Harnessing the winds against climate change

Monday, 25 January 2021

Wind power must increase 10-fold to help New Zealand reach its renewable energy and carbon neutrality goals. But there is the wind and the will to make it happen, writes Janine Rankin.

When it comes to wind, the Tararua ranges above Palmerston North are placed to capture the best.

A series of wind farms established there makes Manawatū the undisputed wind capital of New Zealand.

Turbines dominate the skyline from Tilt Renewables Tararua wind farm, Meridian’s Te Apiti and NZ Windfarms’ Te Rere Hau.

Together they generate 43.6 per cent of New Zealand’s current wind energy, some 400 megawatts.

**READ MORE:

* Towers for Mercury's wind farm assemble with helicopter help

* Founder of failed Windflow Technology still sees opportunity for wind power

* Foundations started to harness Manawatū winds

**

When Mercury’s $465m, 60-turbine Turitea wind farm is complete, that will rise to half of the nation’s wind power.

It’s a huge contribution but, even so, wind currently provides less than 6 per cent of New Zealand’s electricity.

In order to reach the Government’s target of 100 per cent renewable energy by 2030, wind generation is going to have to increase 10-fold.

The Tararua skyline, the windiest, richest wind resource in New Zealand, if not anywhere in the world, according to Mercury’s generation development manager Dennis Radich, has pretty much run out of capacity.

“These hills are the most productive in the world for wind generation.”

Except for some close neighbours, the title of New Zealand’s wind farm capital was something the city wore proudly, said the Palmerston North City Council’s environmental sustainability committee chairman Brent Barrett.

Each development has faced a strong body of opposition, but by last year, just a handful of near neighbours continued to complain to the council about them.

District plan rules have been changed to demand a 1.5km separation between homes and wind turbines.

Given Manawatū’s near-saturation with turbines, it will be up to the rest of New Zealand to harness more wind.

Generating 10 times as much energy from wind was definitely achievable according to NZ Wind Energy Association chief executive Grenville Gaskell.

But that was likely to take until 2050 to achieve, rather than in time to meet the Government’s 2030 target for the transition to fully renewable energy generation.

The wind, the will, the policy framework and the economics were all lining up for renewed investment in wind after several years in the doldrums.

There had been no major wind farm build since 2014, when Meridian commissioned Mill Creek in Wellington.

Some consents had lapsed.

Then in 2019, Mercury announced it would be going ahead with the 33-turbine first stage of Turitea, later committing to the 27-turbine southern stage.

Tilt Renewables is starting to generate power from its 31-turbine Waipipi project in Taranaki.

They were signals the demand for electricity and the economics stacked up for wind generation in a business sense, said Gaskell, as well as a response to the political will to harness renewable energy in response to climate change.

Energy and Resources Minister Megan Woods said wind energy had an important role to play in New Zealand’s electricity generation mix.

Turitea’s development has an extraordinarily long history, stretching from 2004 to within two years of having to relinquish its resource management consents, waiting for the right time to build.

Its genesis was prompted by the Palmerston North City Council, which changed the purpose of the city’s main water catchment, the Turitea Reserve, to enable renewable energy generation.

The original application from the council’s partner, what was then Mighty River Power, was for a 122-turbine development.

It attracted more than 700 submissions, of which 476 were in opposition.

In 2008, then Environment Minister Nick Smith decided the project was a matter of national importance, and took the process out of local hands and under the control of a Board of Inquiry.

The hearing started in July 2009. It did not end until March the next year. It took the board nearly another year to produce a draft decision.

The final decision allowed for 60 turbines, arranged in northern and southern clusters, and protected a view shaft from the central city.

Then for eight years there was no visible activity until the March 2019 announcement Mercury would go ahead with the first, northern stage of the wind farm.

Turitea is built to capture the prevailing northwesterly, but the turbines rotate for any wind direction.

Since breaking ground on the project in October 2019, the wind farm is rapidly rising above the ridges.

The transmission line, with 18 traditional pylons and 20 monopoles, has been completed by contractors Electrix.

It traverses the Turitea Reserve.

The components for the towers were lifted into the reserve by helicopters, including the giant Kahu Black Hawk, to minimise the environmental impact and to avoid having to cut tracks through the bush.

The transmission line runs from the new plantation substation on the wind farm, through the reserve to Brown’s Flat and on to the Linton substation and connection to the national grid.

The city council and its ratepayers will get their rewards for allowing use of the reserve when the wind farm is fully operating, with royalties of about $500,000 a year.

The northern group of turbines, visible from the Pahīatua Track between Palmerston North and Wairarapa, are starting to rise.

Each tower consists of two, 34-metre sections, on top of which go the nacelle, gear boxes and eventually, the blades.

There has been as much activity below ground as above so far.

A network of roads and tracks leads off the temporarily private South Range Rd, supported by a range of detention ponds to capture run-off and silt in keeping with the consents’ environmental controls.

A herringbone pattern of huge holes in the ground has been established to accommodate foundations for each tower that run 5 metres deep and 15 metres across.

Each tower has a foundation of 30 to 40 tonnes of steel reinforcing through an octagonal base of 700 tonnes of concrete.

The 330 cubic metres of concrete for each tower has to be delivered in one pour, explaining the presence of a batching plant on site.

“We looked at whether we could bring it in, but it would require a concrete truck every 10 minutes,” said Mercury’s project manager John Campbell.

The risk of deliveries being held up by traffic delays or incidents on the main road was just too great.

When completed, each tower will weigh 300 tonnes, stretching 125 metres tall to the tip of the highest blade.

But before then, turbine suppliers Vestas has another logistical hurdle to resolve; how to get the 99, 55-metre-long, 12-tonne blades up the hill.

Originally the blades were expected to arrive through the Port of Napier, and be hauled up the eastern side of the hill.

But instead, they have arrived through Taranaki, and have been transported by road to Palmerston North, where most of them are stored at a site in Rangitīkei St.

The change of direction prompted a new plan to get the blades up the Pahīatua Track, with work on a slip road started to bypass an s-bend.

But the slip road slipped, and is most unlikely to be able to handle the special delivery.

“Vestas continue to work on alternatives…” said Radich.

Mercury will then move on to the development of the second, southern stage of the project, where some groundworks have already begun.

The Turitea wind farm stands alone, but the transmission line has been designed to extend to Mercury’s next wind farm, should it proceed.

Mercury has consent to construct the 53-turbine Puketoi wind farm across the Wairarapa.

That consent could lapse if a construction start-up is not confirmed by mid-2023.

“We are very aware of that date,” said Radich.

It is an “extremely high quality” site, but a massive undertaking, with Mercury carefully watching the market, and its competitors.

In the meantime there is a pipeline of wind farm proposals consented or under investigation.

Possibly next out of the blocks might be Meridian’s Harapaki 41-turbine wind farm in Hawke’s Bay, big enough to power 70,000 average homes.

Gaskell was interested to see more diversity in geographical locations for wind farms, and the size of developments.

He said wind was the most reliable form of renewable energy on an annual basis.

But day-to-day, changes in the wind meant it needed to be complemented with other forms of generation such as hydro, which could be ramped up almost instantly, but had bad seasons.

Therefore, it would be helpful to see wind generation spread across New Zealand, because it was almost always blowing somewhere.

He said as technology advanced, it was not always necessary to locate turbines on ridge lines where they caught the most wind, and were exposed to greater wear and tear.

Gaskell was also keen to see more smaller scale wind farms to support regional and community resilience, but at the moment, the “robust” consenting process was complex enough to deter all but the biggest players in the market.

Woods said the NZ Battery Project had been set up to look at potential solutions to New Zealand’s dry-year problem when existing hydro-power catchments did not get enough rainfall and the level of the storage lakes ran low.

The project would provide comprehensive advice on the technical, environmental and commercial feasibility of potential energy storage projects.

The first phase would look at the viability of pumped hydro, and separately, the Government would encourage emerging renewable sources of energy such as green hydrogen, and removing barriers to renewable electricity generation through stronger resource management national guidance.