DIY Wave Energy Reclamation, Not So Complicated After All

We humans are becoming more aware every day that we need to reduce our fossil fuel dependence and move to more renewable methods lest we make the earth a less-desirable place to live. The sun is here today, and it will be tomorrow, harness that energy is one solution. There are places that are commonly windy, we can harness that energy too. [Jonathan] and [Ellen] set out to harness that wind energy but not in the traditional wind-turbine way. Wind creates ocean waves and the pair set out to recover some of that wave energy. They built a proof of concept and they did it on a budget with a side of DIY-style, to boot!

The device consists of a raft, with magnets attached to a sheet metal ruler standing on end. As you would expect, this ruler is flexible and the mass of the magnets easily sways back and forth as waves pass. The magnets move through stationary wire coils and as they do, creating an electrical current in the coils. The output of the coils is AC, which is then rectified to pulsed DC using several diodes and smoothed even further by some capacitors. The two DC outputs are then connected in series to double the voltage to 5 with a max current of about 20mA.

For this experiment the generator powers a modified smoke alarm which keeps burglars away from a coral reef. But the team could see this powering lights on buoys or low-power sensors. What would you use it for?

27 thoughts on “DIY Wave Energy Reclamation, Not So Complicated After All

  1. 5V, 20mA (100 milliWatt) is not going to produce a lot of light/sound, but nevertheless impressive for such a simple device.
    a buoy anchored to the seabed with a floating device attached creating linear motion from the waves seems like something that would be able to provide much more power. Of course engineering stuff for use in seas or oceans is no simple (read very expensive) task.

  2. Buoys have been effectively wave powered almost from the start. Bell buoys, whistles, gongs and the like all work on wave motion or water displacement. For lighting, a solar panel and battery have no moving parts and can be sealed away from corrosion (the project in the article would disintegrate in a few weeks in sun, weather and salt water) and are thus preferred.

    1. I see a real advantage to the idea. Remember, this is just a small prototype. Scale the generator up, modify the project so that it generates power in X & Y directions and encase it in a waterproof & corrosion proof housing and it will produce power 24X7 – not just when the sun is out. And anyways, who says you can’t have solar and one of these on a buoy?

      1. Unfortunatly you cannot scale up in dimension, because the base of this system has to be small compared to the wavelength, otherwise you don’t get the tipping of the top.

        What would be possible is to scale up in number, in a pearl necklace arrangement or like a mesh.

        What I really like is that it is a option to supplement solar power generation because it produces presumably more power during bad weather periods (i.e. clouds).

  3. I see this project more of a proof-of-concept for them. In the mkII version they should invert the generator so the weight is in the base and CG gets lower. Throw in some pointy wire bits to discourage birds and things from roosting on it.
    A few things they could monitor: conductivity, ammonia, DO, pH, turbidity, phosphate, and carbon dioxide. The trouble is all the compact assays for these require a bit more power than this iteration of the wave generator provides. Depending on where you want to monitor it may not be able to harvest enough energy even with a more efficient design. You’re gonna need PVs or batteries.to supplement.
    You need to decide if you want to use a radio to transmit data, which adds to power requirements and equipment cost. Sat phones work well in remote locations but subscriptions are pricey for an individual. Or have someone head out to the mooring regularly to download data.
    Lastly this needs some way to keep biofouling from accumulating and I’m sure there are constraints on what can be used in a reef environment. All of these things add weight, which probably impacts efficiency since heavy things don’t move with the waves as much. Designing the coil in a heavy outer ring with a captive, light, free floating magnet may allow you to get around this. All logging equipment would be arranged on the ring portion.

    @ Thinkerer
    Hardening this project against corrosion wouldn’t be any more complicated than the PV scenario. Panels tend to get clouded by salt spray depending on their location on the buoy.

      1. Saw an interesting use of these systems on an old discovery documentary, Underwater living or something. Anyway, they used a network of these to provide power to the seafloor. It seems they also grew/collected.cleaned algae from the tether lines regularly, and was to be used (the algae) for food and extra fuel. So, sort of stored and complimentary energy?

        1. Actually, now that i think of it they demonstrated several versions.

          Settling on an underwater version of this, with ‘kites’ affixed to long lines as well, so all submersible. Solves the problem of the sun.

  4. Get a bunch of ring magnets, preferably polarized with the poles to the flat faces. Put them onto a long piece of threaded stainless steel rod with poles alternating, possibly with plastic spacer washers between.

    Put a float at the bottom of that rod with an eye for an anchor cable. The power circuit would be simple, a bridge rectifier connected to a coil of magnet wire, just like those flashlights. The coil and everything else could be sealed inside a torus shaped float. Put a cap on top of the magnet rod so the float can come off.

    Toss the anchor in the water and adjust the cable length so during the tide level when you want the most power generated the float will average position in the center of the rod.

    It could also be possible to float things so it will all rise and sink with the tide while still having motion between the float and magnet rod.

  5. Get out of my mind ! I’ve been imagining this kind of stuff like this 3 weeks ago and came up with a lot of differents designs but never took the time to try it (plus I was thinking that the power I could harness would just be enough for a LED. Nothing fancy). Nice to see it applied. That is a good starting point and a proof that it could work.

    1. Give it a try anyway! I would love to see you charge up a super-cap and using it to squire wireless data out once in a while. Weather, pollution, water temperature, all kinds of sensing applications are possible that would never need a battery.

  6. Let’s say they were going for maximum power generation for a given size raft. How many different different types of generators could they stick on it?

    I can think of:
    -wind turbine on top
    -under water turbine below
    -solar panels
    -kite generator
    -electromagnetic wobble generator ala this article
    -Seebeck generator with some sort of heat pipe going down to the chilly water below

    All of these things would make for one mighty raft, what else could they put on it?

    1. Some ssues with a few of those technologies on a raft in the ocean your mentioning…
      Wind Turbine – not enough wind that low to the ground
      Solar Panels – A large strong wave could easy damage such expensive cells especially if something was being carried by the wave such as drift wood. (Although the current design would have the same issue)
      Sizing is also an issue as I am sure they are trying to minimize the footprint of the project so its fairly small.
      Kite generator – what happens if the wind dies down too much at any given point and the kite hits the water. Doubtful someone will be around to try and dry it off and get it back up there. Not that in the ocean the wind dies down very often but still could be an issue.
      Just my two cents on some of those

  7. Why not use a better design and instead use the actual tide and waves to generate more current? But placing the ruled underneath the water and a flat object at the bottom as the wave goes one way the flat object will push one way and as the tide pulls back out reverses… You could place more magnets and more coils in a row and continue to generate. On top of that the potential for using piezo plates if the current is strong enough for the “ruler” portion could produce more energy as the ruler is pushed too far one direction from a strong current such as that experimental wind technology for piezo plate towers that look like grass stalks. Just seems like you could generate so much more energy from the ocean tides and currents / waves with a better design…

    1. Very true, in about 5 billion years from now, the sun will begin to die. Our local star is about 4.5 billion years old. it has already used up about half of its nuclear fuel (hydrogen).

  8. Hum… 20mA at 5v?? I didn’t see the project cost here. But i think a cheap solar flashlight keychain on ebay or something else with a solar painel would get the same amout… This would be fine if the energy achieved with this would be at lest the same with a equal cost solar panel..

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