1. I've heard about methods trying to use a membrane where air molecules could pass through but not water, and using a high pressure to squeeze the air out.

However, either way you're going to need to lug around a heck of a lot of batteries. What happens if you're at 30 meters and your battery pack shorts? I wouldn't be too quick to test one of these out without a standby air supply.

I know in fresh water when you have an algae explosion it can remove a lot of the oxygen from the water (I've seen dams where a bit of warm weather pulled round and killed off all the fish due to lack of oxygen from increased algae populations) - what happens if you're diving in wate that doesn't have such a great "air" content?

Like I said, I'd have to see this equipment in use for quite a while before I'd be comfortable with it.

Posted at 4:19PM on Jun 16th 2005 by Dylan

2. Thanks for the great comment, Dylan. I was especially interested with your point about an algae explosion. Maybe Bodner anticipates using this set-up under "perfect diving conditions"; when divers need to swim through areas with algae blooms, they need to go back to the old model.

The article suggests that the system requires a 2-pound lithium battery for 1 hour of diving. Also, in terms of back-up air: the article never mentions it, but the diagram of the system points to a Reserve Air Supply. You're right, though: I'd like to see somebody ELSE use it first.

Posted at 4:19PM on Jun 16th 2005 by Willy

3. I can see this in use at resorts. Instead of snorkeling, they can be outfitted with lightweight devices and swim for hours below the surface. If there is any trouble they can just surface. I'm assuming that for deeper diving, there will be a long period of testing and redesign.

Posted at 4:19PM on Jun 16th 2005 by jooby

4. If there were such an algae bloom, would you really want to be diving there anyway? I imagine the visibility would be enough to keep you from diving....

Posted at 4:19PM on Jun 16th 2005 by LoveDiving

5. i grew up around chicago
and i dont see diving in the middle of a algae bloom
being much different from diving in lake michigan...

but who knows...

Posted at 10:18AM on Sep 7th 2005 by Bobb

6. Two words: fish farts.

Posted at 4:35PM on Nov 10th 2005 by Doug Jones

7. Yeah, sure. Water is 1/8 oxygen by weight...use the batteries to hydrolyse it. Then use a fuel cell that runs off the liberated hydrogen gas to hydrolyse more oxygen. Aww, wait...there's that pesky problem with the three laws of thermodynamics.

I'd like to meet the guy who thinks that wringing the oxygen out of (even saturated) water with a centrifuge?! could even approximate the efficiency of compressing air into a tank. I'm sure he'd jump at my offer to sell the Brooklyn Bridge.

If you want to quickly decrease water's ability to dissolve oxygen, you heat it. Since water saturates at about 0°C with its maximum load of oxygen (~14 ppm), you'll need 100 calories to take a gram of it to boiling (at sea level) to release all that oxygen.

Hmm, to be equivalent to the 471 Liters of Oxygen (21 moles @ STP) available in an 80ft³ tank, that calls for only 1.5 million moles of water (27000 kg or Liters) (7142 gallons) of water. Let's see, that would be only 2.7 BILLION calories.

Do that over an hour and you're looking at ~3.1 million Watts. Your typical ~20 pound, 40 amp·hour car battery will kick out about 480 Watts for an hour so that'd mean you'd need the equivalent of 6500 car batteries to power this hypothetical TUBA.

I suppose you wouldn't need a weight belt. What are you going to do with the 7142 gallons of boiling water? Check my math--I don't believe I misplaced any decimal points.

Posted at 9:56PM on Nov 10th 2005 by JSBonnell

8. I would also worry about cold temperature and its effect on the battery sub-system. Though, there is more oxygen in colder water.

"Colder water holds more oxygen in solution." (from http://www.conservation.state.mo.us/fish/ponds/laketurn/)

Posted at 9:47PM on Nov 11th 2005 by Mark

9. Seems I did make a mistake in my previous post when I said that water was 1/8 oxygen what I should have said was 1 part hydrogen to 8 parts oxygen (by weight).

Doesn't really make much difference though since it takes too much electrical energy to hydrolyse it to be practical for a self-contained unit. Then, too, if you were hydrolysing sea water, you'd need some way to scrub out the chlorine gas that would result from hydrolysing the NaCl and CaCl2.

I also didn't figure in the battery power necessary to pump 7100 gallons of water through the system. The numbers I came up with assumed a near 100% efficiency. Your mileage will vary.

There just isn't enough oxygen available in water to power a warm-blooded animal. The Good Lord would have probably done it already if there were.

Posted at 11:59AM on Nov 12th 2005 by JSBonnell

10. Why not give this guy a chance to prove his thing. Let him reinvent the wheel again in a more lighter and compact way. Since we are now moving to nano scale machines or nanotechnology I guessed, he got an idea to use them.

Posted at 10:24PM on Nov 14th 2005 by artenc

11. Aloha!

The fish obviously are able to extract oxygen from water without boiling the water, so it's clear that it's feasible to do it. The thing is to be able to engineer something that (a) mimics the technique and (b) scales to provide enough oxygen for a human.

Posted at 3:46PM on Nov 15th 2005 by Joachim

12. we are denser, need more 02 than fish, gill sys large part of fish. assume gills like lungs are vastly more effiecint than current tech. it would take to much area. we even need more air because of the temp diff and needing to maintain our body temp. this tech is a long way off barring discovery/manufacturing of a cataylst that separates the o2 out of water, mechanically its not fessible(see above for cal count), chemically its not on the horizon for the catalyst, biology wise it would be big(10% fish gill sys + we are 1.6x dense + warm + less effic. so 10+6+10+20 i think these conservtive #,s so 46% our mass to do it and roughly 40% our wt. because it bio material(approx mass as us). so we wait for the catayst.

Posted at 6:32PM on Nov 15th 2005 by mike

13. Won't be me that stops him Artenc. He is fighting physics and common sense. The point of the boiling water example is that, unless he has found some way to get around solubility laws, it will take a similar amount of mechanical energy to convince water to relinquish its load of oxygen.

Ignore the amount of energy needed to extract the oxygen and just look at the energy needed to pump the 7000 gallons of water through the device by itself. This will not be a device that is man-packable. "The fish obviously are able to extract oxygen from water without boiling the water" hard to argue with that--also hard to argue that anything we can build will out-perform their gills. Have you considered the percent of a fish given to the respiratory system?

Say that a human, with a metabolism 10 times higher than a fish (very lethargic human), were going to extract oxygen from water--his gills would have to be 10 times the size of a fish's of the same body weight.

The picture I want you to see is Kevin Costner in "Waterworld" with the equivalent of 2 duffel bags dangling from his neck.

Posted at 7:05PM on Nov 16th 2005 by JSBonnell

14. The water could be cold at the surface and become supersaturated with O2. Underwater it would rise to the ambient with no electrical power required, all the while dispensing O2 like bubbles in a champagne glass. If some sort of countercurrent exchange system can capitalize on the dissolved O2, it might function in a manner similar to a rebreather with a water tank instead of air.

Posted at 10:01PM on Nov 20th 2005 by Chuck Wiggins

15. This device aims at extracting disolved Air from water and NOT the O2 from the water molecules.
Think it could be great for shallow dives but if you intend to go deepeer than around 60m you need special gas mixtures anyway.
I would of course keep a small bottle of comressed air for emergengy.

Posted at 6:23AM on Nov 27th 2005 by Alex

16. hahaha......... fish farts..

Posted at 6:32PM on Dec 11th 2005 by Ryan Frimel

17. I'm getting all that is being said but what about a kind of micro organisim that acts something like a leaf and catalist system? Or pore like ability of our own skin. I'm not highly educated on this stuff but I am doing a science fair experiment on it. A.K.A. any other info can be helpful.

Posted at 6:05PM on Dec 13th 2005 by gonehorsey101

18. lol @ fish farts.



But really, as a recreational diver, who cares? Once youre underwater its not like the tanks weigh anything. And unless youre doing really sketchy wreck dives, i cant think of anything a civilian would be doing where this could be useful.

Posted at 8:53PM on Dec 29th 2005 by Dissent