[Johann Mahne]

I was looking at a recent thread in the marine forum that was discussing the use of producing power from tides.
Forum members were calulating the power produced. It was not that much in the uk, which is quite surprising.
  Would wave generated power fare any better? Say in Hawaii?
There was a program on Discovery tv showing wave generators in the UK.
What type of power do they produce?

[Geezer]

I was looking at a recent thread in the marine forum that was discussing the use of producing power from tides.
Forum members were calulating the power produced. It was not that much in the uk, which is quite surprising.
  Would wave generated power fare any better? Say in Hawaii?
There was a program on Discovery tv showing wave generators in the UK.
What type of power do they produce?

I don't think there are any commercial scale systems producing power from wave energy yet, so it's a bit hard to say. By comparison, there are quite a few tidal systems that have been producing for a long time. One of the problems with waves is that they are greatly influenced by weather conditions. Like wind power and solar power, wave power, as surfers will tell you, can be a bit unreliable. Another is that the equipment is going to get significantly beaten-up during rough weather.

Not to say that wave power won't happen of course, it's just that wave power is technically very challenging and probably very expensive at the moment. As other sources of power become more expensive, it could become a more attractive solution.

[Mazurka]

I missed that discussion []

I am not sure that there are any truly commercial systems yet, although there is a bit of a buzz about the the Pelamis machines - and they have recently announced a 10MW scheme off the Western Isles to be developed in 2015.

http://www.pelamiswave.com/

As the Geezer says, it is a pretty aggressive environment and as with all things I expect there are some unforseen consequences.

I am suprised that a discussion about tidal power indicated that it would not generate a great deal - one of the proposals for a tidal barrage across the river Severn suggested it could generate up to 15GW - almost 4 times as much as Drax the biggest coal fired station in the UK. 

The biggest drawback with tidal power are the potential environmental effects - particularly on migratory birds and many estuarine systems in the UK are designated as Special Protection Areas and/or Ramsar (after the The Convention on Wetlands of International Importance signed in Ramsar)  which currently afford them considerable legal protection

[Geezer]

I missed that discussion []

It's not too late to chime in []

http://www.thenakedscientists.com/forum/index.php?topic=41578.0;topicseen

[Geezer]

I am not sure that there are any truly commercial systems yet, although there is a bit of a buzz about the the Pelamis machines - and they have recently announced a 10MW scheme off the Western Isles to be developed in 2015.

http://www.pelamiswave.com/

As the Geezer says, it is a pretty aggressive environment and as with all things I expect there are some unforseen consequences.

I am suprised that a discussion about tidal power indicated that it would not generate a great deal - one of the proposals for a tidal barrage across the river Severn suggested it could generate up to 15GW - almost 4 times as much as Drax the biggest coal fired station in the UK. 

The biggest drawback with tidal power are the potential environmental effects - particularly on migratory birds and many estuarine systems in the UK are designated as Special Protection Areas and/or Ramsar (after the The Convention on Wetlands of International Importance signed in Ramsar)  which currently afford them considerable legal protection

Holy Moly! Look at the size of that thing!

Yes, wave is still a bit experimental, but it might turn out to be an important source. The only way to find out for sure is to build ever larger systems and fix the things that inevitably break. The Real World usually has a few surprises in store. That actually makes engineering a lot more exciting than people might imagine.

Tidal is very reliable, but an enormous amount of water has to be captured to produce a decent amount of energy output, which usually means big dams. The alternative is to use "natural dams" where the tidal flow is accelerated between islands etc., but the problem with those systems is that only a small amount of the total energy can be captured, and there are a limited number of locations where that would work.

If you check out the other thread you will see some very fine artwork that I produced to describe a concept that has very few ecological issues and might actually work. Won't be cheap of course, but it might be viable in certain situations.

I suppose a dam across the Straits of Gibraltar would be a pretty good place to tap tidal energy (anyone care to calculate the kinetic energy?), but I suspect it would not be too popular with the locals.     

[CliffordK]

In Oregon, we do get pretty continuous waves at the shores, even on calm days.  Wind systems are designed to withstand storms.  Likewise, a wave system would have to be designed to withstand storms. 

The problem would be to build something of a scale big enough to power more than a couple of homes. 

If waves are generated by a circular current offshore, could one capture that circular current?

As far as tidal energy.

I looked at it a while ago.  I'm not sure that Gibraltar has as large of a bulk flow of water as one might expect, perhaps because of the big sink of the entire Mediterranean, so one is likely better off with the turbines installed in the current. 

I think Gibraltar may already have problems with the deep ocean cold water currents.  Messing up the circulation in the Mediterranean beyond the natural barriers would have serious consequences.

I had thought that a natural place to put one's tidal generator would be in Baja, California/Mexico.  The North/South direction of the peninsula means that the entire area behind the peninsula should get the flow from the tides all at once. 

I can imagine such a system would wreck havoc with any migratory marine species.  However, the power generation of a dam, or a series of dams across Baja would be extraordinary.

In other places, energy from deep sea currents might be able to be captured with turbines installed without dams.

[Geezer]

I agree. It would probably be a very bad idea to dam the Straits of Gibraltar for more than a few reasons, but isn't there an enormous amount of energy available there? The Mediterranean has hardly any tidal variation, but the Atlantic has a large variation, so there must be a huge flow through the straits, or am I missing something?

[CliffordK]

I agree. It would probably be a very bad idea to dam the Straits of Gibraltar for more than a few reasons, but isn't there an enormous amount of energy available there? The Mediterranean has hardly any tidal variation, but the Atlantic has a large variation, so there must be a huge flow through the straits, or am I missing something?

That must be what I saw earlier.  No large tides in the Mediterranean.
The Tidal Surge traveling from East to West, although I suppose you have to think of both filling and emptying a basin.  However, obviously the Mediterranean is not filling and emptying twice a day with the Atlantic tides.  Perhaps there is just too much volume to transfer, or the tides are a more local phenomenon being held within the sea basin.
 
There are, however, currents and turbine generators being used in the strait, somewhat like underwater windmills.

I believe that Baja experiences much of the same tides as the Pacific, filling and emptying the basin with each tide, and thus about a 6' or 7' vertical change in water elevation over the entire basin twice daily.  One would have to design a turbine system that did not interfere too much with the water flow.  Perhaps rather than building a dam, just installing huge underwater turbines to capture the water flow.

[Geezer]

I agree. It would probably be a very bad idea to dam the Straits of Gibraltar for more than a few reasons, but isn't there an enormous amount of energy available there? The Mediterranean has hardly any tidal variation, but the Atlantic has a large variation, so there must be a huge flow through the straits, or am I missing something?

That must be what I saw earlier.  No large tides in the Mediterranean.
The Tidal Surge traveling from East to West, although I suppose you have to think of both filling and emptying a basin.  However, obviously the Mediterranean is not filling and emptying twice a day with the Atlantic tides. 

I'm guessing (cos I really do not know) that there must be a significant transfer to and from the Med twice a day associated with the large rise and fall in the Atlantic. However, the volume isn't enough to make any significant impact on the level of the Med because the Med still has a very large surface area.

Just for interest, I'd like to know what the total potential energy actually is, but I don't know a sneaky way of making a rough estimate. I'm thinking the Med's tide is so small that it could probably be ignored in a first order estimate.

Perhaps I could treat the straits as a sort of river running down a gradient where the gradient is a function the tidal difference. The gradient isn't constant of course, but I'm guessing it can be treated as if it is by using some fraction of the maximum tide swings. You can see I know a lot about this field []

[Mazurka]

I missed that discussion []

It's not too late to chime in []

http://www.thenakedscientists.com/forum/index.php?topic=41578.0;topicseen

Ahh, that thread, I think I missed the VLCC...


Johann, that thread related to a novel idea, which would appear less promising than traditional barrages (like the River Rance scheme in France) or run of tide turbines (windmills underwater) which are an emerging technology...

[imatfaal]

Mazurka gets a brownie point for not using the accursed term supertanker

[Geezer]

You better give your computer a good carbolic scrub now.

[syhprum]

I think it a great shame that the Severn barrage has never been built, environmental concerns are all very well but we can't maintain England as a big nature reserve

[Geezer]

I think it a great shame that the Severn barrage has never been built, environmental concerns are all very well but we can't maintain England as a big nature reserve

Oh? I thought you were turning it into a museum []

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