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Salt Water Electricity?

 
pollinator
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i saw a show on Netflix (forces of nature- episode2 Elements)last night about how when salt water mixes with fresh water it makes energy. at the end they even do and experiment and shows how to light up a bulb.
I googled and found you can light up a bulb with just salt water.
so my questions are:
1) is anyone using salt water or a mix to make electric for off grid?
2)any ideas on how one could go about doing this?

 
pollinator
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Hmm. My bullshit detector went into the red on this one. Trivially simple to put a battery into the base of these bulbs and either a) wire in a small pressure switch that never gets shown to the camera, or b) edit the video right at the point of dropping the bulb into the "apparatus" when it lights up. Because what they're showing can't work.

These are bulbs designed to screw into a standard household socket and run off mains AC voltage, either 120 or 240 depending on what country you're in. To generate AC power, you either need a coil, a magnet, and movement at a steady frequency, or you need some electronic means of taking a DC power source and manufacturing an alternating current. The simple way to do this is with something that spins, and this is why nearly all power generation is done by turbines of some sort. I don't see anything moving in the plastic cup, nor do I see an inverter, so that means something is fishy.

The second thing I note is that the contacts on the bulb don't get connected to separate conductors...they both get immersed in the salt water. Salt water is a pretty good conductor, so this is about the same as running a single wire to both contacts, which means that there is no potential different between them, hence no circuit and no way for current to pass through the part of the bulb that does the business.

So, in a word: Nope. It's a hoax. They seem to have quite a supply of these videos, all variations on the theme.
 
bernetta putnam
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yes there seems to be a few ways of doing this in the videos even with a speaker ...

anyone actually tried this?
 
bernetta putnam
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looking around some more it seems that there is a battery used. but is the salt water recharging this battery? just like other sources we use do?
here's an article I found, which makes it seem so.

https://www.treehugger.com/clean-technology/salt-water-lamp.html
 
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https://www.redstack.nl/en is a Dutch company developing reverse electrodialysis (RED) technology.
A detailed explanation is at https://www.redstack.nl/en/technology/reverse-electrodialysis-red
 
Phil Stevens
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Osmotic pressure is certainly a gradient that could be exploited, but I wonder about how much water you'd need in order to do this on a scale that would power a modest household.
 
bernetta putnam
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Phil Stevens wrote:Osmotic pressure is certainly a gradient that could be exploited, but I wonder about how much water you'd need in order to do this on a scale that would power a modest household.



exactly I was wondering just how much salt water you would need to charge a car battery or if it would even work...lol
or at least run the lights in a small house.
 
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As Phil Stevens noted above, the linked video is a hoax using an LED lamp with a built-in battery, designed to automatically switch to internal battery power if grid power fails. I have a box of them in my garage.


When removed from the socket, these bulbs can be lit by electrically connecting the center terminal to the metal base. Manufacturers provide a handy cap that screws onto the base and has a switch inside that makes the connection. The caps even have a hook so you hang the bulb upside-down and use it as a lantern. Manufacturers also note that you can light the bulb by simply pressing a piece of aluminum foil (or a damp cloth, or even a wet finger) against the base.


In the video, immersing the base of the bulb in salt water provides the needed connection to light the bulb. Plain old tap water would work just as well. It would be amusing if the video showed what happens when the bulb is removed from the cup -- it stays lit until you break the connection by wiping the salt water off of the base.


However, the reference to using salt water to construct batteries is correct. Just about any ionized solution can be used as the electrolyte in a battery. Inserting copper and zinc strips into a lemon, or even a potato, creates a functional battery. Salt water is a pretty benign electrolyte, but it's easily available and works for the low-power needs given in the reference. For high power, lead-acid batteries work great because sulfuric acid is *viciously* ionized.
 
pollinator
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Dc Stewart wrote:In the video, immersing the base of the bulb in salt water provides the needed connection to light the bulb. Plain old tap water would work just as well. It would be amusing if the video showed what happens when the bulb is removed from the cup -- it stays lit until you break the connection by wiping the salt water off of the base.


At 7:58 in the video it does show the bulb being removed from the water, and as you said, it stays lit. It happens pretty fast in the video, so YouTube's slow motion feature comes in handy.
 
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Tons of articles about this. Even uncle sam has some.... can be run on piss!

Found these several years ago. Solar panels are much better for domestic purposes, but in a bunker a piss charger would be great.

http://www.survivalcampingstore.com/gmag-battery-charger
 
pioneer
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I found this interesting.  I may add a small saltwater sealed pool / pond to my building ideas.

https://phys.org/news/2019-07-ultra-thin-layers-rust-electricity.html
 
pollinator
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Hi Catherine. Welcome to permies!

Great find, by the way. I love the idea of an iron oxide nanoparticle coating for iron piers, for instance. It would be possible to adapt seaside architecture to changing sea levels, and at the same time, potentially generate a sizeable portion of the structure's own power.

I also like the fact that this is essentially harnessing the kinetic power of waves without any moving parts, which suggests that it might be able to operate over the long-haul.

-CK
 
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