The water snakes are back onshore

Local newspapers today are making major headlines again with “the first commercial wave farm of the world". But for the wrong reasons, the state TV website published an article yesterday with the following opener:

The three Pelamis machines of the wave farm in Aguçadoura, that was considered by the Portuguese Government as a “flagship" of the country's leadership in renewable energy, where taken out of the sea and have been onshore, at the Leixões shipyard, for 4 months.

The two Pelamis units deployed in September were at sea for only 2 months and there's no date set for a return to operation.

An audio version of this article can be downloaded here.

The article continues:

Talking to the news agency Lusa, Rui Barros, from the Companhia de Energia Oceânica (part of the Babcock & Brown group, the project owner) said a recurrent problem was detected with the bearings of the hydraulic jack's articulations in all of the three machines, prompting their move out of the sea.


According to Rui Barros, the continuing problems with these bearings that are submerged, forced the transport of the three machines back to shore by mid November, “so that an inspection could take place".

“We then verified that the problem was serious and extensive, a generalized problem and not fortuitous." he explained.

Since then, Pelamis Wave Power, Babcock & Brown's technological partner and maker of these machines, “entered a discussion" with the company that provided the bearings, being set for April the arrival at Portugal of new parts to repair the equipment.

“I'm aware that there's a team from Pelamis ready to come to Portugal to substitute the bearings", said Rui Barros.

According to this official, replacing the bearings will take about a month, after which the machines can again be brought out to sea, resuming the testing they were being subject to.

“I'm convinced that, if no other problems appear, before the end of Summer we shall have the three machines working and preparing for commercial production. But it is all, if, if, if...", he said.

But other problems are menacing the project, the credit crisis has hit Babcock & Brown hard, that was forced to sell assets to cover its debt, including the Pelamis project. Now it becomes known that the consortium announced in September between this company, two local companies an Australian investor was never signed. A second article gives further insight:

[…] the consortium announced six months ago between EDP, Efacec, Babcock & Brown and Pelamis for the development of the Aguçadoura wave farm and of a Portuguese 'cluster' in the field of wave energy never came to be.


“The initial assumptions of this project were altered and EDP is renegotiating them with Babcock & Brown", said to Lusa an official from the Portuguese electric company. Underlining that it is still “committed to the project", EDP didn't clarify if it is interested in buying the stake off the Australian fund.


On the Portuguese 'cluster' for wave energy, Rui Barros considered it “seriously compromised at the moment".

The “race" for Portugal's leadership in this renewable energy field is already lost, for if the Aguçadoura wave farm was the first of its genre at the world level, “soon it will stop being so", concluded Rui Barros.

There are several points worth making on this new development, but first it should be stressed that errors and faults are part of any engineering process. Such is the case for during the architecture phase details are missed and during the implementation phase things don't always go as planned. In fact it is the process of testing, error discovery and correction that allows for the improvement of the final product. Knowledge improves when the product fails, not when it works as expected.

Nonetheless, a bearing leakage at this stage seems somewhat strange, especially considering that in situ tests were previously run in Scotland and in Portugal. Speculation can be made that either the bearing provider changed the manufacturing process or that the provider itself was changed in the meantime. In any event the commercial phase of the Aguçadoura project is now running almost 4 years behind the initial schedule.

The compromise of the wave power development 'cluster' is disheartening. And a proclaimed “flagship" project for the country being put at risk by the collapse of an investment fund managed at the other side of the world has its dose of irony. One gets the feeling it was all fireworks and that unfortunately Portugal might not have either the knowledge or the capital to be the “Denmark of wave power". Being home to the technology and at the moment attracting the investment of E.On, Scotland seems to be righteous owner of that title.

Finally, the reservations I expressed earlier on the maturity of the technology seem to be vindicated by this new development. On the financial front, this new delay almost guarantees that the Aguçadoura project will be a money sink. As for EROEI, every error and fault corrected will improve the design and the assembly and deployment processes, thus also improving net energy. Still it seems now more than justified to at least postpone the 70 million € Aguçadoura II project, until this pilot project reaches a higher state of maturity.

Previously at TheOilDrum:

The First Wave Energy Farm of the World...It's About Time...

Tapping The Source: The Power Of The Oceans

Pelamis: A Shot in the Dark?

Luis - thanks for this. I'd say this must be dismal news for Pelamis. I've had a quick look around their web site and can't see any news about this. Just the continuous barrage of propaganda coming out of Edinburgh about how we are on the cusp of a Green energy revolution.

Would I be right in saying that the most complex bit of equipment ever deployed in salt water by Man was a ship - in fact the drive shaft of the propellor. Most sub-sea engineering work done for the oil industry is driven by pneumatic valves that are encased - protected from salt water.

I've been skeptical about this Pelamis design. Moving parts in salt water and subject to much torque and stress. I just don't see it surviving either time or storms.

Won't the salt spray be hard on wind turbines located out at sea, as well?

Sacrificial anodes and enclosed generators.

I'm not an engineer Gail, but Wind Turbines have just one moving part - the sail attached to a drive shaft (though maybe the blades also rotate about the shaft).

Whilst exposed to salt water corrosion, they are not actually in the water, so any problems will not lead directly to leaks.

Horns Rev wind farm in Denmark (world's first offshore) had significant teething problems, leading to gear boxes being changed on all machines - I believe.

Personally I'd be more optimistic about tidal streams, where you can basically stick a propellor in the water and let it spin, a much more simple design - but still exposed to all sorts of crap that floats around in sea water. Seaweed, fish, half sunken yachts, dead whales etc.

but Wind Turbines have just one moving part - the sail attached to a drive shaft

Not at all. The blades rotate (feather) so they can 'catch' less wind and therefore move slower in high speed wind.

The lower the speed, the more expensive the generator (copper and magnetics)

The way power gets generated is by causing a magnetic field level to change so another way is to 'go fast' - 1800 or 3600 RPM are common. Thus the rotation of the blade is sent through a gearbox to up the rotational speed.

Then you've got to place the turbine blades into the wind so the nacell also moves.

Being near the sea will step up your maintenance schedule.

The gearboxes on large Horizontal Windturbines comprise a number of moving parts and demand maintenance, and there are considerable forces on the Yaw bearing that keeps the blades aiming into the wind.

While rated as less efficient, the vertical axis mills have avoided many of the destructive stresses on the yaw bearing and tower that Horizontals have, as well as the varying stresses on the individual blades and hub as they sweep high and low through wind, rotational and gravity forces. (and far fewer moving parts and high-stress materials required) As with the Pelamis' exposure to unrelenting wave pressure and saline conditions, I think there will be economics revealed in the durability of various designs.

I'm surprised that the pelamis design doesn't just put the moving parts up and out of the water. There are more solutions out there for wave and water.. I think we'll start really looking when we actually start to get hungry.

It's not that simple. The Pelamis device extracts energy from a range of wave heights, above these wave heights, it simply rides through the wave rather than over it to avoid destruction. No part of it will remain permanently out of the water. If you did have bits sticking out they would also probably be ripped off in a big wave.

Secondly, the mechanical parts have to react the wave forces which pretty much mandates their location, or at least most of them such as the hydraulics.

I'm sure it's not simple at all, but I don't think that the sort of changes I'm picturing (but probably not describing all that well) would be as vulnerable as you suggest. But it wouldn't be a matter of just offsetting some joints, it would probably be a different structural concept.. a square-one redraw.

I don't think it's essential that you have your rams or your pivots sitting immersed for much of the concept to still succeed. Theirs is a fairly brash proposal.. let's see what else they do, and who tries the variants on it.

It seems like Matt Simmons has been involved in investments that involve wave technology. Do you happen to know if they are at all similar to this?

I have never heard Matt talk about wave technology, but he is a big believer in energy produced at sea. He has been doing a lot of research into offshore wind. He discusses it in an older video on World Energy titled Energy Crisis. Could produce enough energy to take Main off heating oil all together. Unfortunately he also predicted wide spread gasoline shortages that summer. He got the shortages, but only after Hurricane Ike.

The three final links in the article don't work.

The First Wave Energy Farm of the World...It's About Time...

Tapping The Source: The Power Of The Oceans

Pelamis: A Shot in the Dark?

The first one is not linked, just a mouse-over underline. The last 2 have the correct address, but a " stuck at the end of them. You might wanted to double-check and edit those out if it's not just my browser.

I fixed the first and third. The second one seemed to work for me.

The code that seems to work leaves out the quote marks--it seems strange to me. If the second one still doesn't work, I can take out the quote marks there as well.

ThX for this update !
And in following this story (The water snakes) for some years now I always have had to pinch my arm and wonder : We (the world) are truly in dire straits when it comes to our energy future, I mean when this is something that has to be tried out ... as a possible solution ...

I've had more than a passing interest in wave power for quite some time, even though I am fully willing to admit that it will probably never be much more than a niche technology that is highly location-specific.

The current problems with the Pelamis system (of which I still hold in fairly high regard) have nothing whatsoever to do with the fundamental concept, but rather stem from certain nuts-and-bolts issues which, whilst not as dramatic, will do a project dirty just as easily.

As a totally unrelated example, one of the things that killed the prototype of the huge oddball 'flying wing' bomber of the early post-war era had absolutely nothing to do with the basic concept of the flying wing, but rather involved problems with the large and highly complex counter-rotating propellers. By the time they switched over to jets, the concept started to become obsolete.

I tend to think that this problem with the Pelamis is no different than that of a new model automobile having a massive recall due to some stupid little flaw that only popped up after many thousands of miles of usage. Once it is fixed, then we will see whether the Pelamis can deliver reliable power over a long period of time at a reasonable price.

As far as salt water corrosion is concerned, we already have a great wealth of practical experience with that potential problem: they are called ships, and as far as I know, ships still ply the oceans in spite of it.

As a current Northrop employee who has read about the history of the "flying wing", I would like to say that it worked well and was killed by politics, not technology.

mjcohen -

I am also familiar with the history of the flying wing and agree with you that politics (in the form of Defense Secretary Symington's meddling) is what officially killed the Northrup flying wing as a specific project. Nevertheless, one of the things that caused it to be viewed as a less-than-successful design were the chronic mechanical problems with those big counter-rotating propellers, which had nothing whatsoever to do with the aerodynamics of the plane.

It must also be recognized that jet engines were becoming standard on our bombers and their speeds were going up at a fast pace. The basic design of a very thick wing section such as on the flying wing was not very compatible with high-speed flight.

The Northrup flying wing was a fascinating plane and has sort of found a second life in the form of the Stealth Bomber.

IIRC, wasn't the flying wing configuration unstable ( I think to yaw), requiring constant pilot input to remain stable? Now, that computers are fast cheap and reliable, automatic feedback stabilization can make a lot of formerly impossible -or dangerous designs usable.

enemy of state -

You are partly correct: the Northrop flying wing was pretty sensitive in the yaw axis, though it wasn't what you would really consider unstable. A modern computerized auto stabilization system probably would have easily fixed this weakness. A good many years back I made several models of flying wing type gliders, and they can be rather sensitive to get to fly right.

In certain respects, the flying wing was both ahead of its time and arriving too late. One thing about it that wasn't fully appreciated was it's very small radar signature (some foreshadowing of our current Stealth Bomber). It also had a very long range and a huge bomb carrying capacity. It arrived too late in the the sense that bombers now needed to fly at speeds of 600+ mph, and the thick wing section of the flying wing was not all that compatible with really high-speed flight.

Jack Northrop had a vision of a flying wing aircraft for decades, and when the government suddenly pulled the plug on the project, it broke his heart.

The technotopians must be running out of magic incantations. Wave power in Portugal, dry rock geothermal in Australia, algae and cellulosic biofuel in other places. Some radical technologies seem doomed to stay below 5% of the energy mix. Others may have a practical upper limit such as wind ~20% of electricity and biofuel ~10% of transport fuels. We need something big and soon to replace fossil carbon for 50% or more of the mix.

Just wait for the technotopians to look into their black velvet bag and tell us the next trick will be really special.

Thank god we have hydroelectricity to balance out the intermittant wind power, solar power to take the edge off power peaks in the hot summer days, and nukes for baseload. Otherwise we might have to continue using fossil fuels.

What was that clever thing you said to the Wright brothers that day? It was brilliant!..

Just when I thought you were never going to ask...

Hmmm...let's see: sun warms earth's surface, surface warms layer of air that builds up adjacent to it (creating CAPE), warm air is skimmed off bottom layer by inducing it to flow toward low-pressure point and enter radially into building, air further heated in cross-flow by warm water cascading through packing, air passes through expander generating electricity (eff: 75%), exiting air passes through airfoils arranged in vertical ring which deflect flowing air tangentially into annular plenum, vertical component added to air via upward curving ducting, air exits through annular plane about 50-75m above grade where it passes through second (or third) set of airfoils (angle adjustable) where tangential component can be increased (all flows well below supersonic), warm air rises within vortex, which maintains low-pressure area within, allowing it to penetrate high into troposphere, some water condenses, releasing more heat...

Voila' have the AVE (

But to you, this sequence of processes would seem too much like rocket science for it ever to be useful, would it not?

Correction to above scenario--should have said "...exiting air passes through vertically oriented airfoils arranged along the periphery of horizontal ring (vertical axis) which deflect flowing..."

You keep promoting this, but AFAIK nobody has even tried to verify that the concept is workable.  Known stable vortex phenomena in the atmosphere with the capacity to do serious work (hurricanes, tornadoes) are vastly larger in scale than anything proposed or feasible.  To deliver useful energy, the AVE would have to overcome these roadblocks:
  • Fix the bottom end of the vortex in place, instead of moving with the wind a la dust devils (and everything else).
  • Keep the vortex from stretching at extreme angles with wind (increases friction loss without gaining more energy).
  • Keep the vortex coherent and confined despite loss of rotational energy to friction.
  • Do all of this while converting useful amounts of pressure difference at the bottom of the vortex column to work.
A very tall order.

In responding to your last statement--"A very tall order"--first, I would suggest that finding a means of slaying the two-headed monster--climate-change and depletion of high-quality fuels is, in itself, a "very tall order" that must be met. If we are only to depend on the current collection of renewable technologies to accomplish this, I would humbly suggest that were are indeed in "dire straits" (if you have a dog in the hunt, please enlighten the rest of us). Either way, why do you continue to discourage people from making the effort to "overturn yet one additional stone" to determine if it might be hiding a more transcendental solution?

Secondly, it is interesting that you use the term "roadblocks" instead of the more moderate term "challenges" to describe the concerns that continue to lurk between your ears. It would seem that, like certain extremists have expressed about Obama's policies, that you are "hoping it fails".

With regard to your specific concerns taken in order: 1) An AVE is, by definition, in a fixed position, so it would seem that this concern can just be incorporated into your second "roadblock"--(2, rephrased) what happens when you have a strong crosswind--will the "top" of the vortex be blown off?

Before going there, I would add that a dust-devil feeds off a relatively thin layer of "superheated" air existing near the ground the thermal content of which is diminished quickly as said air is sucked into the funnel. Therefore, it MUST travel to gather up fresh layers or it will immediately die. Accordingly, they may be expected to "slow down and intensify" when they encounter a relatively thick layer of warmed air, regardless whether or not the wind speed or direction has changed.

You previously described dust-devils as "weak" which is a matter of opinion. However, they do not reach the intensity of tornadoes, in part because they are not tall enough to produce condensation of water in the rising funnel, which could be made to occur in an AVE.

The cross wind questioned is addressed under FAQ's at the website (, to which I would add the following: In any "natural" tornadic event, there is always "wind shear". In many, if not most cases the vortex will continue operating, regardless of this wind shear.

The AVE is "ideally" designed to operate under no-wind conditions. However, in most places, some "seasonal" prevailing wind is to be expected, and therefore the question of "how much wind can it tolerate" becomes more of an experimental one, and would vary among specific designs.

While observations would suggest that the amount it could tolerate is considerable, nothing I could say here would be able to convince all the skeptics--that is why we need to build larger prototypes. In principle, it should also be possible to build an AVE with a "volute" to capture the kinetic energy of the incoming air, and use it to strengthen the vortex and make it more resistant to cross-flow. If properly designed, a steady cross-wind would probably even increase the output of an AVE.

At high wind flows, it probably would have to be throttled back, for its own protection, at which point conventional windmills would be producing maximum power to partially compensate for the loss in power output. (If I'm not mistaken, I think this also takes care of "roadblock 3")

Finally, expanders (as opposed to "free-stream" windmills) typically have efficiencies between 75-85%. They would be located in a module where the converging airflow is horizontal. However, they don't really "care" where they are located--they just perform best when they can be designed for flows constrained within a certain range.

Hope this helped, E-P.

In responding to your last statement--"A very tall order"--first, I would suggest that finding a means of slaying the two-headed monster--climate-change and depletion of high-quality fuels is, in itself, a "very tall order" that must be met.

Which has nothing whatsoever to do with the merits of the AVE.  Whether it works well, or at all, has nothing to do with our predicament.

If we are only to depend on the current collection of renewable technologies to accomplish this, I would humbly suggest that were are indeed in "dire straits" (if you have a dog in the hunt, please enlighten the rest of us).

I have no dog in this hunt; I promote what I can point to that works, or that has a very high probability of working.  Conventional wind, nuclear and a variety of solar technologies work.  Gen IV nuclear can almost certainly be made to work.  Wave, tidal and cellulosic biofuels are far more speculative.  I'd put the AVE well below Sky Wind Power on my scale of credibility.

Either way, why do you continue to discourage people from making the effort to "overturn yet one additional stone" to determine if it might be hiding a more transcendental solution?

I want those stones overturned.  I just want it done before the promotional machinery gets into gear; I've seen too many people get suckered.

You previously described dust-devils as "weak" which is a matter of opinion.

That they are weak compared to stable storm phenomena is a statement of fact.  I have driven through dust devils at highway speeds; the winds are quite noticeable, but not overly strong.  I doubt that the available power from a dust devil exceeds 100 kilowatts, and they cover a very small part of the area from which they harvest energy.

However, they do not reach the intensity of tornadoes, in part because they are not tall enough to produce condensation of water in the rising funnel, which could be made to occur in an AVE.

To get condensation, you must start with air which is both warm and humid; where does the humidity come from?  To get differential convection, it must be considerably warmer than the environment, with correspondingly greater water-vapor content.  This thing sounds like a water-consumption nightmare and unusable in arid conditions.

While observations would suggest that the amount it could tolerate is considerable, nothing I could say here would be able to convince all the skeptics--that is why we need to build larger prototypes.

Indeed.  I even suggested a way to perform such a test "on the cheap", using an existing cooling tower.  The skeptics will be convinced by proof, which will be produced before any useful amount of energy is supplied.  It's up to the AVE crew to stop talking the talk and start walking the walk.

I'd put the AVE well below Sky Wind Power on my scale of credibility.

High flying generators making electricity economically???

Now that prediction is one that should be definitely stored in the archives for future reference!!!

Yes.  I stumbled across the "gyromill" news years ago, and even collected a heap of weather data to try to verify the claims about the capacity factor (80% is claimed for the region from Chicago to Detroit; I found the data format too opaque to write a parser).  Since power from a wind turbine scales as wind speed cubed, the high upper-level wind speeds could produce large amounts of power from relatively small machines; even if the machines are much more expensive per square meter, the cost per watt could be quite competitive.

This is something else that needs a demo.

Undoubtedly--hey, E-P this trading of barbs is great fun, but nobody else is listening. Since we're not principles in either of these technologies, why don't you propose to your handlers (oops, there I go again, sorry) to see if they would be interested in inviting the main proponents (Michaud and Caldeira?) to advocate for their respective technologies using "Guest Articles". They would describe it briefly, and discuss why it would be superior to (more likely to work) than the counterpart.

Then we could let oildrum readers vote to determine which has the greater promise...

Just a thought.

Here's another: "WindSky a whole new meaning to the expression:

"when pigs fly"!! lol.

You aren't sorry.

I had a brief exchange of e-mail with Bryan J. Roberts several years ago regarding the topic, but nothing with anyone from Sky Wind.  However, the test gyromills that Roberts has flown are far beyond anything shown so far by the AVE proponents.

Babcock and Brown have been placed in volutary administration and is expected to be liquidated along with any shareholder value remaining. B&B were pretty agressive in power and splashed money around in all directions hoping to hit a few winners along the way. They did build things however which is more than can be said for some for the financial "geniuses" that simply shuffled paper around and skimmed a truckload off the top. It is hard to see where funding for renewables R&D is going to come from now as the private sector is in various states of ill health and governments are focused on propping up consumerism and the banks.

The largest U.S. defense contractor, Lockheed Martin, recently annouced a partnership with Ocean Power Technologies to build an wave power station in (likely) Oregon. OPT's system uses moored buoys with internal linear generators using up & down wave motion. If alternative energy is the new "Manhattan" project, there are many defense contractors with experience finding government financing.

To me, there is a certain element of desperation in the deployment of a system that has not been either fully tested or is being deployed with parts that have not been tested. So it may have been a choice between either going out of business or at least give it a shot. Also, does anyone know of an EROEI/LCA for their generator? It seems to me that a complex mechanical system immersed in salt water waves is going to have tremendous maintenance costs. While I think that wave energy can be harnessed, I just don't think that mechanical wave riders are going to have a high enough EROEI ration to compete other renewable options.

Strange, but with my history of fishing boat hydraulics and diesel-hydraulic heavy construction equipment, I sort of presumed these technical problems were mostly cured.

You want complex saltwater technology, try outdrives, aluminum alloy double right angle drives putting out hundreds of horsepower at high speeds pounding through waves. Lots of seals, torque, impact, rpm, all in a reactive housing.

It could be that the good bearings and seals were changed to cheapos. Happens all the time, and there is a difference between Japanese/Swedish/German bearings, and Chinese, Hungarian, Korean bearings.

It's the kind of thing you learn the hard way. Same thing with quality hydraulic oil, the proper blend of naval bronze instead of brass, the right alloy of stainless to prevent hydrogen cracks, etc.

I've been looking at this construction for a few years now .. and I ask myself everytime : why are not all the hinges and hydraulic's lifted out of the water and thus sealed above water, via some fixed levers or fixed arms ? (.... the bearing quality I take for granted, they are not saving a few Euro's on such I hope, at least not for the prototype)

The Pelamis device extract energy from a range of wave heights, above these wave heights, it simply rides through the wave rather than over it to avoid destruction. No part of it will remain permanently out of the water.

I think that's the point of the question. You can design these floats to be linked in off-set hinges and hydraulic rams, which could remain clear of the water. It might be done by running TWO rows of floats instead of one, like a catamaran, so the hinging isn't going to be rolled under (or just ballasting the tubes to keep them righted.)

I would want these things to be REALLY Visible for navigation, in any case.

jokuhl -

I don't think the problem has much to do with exposure to salt water, but rather inadequate bearing design, resulting in premature wear. It sounds correctable. (Most technical things are provided you have enough time, patience, and money.)

I am quite familiar with the Pelamis design, and I can see why those hydraulic ram connections (enclosed in flexible sleeves) are positioned where they are: right on the float cylinders themselves. Keeps the whole profile quite smooth. My gut feel is that trying to put then on some sort of extended structure to clear the water might very well create more problems than it solves.

The main thing that the Pelamis design has going for it is that it has very high survivability, something that a lot of earlier designs did not. Obviously, the sea can be a very rough place. The Pelamis doesn't fight the incoming waves, but rather rides over them. As the length of each 'sausage' is far less than the wave length of most anticipated waves, even in high-wave storm conditions, the assembly will just undulate up and down with the wave instead of crashing through the wave like a moving ship. This is facilitated by deactivating the hydraulic system, thus removing the resistance to movement between the four sausages, thereby eliminating excessive stress.

The other key element is the mooring system. The Pelamis is very loose moored, in that there is relatively little force on the seabed mooring even in high-wave conditions. The very long mooring line has a clever arrangement of alternating weights and floats along its length, the purpose of which is to have the mooring line sort of act like a shock absorber. A high wave will try to straighten out the mooring line, but the weights and floats buffer that action and try to restored the line to its original position.

Overall, my impression is that the Pelamis is a very well thought-out design. However, the long-term economics remain to be demonstrated, and problems like the current one need to be resolved ASAP lest credibility be lost.


It is a pretty intriguing concept, and I don't mean to write off their approach just because they've still got a few more lumps to smooth out. Just spitballing, really..

At least it came back to shore easily, so the servicablity is feasible.

Projects like this have stopped making waves, whilst tidal energy continues to face a barrage of criticism.

I didn't realise these blades where variable pitch. The blades are composite. Variable pitch is very complicated design. More gearing and hydraulics

idonto -

I didn't think those big wind turbines had variable-pitch blades either. At least from outward appearances it looks like the root of the blades are firmly attached to the hub rather than fixed to some sort of rotatable axle.

Making a huge blade assembly variable-pitch would pose numerous design headaches and raise all sorts of reliability issues. It was my impression that control is accomplished merely by rotating the entire blade/nacelle assembly so as to get the most favorable angle of attack relative to the wind. The rotational speed of the blade is controlled by the load on the generator which (I think) is augmented by some sort of brake
Anybody out there who can tell us for sure whether or not these huge wind turbines have variable-pitch blades?

Here you go
Power Control of Wind Turbines :

have nice web site describing the basic layout for those intrested

WD70(77)-1500KW variable pitch (pitch regulated) wind turbine generator system has three blade, windward and horizontal axis impeller, three stage gear box, double fed induction generator (DBFG) and alternative excitation converter. Power control is based on DBFG variable speed constant frequency technology and independent pitch system driven by servo motor. This kind of power control is the main trend of technology with high reliability and accepted and adopted worldwidely.

'.. adopted Worldwidely.' So there.

jokuhl -

Thanks. So it looks like those really big wind turbines DO have variable-pitch blades. I think I need to take a better look at some of the pictures. That must make for some interesting mechanical design problems, but ones which appear to have been largely solved.

interesting mechanical design problems, but ones which appear to have been largely solved.

Naw, the 2 bladed wind machines are still elusive.

Not to mention things like blade recalls still happen on the multi-MW machines, thus showing the material science problem is also 'not solved'.

And getting the bits TO the erection site - another of the problems to be addressed.

Luis - Since the project was ordered in 2005, and received permitting in 2006 and took some time to order the materials and build the machines and substation I think it is incorrect to say that the project is running 'four years behind schedule'.

As for EROEI on their website Pelamis give the current design a lifecycle energy payback of 20 months. With a 20 year design life it would appear that the EROEI ratio is >12.

Ormondotvos - agree with your comment regarding the availability of complex saltwater technology. The Pelamis design is not anything particularly special from a structural point of view compared to other sea based equipment such as floating oil production storage and offloading rigs (FPSO) or ships, submarines etc. If you check the brochure on the Pelamis website you can see there are no lubricated parts in the water (unlike the driveshaft of a ship's propellor); all the hydraulic rams, motors and generators are hermetically sealed and hence well out of the salt water environment.

Assuming that Babcock and Brown are able to sell the project to a new owner there doesn't appear to be any fundamental reason why it should not continue.

Swedish wave energy company Seabased AB (lousy home page at ) has had their system up and running for almost four years now, without maintainance. Finnish energy giant Fortum has applied for permit to deploy 500 buoys of the Seabased types, for a total effect of 10 MW, and a approx 25 million euros investment.

Swedish press-release;22344;22361;22351;...

Pictures of the three years up and running buoys, and the manufacturing plant in Lysekil, Sweden at;22344;22361;22315;24310;224...

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