Researchers saw small dams in rural Australia could function as unconventional “batteries”.

In Arras, France, the Goudemand apartment building uses a flat rooftop pool to store water. The water is channelled to five basement tanks, with a total capacity of around 50,000 litres. 

When released, this water powers a turbine, generating approximately 3.5 kilowatt-hours of electricity, equivalent to several hours of energy consumption in an average Australian household. 

Solar and wind energy are employed to replenish the rooftop reservoir when weather conditions allow.

The building is an example of a micro-pumped-hydro energy storage system, this time using a rooftop as a reservoir. The primary purpose is to reduce the load on the building’s lithium batteries.

Recent economic analysis suggests that such micro-pumped-hydro systems could be built at water reservoirs.

Experts say that thousands of potential reservoirs are scattered across rural Australia, but they must meet specific criteria. 

They must either exist in pairs or be linked with a river to enable water flow for energy generation and storage. Additionally, suitable reservoirs need a minimum slope of 17 per cent between them to drive turbines efficiently and should be within 500 metres of each other to remain practical and cost-effective.

A team of engineers from UNSW led by Dr Nicholas Gilmore recently conducted a comprehensive mapping exercise to identify suitable reservoir pairs. 

They concluded that there are over 30,000 potential reservoirs that meet these criteria, with an average energy storage capacity of approximately 30 kilowatt-hours. 

Although practical constraints may reduce this number, many viable candidates remain.

To keep costs down and compete with traditional batteries, the researchers designed a simplified system using a single pipe connecting two water bodies and a reversible pump-generator. 

This system, already implemented in a Belgian prototype, is cost-effective on a per-kilowatt-hour basis compared to lithium batteries. 

While household batteries excel in providing immediate power and handling higher loads, micro-pumped-hydro systems offer the advantage of storing substantial amounts of energy, extending the usability of solar power over extended periods.

However, these systems are not without limitations. Droughts can restrict the amount of water and, consequently, power that these systems can store.

Meanwhile, other researchers, such as Professor Andrew Blakers from the Australian National University, have identified potential sites for paired reservoirs in Australia, some with gigawatt-hours of storage capacity. 

These sites could significantly contribute to the country's energy storage needs, surpassing them by up to 300 times. 

Projects like converting old mine pits into pumped hydro storage dams show promise, offering free and substantial water reservoirs.

The Australian Energy Market Operator (AEMO) has identified energy storage as a top priority in the coming decade, emphasising the role of large-scale pumped hydro in grid stability.