How NZ’s plan to drill for ‘supercritical’ geothermal energy holds promise and risk

New Zealand’s North Island options various geothermal programs, a number of of that are used to generate some 1,000 MegaWatts of electrical energy. However deeper down there could also be much more potential.

The federal government is now investing NZ$60 million to discover what is called “supercritical” geothermal power, following 5 years of feasibility research led by GNS Science.

Supercritical geothermal is hotter and deeper than typical geothermal sources. It targets rocks between 375°C and 500°C, near—however not inside—magma.

Water at these temperatures and depths has three to seven instances extra power for conversion to electrical energy, in comparison with odd geothermal technology at comparatively cooler temperatures of 200°C to 300°C.

The funding is staged, with $5 million earmarked for worldwide consultants to design a super-deep nicely, and additional funds to be launched later for drilling to depths of as much as six kilometers. Consultation is underwaywith assets minister Shane Jones hoping to persuade Māori landowners to collaborate.

GNS Science estimates the central North Island might need about 3,500MW value of this useful resource, though truly accessing it is perhaps troublesome and costly. The power consulting agency Castalia was engaged to predict how much would be worth developingsuggesting between 1,300MW and a pair of,000MW, ranging from 2037.

This is able to be numerous further energy. Even higher, it could cut back the peaks and troughs in technology that come up from extra variable photo voltaic and wind sources, that are anticipated to make up a rising share of electrical energy technology sooner or later. Supercritical geothermal is reportedly value efficient, which implies the know-how deserves critical consideration. However such claims needs to be topic to scrutiny.

Successive governments have supported main state power initiatives, together with the Manapouri power station, petroleum exploration throughout the early 2000s, early geothermal drilling and the investigation of a pumped hydro scheme at Lake Onslow. The necessity for power safety clearly motivates such investments.

However New Zealand has a wholesome geothermal business. Up to now 20 years, geothermal corporations have invested $2 billion in hundreds of new wells and new energy vegetation. The business already is aware of the best way to drill wells and revenue from them. So why is the federal government stepping in now?

In observe, supercritical geothermal exploration and improvement faces a number of analysis, technical and financial dangers. Personal enterprise appears unwilling to bear them alone, prompting the federal government to step in to ascertain feasibility.

The way to crack gentle rock

One drawback supercritical geothermal would possibly encounter is that drilling deeper would possibly discover plenty of sizzling rock, however not a lot water. Drilling experiments in Japan and Italy have proven that reaching 500°C is feasible, however in each circumstances the rock was so ductile (pliable and simply stretched) due to the high temperatures that it could not preserve open the gaps wanted for water to movement.

Nevertheless, the expertise was completely different in Iceland the place two wells managed to find water above 400°C. At this stage, it is not clear whether or not it is because Iceland has particular rocks—notably basalts, that are much less ductile—or as a result of the nation is being stretched by way of tectonic forces at a excessive price. New Zealand is much less in a position to depend on basalts however it does expertise fast tectonic stretching.

Deep drilling would take a look at this key speculation: is there permeability (gaps for water to movement by way of) at supercritical circumstances? The one approach to know for certain is to drill down.

If there is not permeability, the federal government might both abandon the funding or look into strategies to create it. Multi-stage hydraulic fracturing (“fracking”) is an possibility which has labored abroad within the North American shale gas industry. It has additionally not too long ago been demonstrated in some US geothermal systems.

Even when we did discover permeability, the water produced in Iceland’s supercritical wells was enormously corrosive. A greater possibility then is perhaps to inject cold water into the nicely, suppressing the corrosive fluids. The injected water would warmth up and rise into the overlying geothermal system—flushing the warmth upwards.

Nevertheless, each water injection and fracking can set off earthquakes, maybe a magnitude 4-5 every year or a magnitude 5-6 each few many years. This happened in 2017 in Pohang in South Korea the place water injection triggered a magnitude 5.5 earthquake. It resulted within the cancellation of the geothermal mission.

However there are a lot of different geothermal initiatives the place injection has not led to regarding earthquake exercise.

Fierce competitors from photo voltaic, wind and batteries

The opposite danger is financial. Supercritical geothermal would possibly sooner or later be technically possible, however its potential contribution in New Zealand shall be restricted if it might probably’t beat different technology applied sciences on value.

Worldwide, the renewable power sector continues to be disrupted by unprecedented value decreases pushed by improvements in utility-scale battery storage and photo voltaic photovoltaics.

However the provide chains are largely abroad, largely concentrated in China. This provides geopolitical complexity to the power safety calculus. Homegrown options are a energy.

Nonetheless, the Worldwide Renewable Vitality Company reports cost reductions for solar and battery modules of 89% and 86% between 2010 and 2023. Photo voltaic prices drop 33% every time the constructed quantity doubles. Drops in battery value are enabling massive deployments for day by day smoothing of the peaks and troughs of intermittent photo voltaic and wind technology.

This shifting value panorama creates monetary uncertainty for power traders. Whereas value declines may not proceed without end, it is laborious to select when they’ll stage off. In the meantime, geothermal prices have been flat for a very long time. A billion-dollar geothermal funding would possibly shortly develop into uncompetitive.

Regardless of all these caveats, we should not overlook the optimistic sign of the federal government taking a guess on New Zealand science and innovation. It will likely be thrilling to see what’s taking place at six kilometers of depth underground. And though the plan is to not drill for magma, an unintentional strike (as happened in Iceland) would result in some superb science.

Lastly, energy security deserves to be taken severely over the long run. Whereas supercritical geothermal will not repair our quick vulnerability to winter shortage, it might assist keep away from related points within the 2040s.

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