New Zealand is taking tentative steps on energy policy that could double the current output of geothermal energy.
This would be done by drilling much deeper than existing geothermal wells and thereby extracting far more energy.
If it works, it could make New Zealand’s electricity overwhelmingly renewable. It would do so cost effectively, because geothermal energy is continuous. The earth’s core is always hot and pressure fluctuations can be averted by injecting fluid as well as taking it out from underground.
By contrast, wind farms don’t work when the wind doesn’t blow, meaning back-up generation is required for calm days but sits idle at other times. This practice is known as overbuild, and is expensive. Similar problems affect solar energy.
At present, about one-fifth of New Zealand electricity is geothermal. That is achieved by drilling wells 2.5 to three kilometres into the earth in places like the Taupo Volcanic Zone, where the earth’s crust is relatively thin. But the new programme would go deeper, to 6.5 kilometres, and get access to far hotter temperatures – 700 degrees C compared with 400 at shallower depths.
In an initial move, the Government has committed $5 million to design and cost the first of three exploratory wells. If it works, $60 million would be available to push the matter further. Private sector and iwi involvement would also be sought.
“Having a secure and resilient energy supply is a priority for the Coalition Government and is critical to rebuilding the economy and giving businesses the confidence to invest,” say the Regional Development Minister Shane Jones and the Science, Innovation, and Technology Minister Judith Collins.
"More use of geothermal energy would reduce emissions and reliance on fuels such as gas and coal, as New Zealand moves to more renewable energy," Jones says.
“Renewable energy, at present, cannot be relied on for our entire energy needs. Hydroelectric generation currently provides 60% of our power needs. However, as this winter has shown, a lack of rain can quickly turn into a crippling issue.”
The initiative will be led by GNS Science and the Ministry of Business, Innovation & Employment (MBIE).
An advantage of the scheme is that going deeper means more energy can be extracted while not expanding the surface area of a power station, according to the GNS team leader, Isabelle Chambefort. And the scale of the resource is huge.
“As part of this programme, we did an inventory of some of our resources and we estimate we can generate more than 30,000 megawatts hours,” she says.
“We would be doubling the percentage of our generation from geothermal, and it is really the key to having renewable energy.
“We need to increase by at least 50%, our electricity generation. We cannot build more dams from an environmental point of view and we cannot build nuclear so really the only solution that we have to increase base load is geothermal.”
The lobby group, Energy Resources Aotearoa (ERA), welcomes the Government’s announcement, calling it a potential game-changer for energy and economic development in New Zealand.
"New Zealand has been a leader in geothermal technology for decades and will now join the US and Iceland in advancing (this technology) and the valuable intellectual property that goes with it," says ERA’s chief executive, John Carnegie.
Chambefort says the costs of generation would be about $100 per megawatt hour, which is compatable with prevailing prices and cheaper than gas, over-built solar or solar augmented by battery storage.
A report published earlier this year by the economics consultancy Castalia estimated deep wells would cost a lot more than existing, shallower wells. But even if the price were to double, the scheme could still make sense, especially under a tough emissions regime or shortages or restrictions or even bans on fossil fuels. And it would help meet growing demand for electricity in sectors such as transport, which conventional geothermal could never do.
Chambefort says New Zealand’s research will match efforts in Iceland, the US and Japan, and is still frontier research at this stage rather than an in-use technology. But she says its potential is huge.
Officially this area of research is known as Supercritical Geothermal Technology (SCGT), and would use water heated well above boiling point, but constrained by the pressure of the earth from evaporating away as steam.
“There is nowhere on Earth right now where a power station is utilising supercritical water in a geothermal environment,” Chambefort says.
“But is it important to note that supercritical water is used every day in thermal plants which use super-heated water to turn the turbine, so this this is technology that does not need a huge development.”
43 Comments
You can't complement geothermal with solar and wind. Read the System Operator weekly reports about the trouble the unreliables already cause. If you had say 3000MW geothermal (currently about 1150MW), then hydro could fill the rest most of the time but still need thermal plant for dry seasons and as reserves.
I've done exactly that for 20+ years, privately.
PV backed up by micro-hydro. These days, I hardly think about whether I should trun something on - and the generator probably hasn't been run for a year.
I have no problem with geothermal - earthquakes and infrastructure maintenance aside (where we're going the latter will be more fraught than most people realise).
You are limited by the intermediate lakes' storage, the generation capacity on each dam and line constraints. Nothing insurmountable but the costs would be a lot higher than the benefits unless the price of power went significantly up. And none of that will solve it not raining for 6 weeks.
The involvement of a private sector partner is surely prudent. Not sure that a government of any side can, under the management of the public service sector, accomplish the construction of anything larger than a toilet block on a public park, without a massive blowout on the original cost budgeted, even then a “Clochemerle” is highly probable.
I'd be concerned about the high risk of drilling 6 odd km successfully. I hope this is not just the govt babbling on without having done some form of due diligence.
The only experienced company that I'm aware of doing the main engineering sections of a geothermal PS is Israeli.
Ormat (now owned by US Venture capitalists but engineering done in Israel) build binary stations with pentane heated by geothermal fluid as their working fluid. Fuji / Sumitomo were the designers of most of Nga Awa Purua and Tauhara. which are multi flash steam turbines. For both, much of the pipework, especially on the steamfield side is done by NZ engineers and the constructors/ fabricators are NZ companies.
https://arstechnica.com/science/2024/04/how-new-tech-is-making-geotherm…
Seems like quite a few people looking into it
Your Castalia report link is to a file downloaded on your computer, not to the online link here
There is nowhere on Earth right now where a power station is utilising supercritical water in a geothermal environment,” Chambefort says.“But is it important to note that supercritical water is used every day in thermal plants which use super-heated water to turn the turbine, so this this is technology that does not need a huge development.”
A comment made by a person who has no experience of geothermal power stations. Supercritical thermal power stations use ridiculously pure water - Contaminant have to be less than parts per billion. Even the wells only 3km deep discharge geothermal fluid with contaminants quoted in percentages. The deep wells in Iceland have discharged salt solutions that near instantaneously precipitate or superheated hydrogen chloride (pH<1). Even gold dissolves in the temperatures quoted. As one of the drill engineers I work with says. "The major thing that would come out of the programme is what doesn't work in emergency well abandonments!"
"The Fervo Cape Geothermal Power Project is an enhanced geothermal system that produces energy by injecting water into hot subsurface rock formations and then extracting the heated water to generate electricity, rather than depending on naturally occurring underground hot water like traditional geothermal systems.
If fully developed, the project will cover approximately 631 acres, including 148 acres on public lands, and produce up to 2 gigawatts of clean energy. "
https://www.publicpower.org/periodical/article/blm-approves-utah-geothe…
Just another hot dry rock project. Note how all the conditional statements abound. No wells drilled yet and no explanation of what is different here. The 2GW is just fantasy stuff, probably another case of wandering decimal points. In real geothermal, best production is about 100MW per square kilometre. That is stuff that actually works though, not a rainbow unicorn fart factory.
What does not come out in the article is that what we are seeing is something like a desperation gamble for security of power supply by the government. The idea is that the result from the $65 million of taxpayer money (no private investment) will be three deep exploratory boreholes, that will provide information to induce private enterprise to take the considerable investment risk to come here and construct the world's first commercial supercritical geothermal power station. If they don't come, the gamble fails.
The presence of supercritical deep geothermal water beneath the central North Island has been known for a long time. So the question is - if the potential is so attractive, why have the relevant corporations thus far shown zero interest in drilling deep test bores themselves? The obvious answer is that they have already decided there is no possible information coming from test bores that would convince them that the financial risk would be worth taking.
This was posted anonymously today as part of a comment in Energy News:
The plant will be first of its kind and very much bleeding edge. No rational commercial business has appetite for this risk profile.
If that's an accurate statement, then the government has just thrown away $65m.
Sorry Eric, but comments like this really annoy me.
"By contrast, wind farms don’t work when the wind doesn’t blow, meaning back-up generation is required for calm days but sits idle at other times. This practice is known as overbuild, and is expensive. Similar problems affect solar energy."
Please ensure the complete energy cycle is encoded in such paragraphs. E.g. "[blah, blah, sun not shining / wind not blowing] ... without the ability to store the surplus electricity generated in some way, or even in another form, e.g. gravitation potential energy as Onslow would have done, ..."
Happy with general thrust though. Drilling for heat - rather than fossil fuels - if fine with me. It's my favorite form of drilling to be honest. (Piles and tunnels come second.)
Why isn't NZ going hell for leather on tidally powered generation?
Tidal has many advantages. It is hugely predictable. And guaranteed. We have many places where the tide flows fast, and slow, and for long periods. It's largely green. Water is so much heavier than air so the potential energy is enormous by comparison. Downside? It's a harsh environment.
Geez. We're pretty good on the water. Let's show we can be good under the water too.
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