Tidal power - an existential threat to humanity?

[Laconian]

It is incorrect to consider tidal power as a renewable, green energy source. Using tidal energy poses more severe problems than using fossil fuels. This study provides quantitative evidence of how using tidal energy can destroy the environment in a short amount of time. Tides are induced by the rotation of the Earth with respect to the gravity of the Moon and Sun. The rotational energy of the Earth is naturally dissipated by tides. Consuming tidal energy reduces the rotational energy, increases the energy loss rate, and decelerates the rotation of the Earth. Based on the average pace of world energy consumption over the last 50 years, if we were to extract the rotational energy just to supply 1% of the world's energy consumption, the rotation of the Earth would lock to the Moon in about 1000 years. As a consequence, one side of the Earth would be exposed to the Sun for a much longer period than it is today. The temperature would rise extremely high on that side and drop extremely low on the other side. The environment would become intolerable, and most life on Earth could be wiped out.


https://cs.stanford.edu/people/zjl/tide.html

[Morris Minor]

We've heard about the birds & the noise & the aesthetics, but I wonder if wind power similarly has any non-obvious drawbacks.

[Laconian]

I don't know if wind power would be any worse than, say, growing a forest or erecting buildings?

[CaminoRacer]

Tides slow down the rotation. If we capture energy from the tides, wouldn't that speed up the rotation?

I guess it depends on the friction of the generator. Is the tide spinning the generator applying torque to the earth? And is that torque more or less that the natural tide's frictional torque?

[Eye of the Tiger]

So, back to nuclear.

[AutobahnSHO]

We've heard about the birds & the noise & the aesthetics, but I wonder if wind power similarly has any non-obvious drawbacks.

Long long time ago I had an idea for science fiction story- that enough windmills were built that it slowed the winds across the globe enough to mess up the natural weather patterns and entire continents went desert...

On the opposite end of the spectrum there's one of the worst movies I've ever paid $1 in the DVD bargain bin for:
https://en.wikipedia.org/wiki/Slipstream_(1989_film)

[GoCougs]

We've heard about the birds & the noise & the aesthetics, but I wonder if wind power similarly has any non-obvious drawbacks.

Yes. Turns out not only are the wind turbines hard on birds themselves, they're WAY harder on insects, which not only affects birds for a double whammy (local starvation and greatly affecting migration) but biodiversity in general, since most animals eat a LOT of insects - lizards, snakes, bats, even bears.

[Laconian]

Pesticides got to the insects first.

[AutobahnSHO]

It's funny how a shift in ecostructure takes a hit in everything!

I've seen talk locally about all the wildlife displaced by new housing developments creates havoc on other roads.

Amazing the difference in our yard between hard clay soil and where the layers of pine needles create a natural compost system where we can dig up real "dirt"...

[FoMoJo]

I would think that the impact of tides on East coasts would have have a "pushing" impact on Earth's rotation whereas on West coasts the effect would be less as the water isn't being "pushed".

[GoCougs]

Pesticides got to the insects first.

Yes, but without pesticides, a goodly portion of the planet would literally starve, and wind power with anything close to the current tech, on a macro scale, is a not a plus.

[SJ_GTI]

It's an interesting theory and I admit I cannot follow the math that it relies on, but I will say that I find it difficult to conceptualize how extracting a small portion of the energy created by tides from the water could have such a dramatic impact on how fast we tidally lock to the sun or the moon.

In fact, if I understand the physics of rotational inertia, if your generators are creating the friction by slightly holding back the tide, that could actually reduce the slowing of our rotation because that would mean slightly less mass would be pulled toward away from the center of the earth's mass making the earth slightly less oblong itself, which would make us spin very slightly faster.

Some googling also shows that while the moon is certainly the most consistent reason for change over long periods, more local events (volcanoes, earthquakes, el nino's) can actually have a greater immediate impact in a given year. In other words, the earth doesn't always slow down every year, some years we spin a little faster, other years we spin a little slower.

[GoCougs]

It's an interesting theory and I admit I cannot follow the math that it relies on, but I will say that I find it difficult to conceptualize how extracting a small portion of the energy created by tides from the water could have such a dramatic impact on how fast we tidally lock to the sun or the moon.

In fact, if I understand the physics of rotational inertia, if your generators are creating the friction by slightly holding back the tide, that could actually reduce the slowing of our rotation because that would mean slightly less mass would be pulled toward away from the center of the earth's mass making the earth slightly less oblong itself, which would make us spin very slightly faster.

Some googling also shows that while the moon is certainly the most consistent reason for change over long periods, more local events (volcanoes, earthquakes, el nino's) can actually have a greater immediate impact in a given year. In other words, the earth doesn't always slow down every year, some years we spin a little faster, other years we spin a little slower.

The Earth's rotation would slow unnatural fast because the energy absorption by the tidal generators, though tiny, would be ever constant - death by a 1,000 paper cuts.

The conceptualization is that standing on the Earth, it appears as if the oceans are moving to cause the tides. However, from a distant macro view, the oceans are actually stationary and the Earth is moving/spinning, causing the tides (see the animation in the section, "How Are Tides Formed?"). From this distant macro view, the tidal generators are in effect braking the rotating Earth against the stationary oceans.

[SJ_GTI]

The water is definitely spinning. Its just that liquid is able to become "less round" than the crust underneath it, so I supposed from a far enough distance away it might appear as if it isn't spinning. But each of the individual molecules that make up the ocean are indeed spinning around like the rest of the surface of the earth.

Even if there was no liquid water on the earth's surface the moon and the earth would still eventually tidally lock. In fact we often forget that the earth itself is not a solid piece of rock with some water on top. It is mostly a molten semi-liquid ball of (mostly) rock.

[GoCougs]

"These bulges (of the oceans) remain stationary with respect to the Earth's rotation. Hence, local observers on Earth see periodic rises and falls of sea levels."

The tidal generators brake the rotating Earth against these stationary "bulges" in the oceans, unnaturally slowing the Earth down.

Not an expert in the slightest, but this is what the paper claims.

[FoMoJo]

"These bulges (of the oceans) remain stationary with respect to the Earth's rotation. Hence, local observers on Earth see periodic rises and falls of sea levels."

The tidal generators brake the rotating Earth against these stationary "bulges" in the oceans, unnaturally slowing the Earth down.

Not an expert in the slightest, but this is what the paper claims.

Certainly the Ocean waters are moving in accordance to the Earth's rotation; essentially they are stationary in the manner of the land masses; but they jiggle around due to various disturbances.  The tide, of course is the bulge created by the Moon's gravitational pull which gives the appearance of a moving wave.  As the Earth rotates towards the East, the assumption would be that, in the Atlantic, the bulge in the Ocean would appear from the West Coast of the European/African coasts and move towards the East coast of North and South America.  As the water is being "sucked" from the West costs of Europe and Africa creating the tidal bulge, and the bulge is driven into the East coasts of North and South America, one would assume that the dynamics on the different coasts would be much different; the pushing into the East coasts of North and South America may well cause a slight increase in rotation whereas the pulling from the West coasts of Europe and Africa may well have a tendency to decrease rotation; by miniscule values.

Of course, this is only assumption based on a complete lack of specific knowledge.

[SJ_GTI]

Again, like all of us, not an expert, but the bulge is the result of the moon causing water that is closest to it to spin slightly slower than the rest of the earth for a bit, but I guess where I get confused is that once those molecules move away from the moon each of them then spins slightly faster than the earth as the gravity of the earth pulls them down back toward the center of mass. Hence why the tide gets higher.

I do see how tidal generators could very slightly impact the rotation of the earth (no energy is free), but the math of how it could be that significant is beyond me.

I think it would take someone who is very talented at math and the physics of the moon to really go through a paper like that and either confirm or critique it.

[GoCougs]

I think you're getting hung up on the "spinning." The bulges are stationary, thus, the tides are caused by the Earth rotating against these stationary bulges (and the bulges = slightly different depths of the oceans = tides). The frame of reference is not from the POV of being on the surface of the Earth.

The math and equations are only used to estimate the time to catastrophe, and even then only high school level math based on equations known for centuries. The concept of how the tides work is mathless and has also been known for centuries. The energy bleed (and thus slow down) by the tidal generators is a minor derivation.

So, confirmed, c. 1680 (with leeway given that the ecological and biological data used for estimates of the Earth's inertia and rotational speed are correct, and they probably are, because Stanford).

[SJ_GTI]

I know what I tide is.

The water is not stationary. The bulge appears to be stationary from a distance because the water is more malleable than rock and therefore the oblong nature of its rotation is more obvious. Even if there was no water on the earth's surface, though, the earth would still have an oblong shape, just as the moon has a slightly oblong shape from the pull of the earth. Given enough time, the two bodies will both tidally lock to each other, it would just take longer.

It is understood that the oceans add to the slowdown of the earth rotation, but it is not the only cause. Again, the quick googling that I did showed that it is not well understood how much the ocean slows down the earth. In fact we know now that the earth does not slow down on a consistent basis (in fact some years it speeds up). This is thanks only to satellites which can make measurements precise enough to demonstrate the data.

So no, I do not take it on faith that the math is so simple and is easily derived based on known quantitative measurements of the oceans impact. I do believe it can be reasonably estimates. I do not know if this person is doing so because I am not familiar enough with the math or the physics in question. He might be right, but it is a pretty big discovery if true, so it should be big news if/when other people confirm his math. He says he has known this from the 1990's, so I am surprised no one has confirmed (or critiqued) his discovery yet.

[CaminoRacer]

The earth rotating around the sun is what causes the spin. The tides slow the spin. Slowing the tides = slowing the slowing of the spin = net gain in spin?

[veeman]

A thousand years from now?  HaHa.

https://www.youtube.com/watch?v=KXzNo0vR_dU

[FoMoJo]

I know what I tide is.

The water is not stationary. The bulge appears to be stationary from a distance because the water is more malleable than rock and therefore the oblong nature of its rotation is more obvious. Even if there was no water on the earth's surface, though, the earth would still have an oblong shape, just as the moon has a slightly oblong shape from the pull of the earth. Given enough time, the two bodies will both tidally lock to each other, it would just take longer.

It is understood that the oceans add to the slowdown of the earth rotation, but it is not the only cause. Again, the quick googling that I did showed that it is not well understood how much the ocean slows down the earth. In fact we know now that the earth does not slow down on a consistent basis (in fact some years it speeds up). This is thanks only to satellites which can make measurements precise enough to demonstrate the data.

So no, I do not take it on faith that the math is so simple and is easily derived based on known quantitative measurements of the oceans impact. I do believe it can be reasonably estimates. I do not know if this person is doing so because I am not familiar enough with the math or the physics in question. He might be right, but it is a pretty big discovery if true, so it should be big news if/when other people confirm his math. He says he has known this from the 1990's, so I am surprised no one has confirmed (or critiqued) his discovery yet.

Maybe he just misplaced a decimal point.  Instead of a thousand years, it could be a billion years.

[GoCougs]

I know what I tide is.

The water is not stationary. The bulge appears to be stationary from a distance because the water is more malleable than rock and therefore the oblong nature of its rotation is more obvious. Even if there was no water on the earth's surface, though, the earth would still have an oblong shape, just as the moon has a slightly oblong shape from the pull of the earth. Given enough time, the two bodies will both tidally lock to each other, it would just take longer.

It is understood that the oceans add to the slowdown of the earth rotation, but it is not the only cause. Again, the quick googling that I did showed that it is not well understood how much the ocean slows down the earth. In fact we know now that the earth does not slow down on a consistent basis (in fact some years it speeds up). This is thanks only to satellites which can make measurements precise enough to demonstrate the data.

So no, I do not take it on faith that the math is so simple and is easily derived based on known quantitative measurements of the oceans impact. I do believe it can be reasonably estimates. I do not know if this person is doing so because I am not familiar enough with the math or the physics in question. He might be right, but it is a pretty big discovery if true, so it should be big news if/when other people confirm his math. He says he has known this from the 1990's, so I am surprised no one has confirmed (or critiqued) his discovery yet.

You should write him a letter.

[SJ_GTI]

The earth rotating around the sun is what causes the spin. The tides slow the spin. Slowing the tides = slowing the slowing of the spin = net gain in spin?

The earth's rotation isn't from going around the sun, the sun actually slightly slows down the earth's rotation in the same way the moon does (although to a much smaller degree). Given enough time the earth would tidally lock to the sun if there was no moon. Mercury, for instance, is already tidally locked to the sun because the sun's gravity is so much stronger to Mercury. That being said, the Earth is spinning so fast that the sun will likely die before the Earth could become tidally locked. I remember hearing one theory on why the earth is spinning so fast is because of the initial impact between the two masses that eventually became the Earth and the Moon. It was an indirect hit so it caused the main mass of "stuff" that coalesced back into the earth to spin super fast.

[Morris Minor]

The next challenge will be to figure out exactly where the narrow band of habitable land will be. And then start buying up the real estate. It will be called Morrisania. My descendants will worship me and be wealthy beyond imagining.

[ChrisV]

Yes. Turns out not only are the wind turbines hard on birds themselves, they're WAY harder on insects, which not only affects birds for a double whammy (local starvation and greatly affecting migration) but biodiversity in general, since most animals eat a LOT of insects - lizards, snakes, bats, even bears.

Do wind turbines really kill thousands of birds?

Yep, they sure do, tens of thousands, in fact.

And it's just fascinating to me how many people who generally don't worry that much about the ecosystem suddenly become bird conservationists when people are promoting renewable power.

Estimates are fuzzy, but it looks like somewhere between 140,000 and 500,000 birds are killed by wind turbine collisions in the US every year. Definitely a concern (and something that design changes are helping to ameliorate.

Coal-powered plants are responsible for about 8 million bird deaths a year, in the United States. But I'm sure everyone who's concerned about wind turbines has been protesting coal plants for years to protect the birds, yes?

Or maybe not. After all, collisions with windows is estimated to kill a billion birds in the US every year. So surely, people would be advocating to redesign windows to protect the birds first, right?

While we're on the subject, house cats in the US kill about 2.4 billion birds a year.

So, if half a million dead birds is an unacceptable state of affairs, that we have to do something about right away, people must be absolutely losing their minds about housecats, give that the problem is literally 5,000 TIMES bigger.

Guess I must have just missed that whole social movement. Weird.

[GoCougs]

Do wind turbines really kill thousands of birds?

Yep, they sure do, tens of thousands, in fact.

And it's just fascinating to me how many people who generally don't worry that much about the ecosystem suddenly become bird conservationists when people are promoting renewable power.

Estimates are fuzzy, but it looks like somewhere between 140,000 and 500,000 birds are killed by wind turbine collisions in the US every year. Definitely a concern (and something that design changes are helping to ameliorate.

Coal-powered plants are responsible for about 8 million bird deaths a year, in the United States. But I'm sure everyone who's concerned about wind turbines has been protesting coal plants for years to protect the birds, yes?

Or maybe not. After all, collisions with windows is estimated to kill a billion birds in the US every year. So surely, people would be advocating to redesign windows to protect the birds first, right?

While we're on the subject, house cats in the US kill about 2.4 billion birds a year.

So, if half a million dead birds is an unacceptable state of affairs, that we have to do something about right away, people must be absolutely losing their minds about housecats, give that the problem is literally 5,000 TIMES bigger.

Guess I must have just missed that whole social movement. Weird.

Well, yes, to be fair, I'm not hung up birds (or insects), but the point is wind power highlights the simple fact The Planners didn't plan (and were essentially paid not to, given the untold billions $ artificially thrown at them).

But you're implicitly correct - wind power is as big a pig-in-a-poke as any of the them even without the unforeseen ecological blow back:

[r0tor]

Well, yes, to be fair, I'm not hung up birds (or insects), but the point is wind power highlights the simple fact The Planners didn't plan (and were essentially paid not to, given the untold billions $ artificially thrown at them).

But you're implicitly correct - wind power is as big a pig-in-a-poke as any of the them even without the unforeseen ecological blow back:

Ever see what happens to the ash from a coal plant?

Nuclear waste from a nuclear plant?

Fracking juice from natural gas extraction?

[GoCougs]

Ever see what happens to the ash from a coal plant?

Nuclear waste from a nuclear plant?

Fracking juice from natural gas extraction?

I must not have made my point clear - forgive me.

This unarguable sin of "renewables" is that at the very least, in total, they are not better than coal/nucular/NG, plus, they've siphoned untold billions $$$ (maybe a few trillion $$$ at this point) and a few decades of engineering from improving the use of coal/nucular/NG.

[r0tor]

I must not have made my point clear - forgive me.

This unarguable sin of "renewables" is that at the very least, in total, they are not better than coal/nucular/NG, plus, they've siphoned untold billions $$$ (maybe a few trillion $$$ at this point) and a few decades of engineering from improving the use of coal/nucular/NG.

I'll take degrading pits of turbine blades over Mt Yucca or contaminated ground water from ash and fracking juice dumps.