Q&A: Pumped hydro

Q

The government is touting pumped hydro as the answer to all our electricity problems. What they do not talk about is the inefficiency of pumped hydro nor for that matter the inefficiency of battery storage.
Pumped hydro has losses due to motor/generator inefficiencies, pump inefficiencies, pipe friction and turbine turbulence. My rough engineering estimate is that for every $1 of pumped storage power out at least $2, if not more, of power is needed fed in.

As for batteries I have no idea but the manufacturers or electric car users should have a good idea. Is there anyone who can advise as to the losses from using either? It could be like John Howard’s carbon capture where it used more power to recover the carbon and pump it than was generated.
—Tony Parnell

A

All energy storage involves some efficiency loss. Lithium batteries have round-trip efficiency a bit lower than 90%—this is published in the specifications for products such as the Tesla Powerpack used in the ‘big battery’ currently being installed in South Australia. Pumped hydro is less efficient, around 80% for the ANU’s hilltop proposal or 72% for the proposed Cultana seawater pumped hydro project.

In a high-renewable grid most electricity consumption would be supplied directly from generators, avoiding efficiency losses in energy storage. The batteries would only be used where necessary to buffer variability in supply and demand. As costs drop to build wind and solar farms, they become economically competitive with fossil fuels even after allowing for the extra generation capacity required to cover energy storage losses. Our report ‘100% renewable grid by 2030’ examines these economics; read a summary on p. 40 or find the full report at www.ata.org.au/news/100-renewable-energy-by-2030

SA wind farms are at times already being curtailed, as they’re generating more energy than the grid can absorb. So energy storage in that state has some free energy to make use of (see p. 41 for more on this).
—Andrew Reddaway, ATA Energy Analyst

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