How does gas-fired power work?

Using abundant natural resources for lower carbon energy

What is natural gas and why is it important?

Natural gas is a colourless, odorless, flammable gas that usually contains about 90% methane.

It can be found in deep underground rock formations, often alongside oil or coal.

It’s one of the main energy sources in the world.

As a lower intensive fossil fuel, natural gas is playing a crucial role in helping the world transition to low-carbon energy production.

Although coal and oil still account for around 60% of global energy consumption, natural gas meets 21% of global demand.

Offering much lower CO2 emissions than other fossil fuels, it’s an important alternative that provides a low-carbon bridge on the road to a zero-carbon future.

Gas-fired electricity generation – such as ENGIE’s Pelican Point Power Station in South Australia – makes an important contribution to energy security and stability, as well as complementing renewables, such as wind and solar.

Following a $75 million upgrade, the 487MW Pelican Point Power Station is one of the most environmentally friendly of its type in Australia.

How does a gas-fired power station work?

Gas-fired power stations burn natural gas to produce electricity.

There are two main ways they do this – open cycle and combined cycle.

Open Cycle Gas Turbine

Open-cycle production is the most common method. Natural gas is burned to create a pressurised gas, which powers a turbine that is connected to a generator. The turbine turns the magnets in the generator to create electricity.

Combined Cycle

The Combined-Cycle Gas & Steam Turbine (CCGT) plant generates energy using two different types of turbines in combination: a gas turbine and a steam turbine. In essence, it recycles its fuel to maximise its electricity output. ENGIE’s Pelican Point Power Station uses this ingenious method of electricity generation.

The hot gases generated by burning natural gas power the gas turbine. The gases are still hot enough to generate steam in a heat recovery boiler which is then used in a steam turbine. The combination of these two thermodynamic cycles increases plant efficiency to in excess of 50%, which is much higher than the 35% to 40% achieved by traditional plants.

Pelican Point Power Station Energy Generation Process
  • Natural gas arrives at the power station via a pipeline.
  • Air is drawn through filters and then compressed
  • The natural gas is mixed with the compressed air, and this mixture is then burnt in a combustor.
  • This process produces high pressure, high temperature combustion gases that drive a turbine connected to a generator.
  • The generator spins an electromagnet at very high speed (about 50 times a second), inside copper wire conductors.
  • This generates electricity.
  • The exhaust gases from the turbines are then directed to the Heat Recovery Steam Generator where it is used to boil water in a series of pipes, producing superheated steam.
  • Any remaining exhaust gas is released through a large chimney.
  • The superheated steam is delivered to a steam turbine, which in turn drives another generator to produce electricity.
  • The steam powered turbine and generator increases the overall efficiency of the gas/steam turbine (or combined cycle) operation of the power station to around 53%.
  • The steam used to rotate the steam turbine is directed to a condenser, where it is cooled back into liquid water for reuse in the boilers.
  • 10,000 litres of seawater per second is pumped through the condenser for this purpose.
  • The seawater is returned to the sea.
  • Each of the three generators at Pelican Point produces electricity at 15,750 volts.
  • The voltage of the electricity is increased to 275,000 volts at the step-up transformers before being delivered to the switchyard and the National Electricity Grid.
  • It is then transformed into lower voltage to be used in our homes, schools, shops and factories.
  • This whole process is monitored and controlled at the station’s control room.

Pros

  • Abundant
  • Emits half the CO2 of coal
  • Relatively cheap
  • A bridge to renewable energy economy
  • Quick to power up to support peak demand

Cons

  • Non-renewable
  • Highly flammable
  • Lower density compared to other fuels
  • Contributes to greenhouse gas emissions
Natural gas is lighter than air
When you cool natural gas down to 260 degrees below zero, it turns from gas to a liquid
Natural gas is called a fossil fuel because the energy comes from the remains of dinosaurs and ancient plant matter
Natural gas is odorless, but a chemical is often added to make it smell like rotten eggs so that leaks are easier to detect
Natural gas is the cleanest fossil fuels, producing less carbon and pollution




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