4 ms·

That would be true if it were a freely oscillating system, but since the tide is 'powered' by the moon I'd think the tidal cycle should keep going until the moo

by jbattle 12y ago

That would be true if it were a freely oscillating system, but since the tide is 'powered' by the moon I'd think the tidal cycle should keep going until the moon stops orbiting. (though I'm not 100% sure I understand how tides work)

happyscrappy 12y ago
He is arguing, probably correctly, that the damping caused by energy extraction will cancel out the natural resonance and therefore not be repeatable.
hanoz 12y ago
I don't see that. Surely if you have two swings hanging from a swaying tree and one of them is swinging wildly because it's the right length to resonate with the moving branch above, you can't say hey this x kg tyre is rising and falling y cm every s seconds, lets harness that. It only has the same renewable energy as the other swing, plus a one time build up of energy that its taken to get it up that extra height.
- DanBC 12y ago
  But the moon is providing an input. So, for your swing example, there is someone on one side giving it a push every pass.
  - hanoz 12y ago
    No one's pushing my swings! I've already accounted for the input, it's the great mass of the swaying tree (and in turn the wind etc.), and like the tides' moon it's the same input to both swings, only one's them is swinging like the clappers whilst the other barely moves. Even though the former clearly has more energy at a given point in time most of that is a one off build up, and there can't be any more repeatedly extractable energy in the big swinger than the small.
- leohutson 12y ago
  Flip the oscillators, the sea is the tree branch, and the swing is the moon. The tree branch is moved slightly each swing, and if I am to extract energy from the branch by forcing it to do work, I will damp the motion of the swing and it will eventually stop. You're right in that it's not renewable, the energy is being extracted from the kinetic energy of the moon, and it will slow the moon to some minute degree.
nmeofthestate 12y ago
The high tidal range is due to water being 'dragged' into a confined space by tidal forces and its kinetic energy becoming focussed as a result.

by jbattle 12y ago

happyscrappy 12y ago

He is arguing, probably correctly, that the damping caused by energy extraction will cancel out the natural resonance and therefore not be repeatable.

hanoz 12y ago

I don't see that. Surely if you have two swings hanging from a swaying tree and one of them is swinging wildly because it's the right length to resonate with the moving branch above, you can't say hey this x kg tyre is rising and falling y cm every s seconds, lets harness that. It only has the same renewable energy as the other swing, plus a one time build up of energy that its taken to get it up that extra height.

DanBC 12y ago
But the moon is providing an input. So, for your swing example, there is someone on one side giving it a push every pass.
- hanoz 12y ago
  No one's pushing my swings! I've already accounted for the input, it's the great mass of the swaying tree (and in turn the wind etc.), and like the tides' moon it's the same input to both swings, only one's them is swinging like the clappers whilst the other barely moves. Even though the former clearly has more energy at a given point in time most of that is a one off build up, and there can't be any more repeatedly extractable energy in the big swinger than the small.
leohutson 12y ago
Flip the oscillators, the sea is the tree branch, and the swing is the moon. The tree branch is moved slightly each swing, and if I am to extract energy from the branch by forcing it to do work, I will damp the motion of the swing and it will eventually stop. You're right in that it's not renewable, the energy is being extracted from the kinetic energy of the moon, and it will slow the moon to some minute degree.

nmeofthestate 12y ago

The high tidal range is due to water being 'dragged' into a confined space by tidal forces and its kinetic energy becoming focussed as a result.