Critics of the proposed Lake Onslow pumped hydro scheme are talking up its costs and warning of a possible blow-out to its speculated $4 billion price tag, even before a decision is made on whether to proceed with the project. But a dam safety expert says the detailed engineering investigations planned by the Government should reduce the risk of any surprises if the verdict comes back positive. Dan Forster, chairman of the New Zealand Society on Large Dams, says the cost of the potential project is likely to be highly dependent on the outcome of geological investigations now underway. A big factor would be whether local materials could be used to build the hydro schemes’ dams, or whether clay and rock would need to be trucked in. The Lake Onslow scheme would serve as a giant battery to help protect against hydro shortages during drought years and to, in effect, store highly-variable wind and solar generation for when it was needed. Enough water could be pumped uphill into its reservoir in a natural schist rock basin high in Central Otago to provide power equivalent to somewhere between five and 15 weeks’ worth of the entire country’s electricity demand, depending on its configuration… It will produce up to 2000MW when drawing down power, but is now expected to cost more than A$5b (NZ$5.4b) and would hold 350 gigawatt-hours of power, which would be less than a tenth of the expected power storage of Lake Onslow… The Government doesn’t expect to be in a position to make a final call on whether to press ahead with a detailed business case for the project until December… ”
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Source: Stuff, Tom Pullar-Strecker 05:00, Feb 20 2022