What is the most air can be compressed?

I guess I should ask 'what is the most air can be compressed economically'.

I have been thinking of using compressed air to bring up sediments from the ocean floor. Sediments on the ocean floor are rich in important nutrients, for instance iron, which phototrophs at the surface require for growth. If they don't get these nutrients most of sunlight is absorbed instead by water.

I'm thinking one could inject large amounts of air underneath the sediments so it would float to the top. It could for instance be brought up through a funnel of some kind (plastic is cheap) which would also create suction as the air expands.

The problem is that 2 km down there is already 200 atmospheres of pressure, so compressing air to even 2,000 atm (which may not even be possible) would still only get you a compression factor of 10 that far down, so it would be best to get pressures even higher than this.

Alas, I do not know much about compressing air, other than it is big business (10% of energy usage, according to the wiki).

Such a machine could be very very simple, it could use the compressed air to move and rise to the surface too. It would release its air-load into the seafloor, bob back up to the surface, collect air, and drop down again, enriching the water column in the process.

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There are already machines for this, I've seen them used by underwater archeologists.

 

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I'd suggest to contact this organization about your questions:

http://www.soest.hawaii.edu/soest_web/soest.contact.htm

http://www.soest.hawaii.edu/soest_web/soest.sitemap.htm

 

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You would also be releasing all the sequestered CO2 by doing that... not a good idea.

 

Interesting, I would think they could also use streams of water for this, as long as the excavation wasn't too large scale. The benefit of compressed air is that it is positively buoyant and can carry particulate matter far away from the initial location.

Thanks, I could use some contacts in Hawaii

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This is true, there is probably quite a bit of carbon in the sediments too, likely in its most metabolized form. But, the idea is to increase fishery productivity by increasing primary production at the surface. Releasing carbon dioxide is not necessarily contrary to my goals.


One question is - whether the nutrients are biologically available. A grain of iron won't really be useful to a microbe 100th its size. I learned in my microbiology class that microbes will form biofilms on debris falling to the ocean floor, and systematically work at these. Another issue would be if the sediment was so fine as to remain suspended for long periods of time - it would absorb light and deprive the phototrophs.

 

They want to make sure they don't lose any small artifacts, so the sediment is filtered above water. I doubt compressed air, even though it rises, would be able to bring tons of sediment to the surface, you would need to pump it. You would need a very powerful pump too, since a column of water and sediment from that deep would weigh a lot.

 

Actually, if the primary tube is ridged or at least not collapsable, once it is filled with water you only need to remove water/sediment from the top of the tube. Flow rate and preventing too much sediment for the rate of flow should be the only issues.

2 km is deep... But dredge pumps are used routinely at dive depths. There should be no real concern at greater depths than making sure that the water to sediment ratio does not go so high as to degrade the flow rate.

Unless you are lifting the water/sediment above sea level the weight of the involved water column is not a significant issue.

 

I think you would have the opposite effect. Large amounts of nutrients traditionally accelerate algae growth. You get algae blooms that remove all the oxygen from the water and kill off fish. In the Gulf of Mexico there's an area where the Mississippi river provides lots of nutrients for algae that is referred to as the "Dead Zone" because there are no fish in it at all.

 

Air has a lot of lifting power though. 1,000 liters of air can lift close to a ton of debris. The thought that it may be more efficient to just scoop the dirt up and lift it using compressed air or other means has dawned on me, and it upsets the entire scheme of air-blasting the ocean floor.

If you have a ship at the surface that does this, it will add a lot of capital cost, while the energy cost may be lower, for the lifting at least. After that you have to factor in fuel costs for the boat, and the crew.

Exactly. And as the air rises inside of the tube it will expand as well- pushing water out the top as it goes. I'm worried the pressure differentials may blow up the tube though if its made of soft plastic, which is pretty much a requirement if it is to be economical.

I have read of another idea, involving a tube and no air, on these forums if memory serves me right. Because of the temperature difference between the bottom of the ocean and the surface it is possible to establish a current through a long tube. This could also be used to lift nutrients to the surface.

Good point. I read the wiki on Algal Blooms, and it appears that there are some algal blooms which are harmful, but predominantly they are not. This is because some phototrophs release toxins as the divide, and other times they use up all the oxygen and suffocate all other organisms. Funny, I guess oxygen has to be considered a nutrient too. :bugeye:

 

Actually I have often thought of rainforest sized algae patches floating around in our oceans producing oxygen, removing carbon (just by becoming life), and as possible emergency food sources for starving countries. Just tow a hundred thousand acres of it to a starving country and yummy algae for the masses, fuel, or paper, etc.

Also; a fish pond covered with seaweed can support double the amount of fish a regular pond can. Algae also equals fish food and happy fishermen.

Okay your idea is to use compressed air to bring out nutrients.,

There is a simpler way. Use wave power to push water through small tubes, and even though the patches of algae are anchored, there would be enough movement that the hose would get dragged around and not always in the same place. Another hose also pumped by wave power can bring water/food from the bottom to the top where the algae is trying to live.

I do not know how the ocean pressure would affect the flow. I would guess since they are in enclosed tubes they should be able to operate quite well, unless the tube was forced closed. The pump tubes would need to be fairly thin however to avoid excess weight, and keep it within the pumps abilities.

There are many variations possible. Nutrients could also be pumped from shore or boats or shallower water where nutrients are abundant, all using wave power.

Large companies could sponsor so many "acres" of a seaweed rainforest, either for public relations or from political pressure to reduce their carbon footprints.

Seaweed forests could be built and seeded from shore pushing them outwards into the ocean with a few boats helping.

Floating orange balls with "wire" (something for seaweed to grow from, something water resistant; plastic maybe). and clips to the next ball.

You could have the balls and clips seeded and attached to each other in triangular formations for stability.

Anyways; not exactly compressed air, but when you mentioned loking for nutrients I had to mention wave pumps.

As for your question. Air can be compressed based on the quality of the pumps and containers used. I doubt it would be feasible to pump air in a tank to its maximum pressure unless you were going for a world record.

4500 psi is a decent amount, and that is about what could run a compressed air vehicle.

 

. . . as an aside . . . . injecting a single miniscule, spherical air bubble at ocean depths (under high static pressure) . . . as the single bubble rises due to bouyancy . . . it expands (to a calculatable extent based on PV=nRT) diameter as it rises to shallower (lower pressure) depths, displacing a greater water volume. . . . . I kind of envision this as an analogy for expansion of the universe. Comments welcome . . .

wlminex

 

I was checking out this formula!Wave energy and wave energy flux

In a sea state, the average energy density per unit area of gravity waves on the water surface is proportional to the wave height squared, according to linear wave theory:[3][7]
[A 2][8]
where E is the mean wave energy density per unit horizontal area (J/m2), the sum of kinetic and potential energy density per unit horizontal area. The potential energy density is equal to the kinetic energy,[3] both contributing half to the wave energy density E, as can be expected from the equipartition theorem. In ocean waves, surface tension effects are negligible for wavelengths above a few decimetres.

As the waves propagate, their energy is transported. The energy transport velocity is the group velocity. As a result, the wave energy flux, through a vertical plane of unit width perpendicular to the wave propagation direction, is equal to:[9][3]

with cg the group velocity (m/s). Due to the dispersion relation for water waves under the action of gravity, the group velocity depends on the wavelength λ, or equivalently, on the wave period T. Further, the dispersion relation is a function of the water depth h. As a result, the group velocity behaves differently in the limits of deep and shallow water, and at intermediate depths:[3][7]

so it looks like location would be important.:shrug:

 

@ Whynot

Ty for the well thought out interest in my plan.

 

Hmm. I agree with the last part, but I don't think I understand the mathematics. It seems to me that some ares of the ocean will have smaller waves than others.

I like this idea a lot! It may help prevent what was mentioned earlier in the thread - toxic eutrophication. When water is pumped into this algal mat it may absorb nutrients much more quickly than the unicellular algae in the area because of higher biomass + surface area. So mostly algal growth rather than anything else.

Another idea - the algae could easily be engineered to absorb excessive amounts of nutrients close to shore and then be floated out to sea and store them in vacuoles. Once at sea these things would grow on their own until they ran out of nutrients.

I like this idea. There is a ton of energy just in the up and down rolling of waves. I am going to try to figure out the easiest/cheapest way to bring up sediment from the bottom using only buckets, pulleys, rope and buoys. I don't like the idea of using pipes, they seem heavy and expensive. I will get back on here once I figure it out.

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Yes, and ocean currents could be used to help push the patch places too.

 

Hi DRZion,

Thank you for such positive feedback on my idea, and hope it helps you solve your own problem.

I often thought it would be easy to get politicians to force heavy carbon industries to sponsor a few hundred acres of this algae forest each. I have been trying to promote this idea for years and believe I even had a thread dedicated to it long ago.

I was thinking lightly anchored small thick plastic fish tank type hoses for the nutrient transfers as opposed to heavy pipes.

I have seen some articles that you might also like

http://www.atmocean.com/sequestration.htm

and about wave power..

http://peswiki.com/index.php/Directory

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cean_Wave_Energy

Hope it helps..

Be a nice Seaweed Solution. The japanese have made some smaller seaweed farms for fuel purposes, I am not sure they are looking at mid ocean projects where nutrients are limited as I have proposed.

 

Wow, thanks for the links! It really seems that these atmocean guys have it figured out. They just take barrels and hook them up to, basically, long polyethylene trash bags with valves at their ends. Its so simple!

I'm skeptical as to their estimate that one pump can bring up 200,000 cubic meters of seawater every day .. thats 1/5 of a cubic kilometers. I heard somewhere that there is gold in seawater. However, the energy cost of raising that seawater even an inch is much higher than the price of the gold in it.

I guess that the energy is free here though, and very efficient since the density differences are very small as well. The way I understand it isn't that difficult to get waves to do work, but it is tricky to convert their energy to electricity because generators are very capital intensive. The buoy itself would only account for 1/100th the cost of the total set up. However, this obstacle is bypassed here since it converts waves directly to lift.

This is another article on the same subject-
http://www.oceanandair.coas.oregonstate.edu/index.cfm?fuseaction=content.display&pageID=183

An idea that I have is to disrupt the pycocline in the ocean by simple gyration of some kind of object through it. The pycocline is basically the boundary between sweeter, warmer ocean water and denser colder water beneath it. Since ocean waves bob up and down an object could be forced through the this boundary very frequently if it was attached to a buoy at the surface. The question is - whether this water would later make it to the surface on its own. If my knowledge serves me it would not - this is why the atmocean people are bringing up water from several hundred feet down ( and I think that is above the pycocline, but I could be wrong ). Without any stirring diffusion would be the sole method of transport.

As for the algal rafts, I would like to see them carry massive supplies of iron intracellularly. I know that people are figuring out how to do this, as there is research at my university focused on iron-binding bacteria. By carrying their own supplies of trace elements I think that they could overcome much of the problems faced by life in nutrient-deprived ocean waters. Even if grazed excessively they would release these nutrients into the ecosystem.