What do you think about a self sustaining underwater city?

Question

I have this awesome idea, that looks more from science fiction than reality, but I really like it.
Can you build a self-sustaining underwater city?

First problem is the placement. I think it would be best somewhere in the ocean not too deep, somewhere where there is a constant source of energy, such as a volcano, geyser or water current, and somewhere where light still penetrates.

There are several needs that we have, in order to live in a place:
1. Food: Ocean is full of it (fish, etc), greenhouses can also be built
2. Water: Ocean is full of it, it only needs desalinization
3. Power: Generators that harvest the power of nature, such as geysers, underwater volcanoes, water currents, and even geothermal energy.
4. Air: This is one of the problems, there has to be a way to generate enough oxygen and replace the CO2 in industrial quantities. Proper ventilation is required.
5. The social element: Since this is a city, the buildings can be linked with tunnels, large parks, or gathering places...
6. Transportation: Tunnels, eventually an underwater railroad system; submersibles can be used for transportation..

These are the problems that exist in creating such a project:
1. Building under deep water, high pressure.
2. Transportation of building materials at large distances
3. Maintenance, any leak can be fatal. Of course, each room has doors that prevent water from going in other chambers, in cases of trouble.
4. The air can be a problem, there has to exist a device to create massive quantities of oxygen


So what is your opinion about such a project. Can it be made?

Frank N · Accepted Answer

Good thinking, and a good exercise.  Yes, most of it can be done, but it's very expensive.  You wouldn't choose to undertake that expense without a good reason.  It has been done for research, and Florida has an underwater motel, but there's not a lot of interest in it.  A nuclear submarine is our best example of such an ecosystem, but it's not self-sustaining.  There would be no point to having it in deep water (too much pressure, too little sunlight, too much isolation from the 'real' world).  A leak would not be fatal; a rupture would.  You'd want the main shield(s) structured so the water pressure works to strengthen the structure.  Like a sphere.  Like a submarine.

The problem is less the supply of oxygen, but the removal of carbon dioxide.  Read how submarines solve this problem.  But it's cheaper just to exchange air with the surface.  There are experimental turbines to harvest energy from ocean currents.  You'd have the advantage of generating the electricity near the point of consumption.  Your better emphasis is to minimize energy use.  Or use nuclear fission.  Like a submarine.

BioLiz · Answer

Your idea is very good, and others have come up with similar ideas. As you already indicated, air ventilation will be the main big hurdle. Another one I could think of is pressure, which is much higher under water! 

Biosphere 2 was something very similar, albeit just on land, not under water. The main purpose was to see if humans could live inside a self containing city. It did not quite succeed, but much has been learned from this project. I once visited that site in Arizona. 
http://en.wikipedia.org/wiki/Biosphere_2

And there are similar ideas to build underwater cities.:
http://inhabitat.com/sub-biosphere-2-a-self-sustaining-underwater-city/

I would suggest reading more on the Biosphere 2 project, because your city could greatly benefit from all lessons learned on that Arizona site.

Good luck!

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What do you think about a self sustaining underwater city?

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