electricity meters rake in millions, page-30

Opaline,

Thanks for looking and responding.

I saw potassium nitrate mentioned, not sodium nitrate?

I've got some info from a pdf document called 'Stirling Set Up' about a hybrid system developed by Patrick Glynn of the CSIRO and Peter Olds of OLDS Eng.
Here's the bit about their salt cell battery being used.
Clearly you could make a battery any size you required.
GDY could use one which the hot rocks keep at 250C and solar thermal panels boost during the day to increase their output for example.
When I find the link to the pdf I have, I will post it.
Found it.

http://www.ecosmagazine.com/?paper=EC124p28

Just add salt.
Attached to the solar dish is a phase change heat cell containing salt and graphite (as a heat conductor). This cell can store 9.5 times more energy than the same sized lead-acid battery used in photovoltaic systems. It can also store 100% of the solar energy directed into it, compared
to only 15% for photovoltaics. Our system will operate at least four times more efficiently in combined heat and power mode than photovoltaics, and the salt cells will last in excess of 25 years, or the operational life of the Stirling engine, Glynn says.
As the salt cell absorbs energy from the solar dish, the salt reaches temperatures of 600900C.While more energy is absorbed, the temperature remains the same but the salt changes phase from solid to liquid and stores energy as latent heat that can be siphoned off to heat air and water.
The process is the same as when you boil water to make steam, Glynn explains. To boil 1 litre of water at 100C you will have to put in about 300 kJ of energy. To change it to steam at 100C you need to put in another 2.2 MJ or approximately eight times that amount of energy. The
temperature stays the same, but the water changes phase from liquid to gas and absorbs energy as latent heat.
Glynn and Slade say the innovative aspect of this technology is the ability to store thermal energy from the sun within a cell containing salt or other material; to
convert this stored energy into mechanical energy with a heat engine; and then to generate electrical energy in the same way organic fuel is used in an internal combustion engine. Instead of having a fuel tank of diesel or petrol, we have a fuel tank of hot salt, Slade says.
The beauty of salt is that you can take it to 900C, where it melts; then you can take it to 1500C. Nothing changes; it just holds the heat. Then it slowly releases the heat
until its solid, and continues to release heat for a number of hours after that. When you measure diesel or petrol, youre measuring kilowatts of energy that are dormant in the fuel and released when the fuel is compressed or burnt. In the case of salt, energy is dormant as latent heat. As the heat is used up, the temperature of the salt drops, just like the level in a fuel tank would drop.When the temperature gets to 550600C the efficiency drops, and we need the sun to top it up to 900C.