4 ms·

Tidal energy is not renewable! We'd be tidally locked to the moon in 1000 years if we used Tidal for 1% of our energy consumption. https://cs.stanford.edu/peop

by riv991 3y ago

Tidal energy is not renewable! We'd be tidally locked to the moon in 1000 years if we used Tidal for 1% of our energy consumption. https://cs.stanford.edu/people/zjl/pdf/tide.pdf https://cs.stanford.edu/people/zjl/pdf/tide.pdf

anovikov 3y ago
That article is based on ridiculous assumptions of future energy consumption growth, and was probably created as a joke. Which backfired since it got seriously quoted in so many places.
- midasuni 3y ago
  They have a 2% increase in energy use each year for 1000 years, currently 10^12W That would mean we’d be well into the type 1 civilisation about 10^19W a year and we’ll be on the way to a type 2 civilisation.
  - pfdietz 3y ago
    Sunlight hitting Earth is around 10^17 W, so that civilization would be rather toasty.
    - midasuni 3y ago
      In theory if you used the power and radiated it to space (via laser, RF, etc) you’d be ok. You could even use also use that energy to put into rotational energy to increase the earths rotational speed
      - pfdietz 3y ago
        Lasers can't radiate heat, as a laser beam has no entropy. Ditto for coherent radio waves.
        midasuni 3y ago
        Fire a 1GW laser at the moon and you will transfer the best part of a billion joules of energy from the earth to the moon every second.
        ben_w 3y ago
        You have to be very careful of Maxwell's Demon when it's a question of entropy: how efficient is that laser? How does the efficiency change when it is in a heat bath of X kelvin? There may be some neat tricks, this is an area I know I'm not good at, but you have to be very careful.
        pfdietz 3y ago
        Sure. And you will transfer no entropy, so this cannot be used to cool the Earth. SF authors (like David Brin) have screwed up on this very topic. Lasers can be used for cooling, by shining a laser on a target carefully set up so that anti-Stokes scattering carries away entropy. The light scattered is quite incoherent, though.

by riv991 3y ago

anovikov 3y ago

That article is based on ridiculous assumptions of future energy consumption growth, and was probably created as a joke. Which backfired since it got seriously quoted in so many places.

midasuni 3y ago
They have a 2% increase in energy use each year for 1000 years, currently 10^12W That would mean we’d be well into the type 1 civilisation about 10^19W a year and we’ll be on the way to a type 2 civilisation.
- pfdietz 3y ago
  Sunlight hitting Earth is around 10^17 W, so that civilization would be rather toasty.
  - midasuni 3y ago
    In theory if you used the power and radiated it to space (via laser, RF, etc) you’d be ok. You could even use also use that energy to put into rotational energy to increase the earths rotational speed
    - pfdietz 3y ago
      Lasers can't radiate heat, as a laser beam has no entropy. Ditto for coherent radio waves.
      - midasuni 3y ago
        Fire a 1GW laser at the moon and you will transfer the best part of a billion joules of energy from the earth to the moon every second.
        ben_w 3y ago
        You have to be very careful of Maxwell's Demon when it's a question of entropy: how efficient is that laser? How does the efficiency change when it is in a heat bath of X kelvin? There may be some neat tricks, this is an area I know I'm not good at, but you have to be very careful.
        pfdietz 3y ago
        Sure. And you will transfer no entropy, so this cannot be used to cool the Earth. SF authors (like David Brin) have screwed up on this very topic. Lasers can be used for cooling, by shining a laser on a target carefully set up so that anti-Stokes scattering carries away entropy. The light scattered is quite incoherent, though.