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Parabolic pool

not that kind of pool
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A large parabola set a slight southward tilt, (in this hemisphere), comprises the bottom of a backyard swimming pool.
Mirrored sides hold the water in this pool at a depth just below the focal point of the parabola.
Near noon each day, (given a sunny day), the converging light rays refract from the under surface of the water in such a way as to keep as much of this light as possible trapped within the pool to maximize heat absorption by particulates and bubbles in the water passively heating the pool to temps which might require covering the pool just to shade it rather than trap the heat.

A safety cage will need to be suspended at the new submerged focal point for obvious safety reasons...
...and the first person to market uv protective swim-goggles will cash out yuge.


Based on this? https://www.science...ring/parabolic-dish
...but a bit more dish shaped? [whatrock, Feb 25 2021]

[link]






       + I think this is just a cool image of a pool of mirrors.
xandram, Feb 22 2021
  

       You'll need to take into account the different refractive indices of air & water; a "common" paraboloid won't work for both at the same time. Hmm... I may feel the urge to throw some maths at this later...
And it will only be pointing in the (exact) correct direction 2 days per year (unless you choose a solstice, then it's only one). But I like the basic concept (even if it doesn't work properly).
neutrinos_shadow, Feb 22 2021
  

       There's supposed to be a way to track the sun with a secondary mirror or heliostat so that it always shines at the correct angle into a stationary parabolic reflector. There's a really cool DIY solar tracker that simply wires two sets of two solar panels so that they drive two electric motors in either direction and the thing moves to keep all four panels in the shade off the grid.   

       As for the refraction of the surface of the water I had thought to play around with using a very slightly convex mirror for the heliostat. If I make it from mylar over a sealed drum I should be able to change the focus until I find the sweet spot.   

       Ooh, pressure-created paraboloid. That could work. Might need careful balance between the pressure & tension to get a nice shape (keep it subtle, I would think... too bulgy = too spherical). A vacuum would probably work for concave, too.
neutrinos_shadow, Feb 22 2021
  

       "A vacuum would probably work for concave"
— neutrinos_shadow, Feb 22 2021
  

       Yes, flexible mylar mirrors - pulled by vacuum into a catenary rather than parabolic curve - are WKTE. No good to make a telescope but adequate for solar ovens.
kdf, Feb 22 2021
  

       Waterhenge [+]
pertinax, Feb 22 2021
  

       This seems like a bright idea, but I have to reflect upon it before diving in.
AusCan531, Feb 23 2021
  

       Water you talking about? It's a great idea!
Voice, Feb 23 2021
  

       I'm sorry but I believe I might need a visual. Not detailed, just a bit of an outline, I believe.
blissmiss, Feb 24 2021
  

       //Water you talking about? It's a great idea!//   

       Swimmingly terrific!
doctorremulac3, Feb 24 2021
  

       [Blissy] I believe this is what they mean (link). A parabolic dish grabs sunlight and focuses it to a single point, but if the dish contains water then the sunlight disperses into the water, heating it. Perhaps bigger than a traditional hot tub?
whatrock, Feb 25 2021
  

       I honestly don't have time to sketch this [bliss].   

       Normally you'd need to make a satellite dish continually face the sun to focus the light to a point.
If the dish is too big to move then you want to bounce the sunlight into it so that it acts as though it is continuously facing the sun using a second moving mirror they call a heliostsat.
Since the sunlight will be passing through the surface of a body of water the light rays will bend or refract and no longer act as though facing the sun, so I intend to bend the incoming sunlight using a convex, (outwardly curved) mirror, like the mirrors in a parkade so that the light bends before it hits the water.
  

       I just need to make the parkade mirror adjustable to figure out how to bend the incoming rays so that they act as though there is no water there at all.   

       See?   

       Or even, a conduction fluid umbrella could be useful, if the focal point was above the pool.
wjt, Feb 25 2021
  

       Thank you, [whatrock]. Got it. I was lost before but now am found. Amazing! Yes, I like this idea. Sorry, you are so busy, 2 fries. I guess I am too demanding at times and not supportive enough. I need extra help for some ideas. But now I get it.
blissmiss, Feb 25 2021
  
      
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