Ratch Thermal Power Plants utilize Combined Cycle Gas Turbines and Open Cycle Gas Turbine technology. 

Combined Cycle Gas Turbines (CCGT)
The principle behind these technologies is to burn a fuel (natural gas) to generate heat and drive a turbine, then capture the waste heat exhaust from the original process to heat water and drive a steam turbine, which also produces energy.

With thanks to: http://www.slideshare.net/DavidGrenier/ppt-combined-cycle-power-plant


Siemens, who supplied the plant at Townsville, and at Kemerton define Combined Cycle power as: 
“In combined cycle power plants (CCPPs) a gas turbine generator generates electricity while the waste heat from the gas turbine is used to make steam to generate additional electricity via a steam turbine.

In other words: The output heat of the gas turbine flue gas is utilized to generate steam by passing it through a heat recovery steam generator (HRSG), so it can be used as input heat to the steam turbine power plant. This combination of two power generation cycles enhances the efficiency of the plant. While the electrical efficiency of a simple cycle plant power plant without waste heat utilization typically ranges between 25% and 40%, a CCPP can achieve electrical efficiencies of 60% and more. Supplementary firing further enhances the overall efficiency.“


Open Cycle Gas Turbine  (OCGT)
Open Cycle Gas Turbine is a turbine fired by a fuel (gas)to turn a generator. The residual heat is vented to the atmosphere. The difference from CCGT is that the Open Cycle GT sucks air in from the atmosphere and compresses it. Fuel is pumped into a compression chamber and mixed with the compressed air.  The fuel/air mix is then ignited to form hot, high velocity gas. The Gas is passed through aturbine blades that turn the shaft, attached to the rotor of the generator.  The rotor turns the stator, and electricity is generated.