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.
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
> Canada
The Annapolis Royal Tidal Station shut down 5 years ago, because it had a strong tendency to chop up all and any fish that went through the intake.
The Annapolis looks like a fundamentally different design: direct turbine driving instead of low-speed / high-torque windmill design.
Yes, the Annapolis station was conceptually very much like a hydroelectric dam generator. When the tide was coming in sluice gates were opened to allow a reservoir to fill, then when the tide was going out the water was sent through a high-speed turbine.
It's unlikely that Nova Scotia will see tidal power again in the near future. There's been some attempts at in-stream generation, but the projects have been opposed by the local fisheries, and the federal regulators don't seem interested in helping define the requirements.
Plus a newer one off Vancouver island BC shut down after a couple years because its operating costs made it economically infeasible. Had to get fixed and upgraded a few times. Which I why the maintenance thing in the headline is probably relevant.
>* 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.
South Korea was going to build a large one but canceled it due to the marine life threat. One way they try to fix it is by having a safety mechanism that turns the blades off when marine life passes through but this increases operating costs on something that is already high maintenance.
> 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.
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.
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.
"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.
the hard part with geographically constrained sources is that they have a harder time getting economies of scale. solar works everywhere and is really easy to install, so the market cap is massive, leading to corresponding increases in production efficiency.
And importantly, China isn't on the list of places this works, and China is the only place in the world for generalist manufacturing at scale.
> * 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.
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.
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%.
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)
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
> * 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
> 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?
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.
The issue is clarified with a map like this: https://i.redd.it/rontertecjqd1.jpeg
Most regions have very small tidal ranges. That doesn't mean they have small tidal currents (think of fjords or straights for example), but it does make it more likely.
And in those fjords and straights, I reckon yhese solutions will compete with boat traffic.
Naively, you'd expect the tidal current to be proportional to (tidal range/water depth). Which causes that map to be a lot less informative.
Fascinating. I wouldn't have expected the English Channel to have the strongest tides. I would have expected it to be the Atlantic coast of Ireland or France.
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.
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 3.8×10^28J, so we can unbind the moon and donate it to Jupiter in only 65 million years.
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.
> 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?
Oh my god! That's an amazing idea!
> "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.
Feh, knew it. Maybe I should have just used ChatGPT.
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.
We have reduced tidal friction much more significantly by removing mangroves and killing coral reefs, general coastal buildup.
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.
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.
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.
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 atmospheric composition of their planet but are clueless about possible negative side effects.
Misplaced misanthropy. The largest and most destructive atmospheric composition change in the history of the planet, against which our slight modification of CO2 levels is just a blip, was performed by completely unconscious species with zero capability for reflection or prediction of the results. Compared to the Great Oxygenation Catastrophe, we've done nothing.
On a more amusing note, if you're interested in a counterexample to your direct claim, which involves another catastrophe that makes the worst predictions of climate change look like human paradise, I would recommend to you "The Nitrogen Fix" by Hal Clement. I won't spoil what the catastrophe is in case you might be interested in reading it, but Google will spoil it readily if you prefer.
But that species didn't call itself Homo Sapiens, and didn't flatter itself that it knew better.
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.
> but are clueless about possible negative side effects
When has that ever stopped greed?
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.
Those are rookie numbers. Exponential growth is real and lvl 1.2 in the Kardashian scale is the kpi.
edit: Kardashev scale
/s if not obvious
Funnily enough, this looks like the same surname with a Persian root for “stone carver” and Armenian and Russian surname suffixes. Given Persian origins, one can speculate that it was russified rather than armenified. So Kardashev’s ancestors might be Kardashians!
Fair enough.
But I have no doubt the energy gained by gifting the Kardashians escape velocity would be scientifically significant.
You can’t extract more energy from ocean tides than are actually in the ocean tides.
> Exponential growth is real
It’s really not. 99% of the energy used by humanity is still sunlight used to grow crops the same it’s been for thousands of years, and crop land use hasn’t been increasing exponentially. The majority of growth has been from efficiency gains not utilizing more energy.
Our ancestors realized irrigation and selective breeding allowed for more production from the same land. Fertilizer, better breeds, insecticides, meant more yield and automation meant less labor but the underlying energy input is unchanged barring increases in land under cultivation or the mouthes of livestock.
Instead many historic curves look exponential when you ignore the underlying population growth driving the whole thing and the recent reductions in fertility.
> 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.
Fact: The Moon orbit moves away 3.8 centimeters per year.
Earth's rotation is already slowing down because of 'tidal drag' by about 1..2ms per century (but surprisingly, also speeding up since recently):
Not in a way that matters (is at all noticeable) until long after the sun expands and wipes out all life on earth in a few billion years. Of course by then, the moon will be quite a bit further from earth than it is today and might become tidally locked with the earth as the earth rotation slows down and eventually matches the speed at which the moon rotates. So there is that.
In the same way, we're not running out of geothermal energy (a tiny part of the heat actually comes from the moon pulling magma around, the rest from radioactive decay and residual hit from when our planet was created). Technically more heat radiates out via our crust naturally than we'll ever need.
So, technically yes but not in a way that actually matters on the time scales we have left on earth, which technically will become a lot more hostile over time anyway. A billion years from now, things will be very much changed here. Minuscule loss of momentum in the moon's orbital movement will be the least of our concerns there.
Given the current rate of development, it probably won't be an issue for a while.
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.
Yes, but tides are already sucking a huge amount of rotational inertia out of the Earth all the time even if we aren't actually using it for any practical purpose. The only reason its not a problem is that the Earth has so much rotational inertia to begin with that it will take a very long time to run out.
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.
There are conversions between each.
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.
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.
They do. But they also keep that heat from reaching the ground, which is a good thing for many agricultural applications.
See also, "Agrivoltaics."
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.
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.
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.
Considering how little of the landmass needs to be covered, any effects are absolutely trivial compared to CO2 gains.
Strictly speaking nothing, including posting HN comments, is guaranteed to never have catastrophic impact.
We all need to live with some calculated risks.
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).
> 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.
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.
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)
Sure, but again, wind turbines are on the scale of millions whereas there are tens of billions of structures swaying in the breeze.
I get your point, but a 1,000x+ difference in quantity cannot be ignored.
> 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.
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.
>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.
"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
> 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.
And to take this to its ultimate conclusion, that electrical energy eventually gets turned back into heat one way or another.
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.
During transfer, the source experiences removal.
Covering the ground in non transparent panels removes heat from the ground.
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.
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.
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)
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.
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.
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.
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.
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.
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.
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.
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.
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)
Yeah, I've done the calculations for 3% at 2%. I didn't feel like doing them again, so just went with a conservative bet.
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. ;)
On the timescales involved here, there is no such thing as renewable energy.
The ocean is brutally unforgiving, and until now the skepticism around durability has been justified. But if projects like MeyGen can show that tidal infrastructure can go the distance, it could unlock a huge untapped energy source
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"
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].
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.
Yep, lifecycle analysis is the key lens we should be using when evaluating any energy technology, especially in emotionally charged debates about what’s "green" or not
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.
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.
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.
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.
If any of the Hinkley Points, Berkeley, Oldbury had an exclusion zone like Chernobyl's, Bristol and half the Bristol Channel would have been in the exclusion zone. (Berkeley, Oldbury would also have forced evacuation of GCHQ).
Dungeness, would have included Dover.
Bradwell, the Thames. The Sizewells, it would have been Lowestoft and Harwich.
Torness, the Firth of Forth, blocking sea access to Edinburgh.
While this is not an exclusive list, and also I grant I'm not actually modelling what the fallout zone might look like when there's a coastline involved (is it better or worse? IDK), I ask you: which major international transit hub can the island of Great Britain do without? I'm sure they can be rapidly evacuated (being transit hubs), but how fast can the capacity be replaced elsewhere, how fast, and at what cost?
Consider that the UK barely had enough stuff in place just for the Brexit-related customs checks, which it saw coming, even though there was a global pandemic at the time that reduced/zero passenger on the same hubs. How much worse if any of these hubs becomes completely off-limits?
That plus the chronic[0] extra demand on the rest of the power grid. Ukraine had to keep the other reactors at the Chernobyl power plant itself running after the incident, just to avoid shortages.
A 2016 estimate said the overall cost of the Chernobyl disaster was US$700 billion, which is approximately [EDIT: not 97%, mixing dollars and pounds, see [3]] 72% of the tax revenue the UK collected in the tax year starting about when that report was published[1][2][3].
Regarding your point about collection of radioactive waste from nuclear plants, that's only the case for correct operations, not when they leak — or, in the case of Chernobyl, explode.
[0] the acute (sudden) part is fine as shutdowns happen at random anyway; chronic is the long-term.
[1] https://globalhealth.usc.edu/wp-content/uploads/2016/01/2016...
[2] https://en.wikipedia.org/wiki/Budget_of_the_United_Kingdom
[3] https://www.wolframalpha.com/input?i=700USD+in+GBP+in+2016
> A 2016 estimate said the overall cost of the Chernobyl disaster was US$700 billion ...
You're taking 30 years worth of expenses and comparing them to the UK tax intake for one year. I am pretty certain the USSR didn't pay for all that up-front.
So $700b over 30 years is about $23b/year. The UK gov budget for the year you selected was about $1045b[1]. So if we are to take your Chernobyl example, it's about 2% of GDP per year. That is roughly half of what was spent on the second-smallest sector of the budget - "Public order and safety". That is a lot of money! But you're implying it would cause the collapse of the UK altogether.
As a comparison, during the 07/08 financial crisis the UK government bailed out the banks to the tune of $185b and managed to not collapse...
[1] https://www.gov.uk/government/publications/budget-2016-docum...
> You're taking 30 years worth of expenses and comparing them to the UK tax intake for one year. I am pretty certain the USSR didn't pay for all that up-front.
Didn't pay all of it ever, that's also the damages of other affected nations after the collapse of the USSR.
So, there was a de-facto if not de-jure default on that cost.
> As a comparison, during the 07/08 financial crisis the UK government bailed out the banks to the tune of $185b and managed to not collapse...
It also owned some of the banks as a result (I was personally affected by this, LLOY shares), it wasn't just a pure cost.
I note that neither of those comments invalidate my point that this would not cause the collapse of the UK ...
They are only intended to show that it is a real possibility by analogy with what happened to the USSR following Chernobyl. It would require a detailed simulation to elevate this from "vibe" to "a clear risk percentage".
I do not have sufficient grounding in any of the relevant fields to create such a simulation, so I'm limited to drawling circles on a map around the reactors, seeing what's inside, and making a best-guess as to the consequences informed more by world news than anything more precise.
You can just say "my bad, I made a mistake by comparing the 30-year cost of Chernobyl cleanup to the annual budget. I was probably wrong on that part"
The weirdly evasive language just undermines the rest of your points and makes you look a bit ... dishonest?
Noted, but I sincerely don't think this changes my point.
Depends on the radius, but it would wreck agriculture and tourism.
> We can just pick some cave in northern Canada or central sahara
You make that sound easy. Finnland did it, France did it.
But for example Germany started to look for one in 1976, failed, rebooted in 2017 and the current estimate is we might one one in 2060.
Isn’t GP’s point, that it’s already enough for those two to have solved it? Not every country with a civil nuclear program needs its own waste containment, it’s just such a small absolute quantity.
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
Anything that stops people fishing a part of the sea is probably a good thing for the environment.
But I don't think the vision here is to fill the seas with millions of machines.
I like the idea of solar and support it in general, but the implementation is some places is bizarre. Instead of building solar panels over parking lots, putting them on top of buildings, or using them as covers over fields of crops sensitive to sunlight, lots of places have clear cut forests and absolutely covered mountainsides with them. The reason being that it's cheap and out of sight for most people.
The vision now might not be to fill the sea with these turbines. But if it turns out they can be made cheaply and deployed cheaply, easily broken machines that nobody will take responsibility for will definitely be littering the oceans by the millions.
This is such a misguided concern I'm wondering if you are concern trolling...
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.
Because the amount of pollution these things generate is clearly totally negligible. Metal in the sea does not matter. And they are an alternative to burning fossil fuels which is clearly far worse.
They may not be a good commercial idea due to the maintenance cost (hence this article) but the idea that they would pollute the seas and therefore we should burn oil & gas instead completely idiotic.
They're not exactly the same thing but for comparison, France has the Rance Tidal Power Station that has been producing 250MW for 45 years. South Korean made a more powerful one at 254MW. This pilot produced 4.5MW when all 3 turbines were operating normally.
This project is interesting but all comparisons are fair with the end in mind, which is the cost per MWh or per "home" over its life. If you need 55 of those to produce 250MW you'll have to multiply the costs by 55 as well. Power also has to be available all the time, when there is no sun, no wind, no waves, etc. Nuclear and gasoline are sadly the top picks because of energy density (and in the case of gasoline also portability).
Rance and Sihwa Lake are different beasts as they require sea walls or dams, which are immensely more expensive and environmentally damaging, and have extremely limited suitable sites worldwide. They would never be built now (Sihwa is only 15 years old, but the seawall was built in 1994). They are essentially low head hydro installations fed by the tidal range.
The installation in the Pentland Firth is a fundamentally different category as it is installed in open water (albeit in a firth or channel) which is much less environmentally impactful and has 2-4 orders of magnitude more suitable sites globally.
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.
Recently saw this design where it's a ball going up and down with a chamber inside, wonder how that will fair out
What do these turbines do to Marine life? Fish, dolphins swimming next to the spinning blades. Krill, other micro marine life in the water, disrupted water currents affecting every forms of life?
Because we are not "allowed" to ask these questions, I suspect these environmental efforts are just the vehicles to make money for certain political groups. Just as "freedom on the march" is a vehicle to make money for other groups.
Who said you were not allowed to ask these questions?
Downvoting that you can observe in real-time.
I downvoted you because you played victim, not because of your opinion on energy production and ecology. I assume many did the same.
Where I live there's a tidemill that's been running for 850 years.
Still provides power today.
Current energy sources are ~all either from solar radiation (indirectly for fossil fuels) or nuclear fission. Tidal energy is cool because it is to a rough approximation from neither of them!
> It’s very hard to take what is essentially a wind turbine normally found on land
To be pedantic, a lot of wind turbines are placed out at sea.
The full quote is:
> It’s very hard to take what is essentially a wind turbine normally found on land and put it under water
With that context your comment looks pretty silly, no?
They are still often found at sea. It might have been better to write it's very hard to take what is a wind turbine normally found above water and put it under water.
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.
Aren’t we just picking up Pennys when solar and wind are available?
Because water is pretty dense, you could in theory get a lot of energy from a relatively small tidal power installation which could be an advantage in some circumstances.
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
Nice.
Tidal power only works where the geography is right. A bay with a choke point to the ocean, like this one, is needed.
Or the mouth of an estuary, or an underwater shelf where currents are forced up or down, or any stretch of water with sufficiently high tidal ranges etc.
There are plenty of places where water is naturally under pressure, tidal power is definitely something we should be pushing for more as a species.
I wish they provided pics of one underwater. I love stuff that invokes a feeling of submechanophobia
Yeah, there's something weirdly mesmerizing and terrifying about giant machines lurking underwater
It will be interesting to see how the right disparages this form of non-fossil fuel based electricity generation.
its a visual blight for scuba divers everywhere. it kills millions of fish. the wave patterns caused by the turbine cause chronic headaches for miles. the production process for the turbine actually creates more carbon emissions than just burning the equivalent of coal for 20 years
See also the Scottish company Orbital Marine Energy with their really cool floating design: https://o2-x.orbitalmarine.com/
I believe they specifically designed it to simplify maintenance
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.
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
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.
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?
this feels solvable with a cage around like you have on every pedestal fan?
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.
[dead]
Out of sight, out of mind...
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.
Doesn’t the moon move away from us?
https://public.nrao.edu/ask/what-happens-as-the-moon-moves-a...
Surely taking energy from it would make it move further away?
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-...
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
If one made it six years, it seems like it should eventually be possible to build turbines that reliably make it that long.
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.
This needs to be a reply to the original comment.
> GPs link doesn't even show what was claimed ("The other 3 have needed costly maintenance").
> complete with a retrofitted wet mate connection system, which more than halves the costs of future turbine recoveries and deployments."
Why do they need recoveries if not for maintenance? Why did they need to cut the cost of maintenance if no costly maintenance were needed?
> after being out of the water for upgrade and maintenance work."
How is this not literally validating GPs comment?
Anyone can say "the new ones won't need maintenance and the only reason we took them out was to improve them", but they could've worked on better ones and deployed them without removing existing ones. Removing existing ones mean they broke. So until the new ones last as long, GPs analysis is the correct one.
> Why do they need recoveries if not for maintenance?
Upgrades. Was already answered.
> Why did they need to cut the cost of maintenance if no costly maintenance were needed?
To improve the ROI. If maintenance is needed, it will be cheaper going forward. How often the average turbine will require maintenance is harder to determine based on the information available. We know it might be somewhere between a few years and ~6 years.
> How is this not literally validating GPs comment?
It does not say anything about maintenance being required or costly.
> Anyone can say "the new ones won't need maintenance and the only reason we took them out was to improve them", but they could've worked on better ones and deployed them without removing existing ones.
That requires more investment (the things ain't cheap), and it does not show whether successful maintenance is possible or how expensive/cumbersome that maintenance would be, which are very important pieces of information for determining ROI.
If they didn't need maintenance why upgrade them? You didn't address that part of my comment. You can put upgrades on new ones that you'll deploy and track performance of each deployed cohort. You only go and remove already deployed ones if you really have to.
>If they didn't need maintenance why upgrade them?
We don't know, but there are other reasons besides maintenance and it is a huge unfounded assumption to say that is the only reason. Upgrading an existing installation for better performance is likely orders of magnatude less expensive than building additional units, building the archor points, and emplacing them, so it could have been getting more data out of less budget.
They may not have permits/authorization for additional locations yet.
The upgrades may provide a significant ROI improvement and the only reason they didn't upgrade all of them was to leave one to look at long term reliability while sacrificing the improved ROI.
But fundamentally, we just don't know. While required maintenance is one possibility, it is by no means the only one.
as this seems test plant, research/testing seems also possible
Yes, 1 success out of 4 test flights — good news, it's possible!
So exact same results as the falcon 1. Seems like they did okay with the Falcon 9.
That's like saying if I roll 4 dice and one of them lands on a six then it should be possible to make one that only rolls sixes.
Yes exactly, see 'Loaded Dice'.
If you made 4 loaded dice and continuously rolled them for 6 years and 1 of them consistently rolled a 6 everytime then yes, it is entirely possible.
Very nicely handled! I am really puzzled why people here are so against this. There's potentially really good news for a plentiful and predictable source of renewable energy with some fairly cool tech and a bunch of HNers are angry? I don't get it.
How am I against it? I'm just pointing out that 75% of the turbines needing major disruptive maintenance within 6 years is not evidence that a 0% failure rate is possible.
I'm hoping for a good renewable energy source as well but that doesn't mean I have to accept shoddy statistics.
or, in other words, 'engineering'
Absolutely but instead of balanced cubes they're experimental turbines.
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.
One benefit that’s difficult to quantify is that the power is extremely predictable compared to other renewables.
It can be quantified by comparing it to the cost of solar or wind plus storage.
It’s not straightforward though is it. It depends on your base load profile, your ability to time shift loads, what level of modal and geographic aggregation you have etc. i.e. not something you can just stick into an LCOE calculation and call it a day.
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.
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.
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.
> That is barely enough for a fridge.
An efficient European fridge uses less than 250 kWh/a, or less than about 30W on average.
E.g. this uses 127 kWh/a: https://www.bosch-home.com/de/de/product/kuehlen-gefrieren/k...
Average electricity usage in the UK is something like 2700 kWh/y [1], which is a bit over 300 W on average. Most UK household energy use is gas.
[1] https://www.ofgem.gov.uk/information-consumers/energy-advice...
I didn't understand why UK government numbers [1] were different from ofgem's numbers, apparently the government uses mean electricity usage (total power use divided by # of households), while ofgem uses a "typical" number which is based on median values.
[2]: https://assets.publishing.service.gov.uk/media/67e3eae39c9de... - see background section
> 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.
In many countries, 1kW is more than enough to cover electricity usage in a household. https://ec.europa.eu/eurostat/statistics-explained/index.php... says “Electricity consumption per capita in the household sector in the EU in 2022 was 1.6 MWh per capita (1 584 kWh)”.
That’s about 4.3kWh/day or 180W. https://ec.europa.eu/eurostat/statistics-explained/index.php... says there were 202 million households in the EU in 2024, on a population of about 450 million, or 450/202 ≈ 2.2 persons/household.
So, on average, a household in the EU uses less than 500W of electricity.
The issue pointed out is that you're comparing average power use to maximum theoretical production. These houses are going to peak way above 500W.
If you want to compare power use of a household averaged on a year to yearly production of these turbines:
- 1.6MWh * 2.2 people per house = 3.5MWh/household
- 10GWh produced in 2023 / 3.5MWh = ~2860 households supported.
It was you that decided it was nameplate capacity. The actual statement is "producing" 1.5MW. Tidal flows are sufficiently predictable that it's not an unreasonable expectation to have reliable power outputs.
The 1.5MW number is what the generator is rated for according to the company building them [1]. i.e. it's what it's supposed to produce in ideal conditions according to the spec. Or, colloquially, the nameplate capacity.
> The actual statement is "producing" 1.5MW.
I have no doubt that the author could write that. My message points out that it simply is not true.
[1]: https://simecatlantis.com/wp-content/uploads/2016/08/AR1500-...
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.
Texas’ capacity was 113000 MW yesterday so 1.5MW doesn’t seem significant. Am I understanding this wrong?
https://www.ercot.com/gridmktinfo/dashboards
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.
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.
Can you even still buy new 1.5MW wind turbines?
Why are you comparing a single turbine in Scotland to the entirety of the state of Texas's supply (thousands of turbines)?
hundreds of thousands.
Are you really comparing a single experimental turbine's handwaved output with the consumption of an entire state with a population as big as the bigger European countries?
Yeah, and a solar panel might only produce 250 watt, that would mean solar is also not significant /s
Even that one proves it's possible, which is huge for an industry that's been stuck in pilot mode for years
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?
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.
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.
Cathodic protection is also a nice option against corrosion on stuff that's connected to the grid anyways.
speaking of carbon fiber and immersion, here's a writeup about Titan's use of carbon fiber:
https://www.popularmechanics.com/science/a60687211/titan-sub...
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.
Steel has the benefit of fatigue limit. Which means as long as the cyclic stress on steel is under a certain amount it won't fail. Aluminium has a much lower fatigue strength than steel and will always fail given enough cycles.
While rust can be a problem it can be mitigated. Also steel is easier to repair than many other materials (welding).
BTW. Aluminium does suffer from corrosion as well. I used to have racing bike, the wheel nipples (these connect the spokes to the wheel rim) used to corrode to the point where they would fail, which meant I would end up with a buckle. I ended up having both wheel rebuilt with higher quality brass nipples.
Plastics under time also suffers from a different set of issues. Plastics can become brittle. Anyone working on old computers (especially macs) can attest to this.
Corrosion, the force of water (being 800 times as dense as air and effectively incompressible, water forces can be huge), objects in the water (again, water being heavy it can move heavy objects around in its flow), fouling through, for example, algae and mussels (https://en.wikipedia.org/wiki/Fouling)
Carbon fibres tend to crack under extreme torque.
AFAIK corrosion is slower underwater. It’s all the shmutz that’s underwater - logs, rocks and boulders that get moved by these huge tidal currents.
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?
Well, they just need to use just the ones that don't require maintenance.
> 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
Over many years, I've yet to hear of an ocean based power generating system that comes anywhere near the $ per kWh cost produced by just covering some less-useful land in ground mount photovoltaics.
Private, entirely for profit companies, have recently answered large government tenders in the middle east to sell power at the equivalent of $0.05 USD per kWh. They are fairly confident that they can make a profit doing this, even with the cost to incur the long term debt to privately build a massive solar power plant.
The cumulative amount of solar power being produced within Germany right now is a good example of its practical use in a less sunny climate.
In terms of placing things in the ocean, hiring the sort of offshore work vessel with a built-in crane can go and place or remove multi ton apparatus is very costly. Maritime construction for things like laying coastal submarine cable, building piers and docks and marinas, setting and maintaining marker buoys isn't cheap.
Laying and maintaining HV AC or DC submarine cables in salt water is also particularly known to be expensive. Hiring a 36'-42' aluminum landing craft for coastal construction projects, with fuel and crew can be easily $500 an hour.
Labor and vehicle costs are greatly increased compared to doing things on dry land.
I used to think the same way, “just use cheaper solar” but I have come around to see the value. Doing science and engineering projects to explore new or different alternatives is valuable. We might find something surprising.
Having different types of power generation provides redundancy. The wind still blows at night, the tide still comes in and out when its cloudy, etc. Grid storage is nowhere near a solved problem, so something like tidal could prove less expensive than storage or overbuilding alternatives to overcome their variability problems. Even if it doesn’t end up being widely useful, it could still end up finding a use in more niche applications.
Finally, it can and will improve. 30 years ago, solar was not price competitive and decades of development and iterative improvements have changed that. We should keep developing alternatives to see their full potential.
I think the charm for a cloudy place like Scotland is that a system like this is unaffected by poor light supply. Your photovoltaics aren't going to fair nearly so well there hence this solution.
> covering some less-useful land in ground mount photovoltaics.
Doesn't even need to be less-useful land (especially in western Europe, ground is becoming a scarce resource), put PV on flat rooves or add them over open car parks. Also helps alleviate pressure on the overstressed energy grid by generating and using power more locally.
But, local power is (overall) a lot more costly than major centralized power generation projects, like a wind farm or what have you.
Ironically, renewables tend to put a different kind of stress on the grid: frequency. In Ireland the grid can't handle windy days, so there are ROCOF issues and "dispatch down" events which means clean energy is lost.
I'd expect storage/batteries can help smooth this out by providing shiftable demand/production (with the right local control software running on/near the inverter)
Eg: https://www.next-kraftwerke.be/knowledge-hub/balancing-marke...
Not sure if this is prominent in the Irish market or not
Imagine if we gave up making cars because we had some failures initially. Everything is costly in the beginning.