Artificial gills are a bad idea?

[DavidPT40]

Artificial gills were invented last year, which circulates seawater and extracts the oxygen from it. This application would be for divers, underwater habitats, and submarines.

The only figures I have is that one liter of seawater contains 1.5% oxygen. And it would take 200 liters per minute of seawater to provide a diver with oxygen.

My first thought is that this would disastorous for sealife. Divers would deplete all the oxygen on a reef. Is this a realistic possibility?

 

[MSilvia]

The invention isn't a new one... there are patents for similar devices going back more than 20 years. There are a number of practical problems with it.

I understand you'd have to move a crapload of water through the device very quickly in order to get enough air out of it to breathe. One figure I read figured it at about four times the output of a running jetboat. Another problem is that air compresses at depth, and you still need to fill your lungs to breathe. If the 4 jetski estimate is based on 1 atmosphere of pressure, then at 33 feet, you'd need twice that, and at 66 feet, you'd need three times that much. Good luck staying still with the amount of thrust that 12 jetski impellors would generate.

In other words, it's possible, but unless you can figure out a way to make humans survive on a lot less O2, I wouldn't hold my breath waiting to dive with one. I heard someone made a working prototype of one that worked without the massive volume of water in the late 60s, but if you took it deeper than 10 feet or so it wouldn't generate enough gas to breathe. With a depth restriction like that, snorkles are a much cheaper, lighter, and more reliable alternative.

Of course, in a habitat equipped with scrubbers, a well designed device like that could probably be helpful.

 

[rakkis]

you'd still need to carry nitrogen. can't breathe pure o2 due to toxicity when pO2 is too high

 

[Walter]

True gills put O2 directly in the blood stream, there would be no need to fill the lungs.

 

[MSilvia]

you'd still need to carry nitrogen. can't breathe pure o2 due to toxicity when pO2 is too high

Of course, if you can't get enough O2 to breathe if you go deeper than 10 or 15 feet, you're not going to have that problem.

 

[devolution365]

We commonly call air "O2" and this is a case where it makes things confusing. These artificial gills (at least the ones I've read about) do not break the hydrogen-oxygen bond from H2O to create "oxygen" to breathe as some people seem to think. They just collect the dissolved AIR in water, which (I believe) is of the same elements as air (and in the same proportions).

[EDIT]
Here's a link to the article that was posted before: http://news.bbc.co.uk/1/hi/sci/tech/4665624.stm

Note that the teaser says this thing "squeezes oxygen directly from seawater", but the rest of the article says the device extracts dissolved air from seawater.
[\EDIT]

 

[espenskogen]

Of course, if you can't get enough O2 to breathe if you go deeper than 10 or 15 feet, you're not going to have that problem.

Ah, but following this logic - If the artificial gills would effectively be injecting a closed cirquit loop (Like a rebreather), and you would be using a diluent to compensate for the gas compression, the gills would only need to produce the amount of o2 that the body metabolizes. Considering this is likely to be a constant amount regardless of depth, and would typically be 3 liters per minute, the gills would need to filter 240 litres per minute, assuming 100 % efficiency. The diver would still need to carry a diluent tank, and a scrubber..

The 240 litres/minute wouldn't need to cause any jet effect necessarily - That depends on the diameter of the "gills" ( If they're really big, you can fit 240 litres through it at minimal speed, and hence if could work in theory at least)

You can see however that the practical considerations of diluent, scrubber etc would be making the artificial gills rather useless - Better use a rebreather with a diluent and o2 cylinder.

 

[crpntr133]

my signature says it all

 

[ba_hiker]

The 240 litres/minute wouldn't need to cause any jet effect necessarily - That depends on the diameter of the "gills" ( If they're really big, you can fit 240 litres through it at minimal speed, and hence if could work in theory at least)

Heck, run that current through a small outlet and make a dive scooter of the thing...

 

[RockPile]

We commonly call air "O2" and this is a case where it makes things confusing. These artificial gills (at least the ones I've read about) do not break the hydrogen-oxygen bond from H2O to create "oxygen" to breathe as some people seem to think. They just collect the dissolved AIR in water, which (I believe) is of the same elements as air (and in the same proportions).

[EDIT]
Here's a link to the article that was posted before: http://news.bbc.co.uk/1/hi/sci/tech/4665624.stm

Note that the teaser says this thing "squeezes oxygen directly from seawater", but the rest of the article says the device extracts dissolved air from seawater.
[\EDIT]

I agree. It would have to be dissolved air that the gills collect. Certainly these units are not breaking the H2O bond. Breaking that bond without the use of another large energy source is still the biggest challenge with which hydrogen car developers are struggling. It’s like the modern “cold fusion” question.

Whatever it would take to effectively power that, I’d really prefer not to have strapped to me when I’m kicking around down there.

JB