7 minute read

Pumping extra supply when it's needed most

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Dean Smith
08 February 2019

Traditional hydro and pumped hydro generation have an extremely important role to play in an energy mix, because they can provide extra energy quickly in the event of rapid changes in customer demand or outages.

How does pumped hydro work?


A pumped hydro plant works much like a conventional hydroelectric station, except that the turbine can also act as a pump, moving water back uphill.

During times of low electricity prices such as the middle of the day when the sun is shining or times of low electricity demand, such as at night or on weekends, cheap electricity is used to pump water to an upper reservoir.

During periods of higher demand or when network services are required water is released from the upper reservoir to generate electricity. The same water can be used over and over again.

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What’s the role of hydro in an energy mix?


For AGL, as our traditional coal-fired power stations progressively reach the end of their operating life, we have had to think about how to replace them at the least cost. We've done the sums and what makes the most sense is cheap, renewable energy from wind and solar, combined with more flexible and firming energy sources (like quick-start gas generation, large-scale batteries and pumped hydro), that can supply energy during peak periods or whenever renewables aren't available. This is an energy mix.

What’s in our energy mix now?


  1. remaining coal-fired power,
  2. renewable energy from wind, solar and traditional hydro,
  3. a large-scale battery that can store and supply energy when we need it most
  4. flexible generation like quick-start gas-fired generation and in time, pumped hydro.

What projects are we considering?


AGL is looking at a number of options for pumped hydro. On 7 February AGL announced it has secured an option over a 250 MW pumped hydro energy storage project at Bells Mountain in NSW, located 11km North of the Liddell Power Station.

Read more about AGL’s generation portfolio in our interactive asset map.