Electrified Water: Feasibility and Applications

[callie123]

I'm working on a Scifi novel, and trying to make it somewhat...scientific! Any advice is appreciated.

Here's my question: I'd like to write about a situation where a body of water is purposefully kept under electric charge for years on end. This body of water would vary in size and depth, but it'd basically be stream-sized, and surrounded by less-conductive material (rock). The stream would probably last a few miles, and would have plenty of conductive elements in it (it's not pure water). I'm not sure what amount of voltage would be going through it. But enough to prevent badly insulated watercraft (metal or thin wooden boats) from crossing.

Is this feasible? Or would the high amount of electricity turn all the water to vapor? I've tried to study this myself, and now I'm confused as to whether this would create electrolysis and cause the water to break down.

 

[berkeman]

Welcome to the PF.

If the main reason for keeping the water in the stream charged is to prevent boats from crossing, it probably won't work as you have constructed it so far. You need a difference in voltage locally, so that current would flow through any boat trying to cross. Just charging up the stream with respect to the Earth does not create a small local voltage difference that will cause a current to flow through a boat. It's much like a bird sitting on a high voltage wire -- it can sit there just fine, but it it were to somehow bridge between two adjacent wires (where there is the high voltage between them), it would be toast.

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjV2vSwm-HgAhXbJTQIHYIcBi0QjRx6BAgBEAU&url=https://spectrum.ieee.org/energywise/tech-history/dawn-of-electronics/bird-poop-can-cripple-power-grids&psig=AOvVaw0coPI7g476sDBs8W-1mmGg&ust=1551539009628107

 

[callie123]

Hm...thanks, Berkeman. I was thinking along the same lines as storm aftermath, when you're instructed not to drive over bodies of water that are connected to downed power lines. Or people that unfortunately die or are injured swimming near boats that have a faulty wire exposed to the water.

Are you saying the difference in these scenarios and my own are that a boat isn't connected to the ground? But would there be danger to...say...a swimmer? And also, I just wondered if it's even possible to maintain that level of energy in the water without it boiling or evaporating or both!

 

[berkeman]

You can have dangerous situations when there is a high voltage source in the water, and current can flow sideways through the water to some other place. Like near boat docks that have AC Mains voltage that is in contact with the water (a common occurrence, apparently), and current can flow to Earth. A swimmer is at risk for getting a strong shock (and maybe even being electrocuted) if they get near the HV source.

So maybe a way you can use this in your stream is to have two wires in the water, one running along one bank and the other running along the other bank. That way you will have a voltage gradient across the stream, and a swimmer could end up conducting a significant current through their body. I'm not sure if it would cause issues for boats, though.

Keep in mind that you would likely need to pump a lot of power into such a setup, since current will be flowing in the water even without any swimmers. The longer the electrified stretch of stream, the more power it takes to maintain the high voltage gradient. It also would only work for fairly narrow streams, maybe a few 10s of meters wide.

 

[callie123]

Thanks for all the thought you put into this answer! It's very helpful.

So, are you saying that the electrical current wouldn't turn the stream into a giant steam bath over time? I've read that if high voltage is run through water, it'll heat it...or reduce it by splitting the molecules...

 

[256bits]

you will have a voltage gradient across the stream, and a swimmer could end up conducting a significant current through their body

Which is one reason you do not want

nd would have plenty of conductive elements in it

You want the swimmer, or boat to provide a better path for conduction of current than the immediately surrounding water.
Think of the bird on the wire - the air is non conductive, not so the bird if it touches both wires.

 

[callie123]

Thanks!

 

[Klystron]

If interdiction is your goal, the great SF author Robert Heinlein used an electromagnetic 'force-field' to fence a border stream in the short story "Coventry". The struggling protagonist overcomes the obstacle using ingenuity; beginning a quest that leads to the question "How does a mature citizen contribute to their society?".

A different treatment of water as an 'aqueous globe' by SF author John Varely appears in anthology "Blue Champagne". If memory serves, the emotionally-disabled protagonist meets the physically-disabled visitor within a large spherical swimming pool; the sphere held together by surface charges and suspended in free fall or by damping the ubiquitous artificial gravity common to space opera.

If Varley represents the cohort of younger writers taking up the mantle of old guard science fiction -- Heinlein, Isaac Asimov, Frank Herbert, etc. -- my guess is that "Blue Champagne" owes much to Heinlein's "Menace from Earth" with high density air in the plenum for the Lunar colony replaced with a beautiful blue globe of water. Heinlein has his teenage characters fly in the moon's low gravity and pressurized air using elaborate wings based on avian anatomy. Varley provides a simple breathing apparatus and swim fins to emulate dolphin anatomy.

Note that air and water are fluids in physics as under the rubric computational fluid dynamics (CFD).

 

[anorlunda]

If you bubbled air up through the stream, essentially making it a froth, it would not be dense enough for water craft to float on. They would sink. But the power requirements would be huge. Maybe you could scale it down to a narrow moat.

But land machines like tanks might be able to drive through the froth. To those you have just a ditch and the froth doesn't matter much. They could also put a bridge over the moat.

It would be better to temporarily inject air underneath a passing boat. Then as soon as it sinks, stop the air and bingo it is under water. This type of effect, but natural not man-made, has been suggested for some of the Bermuda Triangle nonsense.

 

[callie123]

Thanks for the info, y'all!

 

[Klystron]

Howdy @callie123. While researching something else, I found this source of electricity in fresh and salt water the electric ray.

Living fish not only solve your water conduction/insulation dilemma but give you as the author a righteous platform to discuss ethics of species conservation, if so inclined. The literature on electric fish and eels goes back to earliest written records. I am amazed that electric fish were used by doctors thousands of years ago -- supporting the adage "Truth, stranger than fiction".

Not sure of your understanding of electricity but generally the fresher the water (least brackish, less dissolved salts), the poorer the electrical conductance (higher resistance), then the stronger the electric potential within the larger species of fish. Some species use electric organs in place of sight at night and in turbid water. I have seen aquariums housing electric catfish with electronics that make their signals audible to humans.

 

[callie123]

Coolioso, I'll definitely read this. Thanks :-)

 

[stefan r]

Hydrocarbon like diesel fuel or motor oil should be a good insulator. Toluene would have a slightly higher boiling point than water.

You can have a salt water stream with a surface layer of oil floating on it. Have the bottom of the moat in contact with one electrode. Have the top of the bank be conductive and connected to another electrode. Technically you could jump into the moat without getting a shock. That would be the same as a bird on a wire. If you tried to climb out you would connect the circuit. Hydrocarbons are low density so swimming/floating is more challenging.

 

[Klystron]

If your story has moats, author Mark Twain electrocuted a lot of bad guys after sending an engineer back in time to circa 500 C.E. in his 1899 novel A Connecticut Yankee in King Arthur's Court. I forget the exact method but Merlin was furious!

 

[callie123]

Hydrocarbon like diesel fuel or motor oil should be a good insulator. Toluene would have a slightly higher boiling point than water.

You can have a salt water stream with a surface layer of oil floating on it. Have the bottom of the moat in contact with one electrode. Have the top of the bank be conductive and connected to another electrode. Technically you could jump into the moat without getting a shock. That would be the same as a bird on a wire. If you tried to climb out you would connect the circuit. Hydrocarbons are low density so swimming/floating is more challenging.

Interesting idea, Stefan r, thanks. So...about that. If there was an electrode in contact with the bottom of the moat, would it eventually heat up the water, or cause the minerals in it to change through (hope this is the proper term!) electrolysis?

 

[callie123]

If your story has moats, author Mark Twain electrocuted a lot of bad guys after sending an engineer back in time to circa 500 C.E. in his 1899 novel A Connecticut Yankee in King Arthur's Court. I forget the exact method but Merlin was furious!

Thanks for the imput...and yeah, I love that book! You're very right, Mark Twain's character used a good old fashioned electric fence during an epic battle. The knights opposing him touched the fence and their super conductive armor just passed along the charge to the next guys.

 

[member 656954]

If you bubbled air up through the stream, essentially making it a froth, it would not be dense enough for water craft to float on.

My uncle worked for a water authority and he told me once that tragically a member of the public suffocated in one of their treatment plants, not realizing you cannot swim in such aerated water. So that idea definitely could work.

But what's the point of your electrified water? Is it merely to stop intruders? Because there are easier ways to do that than trying to maintain a charge of the kind you asked about.