HOW IT WORKS

In Australia we have three main types of gas power stations:

• OCGT - Open Cycle Gas Turbines: This is like a stationary jet engine. Air is compressed and then heated by burning fuel, then released through a gas turbine to create energy. The "gas" in the name refers to the air used, not the fuel type. OCGTs can use both gas and liquid fuels (not solid fuels like coal, but diesel, kerosene and oil). They’re generally smaller units that burn fuel to create hot air, which drives the turbine and generates electricity.

THERMAL EFFICIENCY: 35-41%

START UP TO FULL LOAD: 1O-20 minutes

• CCGT - Combined Cycle Gas Turbines: Similar to OCGTs, but with an added step: the hot air also heats water to create steam, which powers an extra turbine for more energy. This makes CCGTs very efficient, though they’re more expensive to build and are less flexible due to the steam component. Improved efficiency means that CCGT emit less greenhouse gasses than OCGT.

THERMAL EFFICIENCY: 50-55%

START UP TO FULL LOAD: 20-40 minutes

• RECIPROCATING: This is like a large internal combustion engine with cylinders and pistons, similar to engines in vehicles. After many years of design improvements, they’re as efficient as the best open-cycle gas turbines, with similar build times and slightly higher costs. This plant type stands out for its rapid start capability as they can synchronise to the grid within 90 seconds of receiving a start signal, and reach full load less than four minutes later. The maintenance cost penalty of every start and shut down is also minor. Globally reciprocating plants are also referred to as a CHP plants (Combined heat and power). These plants use less fuel and therefore have lower greenhouse gas emissions.

THERMAL EFFICIENCY: 45-48%

START UP TO FULL LOAD: 5 minutes

This information was sourced from AEMO Integrated System Plan 2019 Input and Assumptions workbook, AGL, Power Engineering Magazine 1.1.18.