Small-scale Wave-power - Free Energy From the Beach!




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Wave power is a much-neglected source of renewable energy.  More consistent and reliable than wind, it is suffering badly from lack of investment.

There are two main focuses for wave-power; off-shore waves, where the rolling action is exploited by floating buoys or the proven Pelamis system, and on-shore systems, where waves are used to push volumes of air through turbines, like the Limpet system, currently running off the Island of Islay.

This project is a proof-of-concept for a micro-scale system, based on the general concepts of the Limpet, that could developed into a useful source of power for remote beach communities, or exploited commercially to charge tourists' gadgets at the beach.

There are three motivations behind this project:

1. Disaster relief / Power-poverty relief.

A device like this (made of light materials) could be delivered as a flat-pack to areas that are deprived of power (through natural disaster or material poverty), and close to the sea.  Although not enough to cook with, it could be used to charge batteries for radios, lighting or cell-phones (there are a surprising number of areas with good cell-phone coverage, and yet no available mains electricity).  The parts for a unit like this are cheaper and lighter than a solar- or wind-based unit, and wave power is usually more reliable than either wind or solar.  It could even be sent as just the turbine unit, with diagrams on how to make the shell from indigenous materials or debris, maybe with a selection of design tweaks that could be chosen from depending on the local beach conditions.

2. Commercial applications.

I can imagine beach-side stalls, the ones that sell sun-tan lotion and trinkets to tourists, could also provide a service charging up tourist iPads, Kindles and phones.  Again, because of the simplicity and low cost of the component parts, it would be easier to fund for an independent start-up in a poverty-stricken area.

3. Education.

For some reason, discussion of renewable resources in the media begins with solar, ends with wind, and mentions nothing else.  Unfortunately, the same is also true in education.

I can tell my students about wave power systems, and show them pictures of experimental or commercial installations, but the only hands-on kits available are all solar or wind-power based.  Having a project like this available encourages younger students to think outside the box, gives them a chance to get hands-on with a real system, and also provides a starter for older students to work on their own projects (this design is far from perfect, and I am really keen to see where other people can take this idea - see the final step).

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Step 1: The General Concept.

The concept is simple - waves move inside a confined space, cyclically driving a column of air in and out through a turbine (see the animated gif taken from their website).

Islay, where the Limpet system is installed, typically has high-amplitude waves, breaking against a steep cliff/shoreline.

Most people who go near the sea, though, go to flatter beaches with more horizontal motion to the water.  That is what I will be working with.

Step 2: The Shell Concept

First, we need a shell or casement that will focus an incoming wave and use it to force a column of air towards and through a turbine.

No need for aerodynamic niceties in a proof-of-concept, so this is made from panels of plywood.  The tower containing the turbines was to be built as a single unit, but for the sake of portability, the shell was to be held together with zip-ties, and air-gaps sealed with duct tape.

The original concept sketches, paper model and a more detailed plan drawn up in InkScape (but saved as PDFs) are attached.

Step 3: The Actual Shell

(This part of the project was done in half a day at NoahW's wonderful workshop in Oakland, a favour for which I am deeply grateful - if I had been forced to use my own resources, the build would have taken much longer.)

I realised quickly during the build that I had made a fundamental error - the sloping rise in height of the "mouth" will compensate for the horizontal narrowing, which will stop the compression effect I am after.

As a basic, prototype-level fix, I just made the roof of the shell horizontal.  This also meant I could simplify the plan and the panels, so the whole thing became a stack of flat panels, with the turbines to be fitted flat against the back wall of the tower section.

I drew up the "final" plan directly onto a sheet of cheap half-inch plywood, using a big T-square and an actual yard-stick.

The main square cuts were done on Noah's table-saw, which is actually bigger than my shed, and the angled cuts were done by hand with a jigsaw.

I drilled holes along the edges of panels that butt together for zip-ties to be fed through later, countersunk on the assumption that this will put less stress on the zip-ties, helping them last longer.

A thick coat of water-based* sealant, and we're ready to install the turbines.

*Yes, I know, but I don't need this particular unit to last a long time, just long enough to prove my idea has legs.

Step 4: The Turbine

The turbine is actually two turbines.

There are designs that will take air-flow from more than one direction, but I am using what is to hand (I'm working to the hypothesis that, if a rough design works roughly, future refinements can be funded on the basis that the concept has been proven.

Two PC fans are fixed over holes in the housing.  Each is connected to a 1K resistor.  Checking the voltage across the resistor will allow me to calculate the power output of the fans.

To make sure that air flows in one direction through each fan, a simple valve consisting of a sheet of polythene bag lays across the outlet side of the fans.  On top of that, it turns out that these particular fans spin merrily when air blows through them one way, and barely twitch when air blows through the other way.

Unfortunately, the frame of the fan did not match up with the best direction to blow the air, so I had to add ducting around the fans to give a flat end for the valve to close off.  The ducting was simply a short section of soda bottle, which happened to match in diameter.


Why two fans, and not one sucking in and out?  It's a matter of efficiency - if I use the same fan for the air to blow back and forth through, a significant part of the available energy will be wasted in stopping the fan turning one way before it speeds up in the other direction.

Step 5: Results.

On testing, I achieved a mixture of success and failure.
  • The venting fan spun madly when waves entered the device (success).
  • The inlet fan did not spin when waves entered the device (success on the valve).
  • The inlet fan did not seem to move at all (failure - the retreating wave did not create any suction).
  • Sea-water and sand spewed out of the turbines (design failure - rectify by using a taller tower).
  • The generator floated too easily as waves entered - I needed to sit and stand on the shell to hold it down (design failure - easily rectified in future by the use of sand-anchors).
I was not able to test the power output of the generator, because I did not want to wreck the meter in the salt-water from the turbines, but I count the rapid spin of the turbine as a success.

Overall, I count the test a success - all the aspects that failed can be fixed with relatively small amounts of work.

Step 6: Next Steps

Obviously, a few minor tweaks and this device will solve the third-world's energy problems...

Well, maybe not that extreme, but any step in the right direction is a useful step in the right direction.

As I said in the introduction, I am keen to see where other people take this project.  So, I want to see other people turning it into a functioning, useful device.  If you do any work with this idea as a starting point, publish it online (either here on Instructables, or on any other website), and send me a link, I will include that link in this step, and also reward you with a "pro" code from my personal, resources.  The better the project, the more pro I will send you.

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    132 Discussions


    2 years ago

    Simple - just follow the instructable and build your own version. Feel free to follow the plans as closely or as loosely as you like.

    2 replies

    Reply 9 months ago

    Is there a specific list of all of the materials? I am doing a group project focusing on energy collected by ocean waves, and if we decide to try and create this project, we will need a list of materials and more specific steps. Thank you!


    Reply 9 months ago

    It's very much a prototype for others to advance - I used plywood, and the dimensions on the templates are only approximate.

    As a group, between you, you should have the skills to recreate this, or something similar, in the materials you have available.


    1 year ago

    Kiteman good project and there is a but. Your neck on the model is not high enough. if you look at the limpet the base is under the water creating a seal. and when the wave comes in it's the air volume is expelled and then sucked back into the sealed chamber hope this makes sense to you.

    A lighter method is cut off the neck and replace it with a gutter hopper upside down with a pie leading to the fans possible 3ft high pipe with another gutter hopper creating a funnel feed.

    hope this isn't confusing

    1 reply

    Reply 1 year ago


    I get what you mean - thanks for the idea!


    3 years ago

    Hi! I'm in 8th Grade. Um, I don't know if it's possible, but I really want to do something with tidal energy for this group science project I have for my advanced science class. I don't think I could do something like this, but I really want to go above and beyond and make some sort of wave powered energy generator. Is there anything I can do, or should I focus on something else entirely? Thanks.

    1 reply

    Reply 3 years ago

    8th Grade? 13/14 years old?

    If you have access to the tools & materials, this should be possible for you to do - I used a big table saw purely because I had access to one. You could use a jigsaw, circular saw or a hand-saw to do this as well.

    You don't have to use the same materials - if you get hold of some old house-sale signs or some political placards (the corrugated plastic kind), they might work (you'll have to anchor them somehow).

    There are many, many ways of extracting energy from waves. Another idea I have been toying with is a vertical pipe mounted against a pier or harbour wall - as waves roll along the wall, they'll push air up and down inside the tube and drive a turbine.

    The design of machine depends on the way your local waves behave.

    If you want to work indoors, you could focus on the kinds of turbine used in "moving air column" devices like this - some use a single Wells turbine, I used a pair of turbines (one for each direction), or you could mount a vertical axis wind turbine across the air flow. You could make a large "syringe" from plastic pipe or pieces of soda bottle to blow and suck air across different kinds of turbine connected to a small generator (a 3V DC motor would be fine) and see which is best. The acrylic box in the video could easily be re-made in card, corrugated plastic or plywood.

    Hope that helps.


    4 years ago on Introduction

    I hope you get back to me Kiteman because I have thoughts and questions and I'd like to have some dialogue here. I just watched the TED lecture on "Global warming at work (chasing ice 2012)" on YouTube. Anyone here who is interested in the far reaching effects of the devastation we have done to this planet REALLY needs to take a look. Fascinating and terrifying all wrapped up into one little rather not so neat package, while our politicians still debate if global warming is even a "thing". It's tragic and our planet is screaming for help.

    And that's where you step in! Which I think is brilliant and amazing! I have always thought the same, that renewable energy comes in two forms solar and wind and what about the big third option, water. It seems to be consistently overlooked. It's as if we've spilled a glass of it and then picked up the throw rug and quickly covered over that option! Why is that?

    What is the reason that we do NOT go this route? I think at least to me it is a huge unanswered question. I'm in the states, so over here we have a huge example in the Hoover Dam that is hydro-electric. I very well know there are other examples. I know in Syria there's a small hydro-electric dam. In Canada they speak in terms of their bill from hydro and how big the bill is. And I know this is slightly off your project here but we're still dealing with the movement of water to create electricity, no matter how you slice it. You are incorporating the movement of water to create wind to harness energy (Gads I love that!) but really why DO we shy away from harnessing the power of water. When our Hoover Dam was built why didn't we put up 49 more? So what holds them back! There has to be something.... SOMETHING .. that makes this NOT a winning proposition for the politicians. What are the reasons why. I mostly ask it because someone said directly to me... "If its such a good idea then why didn't we go with hydro-electric for instance after the Hoover Dam was built?"

    I have an artesian well at my house that has such a strong force of water that it had to be plumbed with an overflow shunt or it would blow the plumbing apart in my house. It flows into a cistern in my backyard. I have always thought its such a waste. Its good clean drinking water. I think about using it for my garden. I also think about trying to harness energy from the flow with an impeller. The water flows through a pvc pipe anyway on its way to the cistern. Maybe I could gather enough electricity to light my chicken coop or something. I honestly don't have these sorts of But I do dream about being able to do these sorts of things.

    Anyway You are brilliant. Its a wonderful instructable. Your energy and excitement seems to come through in your write up! Fantastic. Thank you so much for sharing with all of us! And please remain my friend in pushing for solutions for the planet that made good common sense! Fantastic!

    3 replies

    Reply 3 years ago

    The hoover dam generates a lot of electricity, but dams have problems too. They usually create a reservoir that disrupts the ecosystem, they make it harder if not impossible for fish to spawn or migrate, they keep sediments from replenishing soil downstream, and they can actually lower the water table.

    It is important to look at the environmental effects of any project, especially something intended to help the environment.

    This instructable on the other hand has no negative impacts i can see, great job!


    4 years ago on Step 6

    the russians made something very similar to this during the war and discovered it had to do with the air hydraulics (suction etc) so the shape of the chamber was shaped like a wave and the fans were placed in the small corner of the tip of the wave so the air flow was channeled and concentrated at a focal point of sorts.

    1 reply

    5 years ago on Step 6

    i'd been thinking of my own design, much bigger, but still could be made in a disaster area. mine would have been a large tube attached to anchors that keep it facing the waves, an outlet tube going up the side of a hill or cliff to a turbine. it'd be fixed so it would rise with the tide or sea level rise. i might have been inspired by ovens park.

    for a portable, maybe a box going out into the water, set on driven posts and stones, anchored and weighted so it floats right near the surface, but stays where it is. dig the base in, cover it with rocks, being out past the sand it wouldn't fill up. the shape on bottom would be flat, the sides and top would be straight, going to a funnel shape, then to a straight tube.

    2 replies

    Reply 5 years ago on Step 6

    when i have some land... i'm at least another year in an apartment.


    6 years ago on Introduction

    @kiteman Yeah, since 2006. The wavetank test facility was bought by another company this May and i managed to keep my job, we're still set-up to test WEC's. All the technology was sent to Germany and archived for future reference. It was and still is quite upsetting to see Limpet go, it was a living breathing thing.

    1 reply