Germany facing blackouts...

[JavaScriptDonkey]

It was an understandable misunderstanding given the nature of the map I was responding to and the fact that a tidal barrage has already been considered for the Severn estuary. I assumed what was being proposed was a much larger version of the same thing.

Fair enough.

I really think that these systems can go a long way to fulfilling our base load requirements in the UK. Not a lot of good in Switzerland or the USA of course but pretty good for us.

[Potemkin Villager]

It was an understandable misunderstanding given the nature of the map I was responding to and the fact that a tidal barrage has already been considered for the Severn estuary. I assumed what was being proposed was a much larger version of the same thing.

Fair enough.

I really think that these systems can go a long way to fulfilling our base load requirements in the UK. Not a lot of good in Switzerland or the USA of course but pretty good for us.

All it needs is the inspired political leadership and the finance to make it happen?

[eatyourveg]

It was an understandable misunderstanding given the nature of the map I was responding to and the fact that a tidal barrage has already been considered for the Severn estuary. I assumed what was being proposed was a much larger version of the same thing.

Fair enough.

I really think that these systems can go a long way to fulfilling our base load requirements in the UK. Not a lot of good in Switzerland or the USA of course but pretty good for us.

All it needs is the inspired political leadership and the finance to make it happen?

Sounds like one for Nadine to take up .

[biffvernon]

The beauty of this design is that it works equally well upside down.

[JavaScriptDonkey]

I don't think they'll have much trouble bolting them down to the seabed.

Pipe lines and well heads seem to manage just fine.

[vtsnowedin]

I'd like to see a study of the costs of installing this type of turbine on the sea floor and maintaining them when they break down vs. suspending them down from an anchored ship or barge so that you could just hoist them to the surface when repairs are needed. The winner probably depends on the optimal dept to deploy the turbine and the cost of maintaining an anchored ship or barge in place against the weather and seas it would have to endure.
Has anybody come across such an analysis?

[JavaScriptDonkey]

The technology is rather new although I'd have thought Scottish Power would have done some work on that before approving their Islay deployment.

Hammerfest Strom seem to be one of the suppliers.

Perhaps you need to patent your 'swinging from underneath a line of barges' deployment idea?

[vtsnowedin]

The technology is rather new although I'd have thought Scottish Power would have done some work on that before approving their Islay deployment.

Hammerfest Strom seem to be one of the suppliers.

Perhaps you need to patent your 'swinging from underneath a line of barges' deployment idea?

Not a original idea I could patent but I'd be glad to do an exhaustive analysis of the options for a paying customer.

[JavaScriptDonkey]

Not a original idea I could patent but I'd be glad to do an exhaustive analysis of the options for a paying customer.

Foolishness aside, there are likely to be many such similar schemes in the near future if the Islay one works out well. If it's your area of expertise, get in there quick.

[kenneal - lagger]

I'd like to see a study of the costs of installing this type of turbine on the sea floor and maintaining them when they break down vs. suspending them down from an anchored ship or barge so that you could just hoist them to the surface when repairs are needed. The winner probably depends on the optimal dept to deploy the turbine and the cost of maintaining an anchored ship or barge in place against the weather and seas it would have to endure.
Has anybody come across such an analysis?

Most of them will be going into deep water and won't be a navigational hazard if anchored to the sea bed. Hanging them from a floating barge would be an extra hazard in already hazardous waters. On the sea bed they will only be subjected to tidal forces. Suspended from barges they would be subjected to the tidal forces plus the sometimes very erratic and powerful wind and wave action in this area.

The north of Scotland bears the full brunt of storms built up over 4000 miles of the Atlantic. It gets very rough up there very often.

[An Inspector Calls]

Most of them will be going into deep water and won't be a navigational hazard

No they aren't. The main tidal flows are always in the shallow, surface layers of the oceans. If you go too deep you (a) drop out of the main tidal streams, and (b) make the task of maintenance even more difficult. They submerge them just suffiently to keep them submerged at neaps.

The scheme proposed for the Anglesey Skerries, for example, is quite shallow and may well lead to collisions between small vessels and the blades during storms; for this reason, they are trying to set up restricted sea areas around the turbines.

[JavaScriptDonkey]

Skerries looks to be 9 units in 30 metres of water. No idea how big the tidal drop is or the size of the blades but sounds like a very small restricted 'area'.

They are also talking about it as a test bed site for the technology and propose a 25 year initial period. I suspect it's location was influenced by the need for regular physical assessments by maintenance crews.

For this tidal stream technology to work it isn't important how high the tide runs, only that it runs near constantly. That is a major difference between it and tidal barrage structures.

[An Inspector Calls]

Yes, they are in 30 metres of water, but the generators are lowered (these are the type that can be raised up their support shaft for maintenance) to a position in the upper part of the water depth. If you look at the velocity profile for tidal flows they're always low (in fact, near zero) near the bottom and increase (with what looks like a parabollic curve) to the surface.

I know that Skerries is a test bed for the technology. But they said that about the same design at Stranford Lough.

I think it is important how strong the tide is. It's for that reason the DECC study into marine power identified 6 coastal areas suitable for tidal stream where the strongest tides flow (see figure G.7, page 317 of McKay). They're mostly west coast apart from the Solent and Pentland Firth. Tide does not run constantly, the velocity varies sinusoidally (ish) during a full tide period which lasts about 12.5 hours (where there are two tides per day). Tide strength also varies sinusoidally (ish) between springs and neaps. As a result they get about 20 % capacity factor - but then that depends on how they declare the rated power.

[kenneal - lagger]

Most of them will be going into deep water and won't be a navigational hazard

No they aren't. The main tidal flows are always in the shallow, surface layers of the oceans. If you go too deep you (a) drop out of the main tidal streams, and (b) make the task of maintenance even more difficult.

If you look at the map which caused much of this conversation you will see that they will be in deep water through which most of our and the rest of Northern Europe's shipping lanes pass. They will have to be at least 20m deep at low tide to allow shipping over them.

[An Inspector Calls]

The map you're quoting was simply an overview of the incidence of tidal energy upon the UK. No one in their right minds is suggesting that we build a line of tidal stream generators from Valencia to Finisterre, nor from Malin head to Bergen. Tidal stream generators will be located in the small number of areas identified by MacKay (reference above: page 317 McKay) and DECC where the tidal stream is fast enough to make the turbines 'economical' (using the word in a sense known only to Chris Huhne).

The depth of water in which these generators is located is only material as to the capital cost - the shallower, the cheaper. Placing the rotating generators at depth would take them out of the tidal stream and render them useless.
http://www.carbontrust.co.uk/SiteCollec ... design.pdf
(figure 4)

The intention of the Skerries project, just as per Stranford Lough, will be to position the generators such that they remain fully submerged at neaps:
http://www.rwe.com/web/cms/en/309786/rw ... echnology/

The technology under development by MCT consists of twin axial flow rotors of 15m to 20m in diameter

Given a sea depth of 30 metres, with some clearance, the rotors will obviously be just below the surface at neaps.

The planners will claim for projects such as the Skerries that they are out of the shipping lanes. In that example, they are: the main shipping channel to Liverpool passes outside the Skerries. But this ignores coastal shipping which uses the Skerries channel to avoid the difficulties of the tide race in the outer channel. Since there is demonstrably no guarantee of separation through depth, it seems to be only a matter of time before there'll be some sort of accident, especially when there are large waves in the channel. Indeed, the developers have pointed out that it will be the duty of small boat navigators to avoid their turbines as they'll will be deemed navigational obstacles.