Australia’s Back-Up Plan: Pumped Hydro Energy Storage

Andrew Blakers is emeritus professor at the College of Engineering, Computing and Cybernetics at the Australian National University in Canberra, Australia. A leading expert in renewable energy, especially solar, Blakers along with Martin Green, Aihua Wang and Jianhua Zhao recently received the 2023 Queen Elizabeth Prize for Engineering for the invention and development of Passivated Emitter and Rear Cell (PERC) solar photovoltaic technology. By making solar cells more efficient, PERC has come to underpin recent exponential growth in high performance, low-cost solar electricity.

A country and an economy driven solely by clean energy. This is the goal of Australia, achievable through an alliance signed in the name and on behalf of sustainability: on one side, solar and wind installations, and in general, all those capable of producing green energy; on the other side, hydro pumped schemes, power plants connected to complex hydraulic tunnels designed to store the produced energy and reuse it when needed. According to Andrew Blakers, one of Australia’s foremost experts in sustainability, this alliance is not only the future of Australia but also what the country needs to achieve the production of only green energy, a goal the government aims to reach by 2050.

Where does Australia rank among countries that are investing in renewable energy, and how does it differ from them?

“Australia is number one for per-capita generation of solar and in the top six or seven for per-capita generation of wind.

There’s a bunch of northern European countries, Scandinavia, Denmark, Netherlands, Germany that are doing well in wind and solar.

The key difference between Australia and northern Europe is that Australia is physically isolated. We can’t share electricity across national boundaries. We have to go it alone. We can’t borrow nuclear power or coal power from some neighbouring country this week, and send lots of solar and wind back to them next week to ride through a dark, still period.”

For Australia to go it alone, it needs storage as a back-up for whenever the sun does not shine and the wind does not blow. What is storage and how is it important in maintaining a stable power grid?

“In the middle of the night, you never have solar power. So it is very obvious that, in a solar dominated grid, you need enough storage to ride through the night. And this storage comes in many forms: batteries for electric vehicles, batteries for short-term, high-power applications of a few hours, thermal storage in hot water or in high temperature molten salt in factories. (And then there is) pumped hydro, which is the largest form of electricity storage at the moment for the electricity industry.”

What is the difference between battery and pumped hydro for storage?

“Batteries are typically lithium batteries widely used in electric cars, power tools and increasingly in wind and solar farms in order to provide storage of anything from a few minutes to a few hours. Pumped hydro is the sort of storage you go for when you want overnight or longer storage.

Australia has three pumped hydro systems, two under construction and about a dozen under serious consideration. Pumped hydro means you have two reservoirs, one located at the top of a hill, the other at the bottom of a hill, connected with a tunnel and pipe. And on sunny and windy days you pump the water uphill to the upper reservoir, and in the middle of the night you can let that water come back down through the turbine to recover that energy. You lose about 20 percent of the energy in that up and down round trip, but 80 percent of the energy is available, and this is similar for batteries.

And the pumped hydro system will last 100 years. All you need are hills and the ability to find a place for a square kilometre upper reservoir and a square kilometre lower reservoir. In Australia we have about 300 times more potential pumped hydro sites than we will ever need to support 100 percent renewable energy.”

As you mentioned, the existing pumped hydro energy storage schemes are Wivenhoe in Queensland, and Shoalhaven and Tumut 3 in New South Wales. Snowy 2.0 is under construction in the Snowy Mountains . There are then some under serious consideration like the Pioneer-Burdekin, also in Queensland…

“We need probably those (options) plus three or four more to support 100 percent renewable energy – not just electricity – when we electrify everything including transport and heating and industry, and nearly all energy is supplied by solar and wind. About eight or 10 pumped hydro, and a lot of batteries and other storage, and a lot of transmission, does the whole job – and all of this is off-the-shelf at relatively low cost.”