[HN Gopher] 'World's most powerful' tidal turbine sets sail from...
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'World's most powerful' tidal turbine sets sail from Dundee
Author : Kaibeezy
Score : 141 points
Date : 2021-04-23 08:17 UTC (14 hours ago)
(HTM) web link (www.bbc.co.uk)
(TXT) w3m dump (www.bbc.co.uk)
| m0llusk wrote:
| It seems strange that the fan blades are not protected in any
| way. Isn't this likely to batter marine life and capture floating
| fish nets? In contrast seafaring impellers are usually ensconced
| in a large housing that protects the blades and directs flow.
| bb123 wrote:
| It is almost difficult to describe someone who hasn't seen it how
| powerful tides in the UK can be. Where I live the tidal range is
| over 12m from low to high tide and flows like a massive fast-
| moving river at peak times. It can easily overpower small boats
| and drag them out to sea. The amount of energy moving through the
| waterway is staggering.
| jl6 wrote:
| Why does this have to float on the water? Wouldn't it help avoid
| some of the more extreme dynamic forces by anchoring it just
| under the water level?
| usefulcat wrote:
| Like pretty much any mechanical devices that lives submerged in
| salt water, I would imagine it's going to require some
| significant maintenance at some point.
| KuiN wrote:
| Scotland is aiming to be a world leader in tidal energy [0].
| Which I guess makes sense given we're practically surrounded by
| pretty rough seas. Shetland has just had a tidal energy electric
| car charger installed [1]. Bit of a gimmick but the Scottish
| government is serious about making this a significant source of
| energy.
|
| [0] https://www.gov.scot/policies/renewable-and-low-carbon-
| energ...
|
| [1] https://www.bbc.co.uk/news/uk-scotland-north-east-orkney-
| she...
| TheManInThePub wrote:
| > Scotland is aiming to be a world leader in tidal energy.
| Which I guess makes sense _given we 're practically surrounded
| by pretty rough seas_.
|
| Rough seas damaging your tidal energy kit are the one thing you
| don't want.
|
| I have mentioned above that offshore wind has emerged the clear
| winner with respect to offshore renewable energy. Putting
| moving parts in salt water is always a tough prospect, and
| wave/tidal simply cannot scale to the extent wind can.
|
| I hate to say it, but I suggest many of the experimental
| wave/tidal schemes under trial are simply for green bragging
| rights and/or to grab funding for green energy projects......
| Funding put forward by well meaning bodies that that would be
| better directed to other renewable energy sources.
|
| EDIT: This is Hacker News, not Reddit. If you disagree with the
| above please explain why in comments rather than down voting.
| arethuza wrote:
| I'm not sure that latter point is actually true:
|
| _" Downvoting for disagreement has always been ok"_
|
| https://news.ycombinator.com/item?id=17996858
| seg_lol wrote:
| I would tilt at windmills, tilting at tidal power is a waste
| as the projects always sink.
| Qwertious wrote:
| Ba dum tsssh.
| jacquesm wrote:
| That bar is embarrassingly low. Because nobody really has
| working tidal energy power at scale.
| wolverine876 wrote:
| The same could have been said of wind and solar years ago.
| The same is said of any innovation. Aren't we on HN?
| jacquesm wrote:
| No, the same could not have been said. Solar and wind have
| been working for ages in many ways and forms. Tidal has
| been a pipe dream since the beginning of the previous
| century. It won't work. Windmills are in use the world
| over, the power of the sun is what causes the wind in the
| first place and besides has been used directly using lenses
| since forever.
|
| Getting usable power out of tidal energy is stupendously
| hard and won't scale.
|
| And yes, we're on HN. And yes, having built a windmill (not
| a toy, one that can power a house) and having worked with
| innovative solar plants (specifically: concentrators) and
| finally, having consulted on tidal energy projects I
| actually think I know what I'm talking about. Tidal energy
| = uBeam = Theranos.
| siquick wrote:
| Hopefully the region can start developing more long term
| industry like this as once the oil is over, the north east of
| Scotland is going to really struggle.
| jules-jules wrote:
| It already is. But otherwise I agree.
| GnarfGnarf wrote:
| I live near the Bay of Fundy (40 ft. tides, highest in the
| World). We can't make tidal power work because our ice sinks and
| smashes the turbines.
|
| Why? The ice forms on the shore and encases pieces of rock. Huge
| chunks of ice drift into the Bay carrying the stone nuggets. The
| chunks erode and shed buoyant ice until the density is > 1, then
| they sink and the strong current leads them into the blades.
|
| Neither is it cost-effective for engineering companies to develop
| technology for our geography, the conditions are too unique and
| the inventions don't scale.
|
| Pity.
| 4ad wrote:
| > It will be anchored close to Orkney where it will produce
| enough electricity to power 2,000 homes.
|
| I can't possibly express my existential torment that I feel when
| I read statements like this in an article.
|
| _Just state the damn power in SI units._
|
| A close second is measuring the size of something in terms of
| "football fields" or "Rhode Island" (wtf??). I am pretty sure
| this is tied into the general innumeracy of the population.
| davisoneee wrote:
| I'm an electrical engineer and an academic. A key part of
| communication is _knowing your audience_, and communicating
| what is appropriate for them. Your average reader doesn't need
| to know how many W this generates. While, yes, HN may
| appreciate knowing the expected power output, that's basically
| irrelevant for the average reader.
|
| This is from the BBC, not a scientific journal. While your
| average reader may know that their microwave is 800W, telling
| them "This turbine will generate <x> kW" doesn't mean anything.
| They _do_ have a home. If they don't _need_ to know/use Watts
| on a day to day basis, then the number is just going to be
| forgotten. However, they _might_ remember "a tidal turbine that
| can power thousands of homes".
|
| It would be lovely if everyone was scientifically literate, but
| people have other shit going on in their lives. On a pragmatic
| level, I'd rather society remember the abstract idea of 'how
| many homes' than _forget_ the precise '<x> megawatts'.
| JumpCrisscross wrote:
| As an American reader, home equivalents speaks to the
| political impact of the project better than wattage. The
| latter requires the context of the average home's usage in
| the relevant geography to contextualise.
| loonster wrote:
| Just define the value in home equivalents after the actual
| power amount.
| jakubp wrote:
| Same here. Lack of Watt output and expected (measured?) kWh
| cost in the lead of the story is baffling.
| hinkley wrote:
| I thought you were going to go a different direction after your
| first sentence.
|
| Largest turbine and it's only going to power 2000 homes?
|
| That's apparently about 9% of the power for the island, not
| counting industry (eg, Scotch), which sounds more impressive,
| but not _that_ impressive.
| marcosdumay wrote:
| Any practical deployment would consist of turbine farms. A
| single (couple of) turbine is just something you experiment
| on.
| TheManInThePub wrote:
| I've worked in the UK offshore power industry.
|
| Wave and tidal energy schemes have failed to deliver useful and
| reliable energy after over 50 years of investigation and research
| funding. Putting moving parts in salt water off the UK coast is
| always a tough prospect.
|
| By contrast, UK offshore wind power is delivering energy cheaper
| than ever and has emerged as a clear winner.
|
| Given the above, I'm honestly puzzled why offshore tidal energy
| projects are continuing to attract major funding.
|
| Incidentally, the argument that the tide is more reliable as it
| always flows twice a day is a rather moot point, as like wind,
| the tide doesn't always flow when you want it to.
| Mauricebranagh wrote:
| When I started work 79/80 I worked at BHRA (hydrodynamics
| research) and we had a load of RnD projects for things like the
| Salter duck etc and those still haven't gone anywhere
| mustafa_pasi wrote:
| That is what I was going to say. Is there any particular reason
| why they are trying to harvest wave energy? Is it more abundant
| or more reliable?
| Qwertious wrote:
| In theory, tides are more reliable and independent - it
| happens even if it's not windy or sunny, and it happens on a
| schedule that's more regular than the weather.
| bumby wrote:
| I don't work in the industry, but I've often wondered if the
| allure of wave energy comes from the fact that the
| theoretical energy available is proportional to the density
| of the fluid. So a turbine driven by water would have a much
| higher theoretical power capacity than one in the air for the
| same fluid speed.
| TheManInThePub wrote:
| > the allure of wave energy comes from the fact that the
| theoretical energy available is proportional to the density
| of the fluid.
|
| But the power generated by a turbine is proportional to the
| cube of the air/fluid velocity..... and the wind normally
| moves much faster than tidal flow.
| bumby wrote:
| Right, that's why I wanted to make sure to add the caveat
| about fluid velocity. But the density of water is almost
| 1000x that of air so there's a large benefit to water at
| lower fluid speeds. A rough back-of-the-envelope
| calculation shows the crossover is when airspeed is about
| 9.2x the speed of the water flow under perfect
| theoretical conditions.
|
| It's also worth noting that when dealing with centrifugal
| devices, the realized power never actually follows the
| power law. It's usually degraded quite a bit due to
| linear losses. A common power used in air systems is 2.1
| rather than the cube; using that value, the airspeed must
| be almost 24x the water velocity. I've never personally
| seen anything greater than 2.7 (the higher numbers, IMO,
| tend to be used as a sales pitch rather than an
| engineering decision), but again, I don't work in these
| particular systems.
| toecutter wrote:
| Quick note, confusingly throughout this thread people have
| used the phrase "wave energy" as essentially a synonym for
| "tidal energy", they are separate technologies sometimes
| talked about under the combined category of ocean energy or
| marine hydrokinetics.
|
| Increased power density is indeed one allure of wave energy
| vs wind. In the same way that wind is concentrated solar
| energy, studying the mechanisms and origins of waves show
| they are essentially a form of concentrated wind energy. So
| if the difficult design challenges are solved, there is
| potential for greater energy per unit of structural
| material which some believe could be associated with
| competitive cost of energy.
|
| Other allures of wave energy include that it is fairly
| consistent, with some seasonal variations, and its
| decoupled from solar or wind which decreases the chance
| that all renewables resources aren't producing at the same
| time. Of course this is talking about wave energy where
| oscillations occur with a period of approximately 4-18
| seconds rather than tidal with several periods per day, and
| for these periods of time flow is essentially
| unidirectional. Tidal energy, like the link in this thread,
| often uses underwater turbine but wave energy devices
| rarely use this design.
| klmadfejno wrote:
| I'm not an engineer so this is probably a stupid idea, but,
| rather than moving turbines with the tide, couldn't you:
|
| * Hollow out an area of the beach that's underwater at high
| tide
|
| * Install a big tank that lifts up some number of meters.
|
| * Lift the tank at low tide
|
| * Let water fill the tank at high tide
|
| * Drop your tank of heavy water like a gravity battery to
| generate power, at whatever rate you choose
|
| * Release water so its easy to lift again
| chriswarbo wrote:
| Gravity is incredibly weak; you'd need a _huge_ tank. This
| proposal has a footprint over 11 square kilometres:
| https://en.wikipedia.org/wiki/Tidal_Lagoon_Swansea_Bay
|
| (Sending the water through bi-directional turbines, to get
| power from the inflow and outflow)
| masklinn wrote:
| Sihwa Lake's working basin is _30 square kilometers_. Rance
| 's is 22.5.
|
| And while Rance could take advantage of an estuary with a
| dam just 750m wide, Sihwa uses a 12.7km long seawall.
|
| Sihwa's seawall was actually built for flood mitigation
| before SK realised it could work for power generations,
| building a 10km seawall solely for power generation sounds
| insane.
| Avshalom wrote:
| So instead of that what is done is
| https://en.wikipedia.org/wiki/Tidal_barrage
|
| You open gates; let high tide naturally fill a reservoir;
| close the gates; let the water back out through a turbine.
|
| They have been built but the largest are only producing ~250
| MW (ETA: thats 250 PEAK, actual generation is more like 50MW)
| which is nothing compared to what it takes to get that, like
| if you're already building a seawall it only _might_ be worth
| installing turbines.
| andechs wrote:
| How big is this tank? Water is heavy, and we're talking about
| an insanely massive tank to generate any reasonable amount of
| energy... that can also move and be used as a gravity
| battery. Anything you build the tank from would also be
| vulnerable to the corrosion of the sea water.
|
| Hydroelectric dams essentially build a tank, but they only
| build one wall of the tank. Hydroelectric turbines are about
| 90% efficient, so you're essentially looking to extract the
| same amount of energy from the weight of the sea water...
| with the complicating factor of needing to peak smooth due to
| tides.
| riquito wrote:
| > Release water so its easy to lift again
|
| How? Don't you have to pump it out since it's below sea
| level?
| 542354234235 wrote:
| Other people addressed the specifics but to add more
| generally, the key question is almost always not "can we do
| it". It is almost always "can we do this more economically
| than other methods" and the answer is no. It takes more time,
| money, resources, etc. for a given amount of power than other
| clean energy technologies.
|
| It is not very likely that there are tech improvements that
| would make things like this more viable. Salt water is super
| hard on equipment and that will always be true. Any
| improvements in durability would likely also apply to wind
| components. Gravity is only powerful at large scales, so just
| using tidal forces means you have to harness a lot of water,
| which means use land use and environmental disruption. Water
| batteries are economical only in places with extremely
| specific geography.
| chippy wrote:
| Like how just 30 years ago wind power was to be found at the
| hobby level in hippy farms but now has gradually matured,
| improved efficiency and is more stable, what's to stop tidal
| power gradually maturing and becoming more stable and efficient
| over a similar time frame?
|
| To me, this seems more like a pioneer project and one where we
| will learn lessons from.
| mistrial9 wrote:
| > 30 years ago wind power was to be found at the hobby level
| in hippy farms
|
| factually lacking and basically an insulting word IMO
| idiotsecant wrote:
| Saltwater is the enemy of moving parts. We've been sailing
| ships for millennia and we haven't figured out a way to
| reliably solve that problem. Saltwater boats are constantly
| fighting a battle against corrosion and take huge amounts of
| maintenance and they are basically just painted hulls with a
| few little moving bits sticking out.
|
| This isn't a problem with a magic answer or a problem that
| will benefit substantially from incremental improvements to
| materials and designs.
| chrisseaton wrote:
| > the tide doesn't always flow when you want it to
|
| So what? You can store tidal water and let the store always
| flow.
| TheManInThePub wrote:
| Flow to where?
|
| Low tide only occurs twice a day.
| chrisseaton wrote:
| Other pools, which you then empty on low-tide. That way you
| can start draining your main pool as soon as high-tide is
| reached - you don't need to wait for low-tide. With a set
| of pools you can keep draining 24 hours a day.
| TheManInThePub wrote:
| Schemes such as this have been proposed, see the Swansea
| Tidal Lagoon [0]. The bottom line is that they are crazy
| expensive for the power they deliver and just don't
| compete against other renewables.
|
| [0]https://en.wikipedia.org/wiki/Tidal_Lagoon_Swansea_Bay
| chrisseaton wrote:
| > Schemes such as this have been proposed
|
| Lol well if you knew that then why did you ask me to
| explain it?
| algo_trader wrote:
| Do u have any info on floating-solar-in-salt-water?
|
| (I have seen some in lakes/reservoirs. Surprisingly, less than
| 20% cost premium)
|
| > why offshore tidal energy projects are continuing to attract
| major funding
|
| Yeah. Agreed. Solar/wind/batteries/EVs will dominate.
|
| Everything else will get "scraps" from a $trillion/year energy
| industry ;)
| ashaikh wrote:
| The largest floating solar under development that I know of
| is in Seychelles. It's about 5MW. Haven't heard much on the
| development timeline post Covid.
| roland35 wrote:
| With solar, available land isn't really a constraint so I
| don't think there is a huge need to put solar panels in the
| water versus just putting them on empty land or roofs.
| oh_sigh wrote:
| It could be used with pumped storage to reduce evaporative
| losses. Pumped storage doesn't really care what the
| temperature of the reservoir is, so instead of heating it
| up with the sun, you keep more water in the reservoir
| through less evaporation, and extract the solar energy that
| would otherwise do nothing.
| Qwertious wrote:
| Floating solar makes sense in some dams that want to reduce
| evaporation, as they need _something_ floating there anyway
| and it 's almost always freshwater.
|
| I don't think land is more than 10% of the cost of solar in
| most places anyway - rooftop solar can cost $5000, and I'd
| expect rural areas to cost less than $500 for a paddock with
| the area of a house.
| londons_explore wrote:
| > the tide doesn't always flow when you want it to.
|
| It is possible (although complex and expensive) to construct a
| tidal scheme that can generate power consistently 24x7.
|
| Conceptually, you can imagine two pools - one of which is
| filled on each high tide, and the other of which is emptied
| every low tide. There is always a water height difference
| between these two, so you can generate energy anytime with a
| generator between them.
|
| It turns out such a scheme is less profitable than just
| generating lots of energy when the tide is flowing fast.
| chriswarbo wrote:
| Similar schemes have been proposed before. In the UK the
| Swansea tidal lagoon is particularly notorious, due to
| environmental concerns and the project's dodgy financials
| https://en.wikipedia.org/wiki/Tidal_Lagoon_Swansea_Bay
| jacquesm wrote:
| 100% in agreement with this comment. All the tidal energy
| projects that I've seen to date except the very first ones were
| simply subsidy grabs or even outright scams.
|
| Highly annoying to see ideas that were - solidly - discredited
| decades ago come back in a slightly different guise for a re-
| run.
|
| Based on past performance I predict that this setup will right
| up until the first major breakage, after which it will be
| uneconomical to even salvage it.
|
| The temptation of the tides is easy to understand: the power is
| immense, it is essentially the power inherent in the
| gravitational attraction of the moon orbiting the earth
| conveniently transferred onto a moving fluid. So on paper it is
| trivial. But that's where it stops being simple. The forces
| being immense is also a force that tries to destroy your gear.
| Corrosive salt water is the nastiest working fluid you could
| pick outside of acids. The wind & the waves combined can
| _really_ stretch the limits of engineering (I 've seen a minor
| bit of water hammer effortlessly flip an 8 cubig meter concrete
| cube right across a dam, like a 2x2 lego brick only slightly
| larger and heavier).
|
| The 'head' compared to most hydro installations is limited
| (though in some locations it can be of usable height), the
| flows are hard to trap without interfering with the rest of the
| environment and so on.
|
| As a 'mere matter of engineering' it is probably one of the
| hardest jobs you could tackle including going to space, the
| ocean is an extremely dynamic environment and near the ocean
| shore that is even more true.
|
| And finally, to be economical such an installation has to work
| for a very long time after initial deployment because it is
| very hard to work on once deployed.
| porker wrote:
| > Highly annoying to see ideas that were - solidly -
| discredited decades ago come back in a slightly different
| guise for a re-run.
|
| Any pointers to the ideas that have been discredited? This is
| a technology I dearly want to work, and I had bought into the
| narrative that it doesn't "because we haven't invested
| enough" (compared to offshore oil and gas production).
| jacquesm wrote:
| Gah where to start... anything capturing flow (it won't
| work, you are going to have to deal with _massive_ volume
| with really little head), vertically oscillating elements
| anchored to the seabottom driving pistons, impellers driven
| by waves trying to enter constricted passages, horizontal
| device driven by waves running up the tidal grounds, under
| water turbines of all sorts, shapes and sizes, scissor
| arrangements (with or without floats attached to the far
| end).
|
| You can broadly group all tidal devices into several simple
| groupings and for each of those there were a number of
| initial prototypes and all of those did not make it past
| the POC or initial deployment. Anything the future is
| likely to come up with will be variations on those themes.
| That won't stop people from trying and it won't stop future
| subsidy grabs because this all falls under the 'wouldn't it
| be nice if it worked' heading. Yes, it would be very nice.
| But no, it doesn't work and if you're not going to come up
| with something radically new you are better off reading the
| literature on what exactly made it not work the first time.
|
| Those who don't know history...
|
| Here is a very nice example:
|
| https://teamwork.nl/category/teamwork-technology/
|
| I'm sure they pocketed a ton of subsidy by now.
|
| In the same vane (pun intended): rooftop windmills,
| vertical axis turbines, kites, sound to energy conversion
| and on and on.
| marktangotango wrote:
| > massive volume with really little head
|
| This is really key, there just isn't that much energy
| available in a small enough area for utility scale
| production. I would add the caveat that for small scale
| production, some schemes could actually work quite well,
| like some kite schemes. But no one is investing in small
| scale, all the development is for multi megawatt systems.
| jacquesm wrote:
| The linked article is a perfect example. Created to fit
| one specific location where it just _might_ work and
| produce a pittance of energy twice every day. I 'm
| curious if it will survive the first real test: a good
| storm. Never mind the power that it generates. But for
| sure a lot of money got blown on this.
| toecutter wrote:
| The existence of fundamentally non-effective wind
| capturing technologies, such as rooftop windmills, vawts,
| and kites, does not preclude existance of effective
| designs aka multi-megawatt 3 bladed wind turbines.
|
| By analogy, just because early attempts to build a
| concept does not work, can you prove future attempts
| won't work? As far as I know, the energy potential in the
| ocean is not disputed, just the initial attempts to build
| the machines have not been successful. Many attempts at
| flying machines were unsuccessful before the wright
| brothers.
| nicoburns wrote:
| > By contrast, UK offshore wind power is delivering energy
| cheaper than ever and has emerged as a clear winner. > Given
| the above, I'm honestly puzzled why offshore tidal energy
| projects are continuing to attract major funding.
|
| Having a diversity of energy sources seems sensible...
| TheManInThePub wrote:
| That is why we have a diversity of wind farms!
|
| Wind turbines scale much more easily than wave/tidal, both
| the size of the turbines themselves (much larger than a
| wave/tidal system could ever be) and where they can be
| located around the UK coast.
|
| A diversity of renewable energy sources is sensible (nuclear,
| wind, biofuel etc), but wave and tidal are difficult to scale
| and have failed to deliver.
| Quarrelsome wrote:
| doesn't mean they will always fail to deliver.
| Guthur wrote:
| I think that unless you drastically change the parameters
| of the implementation then yes it does mean it will
| always fail.
| Quarrelsome wrote:
| you're assuming the rate of improvement is constant? I
| feel like progress is a process that staggers. There may
| well be a future where tidal provides better or more cost
| effective yields.
| 542354234235 wrote:
| > There may well be a future where tidal provides better
| or more cost effective yields.
|
| Based on what? With solar, we understood it was chemical
| science that would improve it. With wind, it was blade
| design, materials weight and durability, and generator
| technology. For tidal, what would improve that wouldn't
| also improve wind? Improvements in durability, turbine,
| or generator tech would almost certainly also improve
| wind. Salt water will always be harder on equipment than
| air. Tidal forces are strong on large scales but on
| footprints similar to wind turbines, we aren't talking
| about orders of magnitude more potential energy.
| grey-area wrote:
| Wave has obvious problems with mechanical wave action and
| corrosion quickly destroying any machine you leave in the
| waves, access and maintenance. It's unsurprising this is very
| difficult to scale and it does seem a dead end.
|
| Tidal energy does seem like in principle it should work without
| many moving parts at all save the turbines, which don't have to
| be metal. Is it the turbines themselves which are very
| difficult to maintain in salt water?
|
| This one is a floating design, which isn't ideal for
| maintenance, but I imagine at a large enough scale a dam
| between two bits of land with turbines in it would work -
| something we already do with hydro power and fresh water, and a
| concrete dam with access tunnels would solve a lot of problems
| with access and maintenance.
| 542354234235 wrote:
| >Is it the turbines themselves which are very difficult to
| maintain in salt water?
|
| The real key is they are far more difficult to maintain than
| wind turbines. Also, dams are ecological nightmares and
| disrupting huge swaths of coastline is not ideal. Dams also
| made use of very specific geological conditions where a
| maximum amount of water power could be achieved with the
| least amount of money, time, materials, etc. Coastlines don't
| have steep cannon walls to build up hundreds of meters of
| water to push through turbines at high pressure. Coastal
| tides are moving water meters high, not hundreds of meters.
| It isn't that it can't be done, it is just that it can't be
| done more economically than other technologies.
| nradov wrote:
| In addition to mechanical wear and corrosion, marine growth
| such as barnacles cause huge maintenance problems for any
| equipment in that environment.
| markbnj wrote:
| That's for sure. I don't know anything about this specific
| application but having worked in the shipping business and
| in commercial fishing I can attest to the problems with
| marine growth and corrosion, not to mention electrolytic
| issues for any contacting dissimilar metals that are
| immersed. Presumably all this is accounted for but I have
| to think the maintenance requirements for a long-term
| floating installation like this are no less than they would
| be for a commercial vessel, i.e. about 10% of the "hull
| value" per annum at a minimum.
| kumarvvr wrote:
| I have seen designs where moving tidal water compresses and
| pushes air inside a concrete structure to move air turbines.
| Any idea about those projects?
| TheManInThePub wrote:
| An air driven Wells turbine? As with other wave/tidal
| schemes, they are not viable at scale.
|
| Consider the flagship 'LIMPET' project:
| https://en.wikipedia.org/wiki/Islay_LIMPET
| noneeeed wrote:
| Blimey, I remember seeing that covered on Tomorrow's World
| when it was being built. It seemed like an interesting idea
| at the time.
| throwaway0a5e wrote:
| Wave energy is one of those things that only works at the
| "ghetto contraption I built with crap I had lying around"
| scale.
|
| Combine something that pumps, two check valves, some hose and
| creative plumbing (alternatively, replace creative plumbing
| with a lever and hydraulic cylinder) and you've got a really
| low pressure pump. From there it's just physics.
|
| Doing this kind of thing at scale just doesn't work. Between
| expensive engineers, permitting, code, surveys, OSHA, etc. etc.
| etc. there's no scale at which you can do this where you more
| than break even generating eletricity. Electricity travels
| great so you're competing with all sorts of other sources. It
| just doesn't work.
|
| But if all you want is to pump enough water into a tank so you
| can hose bird crap off your dock and you want to avoid digging
| a 300ft trench for a water line at the same time it works
| great.
|
| If you need real power somewhere remote go solar/wind. If you
| need better uptime than that then add lead acid to the mix. But
| once you start breaking into mid-range power needs (think
| gravel pit mine running crushers or something) it's hard to
| beat diesel.
| MichaelApproved wrote:
| > _Putting moving parts in salt water off the UK coast is
| always a tough prospect._
|
| I'm guessing salt corrodes metals and barnacles grow on them
| which make the moving parts seize up.
|
| What are some of the less obvious issues that they face?
| pony_sheared wrote:
| I work in the sector (offshore renewables and O&G), here are
| a couple of interesting ones:
|
| 1. Short installation window: they can only install this
| machine when the tides are changing (i.e. not much flow), so
| they only have a couple of hours to collect the moorings and
| it hook it up to the grid
|
| 2. Fatigue: loads of areas, not just the turbine blades...
| variable loading on the mooring lines, vortex induced
| vibration of the power offtake cable, wave induced motion on
| the offtake cable
|
| On the two you mentioned:
|
| Marine growth (barnacles etc.) is generally manageable with
| anti fouling paints, or PTFE (teflon) coatings, wipers and
| bearings around the things that you don't want to seize up.
| The animals will have a hard time getting a footing in this
| high flow environment anyway, it'll be pretty well self
| cleaning.
|
| Saltwater / corrosion is also manageable with coating
| systems, cathodic protection and large corrosion allowances.
|
| While these two do cause issues, they're kinda "solved", you
| can generally apply the same straightforward techniques and
| they don't take up as much engineering effort as solving the
| installation, system design and fatigue.
| dboreham wrote:
| Wind. Waves.
| gns24 wrote:
| Tidal energy doesn't compete with wind, it competes with energy
| storage. Having virtually no wind production over the whole UK
| for a week happens regularly; in fact this last week is a good
| example - production has averaged well under 2GW according to
| https://www.gridwatch.templar.co.uk/ On a windy week production
| can average over 10GW, but as yet grid scale storage is about
| as immature a technology as tidal generation (with the
| exception of pumped hydro, and there is a limited number of
| suitable sites for that).
| ggm wrote:
| If tidal or wave had been viable i think by now the offshore
| oil industry would have been exploiting it at their
| installations.
|
| For contrast, some of the fastest deployments of autonomous
| vehicles, solar energy and novel digital communications come at
| Australian remote mine sites.
|
| I badly wanted to read takedowns of your summary, but I'm
| forced to say absent well constructed arguments of viability i
| think you're carrying the room. Obviously the backers, grant or
| seed capital aided believe in what they're doing and we're a
| long way down the road from Salter's ducks. But on balance I
| think this is a niche product.
|
| Some places like the bay of fundy, if you took local ecology
| out of the picture, look like 80% of the construction cost of a
| tidal race is done for you by nature. It doesn't mean they
| would work, it only means the initial capital investment might
| be better. I think the same is true of the Scots waterways used
| for these tests, but the volume of power remains below wind and
| you would be right to say it questions why the investment given
| the balance of returns.
|
| The same is true of Carbon Capture and Storage: huge but
| elusive upside for the coal power sector, exploiting something
| known to work, from gas and oil well injection. It's had
| billions pumped in (hah) worldwide and doesn't seem to work in
| practice. Fugitive gas is a problem and the chemistry is
| complex and consumes energy ferociously to do the conversions.
| Had the same funds been spent on battery tech, improvements in
| transmission and other change to power, we'd be significantly
| better off (in australia)
|
| (Not an engineer, not in the power sector)
| VBprogrammer wrote:
| > Incidentally, the argument that the tide is more reliable as
| it always flows twice a day is a rather moot point, as like
| wind, the tide doesn't always flow when you want it to.
|
| Producing energy on a completely predicable schedule, while
| being less useful than at will, is much easier to deal with
| than producing energy on a modestly predictable but highly
| variable basis.
|
| But on the general point about funding for tidal energy I agree
| with you. To make it work we'd need to make bold and highly
| disruptive changes to the environment, for example the tidal
| barrier across the Bristol Channel.
| TheManInThePub wrote:
| > Producing energy on a completely predicable schedule, while
| being less useful than at will, is much easier to deal with
| than producing energy on a modestly predictable but highly
| variable basis
|
| I agree in theory, but in practice tidal doesn't scale like
| wind does (both in terns of the size of turbines and where
| they can be located around the coast).
|
| The predictable but small amount of energy it can produce is
| of limited use.
| viraptor wrote:
| > I'm honestly puzzled why offshore tidal energy projects are
| continuing to attract major funding.
|
| Is this a globally significant wasted funding? If not, it
| sounds like a reasonable idea to try something new from time to
| time. Worst case, some project trial fails and we learn a new
| failure mode / limitation. Best case, we get a new reliable
| power source.
| jacquesm wrote:
| Except that they are not trying something new. They are
| trying something old. Again. And again.
| TheManInThePub wrote:
| > If not, it sounds like a reasonable idea to try something
| new from time to time.
|
| Oh certainly!
|
| But funding is always finite. Unless some radical new
| wave/tidal technique comes to light (and it hasn't, yet!),
| then the project funding would surely be better directed to
| other renewable energy sources.
|
| The cynic in me says wave/tidal projects based on existing
| technologies (shown to perform or scale poorly) are simply to
| grab funding for green energy projects. The Swansea Tidal
| Lagoon fiasco is a classic example.
| Mvandenbergh wrote:
| Very cool.
|
| One of the challenges about building an energy system with lots
| of variable inputs is that you can't just look at the lowest
| levelised cost and build only that, otherwise you'd just build
| wind and be done with it. Adding sources that are not correlated
| with wind makes the overall grid management problem easier, even
| if those sources are more expensive the system cost may decrease.
|
| Obviously tide, while very predictable, is not dispatchable so
| not quite as valuable for grid management, but still shouldn't be
| written off just because it costs a lot per MWh.
|
| One thing that does make it hard is that peak water flow only
| happens in the middle of a six hour tidal cycle. For every
| location you have a predictable 6 hourly cyclical power curve.
| There's about 75 minutes between the high tide times in the North
| of Scotland and Southern England so on a GB grid basis, you can
| spread the curve out somewhat but still have that cyclical
| element.
| kitd wrote:
| Presumably East/West gives you better differential. IIRC
| there's 20 minutes difference between high-tide time of the
| east end of the Solent and the west end.
|
| Merging the output from eg West Wales and East Anglia would
| give you a pretty constant supply.
| everyone wrote:
| Wow.. Kinda looks like a repurposed submarine
| yosito wrote:
| Does anyone have a link to an explanation of exactly how this
| turbine works? I'm particularly interested to know whether it's
| bi-directional, how power is transmitted back to shore, and how
| it's anchored in place.
| papercrane wrote:
| I can't find a lot of detail, but to answer a couple of your
| questions.
|
| > how power is transmitted back to shore,
|
| Article says there is a static sea-bed cable that that is
| connected via a "dynamic" cable to the turbine.
|
| > how it's anchored in place. > whether it's bi-directional
|
| Very high level overview of the platform here:
| https://orbitalmarine.com/o2/
|
| It shows an forward and aft mooring points, so my assumption
| would be is that at anchors are put in the ocean bed and that
| the whole structure is held in place by cables.
|
| It also shows a "Two-bladed pitching hub allows bidirectional
| operation", so I take that to mean the blades are rotated in
| the hub depending on which way the tide is flowing.
| harry-wood wrote:
| yes I'd like to know more details. This video shows a _bit_
| more: https://www.youtube.com/watch?v=9hN3dBpPu8Q
|
| Bi-drectional? Looks like those adjusting flaps are to make it
| bi-directional yes, but maybe the angled legs mean it has a
| preferred flow direction (I'm guessing).
|
| How power is transmitted back to shore? The video seems to
| show, in red, some good old "big fat cable" technology. It's
| described only as powering the Orkney Islands. I wonder if
| surplus energy there can be fed back to the mainland grid.
|
| How it's anchored in place? Two massive mooring cables front
| and back. The main central cylinder floats, with the legs and
| rotors dipping down into the water (Maybe obvious, but not to
| me at first)
| yosito wrote:
| Thanks! This video was exactly what I was looking for.
| lmilcin wrote:
| What about having huge floating object with huge amount of extra
| buoyancy chained to the bottom?
|
| As the tide tries to lift the object the force could be converted
| for various purposes.
|
| This can be used basically anywhere where there are significant
| tides and where bottom can be reached easily.
|
| It is the same as other gravity storage methods except uses
| buoyancy.
| viraptor wrote:
| There's just not enough energy stored in the mass that way.
| There was a cool comment some time ago with the calculation,
| that I can't find now, but the result was on the order of:
| moving many tonnes of concrete by a few metres gives you enough
| energy to run some appliances for a day. Not enough to be worth
| doing on its own.
| [deleted]
| TheManInThePub wrote:
| I have a report from a first year undergraduate on my shelf
| that suggested this....
|
| A simple calculation shows you need an enormous volume float to
| generate a useful amount of power. A tidal range of a few
| meters isn't that much potential energy applied to a float of
| limited volume: by contrast, there is much greater mass of
| water in the sea to generate energy from.
| [deleted]
| lmilcin wrote:
| Okay, some calculations.
|
| An object displacing 250kt of water (ie. size of Ever Given)
| has a potential of about 0.7MWh per 1m. Most coastal regions
| see tides above 2m and a lot much higher than that.
|
| I say 1MWh extracted daily from from a dumb metal object the
| size of Ever Given (and potentially much more if you are in
| are with exceptional tides)?
|
| I guess it would depend on how efficiently it can be built
| and the cost of additional infrastructure (though it would be
| less if you build it in form of a farm).
|
| Remember, it can be used as energy storage, so if you have a
| large farm you can program it to automatically pull some of
| the containers deeper to provide power when at low tide.
|
| Also efficiency of this can increase with the size of the
| tank as the amount of materials scales less than linearly.
|
| I used Ever Given as an example, but this has been built to
| be seaworthy and pass Suez Canal. If you don't need to make
| it seaworthy and don't need to make it to pass through
| anything and can make it any shape you want you could
| probably design much larger structure.
| TheManInThePub wrote:
| > I say 1MWh extracted daily
|
| Consider a single offshore turbine in the Galloper wind
| farm is rated at 6 MW and this doesn't look so impressive.
|
| > a dumb metal object
|
| That's the thing. It isn't a dumb metal object. It requires
| generating gear, maintenance and protection from weather.
| Also consider the Ever Given is 1/4 mile long. These are
| big volumes you are talking about.
|
| No matter how you look at it, wind is a tough candidate to
| beat when it comes to offshore power.
| schainks wrote:
| A rule of thumb in grid-scale projects is to allocate
| roughly 50% of your capital costs to _just maintenance_
| over the lifetime of the thing you're deploying. Driving
| those costs down is really critical for affordable
| generation for any utility.
|
| The fancier the installation, the more money needed by
| specialist humans to keep the thing running.
|
| Offshore wind at scale is pretty affordable and less
| "fancy", relatively speaking.
| GiffertonThe3rd wrote:
| Does anyone else, of a certain age, get a distinct 'Thunderbirds'
| vibe from this?
| ggm wrote:
| Yes, what's missing is the trapped maintenance crew living in a
| pond underwater for no reason explained in the plot, and a
| secret plan to take over the device involving giant sharks
| hinkley wrote:
| My brain keeps trying to turn that into an airplane.
|
| On satellite maps that's going to look like someone ditched an
| A-10 at sea.
| seastonATccs wrote:
| The pictures looked like a real life Total Annihilation.
| aliswe wrote:
| I thought it looked like a sci-fi "speeder" of some sort.
| Podracer.
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