Geothermal energy “our secret weapon”

New Zealand’s location – astride the boundary between two colliding tectonic plates – shapes our iconic landscape. Take the Southern Alps, Ka Tiritiri-o-te-Moana. They are among the fastest rising mountains in the world, uplifted by 20km in 12 million years, their height kept in check by continuous erosion. The volcanoes of Te Ika-a-Māui, the North Island, tell a different geological story. Under the Taupō Volcanic Zone, the Earth’s crust is thinner than normal, bringing magma close to the surface. With it comes vast quantities of heat – the basis of the country’s geothermal sector.

The reservoirs of geothermal fluid (waiwhatu) – a mix of pressurised water, steam and minerals naturally generated by this heat – provide a renewable and reliable form of energy beneath our feet. For more than 65 years, ever since the country’s first plant opened at Wairākei, geothermal has played a role in the energy mix. Of the 29 geothermal fields known to exist around the motu, eight currently generate electricity or supply heat directly, for use in industry or agriculture.

“Since 2020, we’ve been in a new cycle of growth,” says Kennie Tsui CNZM FEngNZ CPEng IntPE(NZ), CEO of the New Zealand Geothermal Association (NZGA) and Deputy President of Engineering New Zealand.

“We are currently supplying about 1,200 megawatts of geothermal electricity to the grid – about 22.5 percent of the total supply. Our anticipation is that long term, we will double that. Plus, we’ll have more and more opportunities in direct use too. Essity switching their drying machine to 100 percent geothermal is a good example of that.”

Kennie’s optimism is underpinned by broader changes influencing the sector. Amendments to the Resource Management Act are expected to simplify the consenting process for geothermal energy projects, and in August the Government launched From the Ground up: a draft strategy to unlock New Zealand's geothermal potential. In late 2024, funding of up to $60 million was announced to support the development of supercritical geothermal technology in the Taupō Volcanic Zone; drilling to depths beyond 5km, to access even hotter geothermal fluid.

A Māori lens

Something else on the horizon is Stage 3 of the National Freshwater and Geothermal Resources Inquiry (Wai 2358). Focused on Māori rights and interests in geothermal resources, the final hearing stages of this inquiry are scheduled for September. “This is something that I’m keeping an eye on,” says Dr Nona Taute-Hohepa MEngNZ (Te Arawa, Tainui) from the University of Auckland. “I’m on the side of Māori being more involved in all phases of geothermal energy projects.”

Nona’s thesis focused on making the consenting and decision-making processes around geothermal energy more inclusive. One output was a tool that guides people through the impact assessment of a geothermal project, and provides a score on the project’s sustainability. He says the assessment process is lengthy, but “pretty intuitive”.

He continues: “The goal for tools like this is to help iwi and hapū articulate their values, goals and vision effectively, and then to incorporate that into an engineering-heavy process.”

This is something that Andy Blair ONZM is also prioritising. She and her team at geothermal research and consultancy firm Upflow are working on a project to support Māori landowners on greenfield sites.

“It can take a long time to get ready for a geothermal development and the process needs a lot of information. We want to help landowners prepare for that.”

Upflow works closely with several Māori landowner groups, including Tauhara North No.2 Trust, a Rotokawa, Reporoa-based trust. “We support and deliver on their geothermal R&D aspirations,” says Andy. “Māori are intergenerational thinkers. This is deeply aligned with both geothermal developments, which are 50-plus year projects, and long timelines associated with R&D. Māori seek holistic and diverse ways to utilise resources, and geothermal is no different. Additionally, geothermal reservoirs are deemed taonga (treasure) that should be cared for long into the future.”

Nona says: “In terms of partnership between iwi, government and companies, we have made some progress,” adding that if the trend continues, “… we’ll see those partnerships become more robust”.

“I think if we have clear guidelines and patience, then we can avoid conflict and headaches and get a better outcome for everyone.”

Both Kennie and Nona mention the Tūaropaki Trust’s geothermal field at Mōkai as an example of an innovative and Māori-led use of the underground heat. “We see true vertical integration there,” says Kennie, “From electricity generation, to dairy milk powder drying, to gourmet tomatoes, to green hydrogen production – all using the same resource.” For Nona, it’s the people that make it a success. “There are permanent iwi staff overlooking the management process – that’s what you need to ensure a project incorporates kaitiakitanga.”

Innovative thinking

The geothermal sector is awash with good ideas, says Kennie, who is particularly excited about industry efforts to reduce carbon emissions at geothermal sites.

“The 18 plants that we have in New Zealand are not carbon-zero. We emit non-condensable gases like CO2.”

So, over the past four years, NZGA has been overseeing efforts to capture and re-inject CO2 back into the reservoir by mixing it with the expended geothermal brine.

“In 2019, there were 604 kilotonnes of CO2 emissions related to geothermal. We are now down to less than 450 kilotonnes for 2024.” Kennie says the sector has achieved a significant reduction by utilising engineering and design skills.

There are numerous new tools and techniques on offer that can optimise the output of a steam field. Engineering consultancy MTL is working with Toshiba to deliver small-scale skid-mounted geothermal power plants that can be integrated into existing systems here and overseas. Companies like Geo40 are extracting minerals like silica and lithium from geothermal fluid at Ohaaki. Upflow received funding from the United States’ Department of Energy to develop GOOML, a machine learning-based optimisation tool that can increase electricity generation by between 1 and 10 percent.

“We developed this using real data from Contact Energy, Ngāti Tūwharetoa Geothermal Assets and Ormat in the US,” says Andy. “We’re on the commercialisation path now, and are working on how to put GOOML into standard workflows.”

There’s also a growing interest in geothermal energy at both ends of the temperature scale. For Kennie, unlocking the widespread use of low – and medium – temperature geothermal energy (<140°C) would be a “game changer” in helping industry move away from natural gas and oil.

“To us, that is a huge untapped opportunity – it’s a resource accessible all over the country. You don’t have to drill down for kilometres in the Taupō Volcanic Zone to access it.”

Supercritical geothermal fluids are much hotter, offering 10 times more energy than those found at current drilling depths (~3.5 km). Rather than replace conventional geothermal, it is expected to complement it, offering higher efficiency and higher temperatures for specific applications. Andy says: “Supercritical is an amazing long-term opportunity for New Zealand. There’s a lot of science to be solved around materials, handling and utilisation, but both here in Aotearoa and around the world there are great people trying to answer those questions.”

International impact

“New Zealanders are everywhere that geothermal energy is being captured,” says Holger Zipfel CMEngNZ CPEng IntPE(NZ) from MTL.

“I think since the very beginning, NZ Inc. has prioritised sharing our knowledge beyond these shores.” Kennie agrees: “I would claim every geothermal plant in the world has a Kiwi handprint on it. We are the only energy industry that exports – rather than imports – our expertise.”

As early adopters of geothermal energy, our engineers have long been sought to work on overseas projects, starting in 1973 in Indonesia. For 10 years, as part of a government-funded aid programme, Kiwi geothermal engineers surveyed the country’s underground resource, and kickstarted drilling at Kamojang, which became Indonesia’s first geothermal power plant.

“New Zealand has retained a great reputation there,” says Holger. “We’re involved in the Philippines, Taiwan and Kenya on different projects, but Indonesia is a major focus of our work.”

One of MTL’s two Indonesian projects is Muara Laboh Unit 2 – a major expansion of an existing site. “We get to work in a very collaborative way there,” says Holger.

The relationship between Indonesia and New Zealand is broader than delivering new geothermal plants. A key priority is developing the local workforce through the provision of on-site training, and supporting Indonesian polytechnics and institutions. Education is also at the heart of the Geothermal Institute at the University of Auckland. In addition to offering postgraduate courses and a PhD programme, the Institute has delivered training everywhere from Australia, Japan and the Philippines, to the Caribbean, Chile and Mexico.

“All around the world, people want to be able to plug into an ethical, sustainable, reliable energy source,” says Andy. “That’s what geothermal offers. It’s an enabler, opening up so many other opportunities for economies and communities to prosper. Geothermal energy is our secret weapon, but it’s time to shout about it from the rooftops.”

On the WING

From its inception in 2013, Women in Geothermal (WING) – an international movement co-founded by Upflow’s Andy Blair – promotes the education, professional development and advancement of women in the geothermal community. WING has run projects to support working parents, developed a documentary with the United Nations, sponsored student scholarships, and it hosts a Future Leaders cohort – all with the aim of making the geothermal sector more inclusive. One programme is the WINGman Special Taskforce, providing men in the sector with tools and advice on how to better support their female colleagues. “I think what WING is doing is fantastic,” says proud WINGman Holger Zipfel from MTL. “A lot of my geothermal colleagues at MTL are women, but that’s still unusual. It’s important that we see an increase in the number of women in engineering. I recently joined WING’s board, so I hope to do more.”

This article was first published in the September 2025 issue of EG magazine.