[HN Gopher] Galactic-Scale Energy - Do the Math (2011)
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Galactic-Scale Energy - Do the Math (2011)
Author : grey_earthling
Score : 26 points
Date : 2022-07-23 08:46 UTC (14 hours ago)
(HTM) web link (dothemath.ucsd.edu)
(TXT) w3m dump (dothemath.ucsd.edu)
| pdonis wrote:
| The article leaves out a crucial point: the main driver of growth
| in energy usage is growth in human population. The human
| population of Earth is expected to level off this century. So any
| projection beyond that that assumes continued energy growth at
| the same rate is not realistic.
| zamalek wrote:
| The article does mention this:
|
| > Chiefly, continued energy growth will likely be unnecessary
| if the human population stabilizes.
| aaaaaaaaaaab wrote:
| In other words: the exponential function grows very fast.
| NickM wrote:
| I don't think most people advocate for indefinite growth of
| energy usage; when people talk about sustainability of growth
| they are typically referring to economic growth. This has often
| been correlated with energy usage in the past but there's nothing
| that says it has to be that way, and indeed there are a number of
| countries that have shown that decoupling the two is possible:
| https://ourworldindata.org/energy-gdp-decoupling
| api wrote:
| It tends to be tightly correlated to energy use up to a certain
| material standard of living. At that point they start to
| decouple.
| mbbutler wrote:
| They don't even decouple at high material standards of
| living. Recent increases to GDP produced emissions too but
| those new emissions were offset by reductions in emissions of
| existing industries.
|
| This "decoupling" gets us basically nothing because it's not
| like we can just stop emissions tomorrow since GDP and
| emissions are "decoupled".
| epicureanideal wrote:
| Counter example: if we can make computation 1000x more
| efficient per teraflop, we could use computers to trivially
| design drugs to cure cancer etc (just a random example) and
| yet our energy consumption would not change. GDP may be the
| wrong measure, but there would be economic growth or
| standard of living growth for no change in energy
| consumption.
| mathgeek wrote:
| > if we can make computation 1000x more efficient per
| teraflop, we could use computers yo trivially design new
| drugs to cure cancer etc
|
| You're assuming two things: that cancer and disease can
| be cured by any feasible increase in computing power (not
| that outrageous an assumption), and that the energy
| savings won't be offset by keeping an even older
| population of disease survivors comfortable and alive.
| Reality is not as simple as "cure all our ailments and
| we're good to go".
| TheOtherHobbes wrote:
| This has already happened at a higher multiplier.
|
| An Apple Watch has more processing power than a Cray 2,
| but it uses a rechargeable battery instead of a 150kW
| power supply.
|
| The problem is that cycles expand to fill the space
| available, so another 1000X drop in efficiency would mean
| new kinds of applications rather than being limited to
| affordable super computing.
|
| While individual computers are far more powerful and use
| far less energy, the power consumed by computing on Earth
| as a whole is far higher than it was. (Not even counting
| energy vampires like crypto.)
|
| There's no reason to assume that trend would stop.
| Displays could easily have much higher resolutions
| (possibly holographic), IOT could be truly ubiquitous, AI
| could be in everything, entertainment could be social,
| interactive, and immersive, and so on.
| Jweb_Guru wrote:
| This article (and site) are pretty great, and helped shape a lot
| of my worldview. It tends to throw a bucket of cold water on a
| lot of the arguments regularly made on this website, though, so
| I'm surprised to see it here.
| epistasis wrote:
| What sort of arguments do you see made on this website that
| this would refute?
| carapace wrote:
| See also: "Exponential Economist Meets Finite Physicist" which
| covers the same material in the context of economic growth.
|
| > Some while back, I found myself sitting next to an accomplished
| economics professor at a dinner event. Shortly after
| pleasantries, I said to him, "economic growth cannot continue
| indefinitely," just to see where things would go. It was a lively
| and informative conversation.
|
| https://dothemath.ucsd.edu/2012/04/economist-meets-physicist...
| yrgulation wrote:
| > I have always been impressed by the fact that as much solar
| energy reaches Earth in one hour as we consume in a year. What
| hope such a statement brings! But let's not get carried away--
| yet.
|
| > The abundance of deuterium in ordinary water would allow us to
| have a seemingly
|
| I mean isn't it obvious that we are missing opportunities here?
| Are we really that complacent that we can't achieve anything on a
| grand scale anymore? Plant solar panels everywhere that there is
| not agricultural land and meets the criteria for energy
| efficiency. Fill in the all the roofs. It's vacant space. Spend
| billions more on fusion research.
|
| > The merciless growth illustrated above means that in 1400 years
| from now, any source of energy we harness would have to outshine
| the sun.
|
| Hopefully by that time we'd be an interplanetary species. Unless
| we imagine we can keep digging all the way to the core to extract
| resources down here. When all the good stuff is literally sitting
| out there waiting for us to plunder.
|
| > Chiefly, continued energy growth will likely be unnecessary if
| the human population stabilizes.
|
| I doubt our insatiable hunger for more, more, and more will stop
| anytime soon - even if the numbers stagnate, our egos will grow
| bigger and bigger and we'll want more and more. It's in our
| nature. So why not go beyond our planet for that never-ending
| "want"? Consumer everything that's out there and turn into shiny
| new crap for down here. Once we are done, eject it into the sun
| and keep the earth tidy.
| tener wrote:
| Feels like a similar methodology here https://xkcd.com/605/
| [deleted]
| akira2501 wrote:
| Thankfully, the planet contains abundant stores of Uranium.. and
| we are nowhere near peak efficiency in commercial and industrial
| processes. These one dimensional analysis of the problem are
| particularly useless, especially when their only conclusion is
| "we must stop growth."
|
| The average power usage may well be 2000W, but how many average
| consumers are there? If we're facing a multi-mode distribution of
| those users, then this "stop growth" strategy instantly creates
| new "castes" from this distribution. As a long term strategy, it
| seems doomed in one way or another.
| api wrote:
| These analyses have been predicting doom for decades. They just
| keep moving the goal post.
| Arthur8 wrote:
| Huh, I had to re-read the article _.
|
| "But let's not overlook the key point: continued growth in
| energy use becomes physically impossible within conceivable
| timeframes." (conceivable timeframes ~ few 100 years)
|
| As far as I understood, the argument is not "we are doomed"
| but that there is a natural limit to the growth of energy
| consumption in the not too distant future using some naive
| assumptions. In any case, it is implying that 2.9% growth per
| year is a lot! if it is extrapolated by just a few 100 years.
| Do I misunderstand something? Why is this controversial?
|
| _But I did not yet read all the linked later posts.
| Jweb_Guru wrote:
| You are correct.
| lumost wrote:
| The article accounts for this in average earth temperature. The
| earth's surface would be hotter than the sun in 1000 years, and
| would generally be uncomfortable after 200. The only way around
| that would be a substantial change in the thermodynamic
| efficiency of our energy use and/or a non radiative means of
| disposing of heat.
|
| Granted, if we did have the equivalent energy of a sun - we are
| unlikely to be spending it all on earth. Escaping earths
| gravity would be a trivial expense.
| whatshisface wrote:
| That thermodynamic argument was the least convincing part. If
| you wanted to, you could beam your power plant's infrared
| radiation towards space, or put the plant itself in space and
| have it beam its waste heat away from the planet. The idea
| that heat dissipation is limited by the black body radiation
| of the Earth assumes that your house is part of the power
| plant's radiator, which _itself_ implies that you will be
| living in a power plant 's radiator. :-)
| mbbutler wrote:
| But the energy transported to Earth from your space power
| plant still creates waste heat when it is used to do work
| (and also when it is transported to earth). You cannot beat
| the second law.
| betwixthewires wrote:
| That's because you don't understand thermodynamics.
|
| You can't just put the power plant in space and keep the
| heat from generating the power away from the earth, because
| the heat gets created _where the power is used to perform
| work._ You have to avoid consuming any of that power on the
| earth entirely.
|
| And you can't just beam the waste heat from every process
| away from the surface of the earth, that violates the
| second law of thermodynamics. The heat exists because the
| energy performed work, you are keeping the energy organized
| by beaming it in any direction, so it is not waste heat, it
| is direct infrared from the energy you've produced. You can
| only do this by not actually using the energy for work.
| This makes the whole exercise of even producing the energy
| pointless.
|
| I think the biggest hole in the argument is the jump to
| 100% efficiency. we don't consume mor energy because we
| feel like it, we consume it because we need it, and a
| factor of 5 increase in efficiency would equate to a factor
| of 5 decrease in production of energy resources.
| whatshisface wrote:
| > _you are keeping the energy organized by beaming it in
| any direction_
|
| I am afraid it is you who misunderstand thermodynamics,
| my friend. :-) Entropy is a matter of degree, and as long
| as the beam leaving the Earth is less ordered than the
| beam coming down, it can work.
| TheOtherHobbes wrote:
| Large parts of the Earth's surface are going to be generally
| uncomfortable within 10 years, never mind 200.
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