EnviroNova Solar Pond Project.

Salt Gradient Solar Ponds are a long-known solar thermal energy technology.

Solar ponds work as shown in the following diagram.

A 2-3 m deep pond is set up so that the bottom is 1/3rd

filled with almost saturated salty water. Above this is added progressively lower salinity water.

Solar energy collected at the bottom of the pond is not lost via convection because the saltiest water in the lower convective zone is too heavy to rise.

Temperatures at the bottom reach 80-90'C. Australian developed manifold technology is then used to harvest this heat.

Heat from solar ponds can be used directly for industrial and agricultural processes and desalination. This is a very cheap source of heat energy at around 3c/ kWhr (based on pond setup cost and ongoing maintainence). Heat can also be used to generate electricity using a Rankine Cycle engine - final cost of generated power is approx 15c / kWhr.

Solar Ponds have the added advantage, due to the large thermal mass of the water, that they can store and yield and energy during night time or cloudy weather. They are the only known solar energy system that can do this without storage systems.

EnviroNova is involved in the early stages of development of a solar pond with desalination in the Murray Lands of South Australia.

A short history of Solar Ponds

Solar ponds were largely developed in Israel where Ormat Ltd set up a 5 MW electricity generation facility in the 1980s.

Although such electrical generation facilities were not highly profitable, other facilities such as the Pyramid Salt Co Solar Pond at Kerang in Victoria, Australia produced heat energy for use in its gourmet salt production process (at around 1/3rd the cost that it could be produced by burning LP gas).

Cliff Hignett demonstrated solar pond heat enhanced desalination at the Kerang facility using stills produced by an Adelaide company.

The Kerang Solar Pond has currently ceased operation due to the recent move of the Pyramid Salt Company to new salt evaporation basins at another site. Another Australian Solar Pond facility was built to generate electricity at Rottnest Island off Perth in Western Australia.

Other well known international solar pond projects include Elpaso Solar Pond in Texas (which included electricity generation multistage flash desalination).