UC Earth and Environment scientist, Professor Andy Nicol and Civil and Natural Resources Engineering Senior Lecturer, Dr David Dempsey received$11.8 millionfrom the Ministry of Business, Innovation and Employment (MBIE) to answer critical questions for the future of green hydrogen in Aotearoa New Zealand:how can hydrogen be safely stored to be useful as an energy source?
Professor Nicol and Dr Dempsey already know that storing hydrogen in its liquid form isn’t feasible for the massive amounts we’ll need, so their research will focus on storing it as a gas.
“Hydrogen doesn’t become a liquid until around minus 260 degrees Celsius” says Dr Dempsey, close to absolute zero, which is the lowest limit temperature can be recorded at.
“If you want to store it as a liquid it’s a lot of effort – it takes a lot of energy. It’s constantly boiling off hydrogen to keep that temperature low, and that all adds to the cost.
“We’re probably going to have to store it as a room-temperature gas, but even at really high-pressure hydrogen’s density is quite low. We estimate Aotearoa might need about 10% of its annual hydrogen consumption on hand in storage and that’s an enormous volume.
“That’s like covering an area more than the size of 450 rugby fields with tanks if you put it all on the surface… the underground option is quite nice, if you can make it work of course.”
While underground storage solves the problem of scale there are still potential risks to mitigate, says Professor Nicol. “One thing we’ll look at is leakage scenarios because that’s both an environmental and a social licence risk.
“No one wants it to leak but you have to plan for the possibility, so the questions are – how do you detect a leak as rapidly as possible? How do you mitigate the leak? And what kind of impact might you expect it to have on shallow groundwater? That’s all research to be done,” says Professor Nicol.
Maybe you’ve heard of the Hindenburg? An airship full of hydrogen that exploded when leaking hydrogen came into contact with electricity. But don’t worry, it can’t just go bang underground. “For combustion you need oxygen and there’s simply not enough of it underground for an explosion - It’s a good place to put it, it’s safer down there.”
Dr Dempsey says the support for underground hydrogen storage will be the pillar for hydrogen’s success. “For most of us hydrogen is a new source of energy. Through experience from carbon dioxide storage projects we know that if people do not support underground hydrogen storage, it will probably not take place, even if it is technologically feasible.
“An important part of our work will be focused on ensuring that everyone understands the pros and cons of hydrogen storage. We hope that this will provide a platform for future partnerships.”
The team have found a handful of suitable sites in New Zealand, on and offshore. They will continue to investigate these sites to find the most suitable, as Goldilocks would say a “just right” site.
“The storage site can’t be too small or too big. You can think of hydrogen storage as storing water in a bowl, so if you have a bowl that’s too small it’s not very useful, if you have a bowl that’s really big – say a swimming pool – how useful would a swimming pool be for storing 10 cups of water? Sure, you can fit it in there but then you’ve got a puddle and it’s really hard to get it back out again,” says Dr Dempsey.
Due to the buoyancy of hydrogen a space that is too large would create an “upside down puddle of hydrogen” which would make removing the gas quite hard he says.
Once the team has answered outstanding questions, underground storage of hydrogen could enable us to store large amounts of energy for use during times of high demand.
“It could also be a key component of our move away from using fossil fuels and allow some new green industries to really scale up. There is a promising future for green steel and green fertiliser in New Zealand,” says Dr Dempsey.
Ammonia, used to make fertiliser, accounts for 2% of global carbon emissions. Currently the production of ammonia creates CO2as a by-product when the hydrogen is “cracked off” the methane.
“Fertiliser is essential for us to feed 40 million people from our country of only 5 million. If we want to keep doing that we will need to keep making fertiliser, and so companies are looking to decarbonise that with green hydrogen.”
Similar principles could potentially be applied to the creation of green steel. Steel currently accounts for another 8% of global emissions. “People talk about using hydrogen instead of coal to reduce the oxygen in iron ore and then you’re just emitting water instead of CO2. This technology has not been perfected but if it was you could export green steel.”
So, it might not be the unstable crystallised hydrogen that the Glass Onion would suggest, but this research will lay the key foundations for a sustainably powered New سԹ– and that’s pretty amazing.
Read more storiesabout how سԹ researchers are contributing to Aotearoa New سԹreaching its energy goals by 2050.
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