Tidal power generator unveiling hailed as landmark

Posted: August 7, 2014 by oldbrew in Energy, innovation, waves
Propeller power [image: BBC]

Propeller power [image: BBC]

Another technology hoping to make a splash on the renewable energy scene is tidal power. But can it be anywhere near to economically viable? Installation is known to be expensive, but tides are predictable and never take the day off.

My limited understanding of these things is that they work best where the tide is channelling water into a narrow passage so the rate of flow is higher than the open sea, so the number of suitable sites may be limited.

That’s the principle behind the existing and proposed New York schemes.

There’s also a project in the western isles of Scotland at Islay.

One advantage of such schemes over wind power is that they’re installed under water.
That could also be a disadvantage in terms of durability though, as it’s corrosive sea water.

These are the early experiments so we wait to see the results.

More details here: BBC News report

  1. Dave Ward says:

    I would love to know what sort of seals will stand up to years of immersion in sea water, without some form of pumped lubrication. IIRC the new generation of “Azipods” used by large ships, instead of conventional shafts & propellers, are suffering from seal problems. They are just huge motors in a separate housing with their own propeller. A tidal generator will have an alternator instead of a motor, but otherwise will be virtually the same, AND will be operating at greater depths, so the pressure, and risk of water ingress will also be greater.

    On a different tack, any structure which takes energy from the ocean currents will have a long term effect on sediment build up on the sea floor. Just visualise the wake turbulence that is easily seen in pictures of the Horns Rev windfarm, and transpose that to the environment these devices will be installed in…

  2. catweazle666 says:

    The tides may be predictable, but they don’t work at the times when we need the power.

    So we still have to keep watt-for-watt backup running outside its envelope of maximum efficiency available, so we might as well just use that anyway.

    Plus, as you observe, there is no harsher environment on the planet anywhere, so I suspect their useful life will be a great deal shorter than the claims of the sales department.

  3. Me_Again says:

    The good news with tidal power is that unlike the wind or solar, it works over 90% of the time in any one location but but 100% when you look at the whole country due to the time variances of low tide.

    I accept that saltwater is a more corrosive environment than the air but they have I believe overcome this to a large extent using materials which are unreactive in saltwater -Ironically carbon!

    I’d suppose the the trick is to have as few moving parts as possible. But if I had a choice between wind and water I’d choose water everyday.

    In regard to the siting of them, it stands to reason that the faster the water flow the greater the generation but since these are supposedly twice as efficient as wind turbines [not sure whether that is using the same criteria] it would make sense to give them a go with a lower and tapering subsidy, INSTEAD of wind turbines.

  4. Bob Greene says:

    Take the silly propeller off and it would make a fair artificial reef.

  5. oldbrew says:

    catweazle: ‘So we still have to keep watt-for-watt backup running outside its envelope of maximum efficiency available, so we might as well just use that anyway.’

    The counter-argument FWIW is that back-up runs anyway whether there are renewables or not, because unplanned failures or urgent maintenance can/do arise at power stations. No doubt renewables do push up the overall cost of back-up though.

    The crunch issue for me is: what happens if peak demand in an already stretched system coincides with a serious fall-off in average renewable power? It could easily happen in winter.

  6. Do not fret Bob, that exactly where it is headed.

  7. Joe Public says:

    Hi Roger – maybe your older readers will remember the Tomorrow’s World episode which featured Salter’s Duck?

    I can find no Google link to the programme, but the following is helpful:-


    [reply] another link: http://people.bath.ac.uk/mh391/WavePower/saltersduck.html

  8. There have been three goes at Tidal power in Australia using large government grants. They all have been a disaster and a waste of money. Money should be going into better Nuclear power which has a known record of reliability and safety plus development & innovation. There are huge supplies of Thorium. Old working technology for a Thorium reactor is available but soon the Chinese and Indians will start plants with updated technology. Then eventually there are unlimited supplies of deuterium.

  9. Richard111 says:

    Have a look here…


  10. oldbrew says:

    ‘the number of suitable sites may be limited’

    The marketing blurb confirms this:
    ‘The device has excellent export potential for deployment in high energy tidal sites around the world.’

  11. catweazle666 says:

    oldbrew says: “The counter-argument FWIW is that back-up runs anyway whether there are renewables or not,”

    The counter-argument is incorrect.

  12. M Simon says:

    catweazle666 says:
    August 7, 2014 at 2:04 pm

    The correct argument is MORE back-up will need to be running.

  13. Richard111 says:

    I’m not sure I understand tidal flow but doesn’t the flow reverse when the tide changes? This implies the down time is short compared to up time and stations further up and down the coast can fill in. As far as I can tell the tides are reliable. Don’t know the effect of tide height on the water speed but again I think that can be figured in. By careful placement a number of stations could provide continuous power to a specific area.
    All in all I think a far better idea than wind turbines and they do not clutter up the view.

  14. oldbrew says:

    The maker’s website explains how they work including:
    ‘An automated hydraulic yaw mechanism for each nacelle which controls the orientation of the water turbine generators in relation to the direction of the tidal flow.’

    IIRC there’s about an hour of ‘not much happening’ between tide reversals, so as a rough guide there might be 6 hours ‘on’ and 1 ‘off’, repeated in the other direction – etc.

    Comparison with wind turbine performance could be interesting.

  15. M Simon says:

    Shrouding the turbines could increase the flow and efficiency. And power out goes up as the cube of flow rate. I wonder why shrouds were deemed not cost effective.

  16. Me_Again says:

    Bob, don’t be such a Luddite. We will never progress past burning fossil fuels unless there’s an incentive and some research.

    I’m not looking at this from an environmental or economic angle, I’m looking at this from a chemist’s perspective. Burning fossil fuels is just a complete waste of an amazing series of complex hydrocarbons WHICH are finite. The shear number of compounds that can be made using the products of these hydrocarbons is staggering. Nearly everything in your house apart from the bricks, mortar and wood has some hydrocarbon input. That there is a finite supply of these amazing chemical suggests we’re being a bit silly not looking for ways of use that don’t just burn them.

    That’s akin to staying the night in the British library and burning precious written work to stay warm because you’re too damned lazy to got get some wood.

    I totally support that whatever is used must either immediately be self supporting economically or within a short and finite period, but just poo pooing an idea because it hasn’t got there yet does you no credit at all.

  17. Me_Again says:

    Very true OB

  18. Me_Again says:

    Agree regarding Thorium but I was under the impression that no working design currently exists.

  19. Me_Again says:

    I’m curious as to why they’d use exposed props instead of in a barrel-like structure. Such a thing would protect the turbine blades from damage by semi-submerged logs etc. which unsurprisingly tend to fall into rivers and flow towards the sea.

  20. Me_Again says:

    Agreed. Certainly worth looking into. They wouldn’t need back up either.

  21. Me_Again says:

    OB see below. As regular as a metronome in a vacuum.

    “…coastal areas experience two high and two low tides every 24 hours and 50 minutes. High tides occur 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the water at the shore to go from high to low, or from low to high.”

  22. Me_Again says:

    Agreed. Also prevent damage from underwater obstructions like tree trunks.

  23. steverichards1984 says:

    Large ships are dry docked, typically every 3 to 5 years.

    One could imagine that underwater turbines would use identical technology to ships proppellors and bearings.

    As long as these devices can be ‘floated’ for inspections occasionally I can see them as a good resource.

    Wrt bearing leakages on azipods, this usually refers to the azimuth bearing (the large circular bearing that allows the pod to rotate through 360 degrees to steer the vessel).

    A number of cases have arisen where the pod was rotated under high power, over stressing the seal.

    Pods now operate with more restrictions placed upon them and the seals are now good.

    The stern bearing on a regular propeller shaft is pressurised with oil/grease and they do bleed very small quantities of oil/grease.

    The EPA in the states is trying to force the use of water lubricated bearings or the use of biodegradable oils (vegetable oils).

  24. tom0mason says:


    While I admire you spirit of investigating the possible, and that tidal power may be the next big thing, I unfortunately feel that burning those fossil fuels will persist for a few decades yet. Tidal power has just started, the best design(s) and all the maintenance hazards are yet to be found, let alone the remedial and maintenance actions required for them. There is so much to be found out yet.
    Many things can be tried but the bottom line dictates that unless they’re practical, durable, cost effective, and maintainable, they will be a waste of money.

    I feel that your metaphor of –

    “That’s akin to staying the night in the British library and burning precious written work to stay warm because you’re too damned lazy to got get some wood.”

    should be –

    “That’s akin to staying snowed-in and freezing in the British library, burning precious written works to stay warm because you haven’t found the repair manual for the central heating system yet.”

  25. oldbrew says:

    ‘Tidal power has just started’

    Not exactly. The French have had one installation going since 1966, capacity factor 26%.

    If Russia builds this one it will be vast (up to 87 GW quoted).

    Slight problem for Russia in that location though – no customers 😉

  26. Curious George says:

    Shrouding the propellers .. does anybody know what percentage of ships, military and civilian, have shrouded propellers?

    [reply] Sorry no, but some of the technicalities are described here:

  27. M Simon says:

    Hydrocarbons are such a small fraction of the amount used for fuel that it probably doesn’t matter much. We can grow them if needed.

  28. Me_Again says:

    Tomo, I know it’s not an overnight thing. But I was saying we mustn’t stop looking for alternatives just because the windmills were a complete fcuk up.

    The fact remains that what we burn is in fact a precious commodity in the same way as gold and diamonds, we just aren’t using it smart enough yet.

  29. A C Osborn says:

    One original idea was to use Venturi Tunnels (like Wind Tunnels) to accelerate the water.
    I am not sure how the object shown would stand up to a severe Storm though.
    They want to build one in Swansea Bay.

  30. Roger Andrews says:

    The problem with tidal power is the huge difference in generation between spring and neap tides:

    Details at:


  31. Brian H says:

    You seriously misunderestimate the backup problem. There must be 100% available for the down times (which are disastrous and unsupportable in modern society). They must be on alert to ramp when needed, but get relatively few opportunities to sell power. So their output must be outrageously priced; up to 400X normal rates has been recently observed (40,000%). The resulting total costs are always at least double what was previously being paid. Distribution losses are high, because of the necessarily remote siting of renewable generation compared to centers of consumption.

    And much more. It’s retrograde; attempts to make general use of costly niche technologies from past eras made large but relabeled “renewables” to disguise their impracticality, local ecological devastation, and severe limits. All human progress has been fueled by increasingly concentrated and controllable energy sources. Renewables, including tidal power, are the reverse and will have the reverse result.

  32. Me_Again says:

    Brian, no one can ‘misunderestimate’ anything.

    As for “There must be 100% available for the down times” That is the case already then is it not. In which case, adding tidal but removing the unpredictable wind from the grid would be a bonus not a negative.

    I favour nuclear for 80% or more of our needs. I can’t see the point of coal in such an energy mix but I could see a role for gas to take up slack and provide peak. Renewables are only ever going to be a tiny part of the mix BUT such experimentation is necessary I believe especially if it will provide for isolated areas. Providing it costs no more than other forms of energy production it should be in the mix even if just to give engineers jobs and keep people thinking!

  33. Bob Greene says:

    Which fossil fuel do you think this generator will replace? Coal? Plentiful supply for several hundred years. Natural gas? I’m sure you are aware that most of the higher molecular weight hydrocarbons are removed before it is put in the pipeline. Petroleum? Generation from oil is the high priced fossil fuel for electricity unless you need a peaker, emergency generation or are quite some distance from any other source.

  34. Me_Again says:

    You really aught to try and read people’s posts. You find yourself arguing against yourself for some reason. Try again.

  35. markstoval says:

    Did someone say Thorium?

    I been to the national labs at Oak Ridge, Tennessee on many occasions for various reasons. At that site they built four thorium reactors starting in the 1950s and continuing up till the late 60s. They found the liquid-fluoride-salt approach to be superior and they were making good progress. For some odd reason the U.S. Atomic Energy Commission fired the director of the national labs for advocating this form of power generation that can not be used to build a bomb and then disbanded the program.

    As the Americans like to say, “if you can’t blow people up with it, what good is it?”

  36. tom0mason says:

    The UK needs to secure long term, reliability of todays power first. All else can wait, a reliable supply of energy is more precious than gold or diamons.
    Given the vast quantities of coal there is in the world we are not likely to run out any time soon. (Not for two or three generations at least). Just look at http://www.geocraft.com/WVFossils/Energy.html for the known reserves, what else is out there yet to be found, or rendered recoverable?
    So lets keep the lights on by using the coal. Get on with building nuclear power plants, as it is the best option for long term reliability, and thereafter investigate the alternatives.
    This catastrophic rush for alternative now will wreak havoc on the UK if it continues.

    As we still have not got close to finding the manual for the central heating in the library yet, the burning must continue or we perish.

  37. Bob Greene says:

    I read what you said. I’m a Luddite. In your wisdom as a chemist, not considering economics and environmental, you believe that we need to conserve “complex hydrocarbons” which make up most of the stuff in my house that isn’t brick or wood. Or was it petrochemicals?

    You didn’t say which fossil fuel you wanted to conserve these wonderful complex hydrocarbons.

    I’ll have to defer to your expertise in chemistry. My chemical knowledge is limited to post-doctoral research and about 25 years in the chemical industry, some of it in polymers and coatings. I’ve also spent more than a decade in power generation from renewable fuel. Unfortunately I’ve had the restraint of having to consider both the environment and economics. I’ve had the privilege of seeing a number of really great engineering ideas that seem to need constant infusions of other peoples’ money. This seems to be one.

    Luddite, eh? I don’t think so, but I’ve seen enough boondoggles to recognize one.

  38. I was born in Pembrokeshire so it makes my heart swell with pride to find that my countrymen have finally learned how to feed at the government trough.

    In parts of Pembrokeshire we have tides that rise and fall by up to 25 feet which is comparable with the world record Bay of Fundy (40 feet).

    Thus we have cubic miles of water moving back and forth so a single turbine can generate 400 kW. Of course we will not be told how much that water turbine will cost. The UK has invested billions in wind turbines that cost $20 per Watt generated. Clearly if water turbines cost less, those billions would have been invested in submarine turbines rather than windmills.

  39. I hit the “Submit” button prematurely when I sent this:
    “Clearly if water turbines cost less, those billions would have been invested in submarine turbines rather than windmills.”

    That statement implies that governments use “Cost Benefit Analysis”. Sadly that is not so: CBA is not applied to public expenditues.

  40. Richard111 says:

    Some points. This is the most environmentally friendly ‘renewable power source’ currently available. It requires no foundations on the sea bed. The complete unit can be raised to the surface for maintenance or removal. What will happen to the power cable I don’t know. The sea bed in the chosen area is subject to tidal race. Unlikely to be much sand and marine growth to be effected by ‘blade turbulence’. Any seals and dolphins in the area will be there because they can handle the tidal race. The blades turn so slowly (water is heavy!) that dolphins have been seen playing around the blades. What remains to be seen is the operational life of the units in relation to their construction/maintenance costs. I have met and spoken with the designer some years ago. He seemed a very competent person. As a marine engineer? Time will tell.
    Will pop over to Pembroke and see if I can grab a picture or two.

  41. steverichards1984 says:

    “Curious George says: August 7, 2014 at 7:33 pm Shrouding the propellers ..”

    Not used much on vessels except for reason of extreme maneuverability – tugs etc.

    The shroud is carried by the vessel, so massive drag, low efficiency.

  42. oldbrew says:

    Another style of underwater turbine here – looks a bit like a three-way venetian blind.


  43. manicbeancounter says:

    Me_Again says: August 7, 2014 at 11:42 pm

    “As for “There must be 100% available for the down times” That is the case already then is it not. In which case, adding tidal but removing the unpredictable wind from the grid would be a bonus not a negative.”

    Although tidal might be more predictable in terms of energy production, it still suffers from a mismatch with electricity demand. Tidal energy and offshore wind receive the same subsidies but tidal energy is non-existent whilst offshore wind is booming. So, despite potential revenue of nearly three times that received by a fossil-fuel power station, the subsidy is clearly not high enough.

    Data on wind power at http://manicbeancounter.com/2013/12/31/the-rising-costs-of-the-renewables-obligation-certificate-scheme/

  44. oldbrew says:

    New York had a test project with six turbines from 2006-2009. The same firm that ran that is now going large-scale there. NY has semi-diurnal tides so they change 4 times a day not twice.


  45. Me_Again says:

    Sticking to that analogy eh? Ok. I don’t disagree Tomo, I was responding to someone who basically wants to just not bother looking at alternatives. If I was the PM I’d start today by abrogating all the renewables subsidy contracts and halt in mid stride any developments under way, planned or even thought about.

    We’d see how long they stuck it. I’d get rid of payments for when the wind blows too much or the wrong kind of wind or whatever. It’s called its tough in the market place when you’re selling plastic doggy poo at a boarding kennel.

    However a small amount of the money -our money- that the gits in Westminster are throwing at rich gits everywhere but here, should be used to research Thorium reactors, tidal stuff, barrages whatever.

    We need lots of nuclear now. I’d rather have a nuclear plant close by than the 100 wind turbines littering the landscape around me.

  46. tom0mason says:

    IMO the major energy requirements should come from proven modern technologies. Prefered fuels of coal and gas in the short term, until the new nuclear is up and running.
    When that is nailed down the UK can throw serious resources into all the alternatives knowing that failures in the new tecnology will not cripple the nation.
    At the moment the UK grid is heading for instablility, and yet everyone is paying well over for a very expensive (mostly privately git owned) reserve back-up that will not cover a major power station failure. It’s the worst of all worlds – system resilience is worse, while prices increase. I fear it’s likely to get worse before it gets better.
    Useful documents are at http://www2.nationalgrid.com/uk/industry-information/future-of-energy/future-energy-scenarios/

  47. Me_Again says:

    Mere post-doctoral research? Gosh I’m not surprised you’re reluctant to comment being in such august company on here. ‘Boondoggle’ sounds a little foreign to my untutored ears.

    Burning any fossil fuel is a waste. We have to accept though that that will go on and on and on.

    You did not mention which part of the renewables industry you hail from. Presumably either solar or wind in which case both are a large scale flop but excellent for domestic generation.

  48. Me_Again says:

    Now that seems a sensible design, really.
    Oddly enough I saw a wind turbine near me like that quite small about 10 metres max. The only difference was that the slats were vertical. Incidentally it was destroyed not long ago in a storm.
    Hope that’s down to poor maintenance rather than design.

  49. Me_Again says:

    Sorry Mr Bean, I’m just looking at theoretical stuff I wasn’t thinking about units going into production WITH a subsidy. Nothing with a subsidy should be allowed into production since as we all know the last time a volcano farted it put back all the CO2 we thought we’d saved since we started saving it. So saving CO2 is a mugs game anyway. Clean generation is a bit of a Grail isn’t it?
    I wouldn’t be against a reduced rate corporation tax but no way a subsidy.

  50. Me_Again says:

    With you 100% Tomo. Sort the issue now, have a play with the technology from a stable system. Yep all the way. Oh and stop all subsidy tomorrow at the latest, preferably by late this afternoon.

  51. tom0mason says:

    Claw back some of those subsidies would be a nicer way 🙂 But I feel that there may be a little resistance to that.

    Unfortunately I’m sure that things will drift along as is until something catastrophic happens, then there will be furious cover-ups to protect the elite, government maintained, gits.

  52. Bob Greene says:

    Boondoggle An expensive waste of time usually paid for by government money.

    landfill gas

  53. Me_Again says:

    You plainly have a crystal ball without the snow…………..

  54. Me_Again says:

    Now that is interesting. I’m a representative on the liaison group for the two landfills close enough to my little town, to stink us out if we let them get away with insufficient gas collectors and poor procedures -which we don’t. When I became a councillor and attended the first of these liaison meetings they gave me a tour. I was quite prepared to be unimpressed -but actually I was very impressed. The whole operation is pretty damned slick, the only point of contention still left at the time were train loads of waste coming from a city, which had time to ripen before being dumped. No matter how slick the unloading there was always a plume of noxious decomp gas on opening the containers. Fortunately the moaning has worked and that waste now goes to a biomass incinerator elsewhere. As to the gas collection I can get my head around that -and it is quite impressive from an engineering perspective- but what they do with it I have no idea. Presumably burn to generate electricity somehow? I sort of forgot to ask at the time and didn’t want to sound a total dimp by email.

  55. John de Melle says:

    The French built a tidal generating station in 1966 – but have never built another (Why????)


  56. oldbrew says:

    John d.M. – nowhere suitable to put it?

  57. Me_Again says:

    Perhaps they broke it…..

  58. Me_Again: “Burning fossil fuels is just a complete waste of an amazing series of complex hydrocarbons WHICH are finite. ”

    Sort of finite.

    I live in BC Canada. We use 225bcf of NG. Two of the biggest shale plays in BC or shared with our neight have 300TCF (BC’s share).

    1200 years worth. And that is the easily got at. And doesn’t count more discoveries.

    Of course we could probably quadruple our usage if we wanted to wean ourselves off oil …

  59. Me_Again says:

    Pity Canada didn’t go for big style for nuclear [unless it did], you could be selling the gas. Plainly methane isn’t a reservoir of hydrocarbons, being only one. When I’m talking fossil fuels I’m really meaning coal and oil.