R-Squared Energy Blog

Pure Energy

Potential Markets and Benefits from Ocean Thermal Energy

Happy Thanksgiving to those who will celebrate it tomorrow. I plan to spend the long weekend with my family, and probably won’t be on here much.

In the interim, two things. First is that it is about time to start thinking about the top energy stories of the year. As in year’s past, I would like reader’s opinions on the top energy-related stories of 2009. I will put up a post late in December with the ones that I think are most significant.

Second, I present a guest post by Dr. Robert Cohen on ocean thermal energy conversion (OTEC). Dr. Cohen has been an advocate of OTEC for many years, and has posted a guest essay here previously:

Ocean Thermal Energy Conversion

There were some useful comments following that essay that I think explain the challenges for OTEC. Dr. Cohen has a website where he addresses OTEC in more detail, and his contact information is also available there.



Robert Cohen, November 24, 2009

Once the Obama Administration and the Congress put ocean thermal R&D back on a fast track, one that leads to the maturation of this technology within a few years, ocean thermal energy can foreseeably provide baseload electricity to energize at least three major geographic markets (see the ocean thermal resource map on the next page) in the following time-frames:

1) An early market to displace the use of oil, oil that is presently being burned to generate electricity in places like Hawaii, Puerto Rico, and in many developing countries. Places that are relatively accessible to the ocean thermal resource. Years ago we estimated that that early market could utilize about 50,000 MWe, which amount would achieve an oil savings of 2 million BBL/day [calculated @ 40 BBL/day per 1 MWe of ocean thermal].

2) A near-term market for electricity generated (for example) in the Gulf of Mexico and delivered via submarine cable to the U.S. electrical grid at points on the U.S. Gulf Coast, such as Key West, Tampa, New Orleans, and Brownsville. This source of baseload electricity could substantially implement the priority strategies advocated by Al Gore and T. Boone Pickens, which are aimed at providing renewable energy for propelling vehicles.

3) A potentially vast longer-term market for products derived from electricity generated aboard a fleet of ocean thermal plantships grazing on the high seas. Those plantships would convert the baseload electricity (plus air and water) to energy-intensive products such as hydrogen or ammonia, which could be shipped as energy carriers or as final products. For example, ammonia could be used as a hydrogen-carrier, combustion fuel, or for fertilizer.

Note that achieving the third option would mean that energy and energy-products could be shipped to the USA from domestically-owned ocean thermal plantships at locations that are in many cases closer to our shores than are many of our (often hostile) foreign sources of imported oil.

A global map of the OTEC Thermal Resource to supply energy to the above markets

This map shows contours of annual average temperature differences, in degrees Celsius, available in the world’s major oceans between surface waters and the cold water at 1000 meters depth that serves as a heat sink. The most desirable regions (bounded by the areas in yellow) are where that parameter equals or exceeds 20 degrees Celsius.

Energy FROM the oceans, to replace energy from ACROSS the oceans!


November 25, 2009 - Posted by | geothermal, ocean thermal energy conversion, reader submission


  1. There's little question the oceans are enormous collectors of solar energy and that if we can learn to tap it, our energy problems would be largely solved.Theoretically, it's easy. Technically, getting it to work has been the problem.In 1930, the first operating ocean thermal energy plant was built in Cuba (of all places.) It didn't pan out well because of the problems of making the ocean hardware stay intact as waves caused it to rise and fall; the corrosive properties of salt water; and lack of a good scheme for handling tropical storm surges. This news release says the US Navy is making plans to use OTEC plants at several of their overseas bases: Guam, Diego Garcia, and Kwajalein. U.S. Navy Plans Ocean Thermal Energy Conversion Plants

    Comment by Wendell Mercantile | November 25, 2009

  2. Once again, no mention of the big question about the environmental impacts of cooling surface waters/heating deep ocean waters.If OTEC is used on a trivial scale, the environmental impacts will of course be trivial — as will be the useful power it supplies.Why is this huge issue sidestepped by the promoters of OTEC?

    Comment by Kinuachdrach | November 25, 2009

  3. Why is this huge issue sidestepped by the promoters of OTEC?Because the oceans are unbelievably vast and trillions of watt-hours of energy in the form of sunlight fall on them every day.

    Comment by Wendell Mercantile | November 25, 2009

  4. If it is a good idea, why won;t private enterprise fund this?

    Comment by Benny BND Cole | November 26, 2009

  5. A sort-of related story is this one about Norway's osmotic power plant.http://news.bbc.co.uk/2/hi/europe/8377186.stmI think Kinuachdrach has a valid concern. The human economy is so huge that we can alter the climate and empty the oceans of fish, and now we are planning colossal feats of "geoengineering." So it's not farfetched to think that if OTEC is deployed on a large scale, it could affect marine ecology.

    Comment by Rice Farmer | November 26, 2009

  6. "Because the oceans are unbelievably vast and trillions of watt-hours of energy in the form of sunlight fall on them every day."The atmosphere is unbelievably vast. Yet we are told that human-induced composition changes at the almost too small to measure part-per-million level will destroy life on the planet.Thermodynamically, OTEC is incredibly inefficient because of the small temperature difference between the hot & cold ends of the system. That means a huge amount of water has to be heated/cooled to generate a globally-significant amount of power. If parts-per-million can destroy the atmosphere, what are these huge localized changes in water temperature distribution going to do to ocean currents and marine ecology?Why do the promoters never present some calculations to demonstrate that large-scale OTEC would be safe?

    Comment by Kinuachdrach | November 26, 2009

  7. Wow! – I'm with Kinuachdrach on this one. We're told that deep ocean overturning circulation is crucial to an understanding of ocean currents in general, the thermohaline "conveyor belts" in particular, and ocean-atmosphere energy exchange. There's even theories that changes in overturning rates precipitated past ice ages. If AGW based on relatively minor atmospheric changes can be real (and I'm not saying it is), then Kinuachdrach's question is surely valid too — or at least merits a "back-of-an-envelope calculation".

    Comment by PeteS | November 26, 2009

  8. Another nice-to-have would be a succinct list of the current biggest technical and economic hurdles with OTEC. It's true, isn't it, that the biggest US OTEC pilot was a measly 0.25MW? What do the costs look like in terms of up-front investment (e.g. are they gigantic, as with nuclear, or more incremental as with wind).

    Comment by PeteS | November 26, 2009

  9. Deep geothermal has more potential and a much smaller footprint. We probably won't see it happen without a carbon tax though. Geothermal capital costs are competitive with coal. But,drilling miles down for deep geothermal can double the cost of a project.

    Comment by Maury | November 26, 2009

  10. No need for OTEC. As Al Gore explains here geothermal is the answer. He reveals that this is a relatively new concept and that the earths core is several million degrees with the crust also being very hot. Also, this is only now possible because we have new drill bits that won't melt at these very high temperatures.What a dope! I wonder if he plans for these interviews, or if he just makes it up on the spot.

    Comment by Dennis Moore | November 26, 2009

  11. The deep geothermal plant in Landau,Germany produces 3 MW,or enough to power 6000 homes. It cost $30 million and was drilled two miles deep. A similar sized coal or gas-fired plant would cost 3 or $4 million to build. Fuel costs would run about $500,000 per year. Obviously,costs need to be brought down….a lot.

    Comment by Maury | November 26, 2009

  12. "Obviously,costs need to be brought down….a lot."OK, let's think this one through. Much of the cost of "deep geothermal" is for wells. If well costs can be substantially reduced for geothermal, they can probably also be substantially reduced for oil & gas wells — much of which is found at less than 2 miles deep.Rule of thumb — only about 1/3 of the oil found underground can actually be produced to the surface for human use. There are a variety of reasons for this, but it is a safe bet that being able to drill more wells for the same total cost would increase the recoverable volume of oil from known oil fields.So if well costs can be reduced making geothermal less uncompetitive, this would also increase the producible oil volume signficantly, keeping the supply of oil & gas up and their prices down. Bottom line is that the technological breakthroughs necessary to make deep geothermal economically feasible would also obviate the need for deep geothermal, maybe for a century or two. By which time other power supply technologies should be meeting human needs.

    Comment by Kinuachdrach | November 26, 2009

  13. Maury.."Fuel costs would run about $500,000 per year"…that would be about $83 per year per customer, which sounds awful low.

    Comment by David | November 26, 2009

  14. “cost that's competitive with imported oil”But not with barge mounted nukes. Russia is putting its ice breaker nuke plant on barges for a 75 MWe output (IIRC).“a 50-kilowatt OTEC plant mounted on a Navy barge moored off Hawaii produced 52 kilowatts of electricity, but consumed all but 15 kilowatts.” The navy has lots of nuke power plants already in Hawaii and Guam. Personally, I have made both fresh water and electricity in both GITMO and Puerto Rico. Barge mounted nukes would also make good shore duty for sailors. The ingesting barge mounted nukes is that they do not need large concrete containments. This because they can be move away from population if there is an unlikely core damage event. They can also be towed back to Newport News for overhaul and refueling. I suspect Dr. Robert Cohen has no experience producing electricity or maintaining equipment in the ocean.

    Comment by Kit P | November 26, 2009

  15. "The ingesting barge mounted nukes is that they do not need large concrete containments. This because they can be move away from population if there is an unlikely core damage event."Just out of interest, what happens in the case of an unlikely barge sinking event?

    Comment by PeteS | November 26, 2009

  16. I suspect Dr. Robert Cohen has no experience producing electricity or maintaining equipment in the ocean.Kit, there is no call for this. From here forward, I have very little tolerance for posts from you that either 1). Proceed to tell us how smart you are relative to everyone else (see your "debate" with Pete and Clee in the other thread); 2. Suggest that other posters are inexperienced/lack knowledge/etc. Those are the sorts of things that lead to unproductive time being spent. If you feel that you are unable to be more civil, please find another place to hang out.In the other thread, you wrote: there is no federal penalty for making making material false statements in blogs Furthermore, there are no consequences that I am worried about if I found I was found to be wrong. This is true, but there are consequences here. If people constantly have to correct false information/misinformation from you, it wastes everyone's time. So if you make a claim, perhaps given your history you should provide a source. And there will be no more "I suspect so and so has no experience…" I don't give a crap about your suspicions, and I don't imagine anyone else does. So if you only suspect, don't post it.Happy Thanksgiving.RRP.S. For other posters (and even for Kit), if you have specific questions/comments for Dr. Cohen that you would like me to share, I will send them to him and post answers here in a follow-up essay. Looking back at the first essay, there were a lot of good comments, and I would like to hear Dr. Cohen's responses.

    Comment by Robert Rapier | November 26, 2009

  17. I spent a lot of time trying to understand OTEC and why it hasn't been successful. I think it comes down to two major hurdles:1. In low-gradient heat systems the distance between the hot and cold media is very important because the energy expended to transfer the media becomes the major factor in system efficiency.2. Maintenance cost and potential for disaster in the ocean is very high.In everything I have read about OTEC systems, it appears that the relatively large distance between warm and cold ocean water uses up almost all of the power produced moving fluid until point 2 takes over and the system is destroyed in a storm or funding runs out for maintenance. If the heat gradient was larger (as in geothermal) the pumping energy is relatively small to potential output, but OTEC will not ever produce substantial output moving water with a 20-30 degree gradient from surface to deep ocean.

    Comment by Bob Rohatensky | November 26, 2009

  18. Another possibly useful resource for anyone interested in OTEC is the OTEC News web site. On it we have collected information about OTEC for a number of years, including the latest news on the development of OTEC.Thomas, OTEC News editor

    Comment by About me | November 26, 2009

  19. Bob R – I think you put your finger on what's troubling me too. I read that rather than direct pumping you can desalinate the water near the sea floor (how??) and rely on it's resultant buoyancy to raise it to the surface through a pipe. While this might save on energy for pumping, how on earth would you get large (i.e. vast) quantities of somewhat-less-dense water to float a mile or so up a vertical pipe? It's analagous to getting oil out of the ground — it doesn't matter how much is down there if you can only produce it at a dribble.Hence my earlier question — is there an enormous outlay for the equipment to do this at commercial scale?

    Comment by PeteS | November 27, 2009

  20. "Bottom line is that the technological breakthroughs necessary to make deep geothermal economically feasible would also obviate the need for deep geothermal, maybe for a century or two."There's some synergy there Kinuach. The MIT study suggested using geothermal power from injection wells at oil sites. The deeper a well,the hotter the water coming out with the oil. Once the oil is gone,the well can continue to generate power for years to come.

    Comment by Maury | November 27, 2009

  21. "that would be about $83 per year per customer"I think I dropped a zero David. Fuel costs are more like $5M annually. At any rate,only the low hanging geothermal fruit is worth picking at this time. But,innovations are happening almost daily. Just look at the breakthroughs that gave us shale gas in the last few years. Turbines have come out that use lower temperature water. Fluid mixtures have been found that can retain heat longer. Drilling techniques are getting more sophisticated. Deep geothermal can be a reality sooner than most folks realize.

    Comment by Maury | November 27, 2009

  22. Kinu – rather than go horribly off-topic here, I left you two comments at the end of the last thread with a reading/reference list to challenge your "dodgy data" allegations about AGW models. Forced me to into a whole bunch of reading that I have to say I found fascinating. Your mileage may vary.

    Comment by PeteS | November 27, 2009

  23. Kinauchdrach said: The atmosphere is unbelievably vast.Kinauchdrach~The atmosphere is not incredibly vast compared to the oceans — at least not in terms of mass. A one-inch square column of air that goes up through the stratosphere to the edge of space weighs only 14.7 lbs.It only takes a one-inch square column of water 10 meters high to weigh the same.The vast amounts of water in the oceans absorb an incredibly high amount of solar energy and that huge mass can absorb and give up that energy with much more resilience than can the gases that make up the atmosphere.There may be economic, technical, and thermodynamic reasons OTEC will not work, but worrying about the effects they have on the oceans is not a reason to charge ahead with the research.And speaking of research, Isn't it interesting to think what might have been had all the money we sunk into subsidizing corn ethanol over the last three decades had instead gone to R&D of something like OTEC or fusion energy? Ah well, it's always the never ending conflict between political science and real science.

    Comment by Wendell Mercantile | November 27, 2009

  24. “money we sunk into subsidizing corn ethanol over the last three decades had instead gone to R&D of something like OTEC or fusion energy?”So we should invest what is totally impractical and ignore those things that work but are slightly more expensive (maybe) and require incentives for investment?

    Comment by Kit P | November 27, 2009

  25. “at least not in terms of mass”I can see we are back to needing to understand the fugacity of CO2 in seawater. Not that I can explain it either but at least I know it is an important issue that needs to be understood. Recently a micro organism was found in the ocean that concerts CO2 to O2 with sunlight was discovered by accident.

    Comment by Kit P | November 27, 2009

  26. “at least not in terms of mass”I can see we are back to needing to understand the fugacity of CO2 in seawater. Not that I can explain it either but at least I know it is an important issue that needs to be understood. Recently a micro organism was found in the ocean that concerts CO2 to O2 with sunlight was discovered by accident.

    Comment by Kit P | November 27, 2009

  27. "… worrying about the effects they [temperature distributions]have on the oceans is not a reason to [not] charge ahead with the research."Hey, I am big on the human race doing research! (Not so keen on evil politicians choosing what research to spend other people's money on, but that is a different topic).Part of research is doing approximate calculations to see what the consequences of success would be. We know that the human race is using 15 TeraWatt of power 24/7 right now. We need to boost that for future increases in planetary population; maybe triple it to bring the poor of this world up to a decent standard of living; double that again to allow for the lower energy amplification of non-fossil sources — call it a round 100 TW future power demand that we need to plan on meeting.OK — how much water needs to be pumped between ocean depths & surface to generate 100 TW (including recognzing the low theromdynamic efficiency of energy conversion with the low Delta T)? How does this compare to the volume of water in critical natural ocean flows like the Gulf Stream?That is all I am asking. Why don't the promoters of OTEC have those kinds of numbers at their finger tips?

    Comment by Kinuachdrach | November 27, 2009

  28. Kinu You do not have to worry about the environmental impact of OTEC. It does not work. Cocktail napkin power plants have not environmental impact. For whatever reason, some folks are fascinated by what does not work. Again, I do not have a problems with government funding R&D. I do know what the results will be, failure. I only advocate what works.Kinu does have a good general point that advocates of renewable energy tend to focus on the environmental impact of coal while ignoring the environment impact of wind and solar. First these advocates of renewable energy do not the environment impact of coal. Second, these advocates of renewable energy do not the environment impact of renewable energy. If they did , they might stop being advocates.Third, it has to work to displace energy sources like coal and oil. I am an advocate of building wind and solar as fast as we can (and we are) because I know the it works some of the time (10-20% CF). Since the people who run nuke and coal plants are now in the wind and solar business, I expect wind and solar start working better. The art of making electricity includes a phd in equipment reliability.I am a very strong advocate of biomass renewable energy. First because the environmental impact is much less than fossil fuels. Second it works exceptionally well. Not as good as nukes. Third, it creates local jobs for people like me.Solar & OTEC has the potential to provide the region I live all the $500/MWh electricity we need sending a large amount of money out of the region, loosing a lot of jobs, and property taxes. Or we could keep our $30/MWh coal generation and slowly replace old coal units with $70/MWh waste biomass and $50/MWh new nukes. When the capital cost of these technologies are paid we will then have $40/MWh and $20/MWh generation cost.This is the decision that is coming out many of the state PUCs in my region. The reason I am not worried about providing energy to the world pollution is that we do it so well locally. It does require good energy policy.

    Comment by Kit P | November 27, 2009

  29. Robert,Seems like everyone ignored your request. I would vote for these:1. Congress pass ARRA (aka the "Stimulus" package) with substantial energy efficiency code updates.2. House Passes Waxman-Markey3. U.S. Gasoline demand falls year-over-year for second straight year (ok the year's not over, but it looks like it will)

    Comment by SamG | November 30, 2009

  30. Nice list.I feel there's a story in PV, maybe not a single top story of the year, but a bunch of related little ones, many of which seem to swirl around First Solar. A big drop in price, though not quite to true grid-parity.- First Solar broke the $1/W barrier in manufacturing cost, reaching $0.93/W in 1Q09 $0.87/W in 2Q09 and $0.85/W in 3Q09- Thin Film have surpassed 10% efficiency in production modules. Example, First Solar has reached average 11% efficiency on production panels 3Q09.- Thin film is gaining market share in the PV industry, perhaps as much as 25% of the market in 2009. For the first time, a thin film company is the world's largest producer of PV cells. First Solar is expected to produce nearly twice as much solar cells as its nearest competitor.http://www.isuppli.com/News/Pages/First-Solar-to-Produce-Twice-as-Much-as-Leading-Crystalline-Solar-Module-Suppliers-in-2009.aspx- First Solar allegedly reaches "Grid-Parity" with Sempra's 12.6 MW PV system installed at an alleged cost of $3.17 per watt.http://www.greentechmedia.com/articles/read/first-solar-reaches-grid-parity-milestone-says-report-5389/- In the past year, prices for crystalline silicon solar panels worldwide have plummeted as much as 50 percent…Currently, the average selling price for crystalline silicon panels are roughly $2 per watt.http://www.greentechmedia.com/articles/read/thin-film-players-feeling-besieged/- Despite the recession, the PV market is forecast to grow 5% globally over last year, and 26% in North America.http://www.solarbuzz.com/News/NewsNACO1047.htm- China is currently planning an 11,950 MW renewable energy park, the Ordos New Energy Industry Demonstration Zone (NEIDZ), which includes a proposed 6,950 MW of wind energy, 3,900 MW of PV, 720 MW of concentrating solar power plants, 310 MW of biomass and 70 MW of hydro storage. Of that, First Solar is contracted to build a 2GW PV farm, expected to be the largest in the world.http://www.renewableenergyworld.com/rea/news/article/2009/10/companies-see-shining-opportunities-in-china

    Comment by Clee | December 11, 2009

  31. A new Cost Effective OTEC based on Oil and Gas Deepwater Technology by DSI, Houston, Texas, USA. Dr. Nagan Srinivasan, PhD, PE, Please contact Naganus at yahoocom. DSI has made the OTEC cost effective with the modern deep water technology developments. Several innovations are introduced and the feasibility is successfully achieved. OTEC is 100% reliable and very stable plant. It occupies no land space and is designed to withstand 100 years hurricane with our innovative floating vessel. The thermodynamics, flow, pipeline, system design, vessel design had been achieved. 1. 100 MW power plant will be supported by 50 people manned platform with helicopter access and quarters. It costs 450 million USD. 2. 13 MW unit will have unmanned platform with boat landing options. It costs 70 million USD. 3. Desalination could be much cheaper than the conventional. 4. Desalination could be a by product along with power too. 5. Hydrogen fuel can be producedWe study of the ocean environment for suitability. We design the OTEC engine for that location. We design the supporting structure. We fabricate the vessel and install the OTEC plant. In the case of the desalination, we use water storage tank inbuilt with the supporting platform. In the case of the, ocean close tot he land, near shore with deep sea within the vicinity, we install land based OTEC power plant and desalination plant also.We own the proprietary of the technology and the drawings. We shall not give the detail drawings to the client. We subcontract detail engineering company and the fabricators. We purchase the equipments our self. We hire the installation company and we do the project management, procurements, vendor selection, pre commissioning. We take 5% for our licensing fee. Licensing is issued for each project and for each unit separately. We also maintain and repairs for the operation with additional charges. The maintenance and operational cost is very minimum. OTEC has tremendous future. The capital investment could be recovered within 10 years depend on the type of loan and interest. The government tax benefit and other In particular, DSI cost of building 100 mega watt unit power plants is almost equal to 10 mega watt unit of Lockheed Martin's, USA, OTEC power plant. DSI has considerably reduced the cost such that OTEC could be one of the prime sources of energy for the need of the world near equator. Corrosion, bio-fouling, platform mooring, survivability in severe storms, environmental concerns, working fluid leakages, safety issues, coupling of electrical cable to platform, power transmission through cable are all considered and resolved in our design. In general, Government of USA would consider tax credits to serve as an incentive/subsidy the 100% green energy, free of CO2. Thus the investor also could tax credit and government could fund partially to support this effort. This would make this OTEC power plant very attractive and the unit power price cost could reduce. The power plant could be highly profitable in compared to hydro, coal, nuclear, solar and wind based power plant. Considering no operational cost this is very attractive. The future of OTEC would turn into Hydrogen production platform. Excess electricity produced would be used to separate hydrogen from water with conventional method. Hydrogen fuel, hydrogen cells, hydrogen fuel cars etc are modern applications where the usage of petroleum fuel is reduced. There is a huge application behind in this line of industry that would develop after the power plant and potable water plant. In that case, the platform can be installed near equator where the OTEC could be more efficient round the year operation in common water and electricity can be produced. The Hydrogen can be produced and transported as compressed stage to land and then used for the car fuels and for hydrogen fuel cells. Please see the following website in glggroup for DSI on OTEC.

    Comment by Anonymous | March 8, 2010

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