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Power Science

Harnessing Vertical Sea Temperature Gradient 426

Sterling D. Allan writes "Sea Solar Power Inc., run by three generations of James Hilbert Andersons, has developed a solar power technology that does not fluctuate with the weather, but is available constantly. Their solution is to harness the solar energy stored in the sea by tapping the thermal gradient that exists naturally between the surface and deep waters, using a reverse refrigeration cycle. The modeling and testing done by the Anderson family over three generations since 1962 predicts that the cost of energy generation through this method will be within a price range comparable to nuclear, coal, natural gas, and other contemporary grid power plants. Ocean Thermal Energy Conversion, or OTEC, was invented in 1881 by a French scientist, Jacques Arsene D'Arsonval. SSP should be ready to build their first full prototype 2-3 years from now."
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Harnessing Vertical Sea Temperature Gradient

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  • Solar???? (Score:3, Informative)

    by Lifewish ( 724999 ) on Wednesday January 04, 2006 @06:49PM (#14396283) Homepage Journal
    Aquethermal, if you please! It's only solar in the sense that all power on Earth apart from geothermal is solar.
    • Re:Solar???? (Score:4, Informative)

      by MarkPNeyer ( 729607 ) on Wednesday January 04, 2006 @06:51PM (#14396290)
      Nuclear power doesn't derive its energy from the sun.
      • Re:Solar???? (Score:5, Insightful)

        by Lifewish ( 724999 ) on Wednesday January 04, 2006 @06:53PM (#14396307) Homepage Journal
        I knew I missed something...

        Incidentally, does the thought of messing around with oceanic temperature gradients bother anyone slightly? It's probably not on a scale nearly wide enough to destabilise any currents, but it'd be good to have an oceanographer's opinion on this.
        • As opposed to blanketing homes with solar panels. One way or another, energy is being diverted from the land or water. Considering all the energy being released from burning coal, oil, and natural gas, I'm quite sure solar technology will be a relative drop in the bucket for decades to come.
        • by Anonymous Coward
          The US generates and uses about 3800 billion kwh of electricity per year.

          ASSUMING this thing can convert a 40 degree F (22 C) temperature gradient into electricity at 100% efficiency (which it can't, just looking for order of magnitude kind of thing here) then a 6ft (2m) diameter pipe sucking water in at a 20fps (6m/s) velocity will suck up enough water to generate 1500MW.

          Ignoring peak demand and all that, it would take 300 (300) of them to power the entire US.

          Assuming an average ocean depth of 1000ft (300m
      • Re:Solar???? (Score:4, Insightful)

        by networkBoy ( 774728 ) on Wednesday January 04, 2006 @07:01PM (#14396378) Journal
        In fact I think there are three sources of energy on earth:
        Stored friction (hot core)
        everything is a stored form of something else, and the three above are a stored form of the big bang.
      • Re:Solar???? (Score:5, Interesting)

        by JesseL ( 107722 ) on Wednesday January 04, 2006 @07:07PM (#14396432) Homepage Journal
        Nuclear power doesn't derive its energy from the sun.

        No, but it does derive it's power from heavy elements that were created by the explosions of older stars.
        • Re:Solar???? (Score:3, Informative)

          by sploxx ( 622853 )

                  Nuclear power doesn't derive its energy from the sun.

          No, but it does derive it's power from heavy elements that were created by the explosions of older stars.

          And so does geothermal energy, which is feasible because of decaying radioactive elements (K-40 etc.) in the earth's interior.
      • From another sun, as I understand it.
      • Aha! But solar power derives its energy from the nucleus.

        Think about it.
    • Nucular. It's pronounced nucular. ;-)
    • by Roger W Moore ( 538166 ) on Wednesday January 04, 2006 @07:25PM (#14396597) Journal
      Actually depending on how strict your definition of solar is current nuclear power could be considered as such. If you allow solar to mean "from a star" and not just "sol" (which is not unreasonable since we talk of "solar systems" around other stars now) then fission reactors are actually using "fossilized" solar powered.

      Fission reactors, our only current form of nuclear power, split uranium nuclei into smaller fragments and thereby release energy. However, to form the uranium atom in the first place from smaller constituents therefore required energy. This energy is thought to have come from a supernova ~6 billion years ago, predating the formation of the solar system. Thus current reactors are, by some (possibly warped!) definition, still using fossilized "solar" power. The same can also be said of geothermal which relies mainly on natural decay of nuclei formed by the same supernova.

      Only if we ever get fusion reactors working then we really say that we are no longer reliant on solar based power...and that's because we will have made our own mini-sun.

    • Re:Solar???? (Score:3, Informative)

      by Jackazz ( 572024 )
      Tidal energy is based on the motion of the moon, not the sun or its rays.
  • by csoto ( 220540 ) on Wednesday January 04, 2006 @06:52PM (#14396294)
    Just like hydro power, this one has the problem of disrupting the environment, albeit a very local environment. By moving water against the normal gradient, you will warm up water that's supposed to be cold, and cool off water that's supposed to be warm. I could imagine plankton blooms and oxygen depletion, among other side effects.

    Passive solar collection (photovoltaic and otherwise) and wind power are really the only truly "green" power sources.
    • Somebody please think of the bird decapitations.
    • Local? (Score:2, Interesting)

      by MAXOMENOS ( 9802 )
      If this technology gets adopted widely enough, I doubt the problems will be local for long.

      The parent is right on. This is just trading one environmental stressor for another.

    • Bullshit. They both redistribute exactly the same amount of energy as this does, just in different ways. There's no way to remove energy from any part of the ecosphere without having a local effect. The only question is whether the local effect matters or not. And by 'matters' I mean matters, not 'matters to the Green Taliban'.
    • by paco3791 ( 786431 ) on Wednesday January 04, 2006 @07:02PM (#14396389) Journal
      The problem with any power generation scheme is that there are always side effects, you just have to pick your poison.

      With photovoltaic systems you have the nasty chemicals currently associated with manufacture, with wind power you have what some people consider noise and landscape pollution, along with bird strike problems, although this problem is probably over hyped with newer windmill designs.

      There is, as they say, no free lunch.
      • I think really what we need to do is spread out the burden. All power generating facilities are going to cause environmental damage, but they are going to do it in different ways. Small perturbations aren't going to be as bad as large perturbations. So a few wind turbines will cause some noise pollution, but if you stick them out in the middle of Oklahoma and use them for that local area, it won't be such a big problem. You can setup a few solar plants, nuclear plants, coal plants, geothermal/aquathermal sy
      • There is a version of solar that does not use photo voltaic cells. Remember the Sim City 2K solar power plant? It looks a lot like that. An array of mirrors reflects light into a dome atop a tower. The dome contains a circulating supply of water that is heated up into steam and used to drive a turbine. The mirrors are automatically angled to reflect the sun (at pretty much any angle) into the dome.

        No really nasty chemicals involved, and it uses technology that has been available for a really long tim
    • by lilmouse ( 310335 ) on Wednesday January 04, 2006 @07:03PM (#14396399)
      True. What we need is something like Trantor [wikipedia.org] - use the (negative) heat gradient from deep in the earth instead of the gradient in the oceans. Of course, we'll have to do more research drilling, but we're already getting close [msn.com] to the mantle!


      ps - no "think of the earthworms", please.
    • Wind turbines must slow down the wind. PVs must collect energy that would otherwise impact the environment.

      Thermodynamics won't let you continuously pull energy out of a closed system.

      Also, human beings are part of nature.

      I'm glad we could have this little chat.

    • Bt the same line of reasoning wind power would not be passive energy because wind mills slow down the wind. In reality the order of magnitudes are such that slowing down the wind, or changing the temperature of the ocean, is not a problem.
    • by Chandon Seldon ( 43083 ) on Wednesday January 04, 2006 @07:17PM (#14396519) Homepage
      Absolutely any technique to generate power will have environmental consequences. Wind power takes wind energy out of the atmosphere, which could cause climate change if used on a large scale. This proposal is about the same.

      A very important point to remember is that we will use an increasing amount of energy for the forseable future and that energy will be generated somehow. Coal is the default power technology. Every time a wind / nuclear / tidal / etc power plant doesn't get built another coal plant is built instead. So the question isn't "Is there an environmental impact from this power source?" - we know that answer, there always is - the question is "Is this better than coal?".

    • by caseih ( 160668 ) on Wednesday January 04, 2006 @07:22PM (#14396568)
      No, even photovoltaic solar panels aren't passive. They prevent energy that would reaching the ground from doing so, altering the energy balance there. In short there is no form of energy that we can extract from nature that doesn't alter in some way (large or small) the natural energy flows and balance in nature.
    • Aside from valid ecological concerns, there are also mechanical concerns.

      Salt water and weather in general will do a number on these devices. Waves cause variable pressure on this device and salt water is very corrosive.

      Still, its a better choice than tide differential generators, which would die much faster due to moving parts.
    • Passive solar collection (photovoltaic and otherwise) and wind power are really the only truly "green" power sources.

      The processes to manufacture these are also green? Ever seen a semiconductor fab? Clean? Yes. Green? I dunno, what color is arsine gas? If you smell garlic, it ain't the pizza joint next door.
    • Big wind power turbines farms reduce wind velocities which will tend to increase air temperature gradients, making cold places colder and hot places hotter.
  • by mmell ( 832646 ) on Wednesday January 04, 2006 @06:52PM (#14396299)
    For example, they're talking about exchanging a thundering lot of heat here. Will this affect existing ocean currents? Might the thermal change not impact on the underwater ecosystem (a system we are only now beginning to even be able to see)?

    Further, what of the potential for secondary effects? Climate changes brought about by changes in ocean current temperatures? Remember, el nino/la nina are caused by a change of only a few degrees. That's not unforseeable for a large-scale technology such as this.

    Oh, and BTW - it makes a lot more sense to base this on something like an oil rig, rather than a ship. Just sayin', is all.

    • Weren't they recently worried about the ocean currents that carry warm water to Europe essentially turning off?

      Maybe a bunch of these stations strategically placed would keep our various underwater thermal currents moving along.

      As for ship vs oil rig, my understanding was that oil rigs were moored to the seabed, compared to a ship being anchored. I'm not sure how feasible it'd be to moore an oil rig in ultra-deep waters.
    • What will the do when a giant squid inevitably crawls up the pipe and gets stuck.
    • The ocean is so grossly unimaginably big that we would need an absolutely huge operation to even cause a measurable effect. If you really tried to change the temperature by even a fraction of a degree using this method you would have to pump extremely large quantities of water---quantities so large that I don't think anyone would ever consider building something so massive.

      People sometimes forget the scale of things. On a global scale, we are not even part of the equation.

      But you also have to consider the o
  • by Anonymous Coward on Wednesday January 04, 2006 @06:53PM (#14396308)
    "SSP should be ready to build their first full prototype 2-3 years from now.""

    It will run Linux (everything else will by 2007-2008)
  • This isn't news (Score:4, Interesting)

    by remy ( 82535 ) on Wednesday January 04, 2006 @06:53PM (#14396309)
    I did a report on OTEC when I was in junior high--18 years ago--based on an article in Scientific American. There are prototype facilities in a number of countries--I visited the facility in Hawaii five years ago, which was at least a decade old then.

    It's an intriguing idea, but this smacks of somebody trying to get publicity to bring in venture capital or something of the sort.
  • waves? (Score:4, Interesting)

    by User 956 ( 568564 ) on Wednesday January 04, 2006 @06:55PM (#14396332) Homepage
    why not just harness the wave energy [freeenergynews.com]?
    • I keep reading harness as harass for some odd reason.

      "Harassing Vertical Sea Temperature Gradient"
      "Why not just harness the wave enery?"

      Yeah check out those nice smooth bumps! It sure does make me wet...
    • Re:waves? (Score:2, Insightful)

      by jgardn ( 539054 )
      Because dolphins happen to live closer to the surface of the ocean than the bottom, along with the vast majority of sea life. And waves are plentiful near the shore, where they would be seen by people and interfere with ocean traffic.

      This could be built out of sight and away from the vast majority of living sea creatures. You have to build it where the ocean is very deep, namely, away from where most people live.
    • Re:waves? (Score:4, Insightful)

      by lilmouse ( 310335 ) on Wednesday January 04, 2006 @07:24PM (#14396579)
      Waves depend on things like wind and tides to work. Winds change with the weather, and tides change all the time (at least tides are regular). Whereas it's *always* possible to get a 20degree heat gradient.

      Besides, if you put your heatsinks below the surface of the water, you don't have to worry so much about storms and such.

  • SMAC's Realization (Score:3, Insightful)

    by Erioll ( 229536 ) on Wednesday January 04, 2006 @06:56PM (#14396339)
    Nice to see concepts popularized (though hardly invented) by Sid Meier's Alpha Centauri being realized, considering this is basically like a Thermocline Transducer.
  • Choice of phrase (Score:3, Insightful)

    by jtorkbob ( 885054 ) on Wednesday January 04, 2006 @07:00PM (#14396371) Homepage
    'Has developed'? How about 'is developing'?

    I mean, in the last year, I've read about thermal stacks, hydrogen generation using thermal power, horizontally-oriented wind turbines, and probably some other alternative power methods. They're all great ideas, with great possibility, but the summary for every one reads like a sales pitch.
  • Hurricane Control (Score:3, Interesting)

    by truckaxle ( 883149 ) * on Wednesday January 04, 2006 @07:02PM (#14396398) Homepage
    Set up shop in Caribbean or Gulf of Mexico and maybe as a added benefit, such energy harvesting, could decreasing hurricane potential by cooling surface water temperature. This would be win-win, but I am sure that it would also be disruptive to some marine life so maybe a win-win-lose sometime you just can't have it all.

    • How about a huge windmill farm in the hurricane's path coupled to a huge battery bank and/or capacitors. Then we can harness enough energy in a day or two to last for a year.
      Another alternate to that is to build a windmill farm just offshore that pumps water like crazy out of Lake Ponchatrain when hurricane force winds arrive.

      Boy, I'm full of it today. Somebody send me home. (It's not spelled right, but I don't care.)

  • by Fitzghon ( 578350 )
    "...using a reverse refrigeration cycle."

    We have a name for those. They're called engines.

  • Old News (Score:3, Insightful)

    by Belseth ( 835595 ) on Wednesday January 04, 2006 @07:10PM (#14396455)
    I've been reading about this since the 70s. It's a great idea and I can't understand why no one has built a prototype yet. Most of the systems I read about proposed using something like amonia since it was dealing with a temperature difference rather than high temperatures. Some chemicals like amonia boil at very low temperatures. They don't produce the power steam does but it's a stable source. Deep ocean temperatures are near freezing where as surface temperatures can be 40 to 50 degrees higher in the same area. Some have complained about cooling surface water. The ocean is a mighty big heat sink and it's doubtful plants that are spread out would have much affect. In truth it might help offset some of the surface warming caused by global warming. I'm not sure enough plants could be built that would drop ocean surface temperature one degree. Temperatures have already raised that much in the last 100 years.
    • Re:Old News (Score:4, Informative)

      by alienw ( 585907 ) <alienw.slashdot@g[ ]l.com ['mai' in gap]> on Wednesday January 04, 2006 @07:21PM (#14396557)
      There are a few prototypes. Search for OTEC on google. The problem is, there isn't enough of a temperature difference to efficiently extract any useful energy. You basically have to pump HUGE quantities of water (like a 10m diameter pipe) to the surface and have enormous heat exchangers and stuff that extract the energy. You use a lot of energy to pump the water and it requires enormous capital investment for very small amounts of energy.
  • Won't this mess up the natural mixing currents that already go on? The global warming crowd is convinced that the ocean's natural mixing patterns are being disrupted and this will cause unpredictable climate changes and they have some data to back up their statements that a previously stable system is being disrupted, but now people are talking about deliberate disruption of the temperature gradiants and thermocline?

    It really does not sound responsible to me. We're already tampering with the climate and s
  • why can't they use a heat-exchanger with conjunction to the one-way thermal transfer materials (I think a product of nano-technology) that was being tested and was slashdotted last year so they don't have to worry about any marine growth growing or dying in the plant itself?

    And why not also use the energy to produce methanol or methane using the freshwater and probably carbon dioxide from the air or from industrial waste from the mainland? Heck, even ethanol so it can be used in cars to help reduce relianc
  • by truckaxle ( 883149 ) * on Wednesday January 04, 2006 @07:20PM (#14396538) Homepage
    The problem here is the huge quantity of thermal energy that needs to be exchanged for a small amount of useful work. To generate work between a 80 degree f source and a 50 degree f sink the best you can do is around 7 percent efficiency.
    • The amount of energy in the ocean is huge. Really huge. Hurricanes are a really small expression of that, and hurricanes make thermonuclear weapons look like kiddie toys.

      Multiply a kilowatt or so per square meter insolation by the size of the ocean, take seven percent of that, and get back to me on whether you think it's enough.

      • Multiply a kilowatt or so per square meter insolation by the size of the ocean, take seven percent of that, and get back to me on whether you think it's enough.

        So, you're basically going to build this to cover the entire ocean? Either that or you've got a heck of an equilibrium problem, there.
    • The problem here is the huge quantity of thermal energy that needs to be exchanged for a small amount of useful work

      That's why we currently burn a lot of stuff to make steam. However with this ocean idea you have little in the way of running costs and very simple technology for a base load station so that offsets the low output. Sticking it out in the sea with wires attaching it to land makes things more complicated.

      Well over a hundred years ago the first electrical power generated in my state used the

  • by hoka_hey ( 837488 ) on Wednesday January 04, 2006 @07:21PM (#14396556)

    Deja vu!?!

    There is a global circulation system called thermohaline [wikipedia.org]. Basically in three relative small areas of the oceans the water sinks until the bottom, and then spread around the world. This water slowly go up again and the system is closed with surface warmer waters flowing in direction of the areas of generation.

    I'm not even considering the energetic balance of the proposed structure, but if it works it might reduce the vertical thermal gradient and make the thermohaline circulation weaker. Maybe stop it. The movie "The Day After Tomorrow" is a fantasy about it, but be sure at least that the surface temperature on the North Atlantic would reduce since is one of those areas of generation of deep waters. You can imagine how would be the winter on Europe and North America? Would need a lot of energy to keep people warm there!

  • Wikipedia entry (Score:4, Informative)

    by amembleton ( 411990 ) <aembleton&bigfoot,com> on Wednesday January 04, 2006 @07:24PM (#14396584) Homepage
    Wikipedia entry on the subject of Ocean thermal energy conversion: http://en.wikipedia.org/wiki/OTEC [wikipedia.org]
  • by Culture ( 575650 ) on Wednesday January 04, 2006 @07:25PM (#14396596)
    ... any information from a web site that calls stochimetric mixtures of oxygen and hydrogen "Brown's Gas" and claims that it "takes on the properties of what it is exposed to -- not in a physical reproduction, but in essence." Or try this gem: "When the electricity (in the Brown's Gas) is released by the 'flame,' it comes out as electricity and the water 'implodes' to it's original liquid form, with no heat and no expansion first. That's also why the flame is 'cool' yet has high energy effects." Yeah ... right. Take a look at the "Gravity Motors" section. It is even funnier.

    I guess I am being punished by my mechanical engineering background.

    It is possible that there is some good information on this site (somewhere), but quite frankly I do not know what you would want to waste time separating the real information from the quackery.

    • About Brown's Gas:

      Brown's Gas Information [phact.org] and Eagle Research [eagle-research.com]

      As for "When the electricity (in the Brown's Gas) is released by the 'flame,' it comes out as electricity and the water 'implodes' to it's original liquid form, with no heat and no expansion first."

      As you said, pure rubbish. It does explode first to produce water vapor, and the condensation of water vapor to liquid water does liberate large quantity of heat.
  • The technology they are using is interesting, and they have pilot systems up and running, which are working fine in pacific island environments for 'low level' power needs. This is good, as pacific islands typically have to import fuel to burn for their power, and this technology does away with or at least reduces that need/

    The only thing is that you need easy access to deep ocean close to land in order for this to work. In other words you need a 2000m (or deeper) ocean trench a short easy distance from th

  • Under Salt Water (Score:3, Insightful)

    by Heembo ( 916647 ) on Wednesday January 04, 2006 @07:35PM (#14396676) Journal
    Under-ocean electric generation methods are doomed to be radically costly to maintain. Damn, ever see what salt water does to most machines over time? Not pretty.
  • go nuclear (Score:4, Interesting)

    by circletimessquare ( 444983 ) <circletimessquareNO@SPAMgmail.com> on Wednesday January 04, 2006 @08:00PM (#14396823) Homepage Journal
    pebble bed reactors don't go china syndrome. environmentalists attitudes about nuclear is based on decades-old technology and watching too much "silkwood"

    thermocline, solar, biodiesel, wind, tidal turbine, wave generated, etc.: these are all very cute boutique energy sources. but when all put together and maxed out in terms of realization of potential they won't dent 5% of our energy needs

    oil and gas and coal are incredibly dirty and even geopolitically dangerous and increasingly expensive

    put it all together and pebble bed reactors are an environmentalist's and energy policy maker's best friend

    now we just need the lowest common denominator of uneducated environmentalist's opinions to catch up with reality


    educate yourself, don't let your uneducated fears dictate your opinion

    as time goes by, nuclear is only going to look more and more attractive to this world, once everyone gets a real education of the positves and negatives of nuclear compared to everything else

    because the biggest thing going against nuclear really is only inertia and ignorance
  • Duplicate and again (Score:3, Informative)

    by JackL ( 39506 ) on Wednesday January 04, 2006 @08:04PM (#14396847)
    Looks like we have covered this topic rather [slashdot.org] well [slashdot.org].

    The discussions were better on those, too.


  • Sounds like a hoax (Score:4, Insightful)

    by Yartrebo ( 690383 ) on Wednesday January 04, 2006 @08:33PM (#14397036)
    I really, really doubt that this thing is practical. Organic Rankine Cycle Turbines (which are proposed) are very expensive to operate on dry land, as has been shown by research into solar thermal power in California. At least in those cases the efficiency was around 20%. The best they can hope for with OTEC is about 1.5% efficiency. Theoretically they could get 3.25% (Carnot efficiency), but experience with Organic Rankine Cycle Turbines has shown that 300C solar plants (Carnot Efficiency ~50%) only get around 20%, so one could expect to get about 1.25% efficiency out of their OTEC setup.

    On top of this, all the equipment must be marine grade (ie., pricey). Power must be transferred to shore. It also must be a functioning ship with all the expense associated with that.

    But what makes me most suspect is the claim of making fresh water. Ordinary Rankine Cycle Turbines do produce fresh water via distillation, but the Organic Rankine Cycle is a closed cycle and no fresh water is produced. The only condensation you'll get are hydrocarbons, which are recycled to create more vapour.
  • by GrahamCox ( 741991 ) on Wednesday January 04, 2006 @09:34PM (#14397445) Homepage
    Correct me if I've got my wires crossed, but I thought the sea temperature was about a constant 4 degrees all the way down, once you get below a certain distance of the surface. The reason being, that water colder than 4 degrees has lower density, therefore always floats upwards. That's why the ocean isn't frozen at great depths. It doesn't mean you couldn't tap that gradient anyway, but the depth required presumably wouldn't be all that much as long as you'd got at least as far as the 4 degree level.
  • Ah. Yes. (Score:3, Interesting)

    by Amiasian ( 157604 ) on Thursday January 05, 2006 @05:06AM (#14398852)
    Yet again, I am reminded of Marshall Savages thought-provoking work, Colonizing the Galaxy in Eight Easy Steps [google.com]. His belief is that the use of OTECs will relieve the world's energy problems, in addition to providing power for floating sea colonies, thus relieving population density. Furthering his premise, if I recall, the warm water will lead to an abundance of blue-green algae, which can be processed and used as a food source. These things, interestingly enough, are only a stop-gap until we can begin to expand life to places outside of this current biosphere.

    Okay, maybe a tad off-topic, but I certainly find it fascinating.

I've finally learned what "upward compatible" means. It means we get to keep all our old mistakes. -- Dennie van Tassel