A hydrogen economy may be good in theory, but getting there won’t be easy
By David Dempsey, Andy Nicol, Kepa Morgan & Ludmila Adam*
In his project of retool the economythe New Zealand government has pointed out green hydrogen as a revolutionary fuel. It can indeed be used to climate-friendly fertilizer and steel or in power certain modes of transport which are not suitable for batteries.
But to provide a buffer against foreign market volatility, Aotearoa should be as energy independent as possible. Ideally, this would mean consuming only green hydrogen produced here, using abundant renewable water, wind and solar resources.
A hydrogen economy is good in theory, but to effect the scale change in Aotearoa’s climate ambitions would require around 150 petajoules of hydrogen each year, according to a estimate. It’s about a quarter of our current power consumption.
Hydrogen is produced in a process known as hydrolysis – the splitting of water into hydrogen and oxygen gas, using electricity. To produce a quarter of Aotearoa’s energy consumption, hydrolysis would consume a huge amount of water, around 13 million tonnes per year, equivalent to one month of Auckland’s water demand.
This raises both cultural and technical questions, which we must answer before embarking on a transition to hydrogen as a green fuel.
Consuming water has cultural implications
Fresh water is of enormous importance to iwi and hapū. 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 adapt appropriately to Aotearoa New Zealand society and the technology may become orphaned.
Instead, we could start addressing this issue early through wānanga with representatives from a wide range of potentially affected iwi. Recognizing and addressing cultural concerns from the outset will allow Maori to shape how technology is developed and share the economic benefits of a hydrogen economy. The intention is to better understand how green hydrogen technologies and infrastructure could belong to Aotearoa in New Zealand.
Assuming we are willing and able to produce this large amount of hydrogen, our experience with other fuels suggests that we would need around a month of storage at any given time. Storage helps smooth fluctuating market demand, takes advantage of the seasonal excess of renewable energy (during very windy and very sunny weeks) and provides emergency reserves for “dry year» seizures.
Storing hydrogen underground
Unfortunately, hydrogen cannot be stored in liquid form, except in specialized containers which keep it at extremely low temperatures. Like a freezer, it still consumes energy.
Hydrogen could be stored in special high-pressure tanks, but we would need more of these tanks than we have people in New Zealand. These reservoirs would be expensive, would cover large areas of productive land, and would be susceptible to damage from natural hazards. Where would they all go?
We already do it with natural gas in Taranaki. When not needed, the gas is injected into an old field called Ahuroa and then extracted as needed. Underground gas (methane) storage is common practice, providing energy resilience. For example, given the disruption caused by the war in Ukraine, Germany accelerates the storage of gas in geological reservoirs in time for winter.
We recently showed may be enough space in other rock reservoirs in Taranaki to store hydrogen underground. But it won’t be easy.
We know that gas can react with certain types of rock. It can even be a meal for hungry microbes. Both of these processes would consume valuable fuel. But predicting whether they will happen requires special lab experiments that can replicate the extreme pressure and temperature three kilometers underground.
We also learn to predict how hydrogen will move underground. We know that part of the injected gas will never come out. It’s the “cushionwhich acts a bit like a spring that pushes the other hydrogen back to the surface.
Some of the hydrogen can also escape into the atmosphere through small cracks in the rock. We will need to know how much, set up monitoring to monitor it and consider its climate effect.
These are just some of the challenges posed by underground hydrogen storage. But our experience with natural gas storage gives us confidence that we can manage them with the right research and planning.
make it work
The future of hydrogen in New Zealand remains uncertain, but work is underway to prepare. The first signs of underground storage of green hydrogen are promising and there are a lot of enthusiasm for this abroad.
But technical feasibility is not enough: any solution must make economic sense and be acceptable to the general public, especially tangata whenua.
Proving the feasibility of any new idea takes time. We have to develop, sometimes fail, refine and then succeed. But with each new extreme weather event, it’s clear that we don’t have much time. In this new era of adaptation, governments, industry, communities and scientists will need to work more closely than ever.
*David DempseyLecturer, University of Canterbury; Andy Nicholas, University of Canterbury; Kepa MorganDeputy Nga Pae o te Māramatanga, University of Aucklandand Ludmila AdamLecturer, University of Auckland