Wave power: Archimedes Wave Swing

AWS wave energy converter

The AWS wave energy converter is a cylinder shaped buoy, moored to the seabed. Passing waves move an air-filled upper casing against a lower fixed cylinder, with up and down movement converted into electricity.

The concept has been proven at full-scale in 2004 via a pilot plant that was installed off the coast of Portugal. Engineering for a pre-commercial demonstrator is now ongoing.

The converters are at least 18 feet underwater, can survive violent storms, and produce more power in less space than other wave generation methods. Unlike solar or wind, wave power is steady and reliable, the waves are always there. In the coming world, we’ll generate power any number of ways, and wave power sure looks promising. has detailed information and there’s more on the company website, AWS Ocean Energy.

  • Apparently, Scotland could be powered by fully renewable energy within only a generation. That kind of thing shows you what a terrible waste of everything capitalism is.

  • Joe Hartley

    A careful reading of the company’s website shows that the reason that this technology has not been adopted yet by any government, whether socialist or capitalist or in between, is that its energy output is considerably less than than anything powered by oil or coal. The website does not give many specifics–always a suspicioius sign–and suggests the output is roughly the same as a large wind turbine. Under what passes for tehcnical details, the company suggests that the conditions for deployment would be limited:

    *Location exposed to ocean swells – e.g. western coast of British Isles, Ireland, France, Spain or Portugal
    *40 – 100m of water depth outwith main commercial shipping lanes
    *Secure electricity power grid ashore
    *Industrial port within 12 hours sailing time
    *Sea-bed suitable for laying power cables to shore

    (this is all from the company website). I don’t know enough about ocean geography to know where these areas lie, and I confess to being ignorant about ocean wave dynamics, which I always understood was a surface phenomenon. It’s odd that their front page suggests that the devices could work when covered with only 6 meers of water (just about 20 feet) which is clearly too shallow for placing them in any kind of commercial sealane, whereas the specs, such as they are, suggest burying them in at least 40 meters of water, or about 175 feet under. I have no idea whether there’s any significant wave action at the depth, but I should think that the amount of energy generated at those depths is much less than what could be generated on the surface.

    This is essentially the same technology that hydroelectric power uses, except the turbines have to be much smaller. It’s an interesting idea….but let’s not get the cart ahead of the horse. Even the company suggests that the output is relatively small. Without giving any information about how far apart the generators need to be, it’s hard to calculate the efficiency of the units. The company website offers the following description:

    It is expected that AWS units will be deployed in arrays of several tens of units. A 50MW farm will occupy an area around 3 nautical miles long by 2 cables wide. This would generate enough electricity for 25,000 homes.

    So we’re limited as to the number of sites, and each site will need to be 3 nautical miles by about 1200-1400 feet wide to generate enough power for 25,000 homes. That’s a lot of real estate to cover close to the coast to generate not a lot of energy. For example, I don’t think that anyplace in California would qualify for placement because of the sharp dropoffs caused by tectonic action; you simply can’t find anyplace that has a gradual slope between 40 and 100 meters that’s a quarter of a mile wide.

    This is not to say that this technology shouldn’t be used to supplement the power being generated. Indeed, a diversified range of options, with each generating only a few percent of the total power needed, may be appropriate. But this is clearly not going to meet the all the needs of any large urban area.

    Without further data, it’s hard to calculate how much electricity this technology could add. Scotland, for example, has a population of just over 5 million, with about 1 million under the age of 18 and the rest over 18. What’s a fair estimate of the number of households (however the company measures it) for such a population? 2 million perhaps? 2 m divied by 25,000 suggested that they’d need 80 such stretches to generate enough power for domestic use. The west coat of Scotland has dozens of islands and is broken. A linear measurement, north to south, suggests a coastline of about 225 miles. Let’s accept that as the maximum. The problem is that only 63.5 generating units could fit into such an area, and that’s assuming that we could use all 225 miles. (The company measures the length of the wave farms in natuical miles, which is about 6,076 feet, compared to the 5,120 in land miles).

    There are plenty of additional questions to be asked, including how often the units need to be replaced (they’re in seawater, after all, which is highly corrosive to metal), how much energy would be expended in their manufacture and maintenance, and so forth. After answering all these questions, the technology may prove a useful energy supplement in the future. But it’s hardly a panacea that will solve all the world’s problems.

    BTW, I have nothing against wave or solar or wind power in general. The problem is one of thermodynamics, the laws of which do not conform to what economic system you chose. (The physical problems of generating energy are identical for capitalist as for socialist as for feudal societies.) Oil, natural gas, and coal deliver a lot of energy for a comparably small amount of matter and space used to generate them. This doesn’t mean that they don’t have serious side effects and problems, but it does mean that you need to cover a lot of area with wind farms, wave generators, or solar panels to generate comparable amounts of energy, and those technologies are not without their carbon and environmental footprints, either.

  • Joe Hartley

    In reviewing the picture Bob has posted, I had an additional concern: if the generators are that close together, you’re going to cause considerably disruption to the marine environment. 100 meters is about 340 feet deep, so even at your deepest you’re going to have a lot of action on the seabed from fish and plants. (and definitely at 40 meters). It looks to me from these pictures that everything is going to be close toegehrr: generators, floor anchors, and cables taking the electricity to shore. That’s a square mile of destroyed seabottom. Don’t know what the effects are, or whether the cables, etc., could be overgrown after a while, which in turn raises questions about the cost of maintenance.

    The lovely thing about ecology is that there are so many variables to consider! So much more interesting than the typical univariate analysis that is usually done!

  • All good points, Joe. Some of the alt energy plans do seem a bit, um, not well thought out.

    I think the energy future will include lots of smaller generating plants closer to where the power is needed, and it’ll be whatever is best suited for the area; hydro, wave, solar, wind, geothermal, whatever.

    Coal probably is cheaper, but in terms of reversing global warming, it’s not really an option any more.

  • DJ

    I think the image from “Soylent Green” of a man riding a stationary bike to charge the battery that runs his lights may be one possible scenario…

  • Robert Mackenzie

    Scotland actually has over 6000 miles of coastline.
    Why would the buoys need to be in linear fields?

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