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EnerSalt Solar Ponds (Australia)

In Brief: Solar ponds are salt lakes which are managed to act as large, low cost, solar heat collectors.

Solar pond technology produces hot water at very low cost. This cheap energy can be used directly to warm farm buildings, aquaculture systems, glasshouses and other rural, industrial or municipal processes (eg heating public swimming pools). The heat energy can be also be used to desalinate water or produce electrical power for remote areas.

Any lake absorbs heat from the sun. Normally, heat is lost as warm water rises to the surface and cools by evaporation. But water is a very poor conductor of heat and, if this circulation is stopped, the heat can be trapped in the bottom of the lake.

If a salt lake, (about 3m deep), is managed so that the water on top is of (relatively) lower salinity and the water on the bottom is of very high salinity, it will not circulate to release heat because the water on the bottom is so heavy with salt it cannot rise.

The deeper water gets very hot - to over 100 degrees in the right circumstances - 80 degrees is common in the tropics. In Southern Australia 65 degrees C is easily achievable - even in winter.

The main management problem is to extract heat at the right rate so the lake does not boil or 'turn over' and thus lose its heat.

Run like this, such ponds are called 'Salt Gradient Solar Ponds' or just 'Solar Ponds'.

As a renewable energy technology, the solar pond collector has major advantages.
- The heat storage is massive, so energy 24 hours per day- hence it is a source of 'base load' power - no batteries or other storage needed!
- Solar ponds can have a very large heat collection area at low cost.
- The major production potential is during peak electrical power demand (and price) in mid summer
- The technology and scientific principles for collection and extraction of heat and its conversion to electricity have been well researched (but before Enersalt, poorly commercialised