5 ms·

New saltwater electrical generation could power submarines or medical devices

82 points by jonbaer 7y ago

regularfry 7y ago
Submarines sound like a stretch to me - the motion of the water past the hull would be driven by the main engine, so it would just be reclaiming some of that energy (and inducing drag into the bargain). Where I can see it potentially working is on Slocum gliders, where the main motive force comes from gravity. Whether you'd get enough watts off the available surface area to be worth the added drag, though... different question.
- eloff 7y ago
  I think the idea is to run the process in reverse - run an electrical current through the metal to push against the ions in the water. No idea how practical it would be.
  - masklinn 7y ago
    Not very, at 2kW per 100sqm of material, covering an attack sub in this material would give you the power of a compact car's motor: approximated to a cylinder 12m by 110, USS Seawolf has a lateral surface of under 4200sqm, 42 panes, 84kW. The 2018-2019 Kia Soul EV has a 81.4kW engine.
    - clort 7y ago
      I see you've posted this approximate figure and its comparison to a car three times already, but the Kia figure is irrelevant. The relevant comparision is the required power to push the USS Seawolf forward and what speed can you get with 84kW? I myself can push a 6500Kg boat although not as fast as the built-in 10kW engine, admittedly. Don't forget that it is a sub and silent running is likely way more valuable than fast running (nobody is saying they can't have two methods of propulsion) Also, I don't know anything about this USS Seawolf - is it a nuclear sub? IIRC the problem with them is that the pumps cooling the atomic core can't be shut down, meaning there is always detectable sound. Would a hose with this material on the inside be able to pump cooling water silently? Don't forget that the 'pump' in that case could be almost the entire length of the sub..
      - masklinn 7y ago
        > I see you've posted this approximate figure and its comparison to a car three times already, but the Kia figure is irrelevant. It's very relevant as it gives a sense of scale of the issue and how little power is actually produced. > The relevant comparision is the required power to push the USS Seawolf forward and what speed can you get with 84kW Since you're apparently checking all my comments you've likely seen Gotland's 2x75kW AIP gives it a top speed of 5kn. These 85kW would be a smidge above half that on a submarine about 6 times the weight. The relationship is probably somewhat non-linear but I'd say the result would be around "geriatric pacing". > Don't forget that it is a sub and silent running is likely way more valuable than fast running (nobody is saying they can't have two methods of propulsion) You could get about the same effect by just shutting down propulsion entirely. > Also, I don't know anything about this USS Seawolf - is it a nuclear sub? IIRC the problem with them is that the pumps cooling the atomic core can't be shut down, meaning there is always detectable sound. That doesn't seem to have any relevance to my point that this tech doesn't seem able to actually provide propulsion for a sub'. > Would a hose with this material on the inside be able to pump cooling water silently? Don't forget that the 'pump' in that case could be almost the entire length of the sub.. You do realise there's other shit in a sub than just reactor cooling systems right?
      - dogma1138 7y ago
        The reactor on the Seawolf has a shaft horsepower output of 45,000 shp or 34 MW. So yeah 80KW won’t be enough to power the lights.
      - jabl 7y ago
        > Also, I don't know anything about this USS Seawolf See https://en.wikipedia.org/wiki/USS_Seawolf https://en.wikipedia.org/wiki/USS_Seawolf , presumably we're talking about the fourth (and current one). Yes, it's nuclear powered. > IIRC the problem with them is that the pumps cooling the atomic core can't be shut down, meaning there is always detectable sound. AFAIK current generation US and Russian (and presumably other navies operating nuclear subs too) nuclear subs can shut down the primary coolant pumps and rely on convection at low power. As long as they're cruising along at low speed they can be very quiet.
    - jkqwzsoo 7y ago
      It’s not 2 kW/100 m^2. It’s 2-5 kW per a stack of 100 double-sided 10 m x 10 m squares. That’s 2 kW/20000 m^2.
      - masklinn 7y ago
        Ah, I'd missed that wrinkle, so it's completely useless for the use case of sub propulsion as covering USS Seawolf in this material would produce an amazing 420W, or about what you'd get if you put 5 sailors on generator bikes.
  - jerf 7y ago
    The practicality is borderline: https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive#Marine_propulsion https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive#Mari... It's not completely infeasible, but it's beaten by a lot of other things.
gibolt 7y ago
This sounds like a quite promising generation method. They quote 10x10 meter area with 100 layers as potentially generating 2-5 kwh. It fails to mention if water flow can be continuous or has to be droplets and flow speed/salt content required for that generation. Running in reverse to generate propulsion is also mentioned. Covering a submarine and just moving a thin layer of water out of the way to move forward is a super interesting application.
- clort 7y ago
  Also, they are worried about slime build up. but in the case of using that as a motor rather than generator, I wonder if that would be an issue at all, or if once activated it would just push the slime off..?
  - gibolt 7y ago
    It is a fun thought. Probably far less efficient and slower than current propulsion, but no moving parts is a big plus. Small drones that patrol the ocean for long times would be a cool application. Move a bit until the batteries are nearly depleted, float around to recharge, and then resume moving.
    - stevenhubertron 7y ago
      Silent operation is always a big plus for subs that want to stay hidden.
Areading314 7y ago
kWh are units of energy, not power. This method is of no interest if it takes years to generate those kwh! Also those films will rust completely off the slide in a matter of hours. Edit in the case of iron, a 20nm film would fully corrode in about 20 min using a corrosion rate of 0.55mm/y
- t0mbstone 7y ago
  "Energy is the total amount of work done, and power is how fast you can do it. In other words, power is energy per unit of time. Power is watts. Energy is watt-hours."
  - agumonkey 7y ago
    energy is total change, power is change over time
kryogen1c 7y ago
>10-meter-by-10-meter >as much as 2-5 kilowatt-hours of electrical power >could power submarines Not really. I don't know about non-nuclear subs, but this is several orders of magnitude too low to be space effective for use on subs. I cant find any official public info, but suffice it to say subs run closer to 2MWs than 2KWs
- SamBam 7y ago
  I believe the submarine use-case is supposed to be the other way around: > and even (running the process in reverse) a silent propulsion system for boats or submarines. So the submarine would have on-board power generation that powers this, not that this would provide the power to the submarine.
  - masklinn 7y ago
    > and even (running the process in reverse) a silent propulsion system for boats or submarines. 10x10m for 2kW is 2kW per 100sqm. That's pretty much nothing, propulsion-wise. A seawolf-sized sub (108m long and 12m wide) covered in this material would produce about 85kW. That's around the powertrain of a modern compact / city car: the nissan leaf's motor is 80kW.
    - SamBam 7y ago
      > would produce about 85kW It's not meant to produce energy in this case. That's what I'm saying.
      - masklinn 7y ago
        It would convert electrical energy to mechanical, acting like an engine (and drivetrain). An 85kW engine. Which is — as I noted — about what you'd find on a compact EV (that's about 115hp).
        ska 7y ago
        Or for another point of reference, about what a fast-ish medium sized motorcycle of around 400lb/180kg produces.
leoedin 7y ago
The power generation potential given is in units which make it almost useless. A kWh is a unit of energy, converted into a frame of reference more useful than the joule. Saying that a device can generate 2 kWh doesn't really tell you much - it could generate that in 10 seconds (good) or 10 years (bad). I think the quoted figure was meant to be in kW - a unit of power, which is a much more useful piece of information. I looked at the original paper (here: https://arxiv.org/pdf/1907.13170.pdf https://arxiv.org/pdf/1907.13170.pdf) but couldn't find any reference to the 2kWh quoted from the researchers. If the suggestion is correct, and a 10mx10m panel can generate 2kW, then there's some really interesting potential applications. History has shown that the path towards robust technology is normally by making things solid state - vacuum tubes to transistors, solar collectors to solar panels, even helicopters to drones all benefited from a huge decrease in mechanical complexity.
- andy_ppp 7y ago
  Not to mention salt water corrodes almost everything that comes into contact with it...
  - Zenst 7y ago
    One aspect about salt water corrosion/rust is that it pulls off the oxygen and releases the hydrogen, albeit at a very low level, but always seems like some way to produce hydrogen without adding any power. Quick dig shows this is one area of research that is ongoing.
    - leoedin 7y ago
      But then you've basically got a machine which turns iron into iron oxide and hydrogen, which you'll then have to put loads of energy back into to return to raw iron again. At best its an energy storage method. I can't imagine it's got a very good round trip efficiency though.
- thaumaturgy 7y ago
  It might be a nice add-on for desal plants, which already have plenty of waste saltwater getting pumped around. Someday.
t0mbstone 7y ago
So the trick would be to get a vat of salt water with these sheets in them, then set up an electric pump to circulate the salt water across the sheets. Power the electric pump using the generated electricity and... tada! Free energy! :D
- outworlder 7y ago
  Right. Reductio at perpetuum mobile proves this idea doesn't work.
pitaj 7y ago
Reminds me of two works of science fiction: 20,000 Leagues Under the Sea and Red October
ummonk 7y ago
How is running this in reverse different from a magnetohydrodynamic drive?
colechristensen 7y ago
Bad title, it could be used to generate power when it is fixed and there is a source of moving water (tides, fixed implanted medical devices) or generate force for something moving through water (submarine), but not both at the same time. Moving water generates electrical currents, this is a pretty standard physics demonstration and how lightning works. This is perhaps a novel way of utilizing that property with thin conductive films.
driverdan 7y ago
> We’ve got a device that works, and we’ve got a number of ways we can run it. But we have not, for example, yet lit up a lightbulb. IEEE is really hurting their image with these poorly written clickbait headlines. While an interesting idea if it can't even produce enough power for a lightbulb it's not going t obe powering submarines or medical devices anytime soon.

82 points by jonbaer 7y ago

Submarines sound like a stretch to me - the motion of the water past the hull would be driven by the main engine, so it would just be reclaiming some of that energy (and inducing drag into the bargain). Where I can see it potentially working is on Slocum gliders, where the main motive force comes from gravity. Whether you'd get enough watts off the available surface area to be worth the added drag, though... different question.

eloff 7y ago
I think the idea is to run the process in reverse - run an electrical current through the metal to push against the ions in the water. No idea how practical it would be.
- masklinn 7y ago
  Not very, at 2kW per 100sqm of material, covering an attack sub in this material would give you the power of a compact car's motor: approximated to a cylinder 12m by 110, USS Seawolf has a lateral surface of under 4200sqm, 42 panes, 84kW. The 2018-2019 Kia Soul EV has a 81.4kW engine.
  - clort 7y ago
    I see you've posted this approximate figure and its comparison to a car three times already, but the Kia figure is irrelevant. The relevant comparision is the required power to push the USS Seawolf forward and what speed can you get with 84kW? I myself can push a 6500Kg boat although not as fast as the built-in 10kW engine, admittedly. Don't forget that it is a sub and silent running is likely way more valuable than fast running (nobody is saying they can't have two methods of propulsion) Also, I don't know anything about this USS Seawolf - is it a nuclear sub? IIRC the problem with them is that the pumps cooling the atomic core can't be shut down, meaning there is always detectable sound. Would a hose with this material on the inside be able to pump cooling water silently? Don't forget that the 'pump' in that case could be almost the entire length of the sub..
    - masklinn 7y ago
      > I see you've posted this approximate figure and its comparison to a car three times already, but the Kia figure is irrelevant. It's very relevant as it gives a sense of scale of the issue and how little power is actually produced. > The relevant comparision is the required power to push the USS Seawolf forward and what speed can you get with 84kW Since you're apparently checking all my comments you've likely seen Gotland's 2x75kW AIP gives it a top speed of 5kn. These 85kW would be a smidge above half that on a submarine about 6 times the weight. The relationship is probably somewhat non-linear but I'd say the result would be around "geriatric pacing". > Don't forget that it is a sub and silent running is likely way more valuable than fast running (nobody is saying they can't have two methods of propulsion) You could get about the same effect by just shutting down propulsion entirely. > Also, I don't know anything about this USS Seawolf - is it a nuclear sub? IIRC the problem with them is that the pumps cooling the atomic core can't be shut down, meaning there is always detectable sound. That doesn't seem to have any relevance to my point that this tech doesn't seem able to actually provide propulsion for a sub'. > Would a hose with this material on the inside be able to pump cooling water silently? Don't forget that the 'pump' in that case could be almost the entire length of the sub.. You do realise there's other shit in a sub than just reactor cooling systems right?
    - dogma1138 7y ago
      The reactor on the Seawolf has a shaft horsepower output of 45,000 shp or 34 MW. So yeah 80KW won’t be enough to power the lights.
    - jabl 7y ago
      > Also, I don't know anything about this USS Seawolf See https://en.wikipedia.org/wiki/USS_Seawolf https://en.wikipedia.org/wiki/USS_Seawolf , presumably we're talking about the fourth (and current one). Yes, it's nuclear powered. > IIRC the problem with them is that the pumps cooling the atomic core can't be shut down, meaning there is always detectable sound. AFAIK current generation US and Russian (and presumably other navies operating nuclear subs too) nuclear subs can shut down the primary coolant pumps and rely on convection at low power. As long as they're cruising along at low speed they can be very quiet.
  - jkqwzsoo 7y ago
    It’s not 2 kW/100 m^2. It’s 2-5 kW per a stack of 100 double-sided 10 m x 10 m squares. That’s 2 kW/20000 m^2.
    - masklinn 7y ago
      Ah, I'd missed that wrinkle, so it's completely useless for the use case of sub propulsion as covering USS Seawolf in this material would produce an amazing 420W, or about what you'd get if you put 5 sailors on generator bikes.
- jerf 7y ago
  The practicality is borderline: https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive#Marine_propulsion https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive#Mari... It's not completely infeasible, but it's beaten by a lot of other things.

gibolt 7y ago

This sounds like a quite promising generation method. They quote 10x10 meter area with 100 layers as potentially generating 2-5 kwh. It fails to mention if water flow can be continuous or has to be droplets and flow speed/salt content required for that generation. Running in reverse to generate propulsion is also mentioned. Covering a submarine and just moving a thin layer of water out of the way to move forward is a super interesting application.

clort 7y ago
Also, they are worried about slime build up. but in the case of using that as a motor rather than generator, I wonder if that would be an issue at all, or if once activated it would just push the slime off..?
- gibolt 7y ago
  It is a fun thought. Probably far less efficient and slower than current propulsion, but no moving parts is a big plus. Small drones that patrol the ocean for long times would be a cool application. Move a bit until the batteries are nearly depleted, float around to recharge, and then resume moving.
  - stevenhubertron 7y ago
    Silent operation is always a big plus for subs that want to stay hidden.

Areading314 7y ago

kWh are units of energy, not power. This method is of no interest if it takes years to generate those kwh! Also those films will rust completely off the slide in a matter of hours. Edit in the case of iron, a 20nm film would fully corrode in about 20 min using a corrosion rate of 0.55mm/y

t0mbstone 7y ago
"Energy is the total amount of work done, and power is how fast you can do it. In other words, power is energy per unit of time. Power is watts. Energy is watt-hours."
- agumonkey 7y ago
  energy is total change, power is change over time

kryogen1c 7y ago

>10-meter-by-10-meter >as much as 2-5 kilowatt-hours of electrical power >could power submarines Not really. I don't know about non-nuclear subs, but this is several orders of magnitude too low to be space effective for use on subs. I cant find any official public info, but suffice it to say subs run closer to 2MWs than 2KWs

SamBam 7y ago
I believe the submarine use-case is supposed to be the other way around: > and even (running the process in reverse) a silent propulsion system for boats or submarines. So the submarine would have on-board power generation that powers this, not that this would provide the power to the submarine.
- masklinn 7y ago
  > and even (running the process in reverse) a silent propulsion system for boats or submarines. 10x10m for 2kW is 2kW per 100sqm. That's pretty much nothing, propulsion-wise. A seawolf-sized sub (108m long and 12m wide) covered in this material would produce about 85kW. That's around the powertrain of a modern compact / city car: the nissan leaf's motor is 80kW.
  - SamBam 7y ago
    > would produce about 85kW It's not meant to produce energy in this case. That's what I'm saying.
    - masklinn 7y ago
      It would convert electrical energy to mechanical, acting like an engine (and drivetrain). An 85kW engine. Which is — as I noted — about what you'd find on a compact EV (that's about 115hp).
      - ska 7y ago
        Or for another point of reference, about what a fast-ish medium sized motorcycle of around 400lb/180kg produces.

leoedin 7y ago

The power generation potential given is in units which make it almost useless. A kWh is a unit of energy, converted into a frame of reference more useful than the joule. Saying that a device can generate 2 kWh doesn't really tell you much - it could generate that in 10 seconds (good) or 10 years (bad). I think the quoted figure was meant to be in kW - a unit of power, which is a much more useful piece of information. I looked at the original paper (here: https://arxiv.org/pdf/1907.13170.pdf https://arxiv.org/pdf/1907.13170.pdf) but couldn't find any reference to the 2kWh quoted from the researchers. If the suggestion is correct, and a 10mx10m panel can generate 2kW, then there's some really interesting potential applications. History has shown that the path towards robust technology is normally by making things solid state - vacuum tubes to transistors, solar collectors to solar panels, even helicopters to drones all benefited from a huge decrease in mechanical complexity.

andy_ppp 7y ago
Not to mention salt water corrodes almost everything that comes into contact with it...
- Zenst 7y ago
  One aspect about salt water corrosion/rust is that it pulls off the oxygen and releases the hydrogen, albeit at a very low level, but always seems like some way to produce hydrogen without adding any power. Quick dig shows this is one area of research that is ongoing.
  - leoedin 7y ago
    But then you've basically got a machine which turns iron into iron oxide and hydrogen, which you'll then have to put loads of energy back into to return to raw iron again. At best its an energy storage method. I can't imagine it's got a very good round trip efficiency though.
thaumaturgy 7y ago
It might be a nice add-on for desal plants, which already have plenty of waste saltwater getting pumped around. Someday.

t0mbstone 7y ago

So the trick would be to get a vat of salt water with these sheets in them, then set up an electric pump to circulate the salt water across the sheets. Power the electric pump using the generated electricity and... tada! Free energy! :D

outworlder 7y ago
Right. Reductio at perpetuum mobile proves this idea doesn't work.

pitaj 7y ago

Reminds me of two works of science fiction: 20,000 Leagues Under the Sea and Red October

ummonk 7y ago

How is running this in reverse different from a magnetohydrodynamic drive?

colechristensen 7y ago

Bad title, it could be used to generate power when it is fixed and there is a source of moving water (tides, fixed implanted medical devices) or generate force for something moving through water (submarine), but not both at the same time. Moving water generates electrical currents, this is a pretty standard physics demonstration and how lightning works. This is perhaps a novel way of utilizing that property with thin conductive films.

driverdan 7y ago

> We’ve got a device that works, and we’ve got a number of ways we can run it. But we have not, for example, yet lit up a lightbulb. IEEE is really hurting their image with these poorly written clickbait headlines. While an interesting idea if it can't even produce enough power for a lightbulb it's not going t obe powering submarines or medical devices anytime soon.