The Anonymous Widower

New Zealand’s $Bn Pumped Storage Hydropower Project: Making It Worthwhile

The title of this post, is the same as that, of this article on Mirage News.

These are the first three paragraphs.

Greater electrification of the economy is an essential part of Aotearoa New Zealand’s climate policy, as set out in the emissions reduction plan.

But the national electricity system depends heavily on the fluctuating storage capacity of hydropower lakes, which makes the country prone to energy shortages during dry years.

The NZ Battery Project aims to address this. One of the options being investigated is the Onslow pumped storage hydropower (PSH) scheme.

This Google Map shows the location of Lake Onslow in the South Island of New Zealand.


  1. Christchurch is in the North-East corner of the map.
  2. There is a spine of mountains with several large lakes.
  3. New Zealand generates just under 60 % of its electricity from hydroelectric power
  4. Stewart Island is off the South Coast of the island.
  5. Lake Onslow is marked by the red arrow.

New Zealand generates just under 60 % of its electricity from hydroelectric power, with 13 % from geothermal.

This document on the New Zealand Ministry of Business, Innovation and Employment, is entitled Lake Onslow Option.

In a section entitled Facts and Figures, this is said.

The Lake Onslow option referenced by the Interim Climate Change Committee could be anticipated to provide at least 5TWh of annual generation/storage. It is estimated to have a construction timeframe of 4-5 years, with commissioning and filling taking a further 2 years. At its construction peak, it is expected to create 3,500-4,500 skilled and semi-skilled jobs.

The Mirage News article says that Lake Onslow scheme will be able to generate 1.5 GW of electricity.

When full, it could generate 1.5 GW for over 4.5 days.

In The Monster In The Mountains That Could Save Europe’s Winter, I talk about Ulla-Førre, which is a large pumped storage hydro scheme in Norway.

  • Ulla-Førre has a storage capacity of 7.8 TWh and a generating capacity of 2.1 GW
  • Lake Onslow has a storage capacity of 5 TWh and a generating capacity of 1.5 GW

Wikipedia lists Fengning Pumped Storage Power Station in China, as the largest pumped storage hydroelectric power station in the world, because of an installed generating capacity of 3.6 GW.

But it is only a tiddler in terms of storage, when compared to the monsters in New Zealand and Norway.

The Mirage News article also gets serious about advantages of pumped storage hydropower.

Making The Investment Worthwhile

This is said about making the investment worthwhile.

Pumped storage hydropower is well known to be a cost-competitive option for energy storage. While the capital expenditure is high, the cost of the energy is one of the lowest, at 20-40 cents per kWh. Return on investment in pumped storage hydropower is considerably better than for conventional batteries.

Does the return on investment explain, why after nearly four decades in the UK since Dinorwig power station or Electric Mountain, opened in 1984, that the Scottish Highlands are being proposed as the home for several new pumped storage hydro power stations?

In Will Coire Glas Start A Pumped Storage Boom In Scotland?, I estimated that the potential could be over half a TWh of storage.

A Multi-Purpose Asset

This is said about designing the scheme as a multi-purpose asset.

The Onslow infrastructure provides a way of managing dry years by storing water during rainy periods.

It can also participate as a conventional electricity generator. This will have implications for the wholesale electricity market because variability (from renewable generators) is currently mitigated by existing hydropower and fossil-fuel generation.

From a technical perspective, the challenge for Transpower is to maintain a consistent frequency and voltage in the power network. The Onslow infrastructure will assist with frequency regulation for the entire electricity network.

It offers a fast-acting and large-scale dynamic load, as is the case for other pumped storage hydropower projects such as the UK’s Coire Glas project or France’s Grand Maison. Both are also located remotely in the network similar to Onslow.

Globally, PSH schemes are viewed as multi-purpose assets. The Wivenhoe Dam (in Queensland, Australia) is a lower reservoir for a pumped storage hydropower scheme and provides drinking water and flood mitigation for Brisbane.

Another example is the hydropower infrastructure of the Durance Valley in France. It was designed, built and regulated to guarantee the operator provides drinkable water (740 million cubic metres per year) for 5 million inhabitants. It also supplies water to more than 170,000 hectares of cultivated lands (1.5 billion cubic metres per year in a dry season), generates reliable low-carbon electricity (for over 2 million people per year) and protects the valley from extreme flooding – and it’s become a visitor attraction, drawing 2.5 million tourists annually.

Are we developing the new pumped storage hydro systems, so that they provide the greatest benefits to the inhabitants of Scotland and a wider UK?

December 13, 2022 - Posted by | Energy, Energy Storage | , , , , , ,

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