Tidal Turbines

[Sisyphus]

Hey, I've just been reading about some promising-looking technology for power generation. It basically consists of large underwater "windmills" that can be placed in areas of high tidal flow. They require no dams and, because they are harnessing moving water as opposed to moving air, they can get a lot more power than a similarly sized windmill. The downsides: the technology is expensive (though still in its infancy, so that will surely go down), they can only be placed in limited locations, and they only generate power when the tides are going in or out, and only peak in mid-flow.

 

The first working plant will be an experimental version currently under construction in the East River in New York, of all places (which is not actually a river, but a narrows where large volumes of water are forced through with the tides). It will be mostly a proof of concept design, only producing about 200 killowatts. However, if it proves satisfactory, it will eventually be expanded with more units to a total of 10 megawatt capacity. A drop in the bucket of New York's power consumption, of course, but still a good start. The first one will be operational by the end of September.

 

Even more exciting, though, is the ambitious proposed plan to install 7000 such turbines in the Cook Strait in New Zealand, where the tidal flow is around 3m/s. They would be tethered to the sea floor, and float far enough below the surface to pose no obstacle for shipping. They could easily be pulled up for servicing, or even moved around. This would generate enough electricity for the entire country, and could easily be expanded simply by adding more turbines, for which there is plenty of room. They hope to have the first ones in place by 2008.

 

EDIT: Err, what do you think? Is this as promising as it sounds?

[JohnB]

It strikes me as being very promising. Non polluting and hopefully economical. Do you have a link?

 

There are many places in Australia that could benefit from this type of tech, the remoter parts of South Aust and North West West Aust come to mind.

[Externet]

They are proposing the same here under the San Francisco Golden Gate bridge; deep enough and massive flows.

 

The problem is reliability and maintenance. Anything submerged in seawater is prone to failure by corrosion and carried debris. Technology and construction must be very reliable for success.

 

Miguel

[A Fool]

It seems to me that some of my friends and I were talking about this very same idea so I'm pretty excited to see this coming to reallity. I worry about the prospect of location though: even if you found the strongest tide to work with, you still have to find the place where the turbines will have the least impact of the local ecology. This really is exc;iting how were trying to use every type of energy we can.

[ecoli]

The problem is reliability and maintenance. Anything submerged in seawater is prone to failure by corrosion and carried debris. Technology and construction must be very reliable for success.

 

Miguel

 

exactly. You have to weigh maintenaince costs over other types of alternative fuels, such as wind.

 

However, even the wind stops blowing, AFAIK, the tides are as constant as the moon.

[gcol]

A scheme for tidal turbines in the Severn estuary between England and Wales is constantly being proposed here. It appears to be an ideal site with tidal range in the region of 40ft. Technical problems, reliability, and cost seem to be the stumbling blocks.

 

google 'severn tidal turbine'

[silverslith]

The Kaipara harbour in NZ is even better with 5 cubic km of water per tide at up to 6m/s. I've been keen on this idea for a decade. I think the speed would be low enough not to blend the fish stocks, you wouldn't want them put off breeding in harbours though.

[ecoli]

The Kaipara harbour in NZ is even better with 5 cubic km of water per tide at up to 6m/s. I've been keen on this idea for a decade. I think the speed would be low enough not to blend the fish stocks, you wouldn't want them put off breeding in harbours though.

 

I'm curious, are you actively invovled in getting this project to happen?

[silverslith]

I'm curious, are you actively invovled in getting this project to happen?

 

Too involved in commercialising my World Championships winning DH mtb designs for the last few years.

I have suggested it to some members of parliament I know over the years. I do think that the risk of frightening the fishies would make it difficult to get through. Probably solvable with the Kaipara having a 10 mile wide mouth.

[Pseudoswallo]

I assume when you reffer to this as "new" technology and the "first working plant", you are not including those already installed and working stations in Annapolice Royal (since '84) and Rance (completed in '66)?

[Sisyphus]

I assume when you reffer to this as "new" technology and the "first working plant", you are not including those already installed and working stations in Annapolice Royal (since '84) and Rance (completed in '66)?

 

No, I wasn't, because that's not the technology I was talking about. Those are both big barrages, almost like dams. The turbines I'm talking about would be freestanding (or floating, really), and operate just like windmills, harnessing horizontal movement of water. They could be placed anywhere there are strong currents.

[Pseudoswallo]

Well, that really seems much preferable. I'd like to see how this works out, do you have a link? My only issues with this are the environmental impact and the possible long-term effect on the moon's orbit (as if). I might even try to install my own next summer.

[Neil9327]

Following on from the above post, I mentioned this idea to a mate, and he said that these generators would add to the tidal drag and would slow down the moon in orbit round the earth even more, possibly causing it to crash down onto the earth.

 

He's talking nonsense isn't he?

[Sisyphus]

Following on from the above post, I mentioned this idea to a mate, and he said that these generators would add to the tidal drag and would slow down the moon in orbit round the earth even more, possibly causing it to crash down onto the earth.

 

He's talking nonsense isn't he?

 

Yes. Anything noticable would take a billion years, and if the moon slows down, it moves farther away, not closer.

[Phi for All]

Anything submerged in seawater is prone to failure by corrosion and carried debris.

I see this as being the big stumbling block. While a good design can take care of the debris problem, the erosive effects of water and the corrosive effects of salt water are difficult to overcome. Ceramics might be the key here, since gold plating wouldn't be prudent.

[J.C.MacSwell]

Yes. Anything noticable would take a billion years, and if the moon slows down, it moves farther away, not closer.

 

Correct, but drag on the moon speeds it up not down, though I have heard the moon should eventually escape (on a thread here, can't remember which one or why it escapes)

[silverslith]

I see this as being the big stumbling block. While a good design can take care of the debris problem, the erosive effects of water and the corrosive effects of salt water are difficult to overcome. Ceramics might be the key here, since gold plating wouldn't be prudent.

 

 

Nonsense. Epoxy Fibreglass lasts forever in seawater. well kiloyears anyway. You could probably use ferro concrete even. growth of slime on the surfaces is more an issue but solvable too.

Seal tech is no issue either.

Heard of boats?

[silverslith]

Correct, but drag on the moon speeds it up not down, though I have heard the moon should eventually escape (on a thread here, can't remember which one or why it escapes)

 

Guess thats cause the tidal bulges on opposite sides of the planet lag by more than ninety degrees, therefore accelerating the moon. But what is the eventual effect on the rate the earths spin is slowing? (not enough to worry us i'm sure)

[Spyman]

Even tough the Moon won't escape i think this is the thread J.C.MacSwell remembers:

(It also covers the slowing rate of Earths spin.)

 

moon is going away http://www.scienceforums.net/showthread.php?t=22011

 

The effect should be extremely tiny compared to the total tidal stress of Earth.

[Sisyphus]

Nonsense. Epoxy Fibreglass lasts forever in seawater. well kiloyears anyway. You could probably use ferro concrete even. growth of slime on the surfaces is more an issue but solvable too.

Seal tech is no issue either.

Heard of boats?

 

Even slime wouldn't be that big of a problem on the fins themselves because they'll be moving most of the time. And really, the fins are the only parts where staying clean is important.

[silverslith]

The main deepwater trench through cookstraight is about 30 by 100km, or 300,000 hectares

Assuming you could get something like 1000x as much energy as for a wind turbine the same size it seems like a pretty valuble piece of real estate.

No wonder the Maoris want to claim the seabed.

If they were stacked 10 deep per hectare you'd have 1 billion wind turbines worth. Would that power the planet?

Don't tell george. He'll claim its for a giant laser to bounce of the moon and destroy the pentagon and liberate it for US corperations.