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B Brainstorming: Large scale piezoelectricity generation

  1. Feb 12, 2016 #1
    Hello all;

    Just thought I'd throw a brainstorming question to all you smart guys out there about a subject I know only from the youtube videos I've just come across.

    Large scale electricity generation from piezoelectricity. I'm aware that this technology is used mostly on a small scale although there are some applications being used on roadways to power streetlights and traffic controls etc.

    However, there were a few thoughts I wanted to throw out there for discussion to see if any of these applications were at all feasible using the power of the wind and/or ocean:

    1. Large piezoelectric sheets/sails under luff (akin to a sail on a sailboat) - flapping wildly in the wind under loose tension.

    2. Large piezoelectric sheets/sails submerged in large tidal currents either vertically or horizontally.

    3. Piezoelectricity produced by the mass of water generated in tidal lagoons pushing downward on piezoelectric mats

    4. Piezoelectricity produced by massive structures on rollers pushed by the ocean tides/currents.

    These were just some thoughts I had when I saw some very interesting videos on power generation and piezoelectricity. Feel free to tell me I'm out to lunch! ;-)
     
  2. jcsd
  3. Feb 12, 2016 #2

    berkeman

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    Welcome to the PF.

    Since you've been doing some reading (or viewing) about this, what is the single biggest problem with trying to generate power from piezo sources? Why are larger displacement generation technologies so much more efficient? :smile:
     
  4. Feb 12, 2016 #3
    Thanks for the welcome.

    I'm unsure exactly what question you're asking me but hopefully my reply is what you're looking for.

    The main issues I've observed in the little I've seen are multi-fold. But the biggest issues are:

    1. Media such as quartz/ceramic only produce electricity at the moment it is struck/bent/compressed, so finding a source to "steal" kinetic energy from over a consistent time frame or with enough energy is difficult, or

    2. From what I've seen, the source of energy being used/poached to implement this technology is small in scale - using people or groups of people, vehicles driving on roads, mechanical energy in wristwatches etc. I haven't seen anything discussed using larger mass movements such as moving water from the ocean, or capturing energy from air currents.

    I was curious if anyone knew how a technology such as this might produce if the mass of an entire water basin was filled up and pressed down over a piezoelectric field at high tide, or if a sheet of piezoelectric material was oscillating and snapping at high speed due to a wind current.
     
  5. Feb 12, 2016 #4

    berkeman

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    That's the main issue with piezo power conversion (mechanical to electrical) -- piezos work with small displacements, so they would be most efficient with high frequency small displacement mechanical power sources. There aren't many of those around, unfortunately. If we could figure out a way to efficiently convert lower frequency mechanical natural energy sources to higher frequency sources, that might provide a path for economical piezo energy conversion. Nobody has figured that out so far... :smile:
     
  6. Feb 12, 2016 #5
    So there is no positive correlation between size of displacement and power output? - ie. if there is a larger force placed on a piezo there will be more energy produced?

    Also, I suppose your point about high frequency is where I was getting at with my sail question. If you've ever been on a sailboat and the sail has its tension eased, the sail will loosen and begin vibrating, and the more you loosen it the wider the amplitude of the sail flapping as its frequency lowers. But you can adjust that sail where it will be oscillating and vibrating very quickly.

    And furthermore getting back to my thought about tidal usage...the ocean is massive, and constantly moving, and pushing/pulling with unimaginable force, and the mass of water displacement is immense - even if harvesting this was at a lower frequency mechanical natural energy could you not harness that energy in such a way over a large enough volume/area/mass that the sum of the total could be substantial?
     
  7. Feb 12, 2016 #6
    Let me give you an example of a thought (I haven't given it a huge amount of thought...just brainstorming again!)

    In Swansea, Wales they are building a tidal lagoon power plant. There will be large walls enclosing the lagoon area with suiles that allow water to pour in/out and turbines that produce hydro electricity when water is run through them. The area and volume of the lagoon will be substantially large and it will continually be filled and emptied with the tides.

    One of my questions is is there a volume of water that would be sufficiently large enough where if it displaced air over an area covered with piezo media, that the compressive forces could generate a substantial electrical energy output?
     
  8. Aug 9, 2016 #7
    I find this line of thought very interesting. What I have wondered about about is building some kind of device/structure that contained piezo materials surrounded by water inside of something very rigid. Then if this structure where placed into an extremely cold environment the water would freeze, and the expansion of the water would apply pressure to the piezo material. Now the trick would be - could you generate enough power like this so that some of that energy could be diverted to heating the water, thereby setting up a process of expansion and contraction in the water, pressure on , pressure off, and thereby generating an electric flow.
     
  9. Aug 9, 2016 #8

    sophiecentaur

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    You could answer this yourself if you take the total area, the possible displacement and the available water pressure. Work done would be Force times distance or Average pressure times area times distance moved. That amount of energy would be available twice a day - possibly four times(?) The problem is the mismatch, I think. The total amount of Energy put into the system by the tide would be (in the order of) Volume of tidal water times average pressure. That means that most of the tide's energy would be wasted. Many many panels of piezo electric panels could increase the efficiency pro-rata as long as the tidal water could flow into the spaces between them.
     
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