The pond is filled with a dense salt
solution, which naturally separates into gradient levels: a weaker
salt mix exists near the water's surface, and the higher—and thus
denser —saline concentrations settle to the bottom. The topmost
layer is, of course, relatively fresh water. As the sun beats down
on the brine reservoir, its thermal energy passes through the
"lighter" surface levels and heats the heavy saline mass below. The
result is that the dense salt solution—held at the bottom of the
pool and thermally protected by the surface layer—can reach
temperatures between 158 and 176°F. The water at the surface of the
pond, instead, stays at a warmth that's "normal" for the desert
region, ranging from 68 to 90°F.
The hot salt water is pumped through a heat exchanger, which is
surrounded by a vessel filled with a substance similar to freon.
This, in turn, is connected to a turbine that's specially designed
to be driven by a much lower-temperature propellant than that used
in a conventional steam turbine. Since the medium changes from
liquid to gas at a relatively low heat, the sun warmed water
instantly flashes the fluid into a pressurized vapor ... which
drives the turbine and its 150-kilowatt AC generator.
What is the maximum efficiency with which useful mechanical work can be extracted from the pond?
In solar ponds constructed in Israel, the Sun’s energy is concentrated near the bottom of a...
Israel utilizes solar ponds to produce ‘green’ energy. In a solar pond, the Sun’s energy is concentrated near the bottom of a salty pond. With the proper layering of salt in the water, convection is prevented. As a result, the top layer of water remains at surface temperatures of 20 to 30oC, depending on the season, while heat is concentrated in the salty layer of water at the bottom, where temperatures of 70 to 90oC are reached. This heat can...