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Tidal energy is not renewable

cs.stanford.edu

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Re: Tidal energy is not renewable

#51

Post by azernik »

PUSH_AX wrote: post #40
wcoenen wrote: post #27

I'm not sure the author realized this, but they're actually making a statement about how crazy exponential growth is. Not about the sustainability of tidal power. This becomes obvious once you look closer at what that 2% growth rate (as assumed in the post) implies. Our global energy consumption in 2008 was estimated to be 474 exajoules. The total energy received by the earth from the sun during a year is about 5 mil…

Isn't it more likely that demand will just outgrow supply? Energy poverty seems like a classic "planet Earth" kind of thing.

Even more likely is that, as we're already seeing in rich countries, demand does not continue to grow exponentially and economic growth mostly happens in non-energy-intensive sectors.

Re: Tidal energy is not renewable

#53

Post by coldcode »

bobthepanda wrote: post #45
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…

The UN has revised peak projections down several times; the peak is now expected at 10 billion.

More countries are now sub-2.0 replacement, China is down to 1.09 so the peak is unlikely to get much more than that.

Re: Tidal energy is not renewable

#54

Post by Zenst »

So they postulate how the moon will in 1000 years become stationary in orbit due to the tidal energy extraction as to why tidal energy is not renewable. Sorry but I'd need a few more than one institution to be backing this. Otherwise, it seems a bit too reaching to be anything other than a great plot for some cheesy disaster movie that they have phases of doing.

[EDIT - Reversed AI's rewrite of my humble English, raw best with all its flaws, and whilst AI version good, just had an air of sterility and not me.]

Re: Tidal energy is not renewable

#56

Post by Guvante »

archi42 wrote: post #21

One thing I notice is the assumption of unlimited exponential growth by 2% per year. That's a huge fallacy. Quick check, yeah, 1.02^1031 = 735,829,316. I'm pretty sure we will be using magnitudes more energy than today because we're more people and hopefully with better living standards for everyone. But even then that's a lot. And on that scale I'm not entirely sure where the whole energy should go to... Maybe produ…

Was curious so did the math backwards assuming the previous 1000 years had a 2% growth rate.

The world used 9,717 million tons of oil equivalent in 2017.

Plugging in our growth rate that would mean the world used the equivalent of 13 tons of oil in 986 which is 515.84 million BTU.

US residents making While we can argue specifics 10 households worth of fuel sounds a little low for a world with a population of 390 million.

Re: Tidal energy is not renewable

#57

Post by gcanyon »

wcoenen wrote: post #27

I'm not sure the author realized this, but they're actually making a statement about how crazy exponential growth is. Not about the sustainability of tidal power. This becomes obvious once you look closer at what that 2% growth rate (as assumed in the post) implies. Our global energy consumption in 2008 was estimated to be 474 exajoules. The total energy received by the earth from the sun during a year is about 5 mil…

“the rotation of the Earth would lock to the Moon in about 1000 years.” — based on unlimited exponential growth. That’s not worthy of a high school term paper, let alone the work of a PhD. Thanks for saving me the read.

Re: Tidal energy is not renewable

#58

Post by crazygringo »

Tons of comments here highlighting that 2% annual growth rate in energy consumption is ludicrous.

But so what if we made a more reasonable assumption that annual energy usage will stabilize at, say, 5X of what it is currently, and the (unreasonable) assumption that we get 100% of that energy from tides.

Then how much of a rotational slowdown do we get after 1000 years?

Re: Tidal energy is not renewable

#59

Post by hn_throwaway_99 »

joelthelion wrote: post #49

Issues with exponential growth set aside, does wind power suffer from the same problem? If I understand correctly, wind mostly caused by the coriolis force, which is a consequence of the earth's rotation. Would building too many wind turbines slow down earth's rotation?

> If I understand correctly, wind mostly caused by the coriolis force, which is a consequence of the earth's rotation.

You understand incorrectly. Wind is largely a form of solar energy. The sun heats the earth and its atmosphere at different rates depending on the location, and wind is primarily the result of temperature differentials.

The Coriolis effect can definitely affect how wind behaves, but it doesn't provide the energy. E.g. a hurricane's winds travel in a circle/spiral due to the Coriolis effect, but a hurricane is a heat engine that gets its energy from the sun heating the oceans.

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