36 Distributed Generation and Alternative Energy Journal Energy From Salt Lakes: A Primer on Salt Gradient (Solar) Ponds

Abstract

Any lake absorbs heat from the sun. Normally, heat is lost as
warmed water rises to the surface and cools by evaporation. But water
is a VERY poor conductor of heat and if this circulation can be stopped,
the heat can be trapped in the bottom of the lake. A salt lake, (ideally
about 3m deep), managed so that the water on top is of relatively low
salinity (density ~1.0g/cc) and the water on the bottom is of very high
salinity (density ~1.2g/cc), will not circulate to release heat because the
water on the bottom is so heavy with salt it cannot rise—even at quite
high temperatures. The deeper water gets very hot—in the right circum-
stances (the record is 114°C)—70°C degrees is common in even temperate
climates. In Southern Australia 50°C is easily achievable—even in winter.
Run like this, such ponds are called ‘Salt Gradient Solar Ponds’ or
just ‘Solar Ponds’.