Onslow pumped storage

The possibility of a pumped storage scheme at Lake Onslow in New Zealand’s South Island is presently under investigation by the NZ Battery group. If constructed, the scheme could enable significant reductions in national carbon dioxide emissions. This would be achieved by its elimination of extended periods of high electricity wholesale prices, including through dry years. The new price regime and power supply reliability would encourage transition from fossil fuels to electricity as the dominant energy source for transport and industrial heating. At the same time, the absence of high wholesale prices would make fossil fuel power generation uneconomic, leading to a situation of 100% renewable electricity generation.

The scheme, if constructed, would define much of New Zealand’s green transition for many years to come. Current information is that some government announcements will be made at the end of June, with some level of decision in December.

It is possible to make an informed estimate as to how the scheme might be set up and consider various associated possibilities derived from it. Those interested can download a pdf file here, which covers a range of Onslow topics to varying degrees of detail.

The proposed configuration of the Onslow scheme should be made public in May or June.

If it proceeds, the Onslow pumped storage will be the largest hydro engineering project in New Zealand’s history, being equivalent to a combination of the Benmore Dam and the Manapouri Power Scheme. In addition, there are likely to be constructed environmental offsets of various types in the Otago region.

The scheme would also represent the greatest national impact ever achieved by a research concept originating from a New Zealand university. In this regard, I would like to acknowledge the work of my University of Waikato research students, Sarah Bear and Mohammed Majeed:

Sarah Bear (2005). Hydrological evaluation of pumped storage in the Onslow-Manorburn basin (MSc).

Mohammed Majeed (2019). Evaluating the potential for a multi-use seasonal pumped storage scheme in New Zealand’s South Island (PhD).

Onslow and wind power
It is often said that wind will not always blow when the power is needed. The other side of the coin is that a lot of blowing wind at low-demand time is not helpful from the viewpoint of economic generation. Wind power must be sold as it is generated, regardless of the current price. As more wind power develops in New Zealand there will be more situations like that described below. Knowing that Onslow pumped storage will keep prices away from ridiculously low values should encourage more wind power development, if construction of the scheme is confirmed.

From Transpower weekly update May 24, 2022.

Prices continued to hover around the $200 mark, reflecting the below average hydrology, and upward price pressure on thermal fuels including carbon.
The average price at Haywards was $199/MWh, an 11% decrease from $224 MWh the week before. Prices fell drastically to $5/MWh in the early hours of Friday the 20th as a result of 659 MW of wind generation during the overnight demand trough.



Earl Bardsley, University of Waikato



Onslow in the news
Selected items, positive and negative, are listed below in time order. There is inevitably a degree of overlap. Some comments are added in places. Most news items date from the July 2020 election announcement of investigation of dry year alternatives, with emphasis on Lake Onslow pumped storage. There will be a further flurry of news items if the coming government announcements in June 2022 indicate that Onslow is selected as the dry year option of preference for detailed evaluation.

January 2009
Govt eyes price of power as water spilt

August 2018
ANU pumped hydro researchers take out Eureka Prize
This is not about Onslow but there are similarities in that Australian pumped storage sites were identified that would enable 100% renewable electricity there. In New Zealand, the University of Waikato has played a similar role to ANU, but with focus just on the Onslow scheme.

September 2019
Storing energy for a transitioning grid

July 2020
Govt looks to boost clean energy supply, commissions $30m investigation
Includes two 1News video clips about the New Zealand government July 2020 announcement of initiation of investigations into Lake Onslow pumped storage.

Pumped hydro may result in ‘biggest infrastructure project since the 1980s’

Industry figures say Lake Onslow hydro project not worth it

Lake Onslow hydro plan expensive and unnecessary
The Centre for Sustainability at the University of Otago advocates modification of electricity demand rather than increased storage capacity at Onslow. However, it isn’t clear that demand could be sufficiently reduced to take New Zealand through a dry year without significant economic impact.

A prudent approach to New Zealand’s renewable energy goals
Raises the possibility of a Taranaki gas alternative to Onslow.

Solving the critical flaw in our power grid

Time for new nation-building hydro project

August 2020
$4 billion Lake Onslow pumped hydro scheme could ‘tip electricity market on head’
This is something of an over-reaction to the size of Onslow impacting the electricity market. Onslow is only “large” with respect to energy storage capacity. The generating capacity at Onslow will be about 1000 MW, which is just a little larger than the MW capacity of the Huntly power station. Nobody has suggested that Huntly is a huge energy gorilla with capability of tipping the electricity market on its head.

Lake Onslow project: area has seesawing history

Otago pumped hydro a fanciful, rainbow project

Lake Onslow: bold vision or engineer’s pipe dream?

September 2020
Election 2020: Labour pledges 100 per cent renewable power by 2030

Labour pledges extra $70m for Lake Onslow dam project

Labour’s 2030 ‘100 per cent renewables’ goal is realistic if Lake Onslow scheme stacks up

Will pumped hydro result in significant energy price hikes for NZ?

Ardern talks environment and economy on campaign trail in Taupō
Recognition of trade-offs between advantage and disadvantages of the Onslow scheme.

October 2020
The Detail: Is renewable energy the best way for NZ tackle climate change?
The 100% renewable energy mentioned here is actually 100% renewable electricity.

As a minister plumps for hydro, uncertainties loom

November 2020
Contact says Lake Onslow scheme would ‘paralyse’ investment in renewables
The potential ‘paralysis’ of renewable investment is often repeated. However, it is not clear why construction of what amounts to a large battery should deter new investment in renewable electricity in any way. Since November 2020 there have been many announcements of new solar, wind, and geothermal projects.

March 2021
Pumped hydro to take a year longer

June 2021
Power industry ‘openly resistant’ to Lake Onslow, minister suggests

Lake Onslow energy storage proposal ‘fatally flawed’

Lake Taupo possible ‘battery’ for power production
Energy storage possibilities in the Central North Island

Our hydro dams are bubbling up climate-warming methane

July 2021
Understanding Lake Onslow

September 2021
Coal generation rises to highest share in 13 years
Energy Minister Megan Woods points out the potential value of Onslow pumped storage to offset coal use for power generation.

October 2021
Govt awards $11.5m contract to investigate feasibility of Lake Onslow power scheme

December 2021
Project Onslow is the key to unlocking our renewable future

February 2022
Critics warn Lake Onslow power scheme’s $4b price tag may balloon
Includes discussion of some engineering aspects.

March 2022
Genesis imports US wood pellets to fuel Huntly renewable energy trial
Biofuel burning at Huntly is suggested as an Onslow alternative. However, that this would maintain high electricity prices into the future.

The giant puddle that could power NZ
A local view of the Onslow scheme and its environmental setting. Some great pics as well.

Farmers unhappy crucial land to be flooded under Government’s proposed Lake Onslow hydro storage scheme
Some less than optimal dealing with local farmers.

April 2022
Geotech investigations to get underway for pumped hydro at Lake Onslow
Initiation of Onslow geotechnical investigations announced by Megan Woods.



Earl Bardsley, University of Waikato, 2022

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