Renewable energy and Australia’s power

Renewable and non-renewable

Non-renewable energy sources will run out, because they took millions of years to form or exist only in fixed amounts. They include the fossil fuels (coal, oil and natural gas) and uranium. Renewable sources are replaced naturally as fast as we use them: sunlight, wind, flowing water, waves and tides, geothermal heat and biomass (as long as it is regrown).

Fossil fuels have powered industry for 200 years because they store a lot of energy, are easy to transport and can be burned whenever needed. But burning them releases carbon dioxide, a greenhouse gas that traps heat in the atmosphere and is the main cause of climate change. Coal power stations also release fine particles and other gases that cause air pollution.

Solar panels

A solar panel is made of many photovoltaic cells: thin slices of silicon treated so that when light hits them, electrons are knocked loose and pushed around a circuit. The output is DC, so an inverter converts it to AC for the house and grid.

The first practical silicon solar cell, made in 1954, was about 6% efficient. Typical panels on Australian roofs today are 20% to 23% efficient, and researchers have built cells over 30% efficient in the laboratory. The University of New South Wales has been a world leader: a technology developed there in the 1980s (the PERC cell) went on to be used in most of the solar panels made worldwide.

Australia has the highest rate of rooftop solar in the world, with panels on more than one in three houses.

Wind and water

A wind turbine uses long blades to catch the kinetic energy of moving air and turn a generator. Even the best turbines can capture only about half of the wind's energy, because the air must keep moving past the blades. Modern turbines stand more than 150 m tall, and each one can power thousands of homes. Wind farms now supply more than a tenth of Australia's electricity.

Hydroelectricity uses falling water. It is highly efficient (often over 90%) and can be switched on within minutes, which makes it valuable when demand suddenly rises. Tasmania gets most of its electricity from hydro.

The storage problem

The sun sets every night and the wind doesn't always blow, but people still want electricity at 7 pm on a still winter evening. So a renewable grid needs ways to store energy:

• Batteries: big grid batteries, such as the Hornsdale Power Reserve in South Australia (switched on in 2017, and at the time the largest lithium-ion battery in the world), and home batteries charged by rooftop solar.
• Pumped hydro: when there's spare electricity, water is pumped uphill into a reservoir. When it's needed, the water runs back down through turbines. Snowy 2.0, under construction in the Snowy Mountains, works this way. It stores energy as gravitational potential energy.
• Spreading wind and solar farms across the country, and linking states with transmission lines, so that it is usually sunny or windy somewhere.

Australia's changing grid

In 2005 about 90% of Australia's electricity came from fossil fuels, mostly coal. By the mid-2020s renewables (mainly solar, wind and hydro) supplied around 40% of the electricity on the main east-coast grid, and South Australia regularly ran on about 70% wind and solar over a whole year. The federal government has a target of 82% renewable electricity by 2030. Old coal power stations are closing as they reach the end of their lives; Liddell in the Hunter Valley shut in 2023.

Every energy source has trade-offs. Wind farms and transmission lines change landscapes and need land. Solar panels and batteries need mined materials, and old panels need recycling. Hydro dams flood valleys. Nuclear power produces almost no carbon dioxide while running, but it is banned in Australia and leaves radioactive waste that must be stored safely for thousands of years. Deciding the best mix is a question for science, engineering, economics and the community together.