Talk:Ocean thermal energy conversion

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Contents 1 Why so complicated? 2 Stirling Engine 3 Can't get a date 4 Aquaculture 5 Thermocline Transducer 6 link not working? 7 geography 101 8 Global warming?

[edit] Why so complicated?

The process presented here looks pretty complicated. Why would someone want to do this when the same thing could be accomplished by something simpler, like a stirling engine? Is there some subtlety that I'm missing that makes this process more efficient at extracting energy than the Carnot cycle?

--Flatline 19:47, 2005 May 25 (UTC)

This article is written in an over detailed way. An encyclopaedia needs to give the reader an initial introduction to a subject. This early resort to mathematics only serves to obscurify the subject and put off the general reader. A more qualitative approach is needed. Lumos3 16:30, 27 May 2005 (UTC)

I've tried to start doing that by making a first shot at discussing the economics. How about a simple diagram showing a rig with a big pipe and the flow of water? Are there better estimates out there for cost? --Kris Schnee 08:08, 5 May 2006 (UTC)

OK, with the new info on history and the pictures, this article is looking better! I also worked again on the opening, but the wording is still kind of repetitive. Is the total energy really that much greater for OTEC than for wave power? Even if so, the real issue is how much of that energy can be extracted at a profit, same as with any other energy source. --Kris Schnee 03:11, 6 May 2006 (UTC)

[edit] Stirling Engine

Why not use a Stirling Engine using surface and deep water to create the two temperature zones? I get the feeling I am missing something but cannot pinpoint it.

Wow. Slashdot has linked to this article today ... and still noone can answer this. Somehow, somewhere there is a moral to this, possibly in the same day Slashback article.

A sterling engine would be more complicated, not less. You need two heat exchangers both for a sterling engine and a closed-cycle turbine. The turbine itself is much less complicated then a sterling engine (at least IMHO). Both require a working fluid (probably hydrogen for the sterling engine and ammonia for the closed cycle turbine). Economically speaking, a sterling engine might make more sense for a very small scale installation, but there's a reason large power plants use the rankine cycle instead of the stirling cycle. Toiyabe 20:12, 5 January 2006 (UTC)

Also Stirling engines are very inefficient at the low temperature differences available in OTEC. Lumos3 12:28, 11 November 2006 (UTC)

[edit] Can't get a date

Can somebody confirm the 1930 date? I've seen 1928... Trekphiler 03:00, 29 December 2005 (UTC)

[edit] Aquaculture

Can we get an expansion of the Aquaculture entry as it applies to the OTEC? What advantages does an OTEC supply to aquaculture?

As I understand it, deep water is relatively rich in nutrients, so bringing water up from below would be a way of fertilizing aquaculture operations in the shallows. This article [1] mentions such an experiment, which was unsuccessful. This book [2] has lots of info on aquaculture. Also, kelp grows best in cold water, so bringing cold water towards the surface would be good for shallow-water kelp farming in warm areas. --Kris Schnee 07:35, 5 May 2006 (UTC)

[edit] Thermocline Transducer

I was wondering if this technology is or resembles the thermocline transducer base facility from SMACX. If so, shouldn't the article make a mention of it?

[edit] link not working?

Hi, just tried to retrieve reference no. 1, but the link does not seem to work.

Heda62.68.29.247 13:09, 7 September 2006 (UTC)

[edit] geography 101

"the limited geographical area in which it is available"? Have you seen the size of the Pacific Ocean? The Indian Ocean? We're talking about millions of km². Can't access it? Good reason to develop Power Relay Satellites... Trekphiler 06:31, 29 September 2006 (UTC)

[edit] Global warming?

Wouldn't that greatly contribute to global warming? For one, the deeper, colder ocean layers would be heated and could dissolve less CO2, liberating it into the atmosphere. Also the upper sea levels would be cooled and so be able to take up more heat from insolation. Of course there would be no such effects from only a few such power plants, but the effects should be visible if this technology would be used on a large scale. 84.160.255.160 11:28, 11 November 2006 (UTC)

I'd like to see some numbers on this idea. I suspect that the oceans are so fast that it would make no difference. OTEC releases zero green house gases, its these which alter the thermal equilibrium of the earth not flows of existing heat within the atmosphere, oceans and the earth's crust. Lumos3 12:33, 11 November 2006 (UTC)

I think I have a source (in print on the book shelf) that discusses why this is not a problem. From memory is is much as you say, the oceans are too big and replenishing too fast for anythign less than tens of thousands of these to even have any noticable impact. Plus the contribution to reduction in CO2 would actually come from the nutrients in the deeper water being pulled up in the middle of the ocean which is the oceans equivlent of a desert. It woudl cause a boom in growth of biomass which if allowed to die and sink or enter the food chain (rather than being harvested) would act to sequester that carbon in biomass. I will see if I can dig up the source and mention it here on the talk page, if it is relavent enough we can work something into the article. Dalf | Talk 12:54, 11 November 2006 (UTC)

Me too, I'd like to see some serious numbers there, but I don't have any. From first thought, I doubt that OTEC would not release CO2, by heating up sea water in which CO2 is dissolved. And algal blooms are generally not mentioned with a positive ecological connotation. Naturally, the effect of a few such plants on the oceans would be neglectible --- just as the effect of a few thousands of carbon based firings would not significantly change the composition of earth's atmosphere. 84.160.255.160 21:58, 11 November 2006 (UTC)

Well, basic thermodynamics tells you that when you extract energy (here in the form of mechanical or electrical energy) you correspondingly reduce the energy in the system you extracted the energy from. So you heat the cold part of the water and you cool the hot part. Net effect then is a net cooling of the oceans. As for circulation it is well known that the Gulf Stream is flows fast, warm water on the surface towards the Arctic where the cooling (plus the salt pump) make sthe water sink and return to the Gulf along the sea floor. From the North Sea oil operations it is known that the cold return water is colder than 0 degrees celcius, which is the reason anti freeze is injected into the undersea gas pipelines. All in all I canot see that there is a danger of heating, quite to the contrary. And if you are extremelyt efficient in the Gulf of Mexico you might just reduce the incidence of damaging hurricanes. that appear when the surface water is above ca. 27 degrees celcius. --17:01, 27 January 2007 (UTC)