A leading energy scientist thinks geothermal energy could produce around 50% more electricity by 2030 than it does now.
This increase could go some way towards easing New Zealand’s electricity supply predicament, which Transpower warned about in May and again last month.
At that stage, New Zealand had experienced several worries over the supply of electricity, which required the issuance of so-called low residual customer advice notices. On one occasion, the country slipped to within 50 megawatts of the danger zone.
But a presentation by GNS Science has shown there is plenty of opportunity for geothermal energy to take up that slack.
“We are probably around 19% of electricity generation now and we can probably generate about 30% of electricity from geothermal,” says Isabelle Chambefort, who is a geothermal specialist and Energy Futures Theme Leader at GNS Science.
Geothermal power plants use heat from the earth’s core to drive turbines with steam from water or from some other heated fluid. They are most common in geologically active countries such as New Zealand, Iceland, the Philippines or parts of the United States.
New Zealand’s Wairakei plant was opened in 1958, making NZ a relatively early producer of geothermal electricity. Activity then levelled off before being revived with several big generating plants opening in the past 20 years.
That expansion is continuing. New projects include Contact Energy’s plant at Tauhara, near Taupo. This will be in operation later this year and will supply 3.5% of all NZ’s electricity use on its own. Another project is Mercury Energy’s planned expansion of its 82-megawatt Nga Tamariki power plant, also near Taupo.
Chambefort says besides building new power plants, output can be boosted by using improved technology to extract more power from geothermal stations that already exist.
There have been repeated claims that extracting too much energy from a geothermal field will reduce the pressure underground, and so diminish output bit by bit. Chambefort says that is a serious risk, but it is being dealt with by geothermal operators pumping water back into the ground after it has been used.
“As part of the consenting process, companies are limited in the amount of fluids they can take out of a geothermal field,” she says.
“It is based on the simple calculation that what is taken out is going back in.
“So, we have to re-inject the fluid to maintain the pressure, so you don’t have pressure inversion of your geothermal field and therefore the system is sustainable in the long term.”
So, this is the promise of the geothermal power industry. It can provide 30% of New Zealand’s electricity using heat from the earth’s core. And it is economic, because no one has to pay for that heat, unlike thermal producers, who must buy gas or coal for their furnaces. Geothermal energy is renewable, and it is constant, unlike wind or solar, because the earth’s core is always hot. Surely, this is mana from heaven to stressed electricity planners. But is it?
Greg Sise is a veteran analyst from the Dunedin consultancy Energy Link, and he says yes and no. Yes, because geothermal energy adds to the total supply of electricity, but no, because it is not suited to fill in the gaps when the supply of electricity fluctuates.
“We could run a geothermal power plant during a dry year, or a dry period, and we could turn it off for the rest of the time,” Sise says.
“But that is very expensive to do, the economics just don’t stack up. Geothermal power stations take time to heat up and to cool down. They work best when they are operating continuously.”
In other words, the very constancy of geothermal electricity is one of its drawbacks. NZ already has plenty of base-load power, to quote industry jargon, but not enough peak-load power. At present, NZ uses the coal or gas-burning plants at Huntly to provide a lot of peak supplies during a cold night in winter. But those plants were always designed for base-load, not peak-load, and are slow and expensive to turn on and off.
In other words, producing more geothermal power could replicate the problems that already exist with the Huntly power stations.
Despite this, Sise insists there are big advantages in further developments of geothermal energy. But other methods are needed to complement a system prone to intermittent supplies of electricity from wind or solar energy plants.
He says one solution is to have more generating plants that can be turned on and off quickly, and these would have to be powered by gas.
“It is very difficult to do it without gas, for the next decade, anyway,” Sise says.
His comments follow a long line of argument that gas-fired peaking plants can actually assist the environment by giving people confidence to install solar and wind farms, knowing they will still have electricity available on a still night in winter.
Meanwhile, there is another question mark over geothermal energy: it is not always as clean as it might appear. Sometimes, greenhouse gases come out of the ground along with the hot water.
These so-called fugitive emissions can add to the total quantum of greenhouse gas emissions.
Chambefort says this challenge is being faced up to.
“These days, the geothermal industry is putting a lot of effort into being able to solve this problem in the future,” she says.
“They are doing a lot of research and development into capturing and probably re-injecting (greenhouse gases) back into the ground as well."
“So, in the future, geothermal energy is likely to be renewable and carbon-free,” Chambefort says.
Some geothermal fields produce higher fugitive emissions than others.
Even so, their impact on climate change is small compared with other sources of greenhouse gases.
Figures from the Ministry of Business Innovation and Employment show fugitive emissions contributed just 4.62% of all energy sector emissions in 2020. This was dwarfed by 38.64% for domestic transport and 24.60% for manufacturing and construction.
35 Comments
Here is a great idea that a chap is working on at the University of Canterbury.
Basically he is proposing to burn forestry slash and use the heat to super-heat the geothermal steam and thereby recover the energy value of the forestry slash and solve the big problem of geothermal steam being very wet. The liquid water in geothermal steam causes problems for the steam turbines so energy is wasted dealing with it. The really clever thing if it works, is that he is proposing to inject the CO2 with the resulting geothermal water back into the ground where it will react with chemicals that are present down there and be captured as stone. (spent geothermal generation water is re-injected into the ground because it contains poison (arsenic and mercury I think))
https://www.stuff.co.nz/national/gisborne/131593927/the-student-with-a-…
In places with a plentiful supply of wood the transition to coal was quite late. Lake Saima in Finland where my in-laws are from had wood fired steam boats well into the 20th century.
Central North Island where the geothermal capacity is located also has a plentiful supply of wood. Even if the slash option is uneconomic (if it has poor eroei) there would be plenty of waste wood that is by-product of saw mill activity, and cheaper low-grade wood that is not suitable for construction that could be used.
There is a young chap in Canterbury who has started a wood-fired (solid biofuel) locomotive company. He has a new design for the water boiler which is much more energy efficient, safer, and faster to heat up.
He claims the EROEI is really high 25:1.
PDK as a more engineering minded person than me you should check it out.
Important story Erik,as an increase in firm baseline generation,allows for better voltage regulation along with hydro.Whilst Geo does emit Co2 (around 585kt in 22) there are substantive projects for capture and reinjection (with fluids) in delivery.Ngawha will be fully neutral by 25 (reducing 128kt) Contacts Te huka is injecting now and the new extension will also.
Contacts geo projects will see two thermals close with a surplus component (due to plant operating at 95%) this will be tied to the new battery project (100mw ) for use as a peaker.
Why he interviewed Sise, beats me. That fellow, from memory, bargained on behalf of corporates for cheaper electricity. It is/was a zero-sum game, so he was arguing for ordinary folk to lose.
Gas is a red herring; geothermal is good, done well; peak is an arrogant concept (those of us who live off-grid fit in with nature, we don't impose - it's an important lesson.
And our future isn't about economics - it's about getting enough energy to run a societal construct. We need to be past that neoliberal-type ideology - or that assuming ignorance, whichever it is.
Oh, and 30% of what? Current consumption? Current consumption plus FF-displacement and assuming BAU? Renewable-only as maintainable past fossil availability?
Plenty of potential for geothermal.
"It would take approximately four
years of drilling at the rate Texas currently drills for oil
and gas to produce the equivalent energy of all oil and
gas used for electricity and heat production currently
in the State from Texas’ geothermal resources.
An aggressive
geothermal drilling program at ‘home’ such as this may
serve to free up Texan natural gas for export, instead of
being required for domestic electricity production.
Source: Future of Geothermal Energy in Texas, 2023."
"Slovakia's GA Drilling has demonstrated a pair of new technologies it says could unlock geothermal power generation more or less anywhere on the planet. Anchorbit and Plasmabit promise much faster and cheaper drilling into hot rock 10 km underground.
The intense heat under the Earth's surface represents a virtually inexhaustible source of reliable clean energy that would be available 24/7 from anywhere on Earth – you could pull it up as steam to run generator turbines, or pipe it directly into district heating systems."
Energy Startup Says It Has Achieved Geothermal Tech Breakthrough
An enhanced geothermal system expands the range of sites able to be tapped for geothermal energy, and Fervo’s demo is the first time a company has shown it can be done on this kind of commercial scale.
https://www.bloomberg.com/news/articles/2023-07-18/fervo-energy-says-it…
https://www.volts.wtf/p/enhanced-geothermal-power-is-finally#details
I think, to be fair, the idea is to displace fossil energy.
But yes - the enigma is that ex fossil energy, you don't build geothermal plants, hydro dams, nuclear power plants, or PV panels. So few folk get this; I went down the track nearly 20 years ago, walked the walk, and then realised how unsustainable even my level of consumption is, ex fossil energy. And fossil energy is half-gone, and that was the best half.
I'm medical not an engineer. What I do know is that NZ how has the highest mortality per head of capita due to melanoma - a cancer caused by the sun's UV. When we have our sunniest months our hydro electricity production is vulnerable and it's common for high pressure systems to suppress wind.
So why is NZ not storming the gates of photoelectric energy. It compliments our current infrastructure and harnesses a natural resource that is killing us.
Second question. Why would you financially incentivise EV's without the infrastructure to charge them or supply non fossil burnt MW's when a solar panel subsidy was begging to be launched first?
The problem is a very cold winter evening, will result in everyone turning on their electric heaters , if it coincides with a low wind period, a shortage occurs. to make matters worst , heat pumps are not as efficient in freezing temperatures. solar does not help in these cicumstances. E.v's can be charged outside these periods, few drivers would do so many k,ms per day that they need to charge at 6 p.m. financial incentives are provided to charge in off peak hours.
Probably the cheapest battery solution is to store low grade heat. currently it is done in a limited fashion , by ripple controlling hot water systems power supply such a system has been diluted by the power companies needing to compete with gas. bigger hot water cylinders would allow more storage. Heat could also be stored and used to keep heat pumps outside unit above freezing.In a lot of countries , this is achieved by having its air supply pulled through the ground, which is warmer than air temp.
The best way to store heat, is the way I did it today. There were perhaps 4 hours of quality sunshine, and I'm south of the 45th parallel. My house got to 22 degrees, I pulled the curtains at sunset, and we'll be about 16-17 in the morning. Doing it via a hydro dam, transmission, techhnology and complexity - when the water in the dam came from solar energy in the first place - is nuts. Energy-dissipative, entropy-welcoming nuts.
But oh, there's a dollar to be made.
PV cannot manufacture PV. I've lived more that 20 years off-grid, nearly all in this house, nearly all on PV - but all PV will do for humanity, is essentially store fossil energy and release it beyond the time it's available at the pump. I buy panels and think of it as storing oil.
My grandkids will - theoretially - live past the demise of all PV. And they will see human overshoot play out; without fossil energy, they'll see 1-2 billion global population, if the drop-off equalises. How will medicine traverse that?
With all the apocalypse talk the medicine will probably have to be some form of benzo.
I really hope you're not telling them the same stories you're telling on here, with the same level of certainty. They've enough socio-cultural issues relevant to their own age group to contend with as it is.
I don't understand the comment in the article that more geothermal power, being baseload, is problematic for New Zealand in that it is not peaking capacity? Surely the more geothermal baseload there is, the more hydro capacity can be used for peaking (being relatively instantaneous to open the sluices) and thereby displacing gas peakers and coal/gas base load at Huntly.
NZ's hydro system is not very good at peaking either. It is essentially run of river schemes. Only 5-6 weeks of electricity supply can be stored in the water behind the existing dams. So a dry year creates lots of problems for NZ. In comparison big hydro places like Norway and Canada have much more storage so do not have the dry year problem.
P.S Although geothermal doesn't solve the dry year hydro problem it doesn't make it worse either.
P.P.S Geothermal plus biofuel burners as discussed upthread might have more 'peaking' ability
NZ battery's report on alternatives to Onslow is out .
https://www.mbie.govt.nz/building-and-energy/energy-and-natural-resourc…
There are a lot of people commenting who have no understanding of either how the grid works nor what the terminology means.
If we take the way the grid is currently running, the hydro rivers (waikato, Waitaki, Clutha) are doing a mixture as two-shifting and peaking. Lately, the Waikato has been doing about 100-150MW at late night and 900MW over the peak. Most of the Waikato generation at 4am is Karapiro as that has restrictive consents.
There is a big difference between energy and power. The thermal currently fills both gaps. It also is very good reserves, particularly when the wind dies. Even without new demand, there needs to be something to fill that hole, particularly on frosty winter nights.
As pdk has noted, the superheating geothermal with slash is from an academic who has no idea of how anything, especially geothermal steam turbines, actually work. There are no boilers that can do anywhere near this option.
Solarb do you know anything about the Mokai glasshouses?
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