery through the skin,” Chung says. “This way, we can successfully deliver drugs that would typically be ingested or invasively injected. The former methods often cause side effects, but this patch would be a much safer method of drug delivery.”

Think of Alzheimer’s disease, where memory loss and mental function dissipate as neurons in the brain die. While neurons cannot be revived, there are steps that can be taken to supplement artificial additives to help slow the effects of the disease.

“I think iontronic devices could one day be implanted in a brain as part of your body,” Chung says."..

..."

Future of water splitting

But potential applications don’t end with drug-delivery patches. Chung believes that his work in blue energy could mean big things for water splitting applications, potentially leading to the practical and efficient splitting of hydrogen and oxygen to produce energy.

Many researchers in the scientific community have been focusing on water splitting for its potential in renewable energy, but there have been barriers along the way.

“People want to use sunlight to generate hydrogen and oxygen. The problem is that it’s not easy to find the appropriate semiconductor that can harvest enough light and generate a high enough potential to split water,” Chung says. “People working on these devices are suffering from lack of candidates for semiconductors.”

By combining the current semiconductors used in these applications with a salt gradient power source, the necessary voltage could be achieved to do water splitting. Efficient water splitting techniques could open the door to solar fuels and potential shift the energy infrastructure."...

https://www.electrochem.org/what-is-blue-energy