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Chad Macumber

MWD/LWD Engineer, Scientific Drilling International

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Tidal Energy

What do you think about tidal energy? It's not a new idea, but it is one that I think could have potential for success - particularly in poor countries.

In essence, tidal energy may consist of buoys (of some nature) connected to pistons and crankshafts secured to the sea-floors in areas with potent tides. As the buoys ride the waves the pistons turn and create mechanical power which is sent back to storage facilities onshore.

Do you think this technology has potential? Do you think it can be efficient in producing energy? Is it too far-fetched?

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  • Jun 10 2012: Actually the energy density is quite high. At sea level, air is about 800 times less dense than water.

    What you describe Chad is not however tidal power, rather it is wave power. http://www.energyboom.com/10-facts-about-ocean-wave-power. Wave power is actually wind power, which is actually solar power if you trace it back...

    Where I work we tried a significant experiment with tidal power. The biggest problem ended up being fouling by seaweeds and other marine organisms. http://www.racerocks.com/racerock/energy/tidalenergy/tidalenergy2.htm
    Tidal power is the harnessing of the moon and sun's gravitational pull and has a lot of potential... googling the term provides many references.

    Glad you are researching this!
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      Jun 10 2012: i'm very glad that it is so high. can you give us a figure?
      • Jun 10 2012: Here is a source... this is potential energy.

        COMPARING THE DENSITY OF AIR TO WATER

        METEOROLOGIST JEFF HABY

        To the human eye, air is nearly invisible while water is clearly visible. Without dust, smog, and particulates in the air, air would be invisible. It is amazing to many people that this "invisible" air moves substances like tree branches around. Of course, we now know that the air does have mass even though it can not be seen with the eye. If the air does have mass, why is it so hard to see? It is difficult to see because the air has molecular properties that make it transparent. We will now determine how "much less" the density of air is to water. Water has a density of 1000 kg/m^3. If you had a meter cubed of water it would weight about 1000 kg. Air that is near sea level has a density that averages 1.275 kg/m^3. If you have a balloon containing a meter cubed of sea level air, the air itself would weight only 1.275 kg. Therefore, to find how much more dense water is than air all we need to do is find a ratio of water to air. 1000 kg/m^3 divided by 1.275 kg/m^3 yields 784. Therefore, at sea level, air is 784 times less dense than water. Expressed in another way, a volume of air at sea level has 0.1275% of the density of the same volume of water. Dirt is about 2.5 times the density of water.
        http://www.theweatherprediction.com/habyhints/216/
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          Jun 10 2012: and where is the energy density here?

          suppose we have a tidal wave power plant of, say one square kilometer. how much power it produces in electric megawatts?
      • Jun 12 2012: I am not an engineer but I can use the internet!

        There are many emerging technologies that use waves or tidal flow to generate electricity. Like all forms of electricity there are benefits and costs. Waves energy generators can be deployed in a wide variety of places but need swells to produce energy. There are less suitable locations for Fulton Generators that use tidal flow but both have enormous potential. WIth more research there continues to be improvements in efficiencies. This link discusses this issue: http://www.ianswer4u.com/2012/02/tidal-energy-advantages-and.html#axzz1xX6Gqq29

        One estimate I found that answers your question Krisztian is this: Peter Fraenkel, director of UK-based Marine Current Turbines, believes the best sites could generate more than 10 megawatts of energy per square kilometre. (http://www.fujitaresearch.com/reports/tidalpower.html)

        Tidal power is a denser form of energy than either wind or solar power. Seawater is 832 times as dense as air and is not compressible. This means that more power is available per square meter in tidal than for wind or solar. Like wind, tidal power is a function of the velocity of the current flow cubed. As tidal flows peak, the power extracted increases geometrically. This energy density is further leveraged by the massive size of the ocean and the scale of the currents produced with the change of the tides. (http://www.bluenergy.com/tidal_power.html)

        http://www.guardian.co.uk/environment/2011/sep/27/wave-and-tidal-power-alex-salmond
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          Jun 12 2012: so you have said that tidal energy is dense, yet you still didn't present a single number.

          i am an engineer, and i did some calculations in head. i estimate the energy density of tidal waves somewhere around 100kW per square kilometer. this is a joke.

          it can be used in some situations, like narrow gulfs. but its use is as limited as hydroelectric. basically it is the same concept. plus it has a huge impact on the marine life of said gulf.
  • Jun 14 2012: The Bay of Fundy is being looked at seriously for tidal power. It is the body of water that I am next to. So I have been watching this development. The government here has it as part of the sustainable energy targets, not to mention potential economic benefits further down the road, if it were to unfold as they hope.

    The concern is that the habitat there will be severely altered, but nobody can say what the effects might be. The Bay has been harvested for its wealth for a few hundred years now. There has been much alteration of the ecosystem in that time. The Environmental Assessment for tidal power have pretty much focused on the siting aspect of the test facility berths. http://fundyforce.ca/assessment

    I have some images of the area in question, in Nova Scotia, from an exhibition I had a few years back: http://www.novamaz.blogspot.ca/

    http://fundyforce.ca/ has the developers' side of the equation & video of the types of turbines being experimented with. Industry is keen to get as many of the units in the test site as they can–now. However, only one 1 MW closed-bladed unit has been in the Bay so far (the Minas Passage in particular) and it was trashed within 3 weeks by the force of the current. http://www.nspower.ca/en/home/environment/renewableenergy/tidal/projectoverview.aspx

    A couple of the open-bladed units are going in next year, apparently. The lobster fishers of the area are curious to see how long it will take for these to be trashed.

    Living here you often hear it cited that the equivalent of all the water in all the rivers in the world flow through the Bay twice a day: 14 cubic kilometres. And the tidal sweep in & out of the Bay is a calculated 60 GW of harvest-able energy. Apparently you begin to effect the resonance of the tides at around 5% of this, or 3 GW.

    I think it is most viable in a smaller, incremental approach, as the people at Fundy Tidal Inc are doing; a more community owned & operated approach. http://www.fundytidal.com/
  • Jun 12 2012: Well your number is considerably smaller than the 10 megawatts quoted above... and we aren't talking about "tidal wave" energy. There is tidal energy and wave energy; the two are very different. Please do some research. You seem very dismissive of the concept in the first place, yet you don't bother to explain in any detail your reasons. I spent an hour researching and exploring pros and cons, and providing links, while you toss out a few unverifiable sentences trashing the whole concept. Fortunately there are a lot of ongoing projects around the world by people (investors and engineers) who are convinced of the efficacy and profitability of harnessing this renewable energy resource. You agree presumably that water is denser than air, thus there is a lot of potential energy in the movement of the fluid. Harnessing that power is the challenge.

    Do you feel the same way about solar and wind power? Do you favour nuclear or hydrocarbon energy production? The hydrocarbons will run out eventually and the risks of altering the atmosphere are well-documented. Nuclear has many well-documented risks as well. What are you in favour of? And why? Chad may be a budding tidal or wave energy specialist and he deserves more than a dismissive condemnation of this technology.
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      Jun 12 2012: i saw claims, but not so much calculations

      it is this easy to calculate: the total energy that we can use is the potential energy of the elevated water at it highest point compared to the lowest point. tides are like 0,5 - 1 m high. we can practically use half of it. this happens 4 times a day (2 up, 2 down). the potential energy is given by M*g*h where M is the mass, g is approx 10m/s2 and h is the height. if you plug in M in kg and h in m, you get joule. take this joule value for a given area, multiply by 4, divide by the number of seconds in a day to get watts.

      the result is in the magnitude of 100kw per square km. of course, if you can use an entire gulf, the output can reach 10MW, but the locations suitable for that are few. it can be a good local solution at some lucky places, i'm not sure about that, but not a solution we could use worldwide.
      • Jun 12 2012: Now that is interesting! You are quite right that tidal energy is only suitable in a few locations. I can't find the link but I think I read that about 125 locations have been deemed suitable worldwide. Wave power is a different story. Where I live the normal tidal range is 2 meters and at full and new moon is nearer to 3m.

        As an engineer you may find these pages interesting as there are a lot of calculations that I don't pretend to understand:
        http://en.wikipedia.org/wiki/Wave_power
        http://en.wikipedia.org/wiki/Tidal_power
        It seems there is a lot of potential energy available. If you have time please quickly read through them and tell me what you think!
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    Jun 10 2012: energy density too low.
  • Jun 10 2012: Yes. Seems like a good idea. May it be converted into the kind of reality that accelerates our progress toward all people living together happily ever after. We can do that. I am grateful that you are joyously, creatively working together with us, your precious, perfect peers, on our shared goal of elevating the well-being and joy level of our beautiful planet's population. We are succeeding. I acknowledge feeling much impatience. At least, thanks to people like you and others I have encountered on ted.com and in other places, we are accomplishing all of our positive goals at varying rates of speed and efficiency. Thanks for every positive thing you do and every positive word you say. Happy Today.