Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Tidal energy is not renewable

cs.stanford.edu

Post reply on HN
Print view View original

311–320 of 350 posts

Re: Tidal energy is not renewable

#311

Post by dredmorbius »

pcthrowaway wrote: post #228
dredmorbius wrote: post #219

Earlier quoted context omitted.

That energy is already present in the environment, as kinetic energy of wind, which will ultimately be reduced to entropic heat. A wind turbine doesn't affect that fact, though it may change the location at which the kinetic -> thermal energy transformation occurs. The more likely impact would be of wind turbines removing sufficient energy from wind that thermal transport of the atmosphere itself is disrupted, though…

Yeah I was specifically considering that reducing the "windiness" of an area would increase the temperature > A 2018 study estimated that generating electricity demand with wind power in the United States would warm surface temperatures by 0.24 degrees Celsius https://www.instituteforenergyresearch.org/renewable/wind/wi...

Fair enough.

Re: Tidal energy is not renewable

#312

Post by Baeocystin »

detourdog wrote: post #280
Baeocystin wrote: post #118

Earlier quoted context omitted.

Minus the tiny fraction embodied in global temperature increases, all of it. It's the same reason that the Earth radiates exactly as much energy as it receives from the sun, just a larger number of lower energy, higher entropy photons. What the sun really provides is a source of low entropy.

Wouldn't the earth actually release more energy than it absorbs? My thinking is that the energy that got absorb in other processes such a photosynthesis is a delayed release. The energy released must have some time delay. Maybe it all averages out overtime. Difficult problem I wonder if it is worth answering.

Well, if we wanted to really get in to the details, the Earth is releasing more energy than it receives from the sun simply because it is also cooling. The core grows by about a few mm a year because of this, IIRC.

With a brief, 60 million year time frame exception during the Carboniferous, though, the energy stored in life processes is a wash. Assembly and decay are a net balance, and life itself is a strong driver of entropy, so I wouldn't be surprised at all if, on the whole, the biosphere is a net energy sink.

Re: Tidal energy is not renewable

#313

Post by codethief »

joak wrote: post #187
midasuni wrote: post #177

Earlier quoted context omitted.

Where does the energy go then? EM radiation leaving the planet?

Chemical energy. Like the plants, they take sun energy and store it as chemical energy. We could do the same, take CO2 and water and make CH4 and oxygen (electrolysis + Sabatier reaction) and make plastic. Or take ore, aluminum oxide and iron oxide, and "unburn" them releasing again oxygen (we already do that) etc... We mostly use energy to manufacture things. Life takes energy and lowers the entropy of the planet. W…

> Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?

Reducing entropy necessarily produces waste energy + entropy elsewhere. So the technical reason this cannot be done at the planetary scale is called Second Law of Thermodynamics.

Yes, we could try to put all that excess entropy & heat into space but there are limits to that (Stefan-Boltzmann law, among other things).

Re: Tidal energy is not renewable

#314

Post by codethief »

XorNot wrote: post #287
codethief wrote: post #268

Earlier quoted context omitted.

Most of that incoming heat is reflected / radiated off actually. It doesn't "stay" on Earth. https://en.m.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law

That is literally what I said.

My apologies then, I understood your comment differently!

Re: Tidal energy is not renewable

#315

Post by marsa »

megablast wrote: post #254
paulryanrogers wrote: post #199

Earlier quoted context omitted.

Exceptions like 10 EUR flights aren't sustainable. They're just auctioning off empty seats to cut costs. The comparison was conceptual thing to similar thing. Only the rich own and operate private planes, that hasn't changed. The fact that other, more sophisticated planes exist doesn't undermine the point. There are also diminishing returns. And past leaps in lifestyles aren't guaranteed to continue the same trends,…

> They're just auctioning off empty seats to cut costs. No, they are selling off seats that aren't taken. They are making more money since those seats would be empty. Cutting costs would not be selling the seats and saving on fuel.

eh are they really making more money with 9,99 tickets or are they just losing less money (on that particular flight i mean)

Re: Tidal energy is not renewable

#316

Post by Nevermark »

onlyrealcuzzo wrote: post #226
RetroTechie wrote: post #104

Earlier quoted context omitted.

> The single most important assumption in this paper is that energy consumption will increase by 2% per year. There's a 2nd big assumption: That tidal energy extracted is additional Earth's rotational energy loss above what Earth does by itself. According to the paper, tidal energy is dissipated through friction between ocean water & the seafloor. This dissipated energy subtracts from Earth's rotational energy. And s…

It's a bit absurd the idea that humans living on earth are going to produce more energy than the Sun. Maybe I'm naive and simple minded. But that just seems insane. If I'm doing the math right, at 2.3% growth = we produce more energy than the Sun in 4500 years. It doesn't matter how many years it is. It's never happening. Just look at how damn hot and inhospitable the sun is. We're not producing more energy here! It'…

100-500 years from now is enough time for AI to develop small nuclear and/or laser sail micro spacecraft that can colonize other systems at a good fraction of the speed of light.

Which would leave 4000 years or so to colonize every system with 1000 light years.

In each system collecting and engineering with low gravity material (asteroids, centaurs, smaller moons, etc.) and using that to capture solar energy will get routine.

Gas giants are basically massive hydrogen nuclear energy depots.

Earth and even our solar system don’t form any kind limit to resource growth on time scales like that.

Re: Tidal energy is not renewable

#317

Post by [deleted] »

svnt wrote: post #165
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…

> gets us to about 150 trillion humans in 1,000 years I realize the big issue is settled here but just to scope this detail: the total land area of earth is coincidentally approximately 150 million km^2 At 150 trillion humans each human would get just about a square meter. Many of those square meters are uninhabitable.

[deleted]

Re: Tidal energy is not renewable

#318

Post by dredmorbius »

theskypirate wrote: post #305
dredmorbius wrote: post #230

Earlier quoted context omitted.

One problem with "grow quickly, then switch", is that it often leads to high-growth institutions, factions, ideologies, and infrastructure. Countries which grow quickly bake those assumptions into financial, industrial, economic, and political policies. They create companies, regulatory bodies, and financial systems which are predicated on growth. They create economic ideology and the mechanisms for promulgating it w…

Japan essentially reached full stagnation in the 90's and has continued to stagnate to the present day. Transition simply happens and society adjusts.

That's part of it.

Japan also consciously entered on a relatively lower-energy path than the US, largely through energy and vehicle taxation and licencing practices, though there were others. That's not to say Japan doesn't have a large number of automobiles, or a strong automobile sector. It does.

But domestic autos tend to be smaller than those made for export elsewhere, there's a tremendous domestic transit system (famously the Shinkansen), and Japan's electronics industry (with hits and misses) was the result of a deliberate government-directed policy toward more efficient resource utilisation over simply mass consumption.

Not perfectly achieved, by any means, but a contrast to policies elsewhere.

Re: Tidal energy is not renewable

#319

Post by smcin »

anonylizard wrote: post #160
smcin wrote: post #144

Earlier quoted context omitted.

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 (…

When a country makes the one-way generational jump(s) from a TFR of 3 to 2 and then sub-2, and to a post-industrial economy, a bunch of near-irreversible changes set in, from cost inflation and scarcity of education, expectations of years of education and marriage, apartment size etc.

Scott Galloway (and others, like Elizabeth Warren) have been saying this, about the US, repeatedly: US education costs rose (or at least, were allowed to rise by the politicians who were nominally regulating them) by 1400% since the 1970s [https://www.profgalloway.com/inflated/]. This was not sensible policy but if GDP growth via financialization of (third-level) education etc. is your economy's chosen indicator, it's what you get.

Anyway the low TFR is not necessarily a demographic crisis, it's up to the country whether it lets its population decrease (Japan, China), or uses immigration to sustain whatever its target population growth is (US, Canada, EU, SG, Aus).

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

You're getting the direction of causality wrong: apartment size was a reaction to the decrease. Contraception, more years of education and other social changes were the drivers of smaller apartment sizes, not the effect.

Re: Tidal energy is not renewable

#320

Post by Brusco_RF »

Baeocystin wrote: post #312
detourdog wrote: post #280

Earlier quoted context omitted.

Wouldn't the earth actually release more energy than it absorbs? My thinking is that the energy that got absorb in other processes such a photosynthesis is a delayed release. The energy released must have some time delay. Maybe it all averages out overtime. Difficult problem I wonder if it is worth answering.

Well, if we wanted to really get in to the details, the Earth is releasing more energy than it receives from the sun simply because it is also cooling. The core grows by about a few mm a year because of this, IIRC. With a brief, 60 million year time frame exception during the Carboniferous, though, the energy stored in life processes is a wash. Assembly and decay are a net balance, and life itself is a strong driver…

To nitpick your nitpick, the earth radiates more energy than it receives because it is very radioactive. And because it is cooling.
Post reply on HN