Polluting to Clean: How Australia is turning old mines into water-based batteries

Mines are known polluters of the planet. Whether they are dug up for metals or coal, they pollute the land and water around them and estimates suggest that mining and allied activities are also responsible for one percent of global carbon emissions. However, the Australian government is turning this on its head by approving projects that will convert some defunct mines into water-based batteries for renewable energy plants. 

In Far North Queensland, a former gold mine is at the center of a new renewable energy hub, while a former coal mine in Gloucester Valley will bring renewable energy to over 120,000 homes. The idea behind these projects is rather simple – store water in these mines and then use it to generate electricity when required. Technically, this is called pumped storage hydropower (PSH). 

What is pumped storage hydropower? 

A pumped storage hydropower (PSH) system consists of two reservoirs, located at slightly different altitudes and connected to each other. When energy demand is low, excess electricity from nearby wind and solar power plants is used to pump water from the lower reservoir to the higher one, where it has more potential energy. 

During peak energy demand, water from the higher reservoir is allowed to flow to the lower reservoir through a special connector that houses a turbine in it. The flowing water generates electricity on its way down, which is then supplied to the grid. 

In typical PSH projects, the two reservoirs need to be built from scratch. Australia is just ensuring that it uses mines that have already been dug up to store this water, saving time and money in the process. 

How much electricity can it generate? 

The Queensland project is being planned with 2,000 megawatt-hours (MWh) of energy storage. A single MWh is sufficient to power an American home for a little over a month. So, 2,000 MWh can power 2000 homes for a month or a larger number of homes for a shorter duration. It could power about 143,000 homes for eight hours of clean energy.

Similarly, the Gloucester Valley plant can power 120,000 homes with clean energy when demand increases. What is more important though is that this allows defunct mines to be put back into operation and use them to build a cleaner future. 

These mines are planned to be filled with water from rainfall and groundwater. Similar facilities operate in Switzerland and even the US and their continued success allows other countries to repurpose their existing facilities and source clean energy from them.