UC Earth and Environment scientist, Professor Andy Nicol and Civil and Natural Resources Engineering Senior Lecturer, Dr David Dempsey received听$11.8 million听from the Ministry of Business, Innovation and Employment (MBIE) to answer critical questions for the future of green hydrogen in Aotearoa New Zealand:听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鈥檛 feasible for the massive amounts we鈥檒l need, so their research will focus on storing it as a gas.
鈥淗ydrogen doesn鈥檛 become a liquid until around minus 260 degrees Celsius鈥 says Dr Dempsey, close to absolute zero, which is the lowest limit temperature can be recorded at.
鈥淚f you want to store it as a liquid it鈥檚 a lot of effort 鈥 it takes a lot of energy. It鈥檚 constantly boiling off hydrogen to keep that temperature low, and that all adds to the cost.
鈥淲e鈥檙e probably going to have to store it as a room-temperature gas, but even at really high-pressure hydrogen鈥檚 density is quite low. We estimate Aotearoa might need about 10% of its annual hydrogen consumption on hand in storage and that鈥檚 an enormous volume.
鈥淭hat鈥檚 like covering an area more than the size of 450 rugby fields with tanks if you put it all on the surface鈥 the underground option is quite nice, if you can make it work of course.鈥
While underground storage solves the problem of scale there are still potential risks to mitigate, says Professor Nicol. 鈥淥ne thing we鈥檒l look at is leakage scenarios because that鈥檚 both an environmental and a social licence risk.
鈥淣o one wants it to leak but you have to plan for the possibility, so the questions are 鈥 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鈥檚 all research to be done,鈥 says Professor Nicol.
Maybe you鈥檝e heard of the Hindenburg? An airship full of hydrogen that exploded when leaking hydrogen came into contact with electricity. But don鈥檛 worry, it can鈥檛 just go bang underground. 鈥淔or combustion you need oxygen and there鈥檚 simply not enough of it underground for an explosion - It鈥檚 a good place to put it, it鈥檚 safer down there.鈥
Dr Dempsey says the support for underground hydrogen storage will be the pillar for hydrogen鈥檚 success. 鈥淔or 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.
鈥淎n 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.鈥
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 鈥渏ust right鈥 site.
鈥淭he storage site can鈥檛 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鈥檚 too small it鈥檚 not very useful, if you have a bowl that鈥檚 really big 鈥 say a swimming pool 鈥 how useful would a swimming pool be for storing 10 cups of water? Sure, you can fit it in there but then you鈥檝e got a puddle and it鈥檚 really hard to get it back out again,鈥 says Dr Dempsey.
Due to the buoyancy of hydrogen a space that is too large would create an 鈥渦pside down puddle of hydrogen鈥 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.
鈥淚t 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,鈥 says Dr Dempsey.
Ammonia, used to make fertiliser, accounts for 2% of global carbon emissions. Currently the production of ammonia creates CO2听as a by-product when the hydrogen is 鈥渃racked off鈥 the methane.
鈥淔ertiliser 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.鈥
Similar principles could potentially be applied to the creation of green steel. Steel currently accounts for another 8% of global emissions. 鈥淧eople talk about using hydrogen instead of coal to reduce the oxygen in iron ore and then you鈥檙e just emitting water instead of CO2. This technology has not been perfected but if it was you could export green steel.鈥
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 Zealand 鈥 and that鈥檚 pretty amazing.
Read more stories听about how University of mini传媒 researchers are contributing to Aotearoa New Zealand reaching its energy goals by 2050.
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