Article

2008-12-07 Science & Technology

Will oceanic thermal gradients offer endless, cheap power?

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Posted by ryuge 2008-12-07 07:18|| || Front Page|| [11130 views ] Top

#1 Some years ago, the MMGW crowd were bemoaning that very deep, very cold water current patterns were slightly warming and changing, and beyond a certain threshold would no longer continue, radially altering world weather patterns.

Well, some ingenious individual came up with a brilliant solution to that problem.

There is a time bomb of sorts under large areas of the world's sea floors. Methane clathrate, or methane ice, if warmed just a few degrees, can explode, converting into hundreds of thousands of tons of methane gas, erupting into the atmosphere.

So, the theory went, why not start mining this undersea methane ice, and use its energy to chill coolant inside a large, metal pipeline that cuts across the deep sea current?

All it has to do is cool it a degree or two over the course of years, acting like a big stick of ice in a drink, and not only would be dangerous methane ice be dissipated safely, but the deep water current would be slightly chilled to its optimal temperature.

Posted by Anonymoose 2008-12-07 09:08|| 2008-12-07 09:08|| Front Page Top

#2 This technology requires an enormous amount of pipes, all of which have to be resistant to corrosion. It also requires heat exchangers which are incredibly efficient and durable. It requires lots of other stuff too.

My hats off to any engineering group that can pull this off.

Posted by mhw 2008-12-07 09:16|| 2008-12-07 09:16|| Front Page Top

#3 The science is well-known and used extensively in other applications. Once you build the apparatus to extract the power, the power is essentially free and very clean. Geothermal works on the same principle and with a much larger temperature differential and should be even more efficient. The question is economics. It seems like the costs should be able to be determined to a considerable degree of accuracy. So why don't we have a these things all over the place?

Posted by Richard of Oregon 2008-12-07 09:58|| 2008-12-07 09:58|| Front Page Top

#4 Geothermal requires high cost wells with even more extremely corrosive fluids. But you can drive your pick-up truck up to the bulk of the pipes and equipment to maintain them. The pressure and temperature changes associated with the energy extraction would simultanously 'exctract' minerals from solution, which should tend to plug up all the tubing with scale. Hmmm.

Posted by Glenmore">Glenmore 2008-12-07 10:17|| 2008-12-07 10:17|| Front Page Top

#5 So why don't we have a these things all over the place?

Because all the costs are up front. I have one at my house, but it added about 4% to the cost of the house and there is nothing you can see to brag about. It also required 1/4 acre of lawn. But I have about a $75 per month heating and a/c bill for a 4,000 sq ft house in PA. That will go to $100 or $125 when they dereg electricity in two years, but it will still be cheaper than oil.

Posted by Nimble Spemble 2008-12-07 10:29|| 2008-12-07 10:29|| Front Page Top

#6 That's a geothermal thing in the ground, Mr. Spemble.

They're talking about these things in the ocean. Much more maintenance intensive.

Posted by Thing From Snowy Mountain 2008-12-07 10:58|| 2008-12-07 10:58|| Front Page Top

#7 So, the theory went, why not start mining this undersea methane ice, and use its energy to chill coolant inside a large, metal pipeline that cuts across the deep sea current?

Thermodynamics 101

Posted by g(r)omgoru 2008-12-07 11:52|| 2008-12-07 11:52|| Front Page Top

#8 TFSM

So you pump water through a to the proper depth. Construction costs are higher. Where's the maintenance that's different from an oil well?

And maintenance costs should be easily defrayed (if the idea is practical, about which I am sceptical) from the high margin energy sales.

Posted by Nimble Spemble 2008-12-07 12:06|| 2008-12-07 12:06|| Front Page Top

#9 The materials tech for such a project would have to be leading edge and the same for the tech required to maintain it. The petroleum industry has developed a lot of it already but are we there yet with the economics? Only the Engineers know.

Note that the two sites they are discussing are islands with a LONG logistics train and a requirement for power not subject to interruption. Cost is probably secondary. I wonder how they would defend the complex from underwater attack?

Posted by tipover 2008-12-07 12:53|| 2008-12-07 12:53|| Front Page Top

#10 It appears that some of you didn't read the whole article before commenting.

Posted by Darrell 2008-12-07 13:14|| 2008-12-07 13:14|| Front Page Top

#11 "OTEC is basically a large tube running one kilometre into the ocean off a floating power plant; but ocean currents put a huge amount of stress on the pipe and the power plant... A 100MW plant might require a pipe 30 feet in diameter, which would be very difficult to anchor and install."
30 FEET IN DIAMETER! Take it from this mechanical engineer, friends, it ain't gonna happen.

Posted by Darrell 2008-12-07 13:34|| 2008-12-07 13:34|| Front Page Top

#12 Low yield power energy production using vast amounts of labor, materials and upkeep. A sure path to slow ruin.

Posted by ed 2008-12-07 16:14|| 2008-12-07 16:14|| Front Page Top

#13 So you pump water through a to the proper depth. Construction costs are higher. Where's the maintenance that's different from an oil well?

Immersion in very slightly alkalai salt water.

Posted by Thing From Snowy Mountain 2008-12-07 18:29|| 2008-12-07 18:29|| Front Page Top

#14 Oil wells aren't in slightly alkali sale water?

Posted by Nimble Spemble 2008-12-07 18:47|| 2008-12-07 18:47|| Front Page Top

#15 How about 6, 5 foot pipes, no make that 7, (Bundles easier, allows for friction)
That's doable.

Posted by Rednek Jim 2008-12-07 20:28|| 2008-12-07 20:28|| Front Page Top

#16 It would take a bundle of 36. And the bundle's diameter would be a bit larger than 30'.

Posted by ed 2008-12-07 20:36|| 2008-12-07 20:36|| Front Page Top

#17 long pipes are very flexible, a pipe-lay barge will make you realize just how flexible. Stainless Steel is even more flexible, but a project like this would warrant a new product, like a composite or a nano material. The theory is sound, but capitalizing it will cost someone a fortune, and nowdays people don't seem to want to tolerate the inevitable failures that would occur along with the successes to develop something like this.

Posted by bigjim-ky 2008-12-07 22:51|| 2008-12-07 22:51|| Front Page Top

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