[HN Gopher] Underwater turbine spinning for 6 years off Scotland...
___________________________________________________________________
Underwater turbine spinning for 6 years off Scotland's coast is a
breakthrough
Author : djoldman
Score : 129 points
Date : 2025-07-10 14:23 UTC (8 hours ago)
(HTM) web link (apnews.com)
(TXT) w3m dump (apnews.com)
| davedx wrote:
| I did some reading about this yesterday:
|
| * this is a record for the time a turbine has been under the sea
| without any maintenance, which proves its commercial viability
|
| * because it generates powers during high/low tide, and because
| the lunar cycle is different to the solar cycle, it could help
| fill in the parts where solar falls off in a predictable way
|
| BUT:
|
| * Tidal energy is valuable but geographically constrained
|
| * Only a few countries have suitable locations for it (UK,
| Canada, France, South Korea)
|
| * The Global Technical Potential (in TWh/year) is 1/10th of
| offshore wind
| mushufasa wrote:
| > * The Global Technical Potential (in TWh/year) is 1/10th of
| offshore wind
|
| To put this in perspective, less than 1% of the world's land
| area would be needed for wind turbines to power the current
| energy needs of the globe (according to NREL). So this is not a
| limiting factor.
| gmueckl wrote:
| 1% of the world's land surface is massive! That's about 1.5
| million square kilometers. That's more than 4 times the land
| area of Germany or apparently about as much as the entirety
| of the built up area on Earth.
| tonmoy wrote:
| For reference the Sahara desert is 9.2 million square
| kilometers (obviously covering the entire desert in
| turbines is impractical, but we might be able to come up
| with 1% "useless" land if needed)
| bryanlarsen wrote:
| But that's non-exclusive use of 1% of the surface. Land
| under wind turbines can and is actively used for farming et
| al. The actual area that's prevented from other use is much
| less than 1%.
| CGMthrowaway wrote:
| So we would need to cover 4% (1% * 10 GTP * 30% land / 70%
| water) of the ocean to power the world? Seems like a lot
| ksec wrote:
| >* The Global Technical Potential (in TWh/year) is 1/10th of
| offshore wind
|
| I assume the value is still massive? The UK is still aiming to
| 4x its Off Shore wind by 2030. That would be 60% of UK
| electricity. If the new Nuclear Power plant actually deliver
| double its current 15%, that would be total 90%. The rest could
| just be solar and underwater turbine.
|
| I am just wondering if underwater turbine causes any issues
| with marine life. If not we could absolutely deploy them on
| massive scale and avoid the eye sore of Wind Turbine.
| graemep wrote:
| It will be a far higher proportion in the countries where there
| are suitable locations.
|
| it is predictable and reliable, so has significant advantages
| over wind.
| mike-the-mikado wrote:
| Quite possibly, with a suitable distribution of sites around
| the UK coast, the total power generation might be nearly
| constant over time.
|
| A guaranteed minimum power generation would presumably be
| very useful.
| libraryatnight wrote:
| "Tidal energy is valuable but geographically constrained" Is
| this really a negative? Can it not be simply viewed as a boon
| for places where geographically reasonable? I live in Arizona,
| I'll not be upset when left out of tidal energy - I've got
| solar and a sunshine surplus.
| insane_dreamer wrote:
| > Tidal energy is valuable but geographically constrained
|
| Don't tides happen everywhere there is a coast (which is a lot
| of places)? Or is this only effective in certain tidal
| conditions?
| meatmanek wrote:
| Tides happen everywhere, but not to the same extent and not
| always at useful times. If your peak production times don't
| line up with peak demand times, then you need expensive
| energy storage. (This would change with the phase of the
| moon, so sometimes you'll get lucky and sometimes you won't.)
|
| One thing that's relatively unique about the UK is that
| different parts of their coastline experience tides at
| different phases -- meaning with carefully chosen placement
| of different tidal energy plants, you can always have some of
| them operating near peak production. Click around
| https://www.tidetimes.org.uk and you can find places with
| high tide times happening at just about any time of day.
|
| If you look at a map like
| http://www.bidstonobservatory.org.uk/wp-
| content/uploads/2016..., the best places to use tidal energy
| would be red areas with lots of white lines hitting the coast
| -- these would give you the highest-amplitude tides with the
| most opportunity for phasing. The UK has both.
| lostlogin wrote:
| > because it generates powers during high/low tide,
|
| At high and low tide the water isn't moving much. Surely it
| generates most at mid tide, with the flow reversing direction
| causing a lull?
|
| This makes the useful portion of the cycle far far larger.
| worik wrote:
| > * Tidal energy is valuable but geographically constrained
|
| Yes, of course. I do not get the point, this is not a solution
| to every electricity generation problem
|
| > * Only a few countries have suitable locations for it (UK,
| Canada, France, South Korea)
|
| There are more than that. I have a seven knot tidle current 5km
| from my house, not mentioned in your list. I know of others.
| The costal conditions are quite common for this. The same
| technology will be useful in rivers too
| NotAnOtter wrote:
| As cool as this sounds, I'm not sure I'm as enthused with stuff
| our oceans full of more tech, which inevitably will wear down,
| break, and pollute.
|
| It's better than oil (duh), and something that provides power
| when solar/wind can't is great (duh). I just wish we would give
| up on approaches that are basically "If we had a few million of
| these giga-ton structures all over the ocean, they would provide
| power equivalent to a few dozen nuclear plants"
| pjc50 wrote:
| People aren't terribly keen on what happens when nuclear plants
| inevitably wear down, break or pollute either.
|
| Mind you the market has tended to give up on tidal power too.
| The sea is a harsh environment, working there is expensive, and
| solar cost reductions have simply run over most of the
| competition. Scotland has seen quite a few innovative ocean
| energy companies launch a pilot, run it for a few years, then
| go bankrupt.
| NotAnOtter wrote:
| People are broadly misinformed. Nuclear plants release
| significantly less radiation than coal based plants, as an
| example. They do create a lot of waste that we currently
| don't know how to process, but the quantity is actually
| shockingly small in the context of a global issue. We're
| talking several warehouses. Not millions, not all of
| California. We can just pick some cave in northern Canada or
| central sahara and bury it there, it seriously isn't _that_
| much. It 's better than where we currently store the waste
| which is basically the ocean & clouds.
|
| Meltdowns are tragic when they occur - but rare. It just gets
| a lot of press when a city of 50k gets deleted than when
| global ecosystems fail or a billion people die a decade
| earlier than they otherwise would due to pollution related
| helath issues.
| ben_w wrote:
| While all that is true, the problem is specifically how
| much it can cost in the worst case. There's only been one
| Chernobyl out of about 400 reactors, and its cleanup cost
| amortised over all those reactors makes a surprisingly
| small difference to the cost of electricity, but also
| Chernobyl was bad enough to be considered a significant
| part of the collapse of the USSR.
|
| Likewise, although it's absolutely true we're only talking
| about a few football fields of even the more voluminous
| low-level waste (high-level is about the size of one small
| block of flats), this is difficult to collect when it's a
| layer of dust spread over a few hundred square kilometres
| or dissolved in the seawater.
|
| If one of the UK reactors had gone up like Chernobyl, the
| UK would have ceased to exist, not because of the
| radioactive kind of fallout but simply the economic fallout
| would have done it in.
| NotAnOtter wrote:
| It's a massive stretch to think one poorly placed
| meltdown somewhere in the UK would lead to the UK
| collapsing. I suspect it would be visible on a 10 year
| GDP chart but not "trending towards 0" levels of economic
| fallout.
|
| Also I might just be misinformed but I thought nearly all
| of the radioactive waste from nuclear plants is already
| collected. It's not a collection problem, it's a storage
| problem. And a "what do we do when the energy company
| shuts down and stops maintaining their storage yard"
| problem.
| davedx wrote:
| How much will it pollute compared to other technologies? That's
| the question to ask.
|
| Thermal plants like coal and nuclear need cooling water, the
| output of which ends up in the sea too
| nick238 wrote:
| Lifecycle analysis is a common and increasingly detailed field
| which includes impacts to manufacture, transport, install, run,
| and clean-up installations, either cradle-to-grave, or cradle-
| to-cradle (includes the cost of recycling). I assume for
| installations like this, those studies have been done.
|
| There's a whole tirade in "Landman" about wind turbines not
| being green because of this or that thing[0], ending with the
| statement: "in its 20-year lifespan, it won't offset the carbon
| footprint of making it". These are just feelings (of the
| fictional character, but unfortunately ones adopted by real
| people) that are unconcerned with the facts that, no, the
| lifecycle analysis shows that wind turbines break even in 1.8
| to 22.5 months, with an average of 5.3 months[1].
|
| [0]: https://www.youtube.com/watch?v=wBC_bug5DIQ
|
| [1]: https://pubs.acs.org/doi/full/10.1021/acs.est.9b01030
| NotAnOtter wrote:
| Yes, lifecycle analysis is the holy grail.
|
| And I'm not qualified to say the tidal based solutions will
| never beat out Geo/Solar/Win + Batteries. In my informed but
| non-professional opinion, it seems like this avenue will
| never ever work at scale.
|
| From everything I've seen, we have the answer, we're just
| stuck under the boot of old money oil barons. Solar + wind +
| geo (depending on the geographic area) for the majority of
| our power generation. Nuclear + batteries to smooth out the
| duck curve form the bottom, paired with more aggressive
| demand pricing & thermal regulations to smooth it out from
| the top. That's the answer. But lobbyist's going to lobby.
| IshKebab wrote:
| This is such a misguided concern I'm wondering if you are
| concern trolling...
| NotAnOtter wrote:
| How are concerns about ecological impact misplaced when
| discussing solutions to ecological problems. It feels pretty
| relevant to me.
|
| And from everything I've seen/heard, tidal based solutions
| are just fundamentally incompatible with their product.
| Keeping sensitive metalic moving parts in saline solution
| exposed to the sun for years on end - paired with other
| random things like boating accidents or marine life - it's a
| non-starter. Constructing these things creates pollution. If
| it's lifecycle impact is less than oil's, great, I just don't
| believe we'll ever get to a state where it's better than oil
| AND (solar/geo/wind) + Batteries.
| sneilan1 wrote:
| Not to sound like a crazy person, but, does taking energy from
| tidal waves mean taking energy from the momentum of the earth
| itself? I read a long time ago somewhere that if we extract
| enough tidal energy, the earth's rotation could slow down
| somehow. Obviously as a layperson on this matter I'm not that
| well-informed but just curious of the possibilities if anyone
| knows.
| nbf_1995 wrote:
| https://cs.stanford.edu/people/zjl/pdf/tide.pdf
| brian_spiering wrote:
| Given the current rate of development, it probably won't be an
| issue for a while.
| aeve890 wrote:
| Why the downvotes?
|
| The 2004 Indian Ocean earthquake and following tsunami
| shortened Earth's day by 2.68 microseconds. The energy of the
| tsunami alone was around 4.2E15 joules. Considering Earth's
| mass, radius and moment of inertia it would take ~2.9E26
| joules to shorten the day by 1 minute.
|
| It seems it really won't be an issue for a while.
| HPsquared wrote:
| Conservation of angular momentum says no. Energy, momentum and
| angular momentum each have their own conservation laws.
|
| Edit: although maybe it could facilitate transfer of angular
| momentum between Earth rotation and the moon's orbital motion.
| bobmcnamara wrote:
| There are conversions between each.
| nachexnachex wrote:
| That's correct, while clean it'd be a mistake to classify it as
| "renewable".
|
| https://cs.stanford.edu/people/zjl/pdf/tide.pdf is a pretty
| accessible entry.
| MostlyStable wrote:
| I am extremely skeptical of that 1000 year estimate. It is
| almost entirely depending on the assumption of the continuous
| energy increase of 2% per year every year, for the next 1000
| years, and that tidal energy remains 1% of that total the
| entire time.
|
| I think that those assumptions are wrong in multiple ways and
| that reasonable estimates of the amount of tidal energy that
| could be extracted would lead to time scales where the risk
| no longer becomes relevant.
| nick238 wrote:
| Yeah, the "2% growth forever" feels like a sneaky addition
| which is _extremely_ controversial in economic theory: if
| _endless growth is required._ 1.02 ** 1000 ~= 400,000,000.
| So if the world population continued to grow at 2% in those
| same 1000 years, there 'd be 2.8 quintillion people. Evenly
| distributed over the planet (water included), each person
| would get a square 1.35 centimeters on a side.
| theptip wrote:
| On the timescales involved here, there is no such thing as
| renewable energy.
| Symmetry wrote:
| I think if we're positing a world where our energy use
| increases 2% annually for a thousand years and that tidal
| power will remain a fixed fraction of that we're not dealing
| with a reasonable projection. In any event, at the end of
| those thousand years humanity won't be very far from Dyson
| Sphere territory and the tidal locking of Earth wouldn't be
| much of a problem for the civilization implied, but I don't
| think it's possible to extract tidal energy that fast.
| stouset wrote:
| If the world's energy use increases by 2% annually for a
| thousand years and we're generating it with anything other
| than wind/solar/tidal/geothermal, we will raise the
| equilibrium temperature of the Earth by tens of degrees
| _just from thermodynamics_.
| Symmetry wrote:
| Nah, to keep extracting the Earth's rotational energy
| that fast through tidal means we'll have had to import
| all the available liquid water from the rest of the solar
| system, rendering the climate change effects of the other
| energy use moot. ;)
| CorrectHorseBat wrote:
| If the world's energy usage increases by 2% for a
| thousand years we use 3.4 * 10^4 times more power than
| the solar radiation reaching the earth (1.02^1000 *
| 15/170000). Enough power to boil off the oceans in about
| a day (if I can believe Reddit and my math isn't off)
| IshKebab wrote:
| It isn't a mistake to classify it as "renewable" because
| "renewable" doesn't literally mean until the end of time. Is
| solar not renewable because the sun will eventually explode?
| Ridiculous.
|
| And as others have said, 1000 years is a hilariously wrong
| estimate.
| pjc50 wrote:
| Technically it's the momentum of the earth-moon system; tides
| are a continuous input of energy into the oceans taken from the
| rotation of the earth relative to the moon. Tides lose energy
| to friction. I don't think that increasing tidal friction would
| have effects back on the planetary system, but it might reduce
| overall tidal amplitude. Very slightly.
| wat10000 wrote:
| Friction makes the tidal bulges lag slightly, which means
| they're a little bit ahead of where the moon is. That
| produces a net acceleration on the moon that raises its
| orbit. Increasing tidal friction should increase the lag
| which should increase the speed at which the moon's orbit
| raises. Completely insignificant at human scale, of course,
| but technically it should be doing something.
| aeve890 wrote:
| The sci-fi writes itself. Having averted climate
| catastrophe by switching to renewables 23rd century humans
| face the imminent catastrophe of disrupting the entire
| solar system dynamics after wrecking Earth-Moon orbital
| stability with their reckless energy extraction.
|
| This one's free, KSR, sir.
| Retric wrote:
| It's raising the moons orbit and slowing the earths
| rotation. But changing either by even 1cm/second would
| take a long time even if you're extracting 1 TW 24/7.
| aeve890 wrote:
| Those are rookie numbers. Exponential growth is real and
| lvl 1.2 in the Kardashian scale is the kpi.
|
| edit: Kardashev scale
| jerf wrote:
| Less "23rd century" and more like "23,000,000th century".
|
| I've read a lot of science fiction involving macroscale
| engineering on such levels, but I think even the most
| misanthropic science fiction writers have a hard time
| imagining a species that can start meaningfully affecting
| the orbital dynamics of their solar system but are
| clueless about possible negative side effects. By the
| time you're postulating such things, all the negative
| side effects that may leap to your mind involve energies
| many, many orders of magnitude smaller than the
| disruptions themselves, e.g., "oh no our satellite
| orbits", well, divert .000000000001% (I just hit some
| zeros, that's not calculated carefully) of the energy to
| fixing the satellite orbits. You're going to anyhow.
| wat10000 wrote:
| They don't have to be ignorant about the negative side
| effects, just unwilling to acknowledge or mitigate them.
| Could make for a good allegory about climate change.
| worik wrote:
| > but are clueless about possible negative side effects
|
| When has that ever stopped greed?
| aspenmayer wrote:
| > The sci-fi writes itself. Having averted climate
| catastrophe by switching to renewables 23rd century
| humans face the imminent catastrophe of disrupting the
| entire solar system dynamics after wrecking Earth-Moon
| orbital stability with their reckless energy extraction.
|
| In the interest of avoiding spoilers, I will merely
| advise anyone interested in a story with similar themes
| and content to read _Signal to Noise_ and its sequel _A
| Signal Shattered_ by Eric S. Nylund. You may know him
| from his work on the _Halo_ franchise or other popular
| games. I don't really know his other work, since I first
| discovered him via his original works.
|
| https://en.wikipedia.org/wiki/Eric_Nylund
| BurningFrog wrote:
| Fact: The Moon orbit moves away 3.8 centimeters per year.
| juujian wrote:
| We have reduced tidal friction much more significantly by
| removing mangroves and killing coral reefs, general coastal
| buildup.
| flohofwoe wrote:
| Earth's rotation is already slowing down because of 'tidal
| drag' by about 1..2ms per century (but surprisingly, also
| speeding up since recently):
|
| https://en.wikipedia.org/wiki/Earth%27s_rotation
| kryogen1c wrote:
| I have always had this concern about wind and solar. Removing
| energy from one part of the earth always sounded very haphazard
| and untestable.
|
| It's very unclear to me that removing heat from the ground,
| reducing wind speed/pressure, and lowering tidal forces is
| guaranteed to never have catastrophic impact.
| FirmwareBurner wrote:
| _> removing heat from the ground_
|
| You're not removing anything, you're just transforming
| kinetic energy into electrical energy. Energy transforms,
| everything transforms on earth, as per the laws of physics.
| When you die, your body doesn't get "removed", it gets
| transformed into worm food. It's the cycle of matter and
| energy. _" Yeah science Mr. White!"_
|
| I doubt human devices that capture wind and water wave energy
| are enough to negatively impact the climate in a meaningful
| way, considering how powerful nature is.
| kryogen1c wrote:
| During transfer, the source experiences removal.
|
| Covering the ground in non transparent panels removes heat
| from the ground.
| FirmwareBurner wrote:
| That's why you install solar panels where covering the
| ground has little to no impact, like on top of urban
| buildings or deserts where nothing lives or grows.
| nico_h wrote:
| Yes.
|
| The side effects of solar panels is indeed a cooler
| ground underneath. Plants have difficulty growing in the
| shade.
|
| Panels have a darker shade than most ground they are
| covering, so they might actually absorb more heat than
| the typical ground they are covering. They are distorting
| the local albedo.
|
| I think for geocooling by solar panels shade, the effect
| is completely local and only surface deep. After all
| stone/ground is an insulator, and geothermal energy is
| considered renewable.
| rcxdude wrote:
| If anything on average solar panels will warm the earth,
| because they are on average darker than whatever they're
| covering. (this effect is much less than due to CO2)
| rcxdude wrote:
| It prevents some heat from reaching the ground there
| (solar panels are ~20% efficient: most of the energy
| still reaches the ground). The energy (energy + heat is
| generally more than would normally be absorbed by heat in
| the ground) gets used and then turns into... heat. Which
| either makes it into the air or the ground, which is
| where it was going to wind up anyway.
| tonyarkles wrote:
| And to take this to its ultimate conclusion, that
| electrical energy eventually gets turned back into heat one
| way or another.
| FirmwareBurner wrote:
| If you drive an Nvidia 5090 and an Intel i9-14900KS then
| yes, it gets converted back to heat but that can also be
| reused like in some dorm rooms in Finland that are heated
| by the waste heat of the Nokia networking equipment.
| goopypoop wrote:
| "In a closed system entropy always goes up
|
| That's the second law, now you know what's up
|
| You can't win, you can't break even, you can't leave the
| game
|
| Cause entropy will take it all 'though it seems a shame"
|
| - _MC Hawking_
| SoftTalker wrote:
| > I doubt human devices that capture wind and water wave
| energy are enough to negatively impact the climate in a
| meaningful way
|
| Exactly what we used to say about industrial gas emissions.
| nico_h wrote:
| At this point i think removing any heat from ground is a net
| win.
|
| Solar is just transforming light into electricity, i don't
| think it's removing any heat from the system unfortunately,
| unlike radiative cooling paint.
|
| Now that we should be painting any tropical building we can
| with.
| SoftTalker wrote:
| I would expect large solar farms increase heat, as the
| panels are dark and absorb a lot of energy (by design).
| Normal groundcover is not so dark and reflects a higher
| percentage of sunlight.
| lukan wrote:
| Wind turbines can have local effects, meaning less wind in
| areas behind the turbines, which can mean smog stays longer
| in a city.
|
| But like the other comment said, with solar you are not
| taking anything.
|
| But solar panels do heat up the air around them more than
| vegetation would do.
| RC_ITR wrote:
| Do you have this same concern about _literally every
| structure man has ever constructed_?
|
| They do the same exact thing in terms of 'slowing wind down'
| and 'preventing the sun's energy from reaching the ground'.
|
| This idea is understandable, but it falls apart for the same
| reason the wind turbine bird death concern does (the number
| of birds that have died due to humans liking windows is
| 1,000,000x the number that have died in turbines).
| kryogen1c wrote:
| > Do you have this same concern about literally every
| structure man has ever constructed?
|
| To a lesser extent, yes. However, power generating
| facilities are different in that they are intended to
| remove as much energy as possible, whereas sky scrapers etc
| are not.
| Retric wrote:
| This is exactly why science education is so important.
|
| But if it makes you feel better, all man made structures
| combined cover a small fraction of the earths surface
| people tend to be in areas with other people and thus it
| looks like we're doing more than we are. NYC for example
| has 291x the average population density of the rest of
| the US and that's including over a square mile devoted to
| Central Park.
|
| Agriculture has a bigger impact because it cover so much
| land, but that's offset by it being relatively close to
| nature.
| rcxdude wrote:
| Cities probably have a significantly larger effect on the
| way that energy flows around the earth than renewable
| power generation does. It's relatively easy to change how
| much a very large amount of heat moves in comparison to
| how easy it is to harness energy into usable work. (See
| also why the greenhouse effect from CO2 emissions is such
| a big deal in comparison to basically any other thing
| that humans have done, as far as the energy balance of
| the earth is concerned. CO2 is responsible for about 20
| times more energy being absorbed by the earth than
| humanity uses in total, from any source)
| scythe wrote:
| With solar humanity's total power consumption is just a
| fraction of a percent of the Sun's luminance. With wind in
| some areas you get towards a larger percentage. But either
| one pales in comparison to the impact of hydropower which has
| dammed some of the largest rivers and waterfalls in the world
| to offer only a small fraction of our existing electricity
| supply.
| PaulKeeble wrote:
| Its all a question of scale. All these systems can afford
| some extra energy loss just like the planet could cope with a
| certain amount of CO2 production because the plants and
| oceans would grab it and store it. Once we exceed those
| (currently unknown) limits however it can become a problem
| and the biggest solar farms are impacting the area around
| them as they change that energy balance.
| pjc50 wrote:
| > Removing energy from one part of the earth always sounded
| very haphazard and untestable.
|
| .. compared to taking energy and carbon from the ground, and
| changing the atmospheric composition enough to significantly
| change the temperature? Because that's the alternative to
| not-renewables.
| renewiltord wrote:
| Yeah everything has an effect. I have been quietly strangling
| infants in their cots to prevent CO2 increase from their
| breathing resulting in runaway climate change. We need to
| take action and stop disrupting a system in homeostasis. We
| need to go back to the era of 10,000 humans and I volunteer
| everyone else to sacrifice themselves for my future.
| BurningFrog wrote:
| Strictly speaking nothing, including posting HN comments, is
| guaranteed to never have catastrophic impact.
|
| We all need to live with _some_ calculated risks.
| grues-dinner wrote:
| The momentum of the Earth-moon system is 3.61x10^34 kg.m^2/s,
| of which 80% is the moon orbiting and 20% is the Earth
| (https://space.stackexchange.com/questions/50502/how-much-
| of-...).
|
| KE = p^2 / 2m
|
| Energy in the Moon's orbit: 5.7*10^45J
|
| Energy in the Earth's orbit: 4.4*10^42J
|
| So the lower momentum of the Earth (with a square term) and its
| (much) higher mass (Moon is 1.2% the mass of Earth) make Earth
| over 1000 times less energetic. So it's just the Moon that
| matters here.
|
| Assume every joule extracted is coming directly from that
| budget and the moving water wasn't going to hit Scotland and
| turn some into heat anyway. 15.9 TW is average human energy
| usage.
|
| 5.7*10^45J / (15.9 TW * 1 year) = 1.14 * 10^25
|
| So if we generated ALL human power from this method and every
| joule was taken from the Moon's orbital energy that would
| otherwise not be taken, we can spin the system down in just
| over a ten million billion billion years.
|
| This is actually a bit more than I expected, though I knew it
| would be a lot from basic common sense of 80 billion billion
| tons moving at 1km/s. So maybe I've flubbed a few (tens of)
| orders of magnitude? In particular, the 1000:1 Moon:Earth
| energy ratio sounds plausible when I think about it, but it
| still was a bit of a surprise.
|
| In any case, I think it's OK.
|
| Edit, OK, so that was bunk, the orbital energy is 3.8x10^28J,
| so we can unbind the moon and donate it to Jupiter in only 65
| million years.
| perihelions wrote:
| > _" So maybe I've flubbed a few (tens of) orders of
| magnitude?"_
|
| Yeah, a few tens! Part of it is that you seem to have
| reinterpreted angular momentum as linear momentum. That's not
| dimensionally cromulent.
| grues-dinner wrote:
| Feh, knew it. Maybe I _should_ have just used ChatGPT.
| meatmanek wrote:
| The real question is much energy do we need to harvest to
| slow down the moon's orbit enough to get exactly 12 lunar
| months per year?
|
| EDIT: and can we also simultaneously slow down the Earth's
| rotation to have exactly 360 days per year? Fix the calendar
| once and for all.
| nick238 wrote:
| Maybe these are the windmills that drive the whales crazy? To
| paraphrase wind-watch.org (sounds non-partisan)
|
| > The obvious concern that most people might guess will be
| dangerous and damaging to [swimming] wildlife are the spinning
| blades themselves. While large white spinning [turbine] blades
| rotating [below] the horizon or in an advertisement seem bucolic,
| restive, and like the perfect green energy source, the fact is
| that the tips of the blades can be spinning at up to 200 miles
| per hour. Those speeding blades can act like a giant blender for
| large [fish] such as [tuna] and [whales] which fly around the
| commercial [water] turbines and chop those [fish] up. Biologists
| have found that even small species of American [fish] regularly
| get killed from the spinning turbines of commercial [water]
| turbines.
|
| /s
| bad_haircut72 wrote:
| this feels solvable with a cage around like you have on every
| pedestal fan?
| leoedin wrote:
| Did you just post a wind-turbine criticism?
|
| These turbines have a diameter of 18m and a speed of 8 to 20
| rpm. So a tip speed of 7.5 to 19 m/s - about 27 kph to 68 kph.
| I guess that's enough to hurt a whale. Although interestingly
| the water speed due to the tide in this channel is up to 5 m/s
| - so maybe it's too turbulent for whales anyway. Do whales like
| fast flowing water?
| vpribish wrote:
| that reads as nonsense. it's mixing wind and water, and all
| those missing words indicate that it's the product of a broken
| mind.
|
| also, you, the MAGA-hallucinations against windpower are
| contemptible lies AND they have nothing to do with this single
| underwater turbine.
| callamdelaney wrote:
| My intuition is that these will be moving much more slowly than
| that. The turbines that they refer too are usually high
| pressure ones designed for generating energy downstream of a
| huge body of water like a resovoir.
| barbegal wrote:
| Only 1 of the four turbines has been able to operate for 6 years
| without pulling it out the water. The other 3 have needed costly
| maintenance https://www.waterpowermagazine.com/news/sae-secures-
| loan-for...
|
| It's a nice idea but costly compared to solar even in places like
| Scotland.
| badestrand wrote:
| I would love to see a complete cost comparison with solar.
|
| 1.5 MW is nothing to scoff at, so if it costs a bit in
| maintenance that's okay. But overall costs would be great to
| know.
| theptip wrote:
| Also there is theoretically power in the GW range to be
| harvested here (specifically, Scotland's tidal flows), so
| it's worth investing a substantial sum to figure this tech
| out.
| mlyons1340 wrote:
| Texas' capacity was 113000 MW yesterday so 1.5MW doesn't seem
| significant. Am I understanding this wrong?
|
| https://www.ercot.com/gridmktinfo/dashboards
| saberience wrote:
| Why are you comparing a single turbine in Scotland to the
| entirety of the state of Texas's supply (thousands of
| turbines)?
| mousethatroared wrote:
| _hundreds_ of thousands.
| regularfry wrote:
| Wrong comparator. 1.5MW nominal output is comparable to a
| large wind turbine.
|
| For instance, there's the https://www.esig.energy/wiki-
| main-page/general-electric-1-5-..., which has ~40m blades.
| The AR1500 (which is what these tidal generators are using)
| is smaller, with "only" 9m blades.
|
| So it's significant in that these aren't toy devices, they
| fit in a very similar place in the engineering ecosystem as
| conventional wind. They should be a real competitor.
| pyrale wrote:
| In 2025, the large commercially deployed wind turbines
| are like 15MW for offshore and 6MW for onshore.
|
| GE's 1.5MW models are 20 years old.
| pyrale wrote:
| 1.5mw is likely a nameplate capacity for the turbine, not the
| actual output (which should be labeled in GWh per year).
|
| The article likely double-dips on this by saying that 6MW
| could provide for 7k homes, which it obviously can't at peak
| use.
| cycomanic wrote:
| Why is it obvious that it can't? I just looked up the
| numbers and Scotlands absolute peak demand is 6.5 GW and
| there are about 2.5 M households. With those numbers they
| would need 18MW for 7000k households, but that ignores all
| commercial contributors to peak demand (I could not find
| data on commercial vs residential demand), but it seems to
| me the number isn't completely off.
|
| Also I would say the expression "powering a home" usually
| implies average demand not peak demand.
| pyrale wrote:
| Well, with 6.5 GW for 2.5M households, you're at a peak
| around 2.6kW per home.
|
| Assuming these turbines are always at nameplate
| production, which they are not, they produce 6MW. Spread
| among 7k homes, that's less than 1kW, which is not a lot.
|
| Given the previously stated peak of 2.6kW per household,
| 6MW would cover about 2300 homes.
|
| The only way you could get to this kind of number would
| be if you calculate the average use for a household over
| a year. But then you would have to compare it to the
| plant's yearly production rather than its nameplate
| capacity.
|
| Wikipedia quotes MeyGen at 10.2GWh in 2023, that means
| 1.14MW on average instead of 6MW. Assuming perfect
| storage, that would mean an average of 163W per house for
| 7000 houses. That is barely enough for a fridge.
|
| > Also I would say the expression "powering a home"
| usually implies average demand not peak demand.
|
| That's my issue. Comparing average demand to nameplate
| capacity is dishonest.
| terribleperson wrote:
| If one made it six years, it seems like it should eventually be
| possible to build turbines that reliably make it that long.
| micromacrofoot wrote:
| Yes, 1 success out of 4 test flights -- good news, it's
| possible!
| soperj wrote:
| So exact same results as the falcon 1. Seems like they did
| okay with the Falcon 9.
| dinfinity wrote:
| GPs link doesn't even show what was claimed ("The other 3
| have needed costly maintenance").
|
| From that link:
|
| "The first of these turbines is scheduled for redeployment in
| May 2022, with the final turbine to be deployed in March
| 2023, complete with a retrofitted wet mate connection system,
| which more than halves the costs of future turbine recoveries
| and deployments."
|
| "The company's AR150 turbine was re-deployed last month,
| after being out of the water for upgrade and maintenance
| work."
|
| The single long-running turbine can be compared to the
| upgraded turbines to measure the effect of the upgrades, and
| it provides the headlines this thread is about. The upgrades
| themselves are also clearly valuable R&D work.
| lostlogin wrote:
| This needs to be a reply to the original comment.
| Havoc wrote:
| That's useless for commercial operation, but for a trial run
| perhaps not terrible.
|
| If 1/4 make it then you at least know it can be done and
| hopefully learned a couple key failure modes from it
| Goronmon wrote:
| _Only 1 of the four turbines has been able to operate for 6
| years without pulling it out the water. The other 3 have needed
| costly maintenance_
|
| As opposed to other forms of energy production which have
| free/zero maintenance?
| insane_dreamer wrote:
| > costly maintenance
|
| all systems require maintenance, so "costly" is relative; would
| need more specifics to determine whether this is a cost
| effective solution or not
| magicalhippo wrote:
| This[1] article states the following:
|
| _To remind, the MeyGen project's Phase 1A involved the
| installation of the AR1500 onto a gravity-based foundation,
| alongside three other AH1000 MK1 turbines, to form an array of
| 6MW._
|
| From what I've found, the AR1500 has just had routine quarter-
| life maintenance[2], but I can't find anything concrete right
| now which of the four made the 6 year milestone. I do note that
| in the brochure[3] for the AR1500 they claim three service
| intervals every 6 1/4 years, rather than four service intervals
| as indicated by the article.
|
| [1]: https://www.offshore-energy.biz/simec-atlantis-
| troubleshooti...
|
| [2]: https://www.offshore-energy.biz/overhauled-meygen-
| turbines-t...
|
| [3]: https://simecatlantis.com/wp-
| content/uploads/2016/08/AR1500-...
| asdff wrote:
| I assume corrosion is to blame? Crazy how much ocean facing
| stuff is still done with painted steel. You'd think aluminum
| and carbon fiber or even plastic would be making strides but
| it's still the iron age in many ways it seems.
| zikzak wrote:
| All industrial generators undergo regular shutdowns for
| maintenance and recalibration. This is costly and time
| consuming when they are on land.
|
| Also, I am thinking about all the ocean factors beyond salt
| corrosion. There's tons of crap in the water beyond salt and
| minerals. Like fine grit suspended in it. Plus the tidal
| forces etc.
| spandrew wrote:
| Carbon fibres tend to crack under extreme torque.
| saturnV wrote:
| Carbon fibres themselves may be corrosion resistent, but the
| fibers by themselves are like a fabric. If you want a solid
| part instead of cloth, you need to encase the fibers in a
| resin. Imagine it like a piece of cloth soaked in beeswax or
| candle wax: it is solid like the resin but if you pull on it,
| it has the strength of the fibers of the cloth.
|
| The resins used for carbon fibers are usually very bad at
| contact with water over long periods of time. Even those in
| aerospace applications require coating/paint if exposed
| moisture over time. It's a plastic, even the best ones don't
| do so well in water after a few months.
|
| Furthermore, the damage that moisture does to the resin can
| be difficult to detect and even more difficult if not
| impossible to fix. It requires clean rooms, skilled labor and
| machinery that you don't have in the middle of an ocean.
|
| Then take iron corrosion: it is easy to spot by naked eye, it
| may not be easy to repair, but it is relatively simple to
| "halt" further damage by removing the rust and adding new
| paint.
|
| Don't get me wrong: carbon fibers are amazing, but sometimes
| the "boring" solution is best.
|
| PS: steel alloys and coatings can be amazingly high tech too,
| it's amazing what can be engineered.
| semi-extrinsic wrote:
| Cathodic protection is also a nice option against corrosion
| on stuff that's connected to the grid anyways.
| os2warpman wrote:
| I'm not a turbine, or power generation, expert but I am almost
| 100% sure that no non-solar power generation method can operate
| without being taken down periodically for maintenance.
|
| How do the maintenance costs (and intervals) of these compare
| to gas/steam turbines?
| JR1427 wrote:
| Out of sight, out of mind...
| KaiserPro wrote:
| One thing is not immediately obvious is just how hostile that
| area is.
|
| Firstly sea water is corrosive, plus if you add all the sand and
| other particles that are in there it becomes abrasive as well.
|
| BUT
|
| the tide also reaches speeds of 30kmh (18mph) twice a day.
| amelius wrote:
| Caution, by harvesting tidal energy you're tapping into the
| potential energy of the Moon, making it move closer to us at an
| increased speed.
| lostlogin wrote:
| Surely taking energy from it would make it move further away?
| thebruce87m wrote:
| Doesn't the moon move away from us?
|
| https://public.nrao.edu/ask/what-happens-as-the-moon-moves-a...
| sgt101 wrote:
| Where I live there's a tidemill that's been running for 850
| years.
|
| Still provides power today.
| octaane wrote:
| Sounds like they need to get the quality control down pat if only
| 1 out of 4 of the turbines achieved this goal - still a promising
| milestone, though.
| Peanuts99 wrote:
| Engineering for machines underwater is tough because the
| environment is extremely hostile. For a test bed device, 25%
| success is very good.
| lostlogin wrote:
| Upgrades and changes are mentioned, so it's not clear that
| reliability is the only cause of downtime.
| standeven wrote:
| The real problem: if this technology is viable, it will
| immediately be attacked with disinformation campaigns ("but it
| kills dolphins!"), lobbying against it, government red tape, and
| tariffs.
|
| Solar, wind, and storage can solve most of our energy needs,
| TODAY, but look at how it's being treated.
| worik wrote:
| We have debate around this in New Zealand
|
| The problem here is you have a large body of water that is a huge
| and significant nursery for fish, and the best place for the
| turbine is where the water narrows.
|
| If the turbine is a barrier to the fish, (and who knows?), then
| important fisheries may well collapse
|
| This is an objection that needs to be taken seriously and
| investigated, so I was disappointed that the article did not
| address effects on marine life.
|
| Personally I think that the turbines and marine life can co-
| exist, but we need facts, not reckons
| Animats wrote:
| Nice.
|
| Tidal power only works where the geography is right. A bay with a
| choke point to the ocean, like this one, is needed.
| robotnikman wrote:
| I wish they provided pics of one underwater. I love stuff that
| invokes a feeling of submechanophobia
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