Tidal energy is not renewable • Hacker News Board

Re: Tidal energy is not renewable

#151

Post by wmf » Mon, Sep 04, 2023, 9:55 PM UTC

giantrobot wrote: post #90

eldaisfish wrote: post #79

Earlier quoted context omitted.

the rest of the world still has to catch up to these levels. Granted, they won't get to the absurd wastage levels of north america but they will continue to consume more energy. Just looking at the energy levels in one country doesn't tell you much.

Developing countries will increase their energy usage but have the benefit of buying things from developed countries. As we've seen developing countries today have been able to jump right to modern technology for infrastructure. They didn't need to build massive lines of analog telecommunications, they just jumped right to cellular and satellite technology. They can jump right to solar and other renewables as they el…

This doesn't help much on the demand side but it will help if they go straight to clean energy.

Re: Tidal energy is not renewable

#152

Post by dredmorbius » Mon, Sep 04, 2023, 9:57 PM UTC

btilly wrote: post #71

jval43 wrote: post #5

Earlier quoted context omitted.

Isn't wind created by temperature and pressure differentials between regions? How much is due to earth's rotation?

A lot. Look up Hadley cells. https://groups.seas.harvard.edu/climate/eli/research/equable... Warm air rises near the tropics, rotating with the Earth. It then goes towards the temperate zone, still rotating with the Earth to form the jet stream. It then falls, creating the trade winds as it slows down. It then is sucked back towards the tropics, creating a reverse trade wind because it is only going as fast as the te…

Hadley cells determine wind patterns but not the energy content of the wind, to any appreciable degree, which comes from solar flux.

Wind energy is solar energy once removed.

Wave energy is solar energy twice removed (solar -> wind -> waves).

Re: Tidal energy is not renewable

#153

Post by dredmorbius » Mon, Sep 04, 2023, 9:58 PM UTC

uoaei wrote: post #3

Then technically neither is wind, since it slows down surface air currents and widens the effective boundary layer of the atmosphere. Technically-technically, no forms of energy "generation" (technically just conversion) are 100% efficient so something is always lost to heat. I guess the important question is, what is the net effect in changing that kind of energy into purely thermal energy?

No, wind is ultimately fed by solar energy and is driven by differential heating of Earth's atmosphere and surface.

That is, there's a constant incoming energy flux. That's not to say that there isn't some maximum amount of available wind energy, or some maximum amount of energy that can be extracted from wind without causing other effects (even excepting, say, bird strikes and the like).

But wind isn't "used up", there will be more wind tomorrow, so long as the sun shines and there's an atmosphere.

Re: Tidal energy is not renewable

#154

Post by dools » Mon, Sep 04, 2023, 9:59 PM UTC

giblfiz wrote: post #67

Wait, isn't most of that "tidal power" that we would be capturing going into grinding rocks into sand along the coast?

Imagine the rock buildup!

Re: Tidal energy is not renewable

#155

Post by ben_w » Mon, Sep 04, 2023, 10:02 PM UTC

api wrote: post #136

blake1 wrote: post #32

The single most important assumption in this paper is that energy consumption will increase by 2% per year. This kind of exponential growth leads to outlandish estimates for the amount of tidal energy that society will demand. Energy consumption has decoupled from population growth rates and economic growth. How much energy will we consume in 1,000 years? Most projections of the population have it stabilizing at arou…

20000X the energy of a current human shows how absurd it would be for growth and energy use to not decouple. I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? I suppose spacefaring humans might use that kind of power but if they are living in space they are no longer part of the biosphere of Earth.

> I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day?

Sure, why not?

It's absurd today for the average person, but it's the kind of thing rich people get to do already, and looking at the rich today is a decent (though imperfect because inflation and invention don't work like that) hint for what normal people can afford in a richer future.

Re: Tidal energy is not renewable

#156

Post by [deleted] » Mon, Sep 04, 2023, 10:04 PM UTC

blake1 wrote: post #32

The single most important assumption in this paper is that energy consumption will increase by 2% per year. This kind of exponential growth leads to outlandish estimates for the amount of tidal energy that society will demand. Energy consumption has decoupled from population growth rates and economic growth. How much energy will we consume in 1,000 years? Most projections of the population have it stabilizing at arou…

[deleted]

Re: Tidal energy is not renewable

#157

Post by mattmaroon » Mon, Sep 04, 2023, 10:07 PM UTC

ben_w wrote: post #155

api wrote: post #136

Earlier quoted context omitted.

20000X the energy of a current human shows how absurd it would be for growth and energy use to not decouple. I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? I suppose spacefaring humans might use that kind of power but if they are living in space they are no longer part of the biosphere of Earth.

> I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? Sure, why not? It's absurd today for the average person, but it's the kind of thing rich people get to do already, and looking at the rich today is a decent (though imperfect because inflation and invention don't work like that) hint for what normal people can afford in a richer future.

Aviation historically, has not gotten cheaper overtime. If anything, it is more expensive. Only rich people had planes 100 years ago and only rich people own them now and the trend line doesn’t indicate it’ll be different in another hundred.

Re: Tidal energy is not renewable

#158

Post by ben_w » Mon, Sep 04, 2023, 10:07 PM UTC

7speter wrote: post #106

Nition wrote: post #78

Earlier quoted context omitted.

Humanity needing that amount of energy seems obviously absurd, but then I suppose a CPU with 100 billion transistors seemed clearly impossible in 1960. Maybe a few hundred years from now, Internet archaeologists will find your comment as one of the first harbingers of the coming World Energy Crisis, much as we see the 1912 Rodney & Otamatea Times "Coal Consumption Affecting Climate" snippet today.[0] Then they'll fin…

Right now, the minds that conceive of any practical way of a spacecraft reaching the speed of light says we need the energy of multiple suns to be able to even reach that speed, so who knows where humans are in 500 years…

Right now, most of the suggestions for going at actually the speed of light (rather than just very close) require a negative energy, which is much much harder than even a huge positive energy as nobody has any idea if it's even possible[0] let alone how.

[0] no a Casimir cavity won't do that: https://kitsunesoftware.wordpress.com/2017/04/20/can-a-casim...

Re: Tidal energy is not renewable

#159

Post by zamadatix » Mon, Sep 04, 2023, 10:10 PM UTC

crazygringo wrote: post #129

MichaelDickens wrote: post #86

Earlier quoted context omitted.

According to the paper, tidal energy has a total capacity of 10^29 Joules, and current global energy consumption is 10^21 Joules per year, so if we converted 100% of current energy consumption to tidal energy and didn't increase it at all, it would last 10^8 = 100 million years (rounded to the nearest power of 10). Equivalently, after 1000 years, we'd see a rotational slowdown of around 0.001%.

Thanks so much. That feels much more in line with intuition. So maybe not technically renewable, but many orders of magnitude more renewable than e.g. fossil fuels...

Any useful interpretation of renewable energy has to do with purely human timeframes as thermodynamics doesn't allow for any energy source to be endlessly renewable. "If I use this source today will more of it naturally be there tomorrow" type consideration, otherwise you end up with a definition which either includes things like fossil fuels as renewable because you can wait millions of years or excludes things like sunlight because it won't be there in 10 billion years.

Re: Tidal energy is not renewable

#160

Post by anonylizard » Mon, Sep 04, 2023, 10:14 PM UTC

smcin wrote: post #144

popol12 wrote: post #65

Earlier quoted context omitted.

A Google search for “china children per woman” gives me 1.705 Are you talking about something else ?

The Google hit China TFR 1.705 for 2023 is bogus (and 2023 isn't even over yet, which should have alerted you), it's single-sourced from macrotrends.net which is quoting an old (pre-pandemic) UN forecast; you can see from their graph their (forecasted) numbers for 2020-2 turned out totally wrong. Lots of other sites are quoting the Google and macrotrends as fact. So now the #1 Google hit on that is misinformation. (A…

Its now dropping even lower in 2023, long after the lockdowns have ended.

Turns out the East Asian style of hyper-competitive child rearing has its downsides, namely the high costs dissuade parents from having children altogether.

China faces every antinatal problem the west does, except far worse.

1. Extremely high housing prices making family formation expensive

2. Small apartments suppress large family formation (Seen in Europe)

3. General collapse of marriage rates due to changing incentives and thus moral norms

4. Higher education decreasing fertile years.

5. Economic depression, especially for young people, euro debt crisis level of youth unemployment.

You add to that, that China still officially has a 3-child policy (not that many people even have 2), because the birth control bureaucrats still need a job.

China is probably 2nd lowest in the world behind South Korea, and will stay there, if not