
Solar pond - ColinWright
http://en.wikipedia.org/wiki/Solar_pond
======
killahpriest
If you're curious as to how the thermal energy is extracted:

[http://www.sciencedirect.com/science/article/pii/S0038092X10...](http://www.sciencedirect.com/science/article/pii/S0038092X10002161)

> Heat has generally been successfully extracted from the lower convective
> zone (LCZ) of solar ponds by two main methods. In the first, hot brine from
> the LCZ is circulated through an external heat exchanger, as tested and
> demonstrated in El Paso and elsewhere. In the second method, a heat transfer
> fluid circulates in a closed cycle through an in-pond heat exchanger, as
> used in the Pyramid Hill solar pond, in Victoria, Australia.

~~~
david2777
They use the hot brine to vaporize a motive fluid such as liquid pentane in
the heat exchanger, when the liquid is converted to gas it creates a high
pressure environment and is piped into a turbine which spins the generator.
Then they condense the motive fluid back to a liquid so they can vaporize it
again. It's the same way binary geothermal power works, with the Organic
Rankine Cycle.

[http://en.wikipedia.org/wiki/Organic_Rankine_cycle](http://en.wikipedia.org/wiki/Organic_Rankine_cycle)

------
IvyMike
A do-at-home demo:
[http://matse1.matse.illinois.edu/energy/b.html](http://matse1.matse.illinois.edu/energy/b.html)

Note: I haven't tried these particular instructions myself, although I did do
a similar demo around 20 years ago.

They used this, and maybe still do, at UIUC to heat the Vietnamese potbelly
pig barns south of campus.

------
atlanticus
>This means that the temperature at the bottom of the pond will rise to over
90 °C while the temperature at the top of the pond is usually around 30 °C.

Can that really be right, it seems like a very high gradient.

~~~
ISL
Depends upon the depth (and geometry) of the pond. Without convection, some of
our intuition for thermal conductivity in liquids and gases is lost.

I'm not sold on the numbers, but I'm also not yet convinced of the idea's
physical impossibility.

------
wehadfun
Is this cheaper or better then solar panels?

