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Tidal energy is not renewable

cs.stanford.edu

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Re: Tidal energy is not renewable

#21

Post by archi42 »

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 produce mass/objects out of it?

If we reach peaked our energy consumption in merely 250 years, that's less than 150 times our current consumption. I didn't do the math, but would date to suggest this gives us a few years more time on this planet.

Re: Tidal energy is not renewable

#22

Post by uoaei »

NBJack wrote: post #13
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?

Air currents have a purpose, and I actually believe large scale wind farming will have negative impacts on climate. Not to mention the impact on birds killed by the things. I would even go as far to say nuclear energy has less of an impact (as long as all goes well). The question few seem to ask is should we be this (literally) power hungry in the first place?

> The question few seem to ask is should we be this (literally) power hungry in the first place?

Absolutely!! Reducing excess consumption will always be easier than making up for it later because the latter inevitably causes losses which become heat from which "useful work" can never be recovered. We can avoid those losses by simply never requiring them in the first place.

But too many have the Myth Of Progress burrowed deep into their core ideologies and will fight tooth and nail to keep the trivial conveniences they've built their daily routines around.

On your first point, though, I'm not sure it will be a net negative considering the human component in the equation, and anyway, outdoor cats are orders of magnitude worse for birds than wind turbines are, not to mention concrete jungles with no trees and high average noise levels.

Re: Tidal energy is not renewable

#26

Post by JumpinJack_Cash »

obastani wrote: post #16

> So, the 2% growth rate for world energy consumption should be a conservative assumption. An important caveat: this article assumes that energy consumption will continue to increase exponentially to get the 1000 year timeline of draining the rotational energy of the Earth.

That better be the case , we are already seeing that if the pie can't grow then we start fighting each other violently to enlarge one's piece of it.

Re: Tidal energy is not renewable

#27

Post by wcoenen »

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 million exajoules, a fraction of which reaches the surface. 5 million is much more than 474. But at a seemingly modest 2% per year growth rate (as it was between 1980 and 2006), our energy consumption will match those 5 million exajoules in less than 500 years!

Think about that: if energy consumption growth continues at the current pace, then in 500 years we'll either be using ALL solar energy received by the earth (leaving none for the biosphere), or we'll have figured out some magic technology to produce 5 million exajoules of energy per year. Assuming the magic technology, where are we going to get rid of all that extra heat? It would effectively be like having a second sun on earth, cooking us in place.

edit: I copied the numbers above from a post I wrote in 2010, so it may be a bit out of date. But Sabine Hossenfelder recently made a video where she talked about a similar timescale, i.e. boiling oceans in 400 years: https://www.youtube.com/watch?v=9vRtA7STvH4

Re: Tidal energy is not renewable

#29

Post by jccooper »

This is mostly based on the assumption of a 2% growth rate in overall energy consumption, with tidal power as an ever-growing 1% of that. The effect of covering 1% of our current energy usage would be minimal. And, likely, the ability to exploit tidal power will plateau at some (fairly small) amount, due to geographic constraints.
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