Geothermal energy recovery is normally via the Rankine cycle,...

Geothermal energy recovery is normally via the Rankine cycle, where a pipe filled with super-heated water is 'coiled' around another pipe full of an organic compound. The water transfers a percentage of its heat energy to the O.C, and the heated O.C, upon vaporisation, drives a turbine.

The main simple difference between this and the Kalina cycle is that the Kalina cycle uses an ammonia/water solution rather than an O.C. The water/ammonia soln. has an increased capacity to absorb heat energy, and boils over a range of temperatures.

Near the end of the circuit, when the Rankine cycle can absorb no more heat, the Kalina cycle, with it's increased capacity to handle the 'tail end' geothermal fluid, will continue to utilise the heat.

There have been a number of studies on this. Almost every conclusion puts the kalina cycle between 10 to 30% more efficient at extracting heat.

Best thing to do is just google Kalina Cycle if you want to know more.

PTR will most likely use the Rankine Cycle (GDY hold exclusive rights to Kalina). However, keep in mind PTR are closer to demand for electricity. What is very hard to pick is which company comes off on top...

I have the view that GDY and PTR are the two leaders of the Australian geothermal industry. What it may come down to is whether GDY and it's MUCH higher efficiency (hottest rocks + best cycle) will deliver the highest SP rise, or PTR and it's reduced risk, reduced capital costs, and diversified tenements.

But there's alot of demand, so it might pay to buy most.