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Science

New Power Plant Produces Both Energy & Fresh Water 388

Posted by chrisd from the yahoo-seriously dept.
joshmccormack writes "An article in Sunday's New York Times (Free Reg, mah peeps) tells of how Japanese scientists have found a way to make fresh water and energy from temperature differences in ocean water. This may change the rules of what land is considered habitable, and the value of energy." Fascinating stuff, next step is rumored to be beer and power.
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New Power Plant Produces Both Energy & Fresh Water More

New Power Plant Produces Both Energy & Fresh Water

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  • Isn't that outlandish... (Score:3, Interesting)

    by httpamphibio.us ( 579491 ) on Tuesday March 25, 2003 @06:25AM (#5589919)
    After reading the headline, the combination of these two things is like starting a company that sells fireworks and flamethrowers... but after reading the article it actually makes a good deal of sense.

  • There is one OTEC plant in Kona, Hawaii (Score:5, Interesting)

    by g.a.g ( 16798 ) on Tuesday March 25, 2003 @06:26AM (#5589920)
    FP? Anyway, I've visited that type of plant (OTEC, Ocean Thermal Energy Conversion) already in Hawaii (near Kona), where there is one running since quite some years. One problem is that it only works for steep ocean wall drop offs, since otherwise the pipe is getting too long.

    It uses about half of the created energy (through a normal Carnot cycle) for pumping (about 120kW). The other half is not quite competetive, but with the nutrient rich and cool water, fish farming and air conditioning can be done, heaving the whole investment to a black zero (or better).

    I leave the exercise of finding the link to a Karma-hungry reader.

  • Thermodynamic law (Score:5, Insightful)

    by very ( 241808 ) on Tuesday March 25, 2003 @06:26AM (#5589923) Journal
    Temperature difference in sea.
    the temperature difference is enough to liquify certain gasses, and then expand it again.

    Just like the refrigerating unit.

    Not to mention the increase of pressure water gets deeper.

  • Interesting Idea (Score:5, Interesting)

    by ItaliaMatt ( 581886 ) on Tuesday March 25, 2003 @06:27AM (#5589925)
    Having lived on a island in the south pacific for a year I learned how important fresh water is. The aircraft landing strip that we had acted as a big water collector - water would drain into pipes and then was cleaned by a chlorination process. The idea they propose is a good one and would work in many islands out there - where they desperately need easy access to electricity and fresh water.
    • Even at that, unless the technology has improved remarkably, this only works in special situations with marginal positive net cost. (Plus possibly beneficial side effects.)

      Most islands aren't good candidates. Look first at solar evaporation + solar heating. (Less initial cost for *some* immediate payback.)

      Still... if you are in just the right location, it *can* be a positive payback system.

      • Not solar heating... solar cell electricity.

        N.B.: Unless you're buying right now, look at the cell designs that aren't quite on the market yet. I especially like the one that drapes like canvas. (Though I haven't looked at them with an eye toward buying them.)

  • Light on the details (Score:5, Interesting)

    by billstr78 ( 535271 ) on Tuesday March 25, 2003 @06:28AM (#5589929) Homepage
    I am sure more will be available about the subject at a later date but, here is what would be interesting to know:

    + How much power/water does one of these amonia powered drinking fountains produce?

    + Is it scalable, should I start writing my congress person to de-comission Califoria's oil powered plants?

    • Re:Light on the details (Score:5, Informative)

      by AlecC ( 512609 ) <aleccawley@gmail.com> on Tuesday March 25, 2003 @08:14AM (#5590147)
      It is scaleable - provided you have the right sort of coast, with very deep war relatively close to the shore. It will therefore be very suitable for most Pacific islands, many of which are the tops of seamounts. I don't think the coast of Calif is quite so precipitous - and the power consumption per mule of coast is probably thousands of times that of (low population, low power consumptoion, lots of beach) Pacific islands. So don't get too excited.

      • Re:Light on the details (Score:4, Funny)

        by BJH ( 11355 ) on Tuesday March 25, 2003 @08:25AM (#5590171)
        You measure your coastlines in mules? Hmmm... how many Libraries of Congress per hogshead do your mules get?

      • Re:Heavy details. (Score:4, Interesting)

        by fshalor ( 133678 ) <fshalor@comcas t . net> on Tuesday March 25, 2003 @09:41AM (#5590405) Homepage Journal
        Considering I had a conversation about this about a week and a half ago while camping: 1 OTEC with a 40 ft pipe in the indian ocean slightly over 3000 ft in length(going down of course) with a temperature difference of around 45 degrees C year round can produce around 100 MW. About 40MW is used for running the system. Source: The Millennial Project: Marshal T. Savage. Foward by Aurthur C. Clark and jacket note by Pournelle. Out of print. I've applied some of my Chemical Engineering skills and verified the scale of the figures. Cost per OTEC of this size: about 1.1Billion USD (slightly adjusted.)


        I think the DoE deep sixed research on this in the late 70's becasue these would have to be in international waters halfway around the world in order to be effieient.

      • It is scaleable - provided you have the right sort of coast, with very deep war relatively close to the shore.

        So it should work great in Iraq, right?

    • Other options (Score:3, Interesting)

      by squaretorus ( 459130 )
      One interesting power / water / greenhouse idea I read in New Scientist a while back involoved building a big glass air hanger in a hot climate on a reliably windy spot near the coast - the windward wall was built as a metal framework filled with porous wate absorbant material (straw in the example) which had sea water running down it in a waterfall.

      As the hot wind entered the hanger it evaporated a large amount of water, and cooled substantially. The climate within the hanger was therefore wet and cool an

      • Re:Other options (Score:2, Insightful)

        by Hadlock ( 143607 )
        how about a kilometer radius circle of glass that sits about 15 feet off the ground with no walls other than support beams, in the middle sits a kilometer high concrete tube, inside of it are multiple generator turbines. as the sun heats up the air underneath the glass, it moves to a low-pressure zone, the top of the concrete tube, where the ambient air temperature is nearly twenty degrees lower than at ground level; and somthing to the effect of 60 degrees (farenheight) difference between the top of the tu
  • I first read about this as a kid years ago in the 70s. I think it's called OTEC.

    The twist seems to be usage of ammonia water instead of plain ammonia - which was what I read about then.

    http://www.ioes.saga-u.ac.jp/about-otec-lab_e.ht ml

    One thing for sure it's definitely closer to being practical than hot fusion power stations.
    • Here is a far more original idea I just saw on news.google.com. It's [yahoo.com] a power source that runs on vodka.. yeah!

  • Good news for arabs. (Score:4, Interesting)

    by sokkelih ( 632304 ) on Tuesday March 25, 2003 @06:32AM (#5589938)
    I heard that in some arabian countries beer is less expensive than water.. In near future this could also allow folks down in US to get their industrial energy(Oil) from somewhere else than Irak? ;)

    • Re:Good news for arabs. (Score:5, Funny)

      by archetypeone ( 599370 ) on Tuesday March 25, 2003 @06:45AM (#5589973) Homepage
      I heard that in America Beer is less tasty than water.
    • Ok, YOU try to find beer in Saudi Arabia. Besides no cruise lines go to the Middle East.

      Now I do know that beer is cheaper than water in the Carribean. At least in St. Maarten. They have some really interesting drinking and driving laws too. Basically as long as holding the bottle doesn't interfere with driving.

      • Moral, they really need the beer-producing energy-source in Saudi Arabia.

        This must be the next biggest market for anything, second just to TV-shop marketing.
    • I heard that in some arabian countries beer is less expensive than water.. In near future this could also allow folks down in US to get their industrial energy(Oil) from somewhere else than Irak? ;)

      Well, everyone needs water, but there's not much demand for beer because it's forbidden under Sharia (Islamic law). The only people who drink it are expats, and only then in the (relative) privacy of their own homes, bars in international hotels, and so on.
    • I'm not too sure about that. One of the links above mentioned that you need a high temperature gradient for this process to be effective. I don't think that gradient exists in either the Persian gulf or in the Medeteranian.
    • I saw on a commercial that Canadians can tap maple trees for beer (molson canadian specifically) is THIS true?

      When I visited Cuba on a trip the rum was cheaper than the Coke...is THIS true???

      And I heard that anyone that drinks water is a pansy! Brush your teeth with beer!

      On a serious note, if beer was cheaper than water, I would probably drink more beer, less water. And be drunk all the time. And buy a beer cooler for work...and then pee my name into the desert...
    • Locally produced Cruzan 151 Rum..
      $3.00

      2L bottle of Pepsi..
      $3.00

      Saving $3 and getting completely shit-faced on the beach by drinking that nasty ass rum straight..
      Priceless.

      Welcome to St Croix in the US Virgin Islands.

  • Free for all (Score:4, Informative)

    by Anonymous Coward on Tuesday March 25, 2003 @06:34AM (#5589947)
    Japanese Technology May Help Islands Reap Pacific's Waters [nytimes.com]
    By AGENCE FRANCE-PRESSE

    KYOTO, Japan, March 22 -- A number of Pacific island nations are discussing using new Japanese technology that can both desalinate seawater for drinking and produce electricity by exploiting the difference in temperatures between the surface of the sea and the depths of the ocean.

    The Republic of Palau in the western Pacific is working with Saga University in southern Japan to build a system that can produce enough drinking water to meet the needs of its 20,000 residents, while producing electricity, said the country's president, Tommy Remengesau Jr.

    The concept was highlighted this week at one of the 350 sessions at the Third World Water Forum, which is under way here. It has attracted 10,000 participants from around the world, along with ministers and some heads of state from more than 150 countries.

    The university is preparing to build an experimental power plant off the coast of Palau that brings up cold seawater from the depths of the sea to an evaporator chamber near the ocean surface.

    As the water is heated by the surrounding warm surface water, it releases ammonia gas, which then drives the system's power generator, said Yasuyuki Ikegami, deputy director of the Institute of Ocean Energy at Saga University.

    Meanwhile, the heated water would be transferred to a separate low-pressure chamber where it boils at a lower temperature, producing steam, which would be condensed and collected as fresh water for human consumption, leaving salt crystals behind.

    One experimental system, which produces power but no usable water, is scheduled to be put into use off the coast of India this month, Mr. Ikegami added.

    "It works well especially in the western Pacific, where the temperature difference between the ocean's surface and deep seawater is" as much as 43 degrees Fahrenheit, he said. "It is environmentally sound."

    With some financial assistance from the Japanese government, the university was hoping to build the experimental plant in Palau for $7.5 million, said Haruo Uehara, president of Saga University, although he declined to disclose details of the financing because it was still being negotiated.

    Palau was hoping the plant could be built next year, Mr. Remengesau said.

    "It is a big help for us," he said. "When there is rain, we have no problem. But we are hit by the drying effects of El Niño. When there is no rain, where can we get drinking water?"

    The fresh water produced by the system will cost less than $1 for more than 250 gallons, Mr. Uehara said. "It is no more costly than regular tap water in other countries, including Japan," he said.

    The system, while more expensive than ordinary generators, has raised hopes among leaders of other Pacific islands, which are too small to build many dams to catch water and are trying to cut back on their consumption of oil to run power generators.

    Allan Marat, deputy prime minister of Papua New Guinea, said Pacific island nations had fallen victim to global warming, adding that he too was interested in the university's system.

    "We are in the middle of the largest body of water" on earth, said Robert Woonton, prime minister of the Cook Islands. "Yet, we are faced with lack of safe potable water." He said he wanted to consider setting up Saga University's system in his country.

    Other countries in arid zones have also shown interest, including Saudi Arabia, which was sending a delegation to the university, Mr. Uehara said.

  • Very interesting (Score:3, Interesting)

    by The Clockwork Troll ( 655321 ) on Tuesday March 25, 2003 @06:42AM (#5589965) Journal
    This is very interesting stuff but the headline is a little misleading.

    Strictly speaking, complete combustion releases energy and water (and carbon dioxide), and combustion engines are power plants that have been producing energy and water for quite some time.

    Of course the operative word there is complete and as we all know your typical combustion engine passes (at least) a few PPM of unburnt hydrocarbons along with the other combustion products.

  • Environmentally safe? (Score:4, Interesting)

    by Redmega ( 641324 ) on Tuesday March 25, 2003 @06:42AM (#5589967)
    The article wasn't clear whether the ammonia is re-absorbed or released into the atmosphere. I'm guessing it would have to be released, otherwise it'd be some kind of perpetual energy system. Assuming that's true - surely this system is just the same as burning fossil fuels? except it's releasing nitrogen based nasties instead of carbon based ones. Or am I misguided again?
    • I'm sure that anything that's over-utilized is going to damage/change the environment in some way. Amnonia is a great fertiizer for plants and any that is not used could be injected back into the efluent stream and would re-disolve as presure and the cold from the depth increases and although it may cause localized concentrations the net effect would be pretty neutral. A little less neutral would be the gradual warming of deep water and its effect on the local deep water enviroment, but the incredible mass

    • I'm guessing (Score:2, Informative)

      by e_pluribus_funk ( 648835 )
      You don't know much about science at all. Do you really think it's appropriate for you to be spouting out pet environmental theories given your stupendous lack of knowledge of basic mechanisms of energy transfer?

      Did you bother to read the article to see how this works? No.

      But that sure didn't stop you from rushing out and writing a post about the potential environmental horrors of the release of ammonia gas.

      Conservatives and big oil don't have to destroy the environmental movement...their own stupidity

  • Ecological Impact (Score:5, Interesting)

    by soundofthemoon ( 623369 ) on Tuesday March 25, 2003 @07:05AM (#5590010)
    Bringing cold water from the depths has an unmentioned potential side-effect. Will it be replaced by warmer water from elsewhere? Cold, deep waters often support amazingly rich ecosystems. Raising the temperature even a few degrees could easily destroy entrie habitats. Will these generators warm the depths, and what effect will that have on the deep ecosystems?

  • Protest! (Score:5, Funny)

    by Carewolf ( 581105 ) on Tuesday March 25, 2003 @07:07AM (#5590016) Homepage
    Fresh water and clean energy? Sounds awfully unamerican and likely to support terrorism.
    • Who said this energy was clean? I believe it deposits waste on the sea floor, thus harming the sea ecosystem around it.

      Or was that another new powerplant I'm thinking of?

  • Considering... (Score:4, Funny)

    by forgoil ( 104808 ) on Tuesday March 25, 2003 @07:19AM (#5590038) Homepage
    Considering that they have Beer Water (whatever that might be) in Japan, the rumor might hold some truth;)
    • I think that would be "Budweiser."

      In any case, since they are pulling ammonia from the water, that would lead me to believe that even if they pull beer from the water, someone drank it first.

      Can't buy it, only rent it.

  • Before we get carried away (Score:4, Insightful)

    by jandersen ( 462034 ) on Tuesday March 25, 2003 @07:25AM (#5590045)
    - it's worth thinking about the environmental impact. Since the industrial revolution we've kept saying that 'of course pollution is no problem' - first we created smog in the cities, then we filled the seas and rivers with shit, now we have global warming etc etc. So lets just stop briefly before we plunge into this one, OK?



    This affects not only the athmosphere by releasing ammonia (which is only a minor problem), but also the temperature balance in the ocean. Things such as the major ocean currents are driven by differences in salinity and temperature of the water. The big currents control at least part of our climate - eg. if the Gulf Stream were to shut down (which some think it might all too easily do if the polar ice cap melts), we will probably have a new ice age



    And before you start jeering and making stupid jokes about it, remember that only 30 years ago the idea that human pollution could affect our athmosphere and the seas, was regarded as utter nonsense and hysteria.

    • Re:Before we get carried away (Score:5, Interesting)

      by Troed ( 102527 ) on Tuesday March 25, 2003 @07:34AM (#5590065) Homepage Journal
      And before you start jeering and making stupid jokes about it, remember that only 30 years ago the idea that human pollution could affect our athmosphere and the seas, was regarded as utter nonsense and hysteria.


      It still is. As it turns out in reality, the 20th century was the one with the least chaotic "earth weather" and we now try to use _that_ as a baseline for "how it should be".


      It won't work. The earth has a weathersystem totally independent of what us tiny humans do. Read up on the "small ice age" just a few hundred years ago, or where the "dark middle ages" got the nickname from.


      "Global warming" is a myth. A popular one, but a myth nonetheless. "Global cooling" - which was popular a few centuries ago - is actually more likely to happen.

      • "Global warming" is a myth. A popular one, but a myth nonetheless. "Global cooling" - which was popular a few centuries ago - is actually more likely to happen.

        Hey look, it's an astroturfer. I thought they were just a myth.

      • Asthma in the majority of Europe is massively more prominent in the past 50 years than before - (yes - accounting for shifting infant mortality, better treatments for other ailments, better diagnosis etc...).

        Global Warming is easy to poo-poo - as the evidence will only be convincing in about 3 or 4 hundred years - if then. But large scale localised atmospheric issues are very real and apparent.

        By shitting on the evidence for global warming effects you justify the ongoing pollution of the atmosphere. By ig
        • My wife raised an excelent point a while ago.

          SUVs aren't bad for the environment. Neither is central air, speed boats, or countless other energy hungry luxuries.

          Why?

          Because there is a finite amount of fossil fuel on this little rock we all live on. We're going to burn it until it's gone. We all know that.

          Once you realize that you realize that how FAST you burn it doesn't really matter that much. It just means you need to develop an alterntive energy source in 25 years instead of 50.
          • I'd mod you up if I could, but instead I'll disagree with you.

            One of the effects of fossil fuel use is CO2 production. How fast we use our (assuming nobody else wants them) fossil fuels effects not only how quickly we have to find an alternative, but also CO2 concentrations in the intervening time.

            If we burn all of our fossil fuels this year, then air quality would worsen dramatically. I think you are right that in the long term it will make very little difference. However, if this is the case, it also se
      • "Global cooling" - which was popular a few centuries ago - is actually more likely to happen.

        You mean a few decades ago. When I was a lad going to college in the 70s, there was a concern we were entering an ice age. I have sometimes wondered if scientists make up these apocolyptic theories to gain funding for research. If so, more power to them. There isn't enough investment in basic research anyway.

        Anyway, global warming will happen eventually. In 5 billion years the sun will run out of hydrogen f
        • Ah, but before that happens the Andromida galaxy will collide with the Milky Way. The resulting super black hole will more than likely suck us in.
        • The coming Ice Age hasn't gone away. It's just on a longer time scale than the immeninent global warming. Which is currently happening quite impressively, if you look.

          I don't expect the next Ice Age until after the Arctic Ocean is totally melted. (Not quite sure how thorough this needs to be. Clearly Greenland doesn't need to melt.. at least not at the center.) I don't know just how though the warm spell will be, but at some point the oceans will become warm enough to start massively increasing their
      • "Global warming" is a myth.

        Not really. Global warming is a fact. Whether or not humans are warming up the place is another thing. Could be the sun is getting hotter, could be our emissions doing it, could be natural climate cycles, could be a precursor to a magnetic pole shift.

        The cause does not really matter.

        Whatever the cause may be, the climate patterns of several hundred years (as far back as we have fairly complete and accurate data, basically) have changed markedly in the last decade and it see

    • Save the Plankton! (Score:4, Insightful)

      by sssmashy ( 612587 ) on Tuesday March 25, 2003 @08:36AM (#5590203)

      More studies are needed, but the real environmental problem with OTEC is not ammonia, nor is it the temperature balance of the ocean. Ammonia would only be released by accident, and even then it wouldn't be much of a problem.

      Temperature balance is regulated because hot and cold streams of water leaving the OTEC are mixed, and then discharged by pumping it to a depth of about 60m, where the water temperature is about equal to the discharge temperature.

      The real environmental issue is the fact that 99% of the seawater going through the plant is discharged back to the ocean (rather than being evaporated to fresh water). This means that huge volumes of water - thousands of gallons per second - most be pumped to generate a relatively small amount of electricity. The problem is that for every gallon of seawater that passes through, most of the plankton, algae and other tiny sea creatures who live in that gallon don't survive the amazing journey. A 10 MW island OTEC plant would inevitably destroy thousands of tons of biomass at the bottom rung of the local food chain.

      • The problem is that for every gallon of seawater that passes through, most of the plankton, algae and other tiny sea creatures who live in that gallon don't survive the amazing journey.

        Big deal - put a restaurant next to the power plant and serve boiled plankton and algae as a specialty.

        Once humans start exclusively eating plankton, we won't even need all those other pesky animals like steer or pigs or lamb - we'll be at the top of a very short food chain. That should help eliminate a lot of other worr

        • Cute plan.

          Without addressing the culinary merits, I should point out that the energy required to extract plankton and process it would probably exceed the energy generated by the plant... so why bother in the first place?

          Remember, we're talking razor-thin energy margins here... a couple of Watts per gallon of discharge water. So if you expend more than that per gallon to filter out the bio-gunk, forget it.

          Also, raw plankton is not edible to humans... sort of like pond scum. It would have to be not on

      • Re:Save the Plankton! (Score:4, Informative)

        by cybercuzco ( 100904 ) on Tuesday March 25, 2003 @09:59AM (#5590489) Homepage Journal
        Except, Deep ocean water comes from a high pressure, and it has a significantly higher nitrogen content than the surface water. Algae blooms will be common near the outlets because of this, and plankton feeds on algae. these plants will be like deep water upwellings that occur due to geography in places around the world, like antarctica. In places where there is a deep water upwelling life is extremely abundant. This is why the effluent could be used for aquaculture as mentioned in another post.
    • And before you start jeering and making stupid jokes about it, remember that only 30 years ago the idea that human pollution could affect our athmosphere and the seas, was regarded as utter nonsense and hysteria.
      And it still is. Remember the Slashdot article about the sun getting hotter? Ever hear of something called "crustal rebound" - the North American plate is rising some mm's per year due to the released weight of the ice shelf 15,000 years ago - that is releasing heat. Add the fact that volcanoes

  • few coastal OTEC locations (Score:5, Insightful)

    by wfmcwalter ( 124904 ) on Tuesday March 25, 2003 @07:26AM (#5590047) Homepage
    Last time I read the OTEC literature (which, I admit, was a couple of years ago) the prevailing thought was that there were only a handful of places on earth where a coastal OTEC would be viable. You needed to have a location with a large temperature difference between the water at different depths, and have the relief of the seafloor be sufficiently steep that you didn't have to trail pipes out tens of miles in order to harness this differential. Hence there being only a few steep'n'tropical locations, like the Hawaiian one.

    When I was about ten I read one of those cool-science-futures-for-kids magazines, which showed a floating OTEC with a vertical downpipe - that makes more sense, as it doesn't rely on rare coastal relief. I believe Bruce Sterling's novel Islands in the Net also had similar floating OTECs. Perhaps building such a device of the necessary scale (you have to pump a lot of water around, after all) just isn't economic?

    Even if you do get mass OTEC production working, its quite debateable if it's really such a good idea. It's a lot of effort (money, materials, time) devoted to something that doesn't generate a terribly impressive amount of energy, and by its very nature it both warms the deep water and cools the surface water, which will have localised environmental consequences.

    I despair that everyone is concentrating on renewable resources while so many people (particularly in hot western US states) live in essentially uninsulated houses with single glazed windows. Biomas, geothermal, wind, solar, and ocean generation are all expensive and uncertain - tripleglazed solarglass windows and super-thick wall insulation are available fairly cheaply right now, are guaranteed to pay for themselves way before a windmill, an OTEC, or even a biomass plant. Yet still we're paying to air condition the sky.

  • No Free Ride (Score:2, Insightful)

    by ElBeano ( 570883 )
    It would be tempting to think of this as a "free" source of energy. We have to remember that we probably can't stick these plants everywhere because the oceans are the engine behind our weather.

    • We have to remember that we probably can't stick these plants everywhere because the oceans are the engine behind our weather.

      Parent post is clueless. We have to remember that we can't stick these plants everywhere for the same reason we don't cover ever square foot of land on the planet with solar panels. It's impossible, prohibitively expensive, and pointless in terms of efficiency.

      OTEC will only ever be implemented in a handful of warm island locations, on such a small scale that it will have a

  • OTEC = Good bet if your near equator (Score:3, Interesting)

    by Arislan ( 589775 ) on Tuesday March 25, 2003 @07:33AM (#5590063) Homepage
    OTECs Have great capabilities but have some limitations. The best way to get energy from thermal exchange is by having the greatest temp contrast. Equitorial waters are the most suited. OTEC that use an amonia to enhance the reaction do not leak it out. Basically deep cold water is mixed with warm surface water in a vaccum turning it to steam. The by-products are clean fresh water and hydrogen. Also the water brought up is heavily mineralized which has its uses in secreting a concrete like substance. Sea-Crete as some call it basically is same thing sea shells are. By using iron rebar for instance you immerse it in this heavily mineralized water and apply a slight electrical charge and you can grow this sea shell sea-crete stuff, its not fast but its strong and natural. Theres this group that has a idea of using a few OTECs and building a city near the equator on the ocean. The mineralized water is also usefull in mariculture, aka growing fish and crusteaceans. They plan to grow spirulina on the surface of the mariculture ponds. Spirulina is a plant/algae that when dried to powder is a potent source for nutrients. They think they can make a stable economy for this said city off exporting fresh water, sea foods, spirulina, and the hydrogen which the OTECs are central to producing all those including power in excess. And we all want clean power and hydrogen for those new fuel cell laptops coming next year. Course, if they built it exxon or someone the like would probably run into it and sink it. Or maybe a US submarine??? Though seriously, if the petro companies were real smart instead of fighting and stifling new energy theyd help develop it and get in at the ground floor of a new industry. Rant mode off...Those who use power without wisdom cannot claim courage...

  • Why OTEC is NOTscalable (Score:5, Informative)

    by sssmashy ( 612587 ) on Tuesday March 25, 2003 @07:38AM (#5590072)

    I've seen a few posts here speculating that if ocean thermal energy conversion is scalable, we potentially have a miraculous supply of renewable energy. Sorry to pop bubbles, but OTEC is way too inefficient, expensive, and low-density to work on a larger scale. It's only viable for remote islands that need fresh water, in very warm areas, with a seawater temperature gradient of at least 20 degrees celsius. Otherwise, it's too expensive and inefficient to bother.

    A theoretical 100MW plant (Current experimental sizes are lower than 1 MW) would require a hugely expensive floating platform, connected to the mainland by a hugely expensive submarine electric cable.

    Because OTEC is a very low-density resource, a 100 MW plant would have to be massive... pumping, processing and discharging a volume of water equal to the flow of the Colorado River into the Pacific Ocean. On top of the massive construction costs, electricity generated would cost about $0.22/kW (as opposed to wholesale price of $0.02-$0.03.kW in the US). If just 1% of world energy consumption (60,000 MW) was met by OTEC, the cost of building the infrastructure would be $1,000,000,000,000 (one trillion dollars) and the discharge from the plants would exceed the combined discharge of every river one the planet into the oceans. Scalable? Maybe not.

    • Re:Why OTEC is NOTscalable (Score:5, Funny)

      by guacamolefoo ( 577448 ) on Tuesday March 25, 2003 @10:15AM (#5590584) Homepage Journal
      pumping, processing and discharging a volume of water equal to the flow of the Colorado River into the Pacific Ocean

      Is there any water left anymore in the Colorado by the time it hits the ocean? I was under the impression that the Colorado River flowed into toilets, mostly.

      GF

    • I am trying to be tres troll here (french, funny not a karma "troll")

      But does if we, by we being americans, and Im not even american, anyways Ill start over.

      If the US can pay 75 billion dollars to get rid of Saddam, can they not pay 10 times that to provide the infrastructure to provide renewable, clean??, energy sources to the world?

      Even if this particular solution is not viable, why can the world not drop a trillion dollars putting infrastructure for clean, renewable energy.

      I would personally prov

  • Sid Meier said it best... (Score:3, Interesting)

    by meringuoid ( 568297 ) on Tuesday March 25, 2003 @07:41AM (#5590080)
    'The boundary between cold water and warm, the thermocline, has been important to undersea warfare for hundreds of years of Man's history. Now we have found a way to harness that power for constructive purposes. What once cloaked us can now feed us. What once shielded us from death now brings us life.' - Captain Ulrik Svensgaard, 'The Ripple and the Wave' THERMOCLINE TRANSDUCER All tidal harnesses worked by base produce one extra energy.
  • .. & Fresh Water & salt. The salt build up seems to be a maintenance issue for this system. Sounds like a more expensive method for either water or energy than the article makes out.

  • This has more info (Score:3, Informative)

    by watzinaneihm ( 627119 ) on Tuesday March 25, 2003 @07:52AM (#5590101) Journal
    This [saga-u.ac.jp] link has more info about the prototype plant, price estimates etc.

  • One of Clarke's pet theories... (Score:3, Interesting)

    by Anonymous Coward on Tuesday March 25, 2003 @07:57AM (#5590115)
    Arthur C. Clarke has been promoting this kind of power generation in fiction since the 1940's. Be interesting to see how many of his pet theories become reality in the 21st century (I see that the space elevator is getting some serious attention as well).
    • Ah, yes, another one of ~Clarke's~ ideas. Like how he invented the communications satellite in his article in 1945. Try reading George O. Smith's "QRM interplanetary" 1942 (easier to find it in print as part of "Venus Equilateral"). I hear Hugo Gernsback had something earlier, but I haven't read it. I don't wish to disparage Clarke as a writer, but he hasn't actually come up with any new ideas, just adapted existing ones for fiction. More people read his works, and then somehow he gets the credit for t
  • Fascinating stuff, next step is rumored to be beer and power.

    Yeah, except that, instead of ocean water, piss is used.

    --Flam
  • This type of deep-ocean evaporator was mentioned in Marshall T. Savage's 1955 book The Millennial Project: Colonizing the Galaxy in Eight Easy Steps [amazon.com]. I'm not sure this idea was of Japanese origin, as the NYTimes claims. Fascinating idea though, regardless of who thought it up.

    Also, you can access the NYTimes article without registering by replacing "www" in the link URL with "archive".
  • This could work with respect to a hydrological occurrance known as a thermocline. A thermocline is a barrier that naturally forms between two different areas of temperature in water. This barrier is an interesting phenomina and by bringing in water from above and below the termoclines, you can get access to consistant temperature differentials. A peltier device could actually generate energy from this difference. This just shows that it could be done, not necessarily done well. Any system creating ener

  • py 413 (Score:3, Informative)

    by sstory ( 538486 ) on Tuesday March 25, 2003 @11:37AM (#5591220) Homepage
    We discussed this in thermo. I think it's a pretty fantastic idea. The objection is that there's big bad environmental consequences to moving that much heat down into ordinarily colder ecosystems. Seems like a reasonable objection. Personally, I think nuclear is the way to go, in terms of cleanliness. If you take a rational look at it, it seems to come out on top.

  • Gilligan had this... (Score:4, Funny)

    by MojoRilla ( 591502 ) on Tuesday March 25, 2003 @12:21PM (#5591545)
    The professor hooked this up with coconuts and bamboo, but Gilligan broke the contraption just before they could commercialize it.

  • But... (Score:3, Funny)

    by DCowern ( 182668 ) on Tuesday March 25, 2003 @12:24PM (#5591567) Homepage

    Fascinating stuff, next step is rumored to be beer and power.

    But I thought beer IS power...

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