To scale up the production of hydrogen — a major goal of Alberta’s Hydrogen Road Map — the province will need a place to store large quantities of the fuel.
Petroleum engineering researcher Hassan Dehghanpour says he may have a solution: enormous underground salt caverns each capable of holding more than 2,000 tonnes of the compressed gas.
Dehghanpour and his team have received $500,000 from Alberta Innovates’ Hydrogen Centre of Excellence to explore the possibility, with at least another $500,000 from industry partners, the Natural Sciences and Engineering Research Council and the Mitacs Accelerate Grants Program.
“To the best of my knowledge, we will be the first lab in Canada testing salt rocks for hydrogen storage,” says Dehghanpour. If all goes well in the lab, field trials will begin in a couple of years, he adds, with storage caverns going into operation in about five years.
A crucial piece of the hydrogen puzzle
According to the Hydrogen Roadmap, the worldwide market for hydrogen is estimated to be worth more than $2.5 trillion per year by 2050, especially in North America, the Asia Pacific region and Europe.
Alberta is aiming to become a leading source of the fuel for local markets and other parts of the world eager to decarbonize, while also reducing its own carbon footprint. The province is already Canada’s largest producer of hydrogen, given its use for decades in upgrading bitumen to synthetic crude oil.
For the past 50 years, more than 100 salt caverns in Alberta have already been used to store natural gas and other hydrocarbons, but hydrogen presents unique challenges, says Dehghanpour. Its molecules are smaller — the smallest of all elements — making it potentially more capable of penetrating cavern walls, and the gas is more explosive.
After spending years in the hydraulic fracturing industry, Dehghanpour says he and his industry partners are confident natural gas caverns can be repurposed for hydrogen. With the transition to large-scale hydrogen production, sufficient storage capacity will be crucial to hedge against fluctuations in supply and demand.
“If down the road we convert green electricity from wind and solar to hydrogen, we probably won’t need that much for residential heating during the summer — the excess has to go somewhere.”
Working with industry to solve challenges
The first challenge is determining the right size, shape and depth for optimal caverns, some of which are up to two kilometres deep, up to 60 metres in diameter and up to 80 metres high. All of that affects the stress and pore pressure of the surrounding rock.
“We have to make sure the hydrogen doesn’t leak through the cavern walls, where it could react with brine and other minerals,” says Dehghanpour, potentially causing contamination.
His team will begin by testing core samples in his lab where they will simulate conditions similar to a salt cavern.
“We need to know the issues, then we can come up with solutions. For example, if we know the rate of leakage in the rock, we can control the injection pressure and withdrawal rate to minimize that.”
Dehghanpour will work closely with industry partners Keyera and Cenovus Energy, and with Sanjel, an oil well cementing company that uses additives for a tighter seal around the cavern’s wellbore — “a critical part of the design,” he says. The partners will provide both direct and in-kind funding for the project, including data, core samples and access to existing caverns.
Dehghanpour estimates the initial cost of each salt cavern at about $20 million, with minimal costs once they are operational.
“Right now, we have only small-scale, surface storage tanks used by refineries for their own purposes,” he says.
“Compared to those, salt caverns are massive, and safer if operated properly. If anything happens, it’s underground with less oxygen for flammability, so I believe it's the best solution for large-scale hydrogen storage.”