Energy from Ocean Waves

(2007 Jan 17 blog post)

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In 2005, I ran across an interesting story (published Nov 2000 at wire.com), about an ocean-power generation method, devised in Scotland.

The method sounds like a concrete (in more ways than one) implementation of a general waves-in-a-tube concept that I have been day-dreaming about as a practical way to capture energy from ocean waves.

    (The Scotland implementation is "heavy-weight" in that it would require huge wave guides, generally made of concrete. This would be "intrusive", to say the least, on coastlines, like the beautiful Oregon coastline. I would prefer a light-weight implementation based on smaller tubes and smaller electricity generators --- a thousand points of light, so to speak.)

I provide this information here in hopes that U.S. readers will push their state governments and federal government to aggressively investigate "green" energy systems like this ... systems to replace fossil fuel burning that is contributing to global warming by releasing energy --- that was stored in the ground over millions of years --- into our atmosphere in the space of about one hundred years.


Introduction :

I grew up on the gulf coast in Texas and worked several summers, while a college undergraduate, for a couple of oil exploration companies.

From those summer jobs (in the 1960's), I found out that U.S. oil companies were having to drill at that time to maximum depths --- down to the point where relatively soft sedimentary rock ends and where the non-oil-bearing extremely hard igneous rock begins.

From 1-year-old through high school years, I went to the beach, such as Padre Island, with family or friends, where waves are constantly crashing, every day, without stop --- especially when the wind is high.

From these experiences, when it became clear in the 1970's that world oil supplies would be running out (after less than 200 years of exploration and development), I developed an interest in somehow tapping the energy in waves.

Like the wind, waves offer a challenge in energy generation because they do not release their energy at a constant rate. Some days, beaches are bathed with only very small waves.

Furthermore, it is a challenge to construct ocean-wave energy-capturing devices that can stand up to the pounding of waves and wind when the weather is at the other extreme.

In addition, there is the problem of corrosion due to sea salt.

In spite of these challenges, it seems that with the growing energy needs of mankind and the need for a replacement for fossil fuels, it would be a beautiful thing to capture the energy in all those waves crashing onto coastlines around the world. (A statement quoted below indicates that ocean waves could supply world energy needs.)


The Wavegen method :

Here is a description of the energy capturing method mentioned in the story about the Wavegen company in Scotland.

There have been many hydro-energy-capture and ocean-energy-capture designs based on driving turbines or other devices directly from the force of moving water. But the Wavegen design is different in that it uses wave motion to drive a column of air through the blades of a turbine.

"The LIMPET (Land Installed Marine Powered Energy Transformer) uses an oscillating water column in an inclined concrete tube that has its opening below the water level. Wave action causes the water level in the collector to oscillate, and this variation alternately compresses and decompresses the trapped air in the column. The air flows back and forth through a pair of generating turbines which are driven in the same direction at all times, regardless of the direction of the airflow.

The unit is designed to operate on the shoreline, or can be incorporated within rubble mounds or caisson breakwaters to provide coastal protection schemes as well as power generation. Key features include low cost power, maximum local content and a 60-year life with minimal maintenance."

Some web searching on "limpet" or "wave power station" or "Wells air turbine" -- or searching on the developers, "wavegen" or "Queen's University Belfast" -- would find some follow-up information.

Here is the location of the Nov 2000 news article at wired.com

And here is a link to research papers of the Wavegen company. (I found that the Wavegen company was bought by the German company Siemens a few years later.)

A valve-configuration that Wavegen shows on their web site, in the "Information for Schools" section, is clever. Here is one of their diagrams to indicate the concept. (OWC = Oscillating Wave Column)

Note that the airflow through the turbine blades is always in the same (linear) direction --- so the blades will rotate in the same (circular) direction no matter whether the air gets pushed UP through the air-guide configuration on the wave surge --- or the air gets pulled back DOWN as the wave recedes.

In other words, this diagram of valve-arrangement indicates that they try to get the air flow to go through the turbine in one direction only --- no matter the direction of the water surge.

They provide an animated diagram, as seen at the top of this page, but it does not give the details of the routing of the air flow through the turbine.

A simplistic diagram of a small battery-recharging system on a floating buoy is also seen on the Wavegen web site. (It is reproduced here just in case the image disappears from their web site.) From that diagram, you would think that they are allowing the flow of air to reverse the rotation of the turbine blades.

In fact, in the "Information for Schools > The Demonstration" page, the Wavegen folks say to the student/teacher "see the turbine blades reversing direction at the top and bottom of each stroke (Figure7). Ask them to speculate on the negative consequences of this direction reversal ('interrupted or uneven flow of power', 'high stress on the turbine')."

Thus they imply that they generally try to get the flow through the turbine blades to be in one direction only.

The high-stresses (during storm surge), salt corrosion, and longevity-requirements, probably led Wavegen to reject other designs, such as a piston-crankarm arrangement.

    (On one web page, Wavegen claims a 60-year life of their system. That is hard to believe. Maybe they mean the concrete structure. It seems likely that the turbines and/or valves would wear out or become obsolete in 10 years or less. In any case, the life of the turbines and valves were probably not verifiable around the years 2000-2005.)

The Wavegen turbines are probably turbines like those in aircraft jet engines --- or in a gas-turbine energy-generation plant, like the turbines used in electric utilities when they burn natural gas as a fuel.

In fact, on another page of the Wavegen web site, they have a small picture of a new (circa 2005) modular turbine, being installed in the Islay (Scotland) breakwater. The image is reproduced below, in case it disappears from their website.

It looks like there is a huge, gun-barrel-like hole on the right of that picture, into which they are going to insert the turbine --- which includes valves and noise-attentuators, according to the description.

The description on the "What We Offer > Breakwater Turbine" page :

"Wavegen has developed small power take-off modules for incorporating into breakwaters, coastal defences, land reclamation schemes and harbour walls. The 18.5kW power modules consist of a Wells turbine, valve, and noise attenuator. The complete modules weigh less than a tonne so installation or removal is easily achievable using a small mobile crane. The modules are very simple and rugged: the blades are fixed onto the rotor, have no pitching mechanism, no gearbox and have no contact with seawater.

These turbines are the fifth generation of Wells turbines and incorporate all the learning and cost reduction experience from previous designs and operational experience gained from the Limpet plant.

Wavegen is currently in discussion with a number of European port authorities interested in installing this technology."


The Promise --- and Wavegen Challenges :

It is encouraging to read, from one of the Wavegen publications, that "The energy from waves alone could supply all of mankindís electricity needs many times over."

    (I am not sure if they mean the waves in all the world's oceans, covering about 2/3 of the earth --- or just the waves at coastlines or in coastal waters within, say, 10 miles of shore.)

It seems that a large part of the problem, in the Wavegen design, will be developing a system of valves that will allow for one-way air flow through the turbine --- yet stand up to at least 10 or 20 years of opening-closing motion, even under extreme storm conditions and salt water corrosion.

Note that most turbine energy generation systems, like those at a hydro-electric dam, do not require a fancy set of valves to redirect flow --- because they do not have to deal with an oscillating flow.

    (I was rather surprised to find that Wavegen is using an AIR turbine, rather than direct contact of the water to a turbine --- like in hydroelectric plants. Perhaps the corrosive effects of sea water is the main reason --- or the damage from water pressure versus air pressure during storm conditions.)


Some Wavegen projects :

On the subject of projects in Europe -- Wavegen says they have a project coming up (circa 2006) in Germany. Germany is the home of their parent company --- Voith and Siemens Company--- who acquired Wavegen (Scotland) in mid-2005.

You can see some info on this in the "News" link, at the top of their web pages. Click on the 29mar2006 press-release news item. Some quotes follow.

"The development and construction of the first wave power station in Germany will rely on the know-how and technology of Voith Siemens Hydro Power Generation.

Voith Siemens Hydro through its subsidiary company Wavegen is operating the first commercial scale grid-connected wave power station in the world, supplying energy for private households.

The project planned in Germany is a milestone on the way to the commercial use of marine energy.

...

The envisaged nominal capacity of Germany's first near-shore power plant will be up to 250 kW, resulting in annual electricity generation of 400 MWh."


It looks like Germany is leading the way in Europe in alternative energy implemenation again --- like they are in solar power manufacturing and implementation. They seem to want to shake off their dependence on Middle East and Russian oil as soon as possible. I wish our government (and/or companies) would start making some moves in this direction.

Perhaps, like IBM and Microsoft did when they were building up their "intellectual property", the U.S. government and energy companies will make a move when it looks like these "green" technologies are more mature.

Other pages of the Wavegen site indicate that they may have other projects in the works --- in Spain and elsewhere. That is good to hear.


Other ocean energy capture methods :

[I may someday add some text and pictures, or links, here on about 5 other methods of ocean-energy capture that have been proposed --- several of which are being implemented.]


Conclusion :

It appears that Wavegen has not settled on an end-to-all-debate implementation of the turbine-and-valve system. And other energy-capture inventors are working on other methods of capturing energy from the ocean (waves, tides, currents, heat-cold, wind). Hopefully they will continue to refine their designs --- and, hopefully, ocean-wave power-generation will become a viable means of energy generation for this planet.

Keep the issue of "green" energy versus fossil fuels in front of your congressmen (state and federal). Write letters-to-the-editor. Contact energy companies. Post comments on web sites (blogs and forums). Make yourself heard.


Other "green" energy :

Besides wave power, there are other ways of capturing energy that is just "going to waste". I read an article that said an exercise-and-dance studio was installing a system in the floor that would generate (and store) electricity for the building from the pounding the floor received from exercisers and dancers.

That concept is not really surprising. Probably most of us have thought of how the energy from exercisers could be put to good use.

Here is an idea that comes from really thinking "out of the box".

Japan is producing electricity from train station ticket gates.

As one of the comments to this article points out, some train stations in India could generate a lot of electricity.

Maybe it is time to invest in Pacific Rim train stations as energy stocks --- :-) .

There is a page of solar energy links on this web site, among the Links on the home page.

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Posted 2007 Jan 17.
Changes made 2007 Jan 20.
Changed to allow for better printing 2009 Aug 23.
Changed page format slightly 2013 Apr 26.