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Ocean Energy

Discussion in 'Energy, Environment, and Policy' started by Robert.Boston, Nov 16, 2012.

  1. Robert.Boston

    Robert.Boston Model S VIN P01536

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    Add hydrokinetic to that mix please -- ocean waves, tides, and currents. Water has much higher energy density than sunlight or wind.
     
  2. Robert.Boston

    Robert.Boston Model S VIN P01536

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    He's a smart man, but wrong on this. His calculations mistakenly consider waves to be linear fronts rather than having depth; furthermore, he assumes very poor conversion efficiency. The US West Coast, the British Isles, Portugal, South Africa, and several other regions could easily generate 100% of their total power requirements from ocean waves using technology that is currently under construction. It doesn't solve the problem of matching generation to load, however; we either need a lot of storage (including existing hydro and pumped hydro) or fossil generation.
     
  3. eledille

    eledille TMS 85 owner :)

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    Robert.Boston, this is really interesting. If you have any links to better info on the energy content of waves, then I would be very interested.

    I don't immediately understand how the linear front idea can be wrong - is it not true that incoming waves only can be harvested once?
     
  4. Robert.Boston

    Robert.Boston Model S VIN P01536

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    At this point, details are still proprietary. Waves have depth, so the energy drawn off the top by a floating device is quickly replaced by energy from lower depths.
     
  5. RDoc

    RDoc S85D

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    I don't know anything proprietary about wave energy, but I did study oceanography at one point.

    An ocean wave internally consists of long horizontal cylinders of water laid on top of each other rotating in opposite directions. Think of a stack of squishy cylinders all aligned horizontally with the top layer cylinders all rotating towards the direction of travel due to wind friction on the surface. The cylinders in the next layer down rotate the opposite way due to friction from the top layer, the next down opposite the ones above, etc. The lower ones have much less power than the top ones since water isn't much of a gear material.

    Perhaps the notion is to extract some of that rotational energy.
     
  6. eledille

    eledille TMS 85 owner :)

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    #6 eledille, Nov 18, 2012
    Last edited: Nov 18, 2012
    RDoc: Aha, thanks.

    Robert: As far as I can see, MacKay's estimate of total incoming Atlantic wave power to Britain uses the correct formula and is in agreement with published data. His wave formula gives total wave energy content, not just potential or kinetic. After extracting this energy, there is no energy left. This paper by Mollison gives the total wave energy crossing an optimally oriented line on Britain's west coast as 40 to 50 kW/m. Total energy content from waves travelling in all directions is 60-80 kW/m. There isn't any wave energy to speak of on the east coast (4-6 kW/m).

    MacKay then assumes that only half of the coastline can be utilized (quite a substantial amount if you ask me), the wave machines are 50% efficient and that they must be arranged in a line and therefore only have access to the energy that crosses that line. 50% efficiency for an energy conversion system is very ambitious and *way* better than any wave machine made thus far. The result is 4 kWh per day per person. This is a substantial amount and I think this should be explored, particularly since wave is much more reliable than wind, but it's nowhere near enough.

    Assuming a device that absorbs every bit of wave energy travelling in any direction can be made and deployed along the entire UK west coast, that still only yields 24 to 32 kWh per day per person. This is the absolute upper bound, completely unachievable in practice, and is about 20 to 25% of UK energy consumption, unless the published numbers for total wave energy are completely wrong.

    The UK Department of Energy and Climate Change is less optimistic than MacKay, they estimate the UK wave resource at 50 TWh/year, which works out to about 2.3 kWh/d/p. They also note that the UK has 35% of Europe's total wave resource. 40 watts of incoming wave power per millimeter of shoreline is a truly impressive amount! The fundamental problem is that there is only 17 millimeters of western shore per UK citizen.
     
  7. dhrivnak

    dhrivnak Active Member

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    There is a great book "Sustainable Energy Without all the Hot Air", yes the book is better than the title. The book is by David McKay and is free on-line at http://www.withouthotair.com/. Mr. McKay comes to a similar conclusion that wave power is unlikely to provide more than about more than 4 kw/person. What I like about the book is he goes into what it would truely take to transform to sustainable CO2 free power. And while possible it is very unlikely to come about without nuclear.

    He is very pro, solar, wind, tidal, and other forms of sustainable power. But he also shows how challenging it will be to keep everything balanced.
     
  8. eledille

    eledille TMS 85 owner :)

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    #8 eledille, Nov 18, 2012
    Last edited: Nov 19, 2012
    dhrivnak: That's the book I'm linking to above :) I also think it's very good. Chapter F, here, explores the physics of wave power.

    There are two big omissions in his book, though: The first is that he seriously underestimates the difficulty of backing up wind and solar. He considers outages lasting a few days, but the truth is that wind and solar frequently fall below 10% throughout entire continents and for weeks at a time. The second omission is osmotic power. There's an old thread on TMC about it. This technology might provide substantial amounts of reliable sustainable power. Only prototypes exist so far, but I think the future potential may be large. That does not mean that nuclear power can be ignored, of course.
     
  9. Robert.Boston

    Robert.Boston Model S VIN P01536

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  10. Robert.Boston

    Robert.Boston Model S VIN P01536

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    #10 Robert.Boston, Feb 7, 2014
    Last edited: Feb 7, 2014
    An update about the ocean wave energy company, GWave LLC, where I run commercial & business development:

    Yesterday, Dynegy filed a pair of preliminary permit requests with the Federal Energy Regulatory Commission which, if granted, will allow Dynegy the right to conduct further studies regarding the feasibility and impact of a wave park off the coast of Morro Bay.

    In November Dynegy announced its plans to retire the existing 650 MW plant and stated it would be exploring opportunities to develop energy projects that would support California’s green energy goals. One wave energy technology that holds promise is with GWave LLC. Dynegy is in negotiations with GWave and hopes to begin preliminary testing at the wave park in 2014.

    Article about this is here: Dynegy officially closes the Morro Bay Power Plant | Local News | SanLuisObispo.com

    The preliminary permit is an initial step that will help us determine, through careful study, if Dynegy can develop a responsibly sited, environmentally safe, and compatible with community needs renewable energy project. Only time, a review of study results, and engagement with the local community will determine if Dynegy moves ahead with wave park development. This is a multi-phased process and we are at the very beginning of the first phase.

    On a personal note, I know that a few Tesla fans live in this area. I'll be spending a lot of time in San Luis Obispo County over the next three years, and I look forward to meeting many of you.
     
  11. bonnie

    bonnie Oil is for sissies.

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    Congrats, Robert!
     
  12. omgwtfbyobbq

    omgwtfbyobbq Member

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    He's referring to the UK for his analysis, not entire continents. You can't reasonably claim he's underestimating something when that something is explicitly excluded from his analysis.

    Ch 26 Page 186: Sustainable Energy - without the hot air | David MacKay
     
  13. Auzie

    Auzie Tree Hugger Member

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    #13 Auzie, Mar 14, 2015
    Last edited: Mar 15, 2015
    Wave energy

    I searched the forum for the best place to post this. There seems to be no thread for renewables.

    Carnegie Wave Technology has been working since 1999 on CETO technology - harnessing ocean wave power for electricity generation.

    Wave.JPG
    From the Economist:
    This way of generating electricity may be attractive to some island countries. The technology is unlikely to become mainstream.
     
  14. Raffy.Roma

    Raffy.Roma Active Member

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    Interesting! Amazing how much energy the Earth could produce to help us to get rid of fossil fuels.
     
  15. Auzie

    Auzie Tree Hugger Member

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    Perhaps the correct way to put it - energy is everywhere, coming from space and perhaps stored on earth, we just need to harness it in more elegant and efficient ways.

    I personally find harnessing both waves and wind a bit cumbersome, but better than digging and processing fossils.
     
  16. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Me too. I always feel kind of tired and worn out after being outside harnessing wind or waves for a couple of hours. Now tanning on the other hand relaxes me. ;)
     
  17. Gwgan

    Gwgan Almost a wagon

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  18. Auzie

    Auzie Tree Hugger Member

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    :biggrin::biggrin::biggrin:
     
  19. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    The co-generation aspect is particularly interesting. Still, with even the projected costs high, it's looking like a wet-island solution at best,
     
  20. Electric700

    Electric700 Member

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