Quote:
Originally Posted by julianh72
Eratosthenes' first post was simply a claim about the amount of energy in a single raindrop, with no other context:
...and yet a single rain drop at rest can potentially unleash about 9,000,000,000,000 Joules in energy
I took it as self-evident that this referred to the potential fusion energy, as this is a totally unfeasible amount of kinetic or gravitational potential energy for a single raindrop. (But my later "back-of-the-envelope" calculation suggests a more credible figure is actually about 9 GJ not 9 TJ.)
I then made the comment that the useful stored energy of 18 TJ in the Wivenhoe Pumped Storage Hydro Scheme is "about the same" as Eratosthenes' figure for a single raindrop - and yes, the stored energy of Wivenhoe pumped storage is simply the gravitational potential energy of 28 GL of water sitting 100 metres higher than the main dam reservoir.
However, it seems that it would actually take the fusion of the hydrogen in about 1,000 raindrops to liberate the same amount of energy - so it's actually a one-shot espresso cupful (50 mL), rather than a single raindrop ....
Even with these "back-of-the-envelope" figures, it's pretty obvious why nuclear fusion of hydrogen is such an attractive source of energy for the future.
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If you believe that is what he meant I respect your decision.
On a different subject your own calculations are wrong.
It looks as if all you have done is to take p-p reaction mechanism for solar fusion and simply assumed it applies here on Earth.
It's not that simple.
A parameter used in nuclear physics is the scattering cross section for fusion which is the probability that two colliding nuclei will undergo fusion.
This depends on conditions such as temperature, pressure and density.
The fact is that none of these conditions can be replicated on Earth so your figure of 0.7% conversion is rather fanciful.
Secondly the source of the protons are from your rain drops, so it has no relevance to the p-p chain mechanism.
You need to use energy to completely ionize the water in order to minimize the Coulomb barrier, then there is the complication of how the Coulomb barrier from O nuclei will effect the scattering cross section of the protons.
Do you know, does anyone know?
