Energy Update: Ocean Thermal Energy Conversion – Ever Heard of It?

A resort hotel to be built in China plans to use surface heat from the ocean to provide its energy requirements. Called Ocean Thermal Energy Conversion or OTEC, this is technology that uses the difference between warm tropical ocean surface water and colder deep water to generate electricity. The temperature difference powers a turbine attached to a generator by passing warm surface sea water through a heat exchanger where it vaporizes an encapsulated fluid with a low boiling point. That creates steam power.

The resort is to be located in southern China. The technology developer is Lockheed Martin who are working with the Reignwood Group, a multinational Chinese corporation headquartered in Beijing. Reignwood is a diverse company involved in property development, new energy initiatives, aviation, agriculture, healthcare, sports and culture.

The Lockheed Martin plant will generate 10 Megawatts and will be the largest OTEC project yet to be developed. The power is base load unlike solar and wind, meaning it can be generated 24 x 7 without interruption. Lockheed Martin sees the technology as suitable for coastal and island communities where other energy sources are restricted by a lack of infrastructure or ready access.

The plant is considered a pilot project. Lockheed believes they can scale OTEC to power a small city. It has identified as many as 100 sites globally where OTEC would make economic sense. An added benefit, OTEC can be used to process freshwater for drinking and hydrogen for use in fuel cells. In partnership with Reignwood the company has two projects on the go. These will be low-carbon resorts and will help to establish the first net-zero communities.

 

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Len Rosen lives in Toronto, Ontario, Canada. He is a researcher and writer who has a fascination with science and technology. He is married with a daughter who works in radio, and a miniature red poodle who is his daily companion on walks of discovery. More...

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  • Niccolo5

    ((These will be low-carbon resorts and will help to establish the first net-zero communities.))

    Most of the world’s CO2 is dissolved in the cold deep ocean waters. The amount of CO2 they hold is a function of temperature. The colder the water, the more CO2 it holds. The ocean thermal energy scheme is anything but carbon neutral. It heats the CO2 laden deep waters, which will release some percentage of the CO2 they sequester. Guess where that CO2 will wind up?

    • lenrosen4

      I am going to check this out with Lougheed Martin. If you are right then the technology is being promoted with a big lie.

  • Niccolo5

    ((These will be low-carbon resorts and will help to establish the first net-zero communities.))

    Most of the world’s CO2 is dissolved in the cold deep ocean waters. The amount of CO2 they hold is a function of temperature. The colder the water, the more CO2 it holds. The ocean thermal energy scheme is anything but carbon neutral. It heats the CO2 laden deep waters, which will release some percentage of the CO2 they sequester. Guess where that CO2 will wind up?

    (( If you are right then the technology is being promoted with a big lie.))

    The physics is elementary.

    Wiki, “Carbon dioxide dissolves in the ocean to form carbonic acid (H2CO3), bicarbonate (HCO3-) and carbonate (CO32-), and there is about fifty times as much carbon dissolved in the sea water of the oceans as exists in the atmosphere. The oceans act as an enormous carbon sink, and have taken up about a third of CO2 emitted by human activity”

    Ever “pop the top” on a can of warm beer or carbonated soft drink? Did the CO2 stay in solution or come fizzing out? Yep, you should expect a straight answer from Lockheed Martin on this one.

    Should be obvious that as CO2 from warmer deeper waters diffuses into surface waters, the partial pressures will reverse and the surface waters will release, not absorb, CO2. But, the “baffle them with complexity and math BS” defense that Lockheed Martin will throw up will likely be slick enough to justify continuing with the project.

    The ordinary village rustic fact is the temperature differential, and resulting pressure differential and mass flow that will drive the turbines results entirely from heating the CO2 charged colder deeper water. That means some of the dissolved CO2 is certainly going to come out of solution. Whether a little CO2 comes out over each square meter stretching for hundreds of square miles, or if a lot of CO2 comes out of each square meter only in the area near the power plant, the net result is the same. There is nothing to keep as much CO2 in solution once the water is warmed.

    Don’t take my word for it. Buy three identical cans of soda. Let one reach room temperature, heat one to 86 F, and chill the other to 33 F in the fridge. Open all three at the same time at the sink. Observe CO2 fizz out of room temperature can. Notice more energetic fizz from 86 F can. Notice very little or no fizz from the chilled can.

    Any process that heats the deep ocean either releases CO2 or retards natural sequestration. It’s nothing close to CO2 neutral.

    • lenrosen4

      I have no doubt that the ocean is the primary carbon sink on the planet and that cold water releases CO2 at a slower rate than warm water. What I am interested in learning is about the heat exchange mechanism being employed here and how Lockheed Martin has put controls in to ensure that CO2 is not a byproduct of the engineering process to create steam. What you are describing in your last two comments would indeed be alarming. So hence the need to find out more from the so-called “horse’s mouth.”

      • Niccolo5

        Well, since my last response I’ve done a little detective work on this one. Back in 1980 NOAA did a fairly comprehensive treatment and report on hypothetical OTEC systems; see chapters 3 and 4: http://hinmrec.hnei.hawaii.edu/wp-content/uploads/2010/01/OTEC-Programmatic-EIS-NOAA-1981.pdf

        Little has changed since this report was published some thirty years ago. NOAA seems to have had grand plans for a huge OTEC industry by the year 2000 that never materialized. Careful reading of the report reveals NOAA knew a lot of CO2 would be released, but didn’t give a definite estimate. The report estimated that an OTEC plant might release anywhere between 25% and 250% as much CO2 as an equal capacity coal-fired plant. I have no idea how one could get to a definitive numerate answer. Still, it’s obvious that Lockheed Martin knows their OTEC plant is going to release a lot of CO2.

  • Niccolo5

    ((What I am interested in learning is about the heat exchange mechanism being employed here and how Lockheed Martin has put controls in to ensure that CO2 is not a byproduct of the engineering process to create steam.))

    It’s obvious that a surface-based heat exchanger would be lowest cost. Then it’s just a question of whether the warm water discharge from the heat exchanger (which will be somewhat, but not much, cooler than the surface waters) will be re-injected into the depths, or whether the discharge will be near the surface (which would be lowest cost). In either case CO2 charged cold water must release some of its CO2 when the pressure drops and it warms. In the surface discharge case the CO2 release will be distributed over a relatively small area near the plant. In the deep ocean case the CO2 release might be distributed over hundreds of square miles.

    Lockheed-Martin will not be creating any new CO2; it will merely be releasing CO2 that already exists dissolved in the deep ocean water, and they will retard the rate at which the deep ocean can sequester CO2. There are tricky unanswered questions about how much CO2 will be released for each BTU or KWh of energy produced. I think it doubtful that L-M can, or cares to, answer these questions. The most common phrase in the jargon of environmental engineering might be, “Dilution is the solution.” This seems to be Lockheed-Martin’s doctrine in this case. At least ten of L-M engineers working on this project could say what I have just said, but they won’t because they don’t know where to get another job they like as well as the one they would lose.