UC academics Andy Nicol and David Dempsey join Ludmila Adam and K膿pa Morgan to dig deeper into New Zealand's green hydrogen future, raising cultural and technical issues to be addressed, in an article on The Conversation.
In its plan to听, the New Zealand government highlighted听听as a game-changing fuel. It can indeed be used to make听听and steel or to power听听that aren鈥檛 suited to batteries.
But to provide a buffer against the volatility of overseas markets, Aotearoa would need to be as energy independent as possible. Ideally, this would mean consuming only green hydrogen produced here, using abundant renewable hydro, wind and solar resources.
A hydrogen economy is good in theory, but to make the switch at the scale of Aotearoa鈥檚 climate ambitions would require about 150 petajoules of hydrogen each year, according to one听estimate. That鈥檚 about a quarter of our听.
Hydrogen is produced in a process known as hydrolysis 鈥 the splitting of water into hydrogen and oxygen gas, using electricity. To produce a quarter of Aotearoa鈥檚 energy consumption, hydrolysis would consume an enormous amount of water, about 13 million tonnes each year, the equivalent of a month鈥檚 worth of Auckland鈥檚 water demand.
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Consuming water has cultural implications
Freshwater has enormous significance to iwi and hap奴. However, their views on hydrolysis as a consumptive use of water are not widely understood. If cultural complexity is ignored, hydrogen infrastructure or processes may fail to achieve an appropriate fit within Aotearoa New Zealand society and the technology could be orphaned.
Instead, we could start addressing this early through w膩nanga with representatives from a wide range of potentially affected iwi. Recognising and addressing cultural concerns at the outset will allow M膩ori to shape how the technology is developed and to share in the economic benefits of a hydrogen economy. The intention is to better understand how green hydrogen technologies and infrastructure could belong in Aotearoa New Zealand.
Supposing we are willing and able to make this vast quantity of hydrogen, our experience with other fuels suggests we would need about a month鈥檚 worth in storage at any given time. Storage helps to smooth fluctuating market demand, takes advantage of seasonal excess of renewables (in very windy, very sunny weeks) and provides emergency reserves for 鈥溾 crises.
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Storing hydrogen underground
Unfortunately, hydrogen can鈥檛 be stored as a liquid except in听听that keep it at extremely low temperatures. Like a freezer, this is always consuming energy.
Hydrogen could be kept in special high-pressure tanks, but we would need more of these tanks than we have people in New Zealand. These tanks would be costly, cover large tracts of productive land and would be prone to damage by natural hazards. Where would they all go?
Scientists have been looking at the possibility of听, in great caverns carved in salt or in听.
We already do this with听. When it鈥檚 not needed, gas is injected into an old field called Ahuroa and then extracted as required. Underground storage of gas (methane) is common practice, providing energy resilience. For example, given the disruptions caused by the war in Ukraine,听听is accelerating gas storage in听听in time for winter.
We have recently shown there听听in other Taranaki rock reservoirs to store hydrogen underground. But it won鈥檛 be easy.
We know the gas can react with certain kinds of rock. It can even be a meal for hungry microbes. Both these processes would consume a valuable fuel. But predicting whether they will happen requires special laboratory experiments that can replicate the extreme pressure and temperature three kilometres below ground.
We are also still learning how to predict how hydrogen will move underground. We know that some of the injected gas will never come back out. This is the 鈥溾 that acts a bit like a spring that pushes the other hydrogen back to the surface.
Some hydrogen may also escape into the atmosphere through small cracks in the rock. We鈥檒l need to know how much, set up surveillance to watch for it and consider its听.
These are just a few of the challenges posed by underground storage of hydrogen. But our experience with natural gas storage gives us confidence we can manage them with the right research and planning.
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Making it work
New Zealand鈥檚 hydrogen future remains uncertain, but work is underway to prepare. Early signs for听听of green hydrogen are promising and there鈥檚听听听for it overseas.
But technical feasibility is not enough: any solution must make economic sense and be acceptable to the wider public, particularly tangata whenua.
Proving the feasibility of any new idea takes time. We need to develop, sometimes fail, refine and then find success. But with each new extreme weather event, its clear we don鈥檛 have a lot of time. In this new era of adaptation, governments, industry, communities and scientists will need to work more closely than ever.
This article was originally published on .
