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Blog Post Thursday 21 June 2018

Understanding How Gas-Fired Electricity Works

Understanding How Gas-Fired Electricity Works

We tend to associate natural gas with many direct uses, such as for cooking, heating, and hot water systems, but did you know natural gas can be used to generate electricity? Coal-fired electricity is widely used, but it's polluting, and natural gas provides a cleaner alternative. Natural gas is Australia's third largest energy source, providing for a quarter of our energy needs. Given this, it's worth taking a little time to understand how gas-power works, all the way from generation to your power socket.

 

Types of gas used

The term gas refers to natural gas and coal seam gas, which contain mostly methane. These two types of gas are naturally occurring gases. However, gas can also refer to liquefied petroleum gas, which is a byproduct of the petrol-manufacturing process.

 

How is it produced?

Gas-fired electricity is produced in two main ways: open cycle and combined cycle.

 

1. Open-cycle production

Open-cycle production is the more common method of the two. With this method, natural gas is burned to create a pressurised gas, which in turn powers a turbine connected to a generator. The turbine turns the magnets in the generator to create electricity.

 

2. Combined-cycle production

Combined-cycle systems are usually found in newer gas-fired plants. They combine a gas turbine and a steam unit. This type of system works by using the hot gases released from one gas turbine to power another turbine. The hot gases are used to generate steam by heating water, and the steam is then used to power up the second turbine to create more electricity. While combined-cycle production is less common than open-cycle production, it's more efficient and can achieve thermal efficiencies of great than 50%.

A less common production method is steam generation, in which natural gas is burned to produce steam and power a turbine to generate electricity. Distributed generation, industrial gas-fired turbines, microturbines, and natural-gas fired reciprocating engines are other ways gas-fired electricity can be arranged or applied.

 

Transmission and distribution

Once the gas-fired electricity is generated, it gets to your household or business through the transmission and distribution network.

 

Transmission network

The transmission network delivers power from the generator, which can be in remote or rural areas far away from end users, to the distribution network. The electricity is transported at a high voltage to cities, towns, and other major demand centres. The transmission network is made up of towers, wires, underground cables, transformers, and other equipment supporting delivery and monitoring.

 

Distribution network

The distribution network receives the electricity from the transmission network and converts the high-voltage power into lower voltages by passing it through substation transformers. The electricity is then transported in wiring over poles or through underground wiring, directly to businesses and households.

 

Benefits of gas-fired electricity

Gas-fired electricity offers benefits for consumers, businesses, and the environment. It's a cleaner way to generate power and its generation can be easily ramped up and down.

  • Cleaner - In power generation, gas-fired production, especially the combined-cycle method, results in 50% less carbon dioxide than coal-fired plants. This makes gas a cleaner alternative for power generation. Additionally, coal is by nature a highly polluting input for power generation, as it releases the highest levels of pollutants into the atmosphere beyond carbon dioxide. As an alternative to coal, gas is far cleaner.
  • More efficient - Coal-fired stations average around 33% energy conversion, while combined-cycle gas-fired stations can convert up to 50% of the input gas into electricity. This means gas is a much more efficient input for electricity generation.
  • Quick start-up times - Gas-fired generation provides short start-up times, which means these types of plants can be used to quickly ramp up production when demand peaks. While coal-fired plants can take hours to reach full capacity, gas-fired plants could reach maximum output within 20 minutes.
  • Abundant supply - Australia has an abundant supply of natural gas to draw on, so access and supply isn't a problem.
  • Less land and easier to construct - Gas-fired power plants require less space than coal-fired plants when it comes to generating the same level of output. Additionally, they require less time to construct.

 

What does this all mean for you?

Gas-fired electricity is a cleaner, more efficient alternative to coal, and the abundance of natural gas in Australia makes it a viable option for electricity generation. In addition to being more environmentally friendly, gas-fired power offers the advantage of quick start-up times. With an understanding of the complex processes required to turn gas into power, you'll likely have a newfound respect for the electricity at your home or place of work.

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