One of the most promising renewable energy carriers is clean hydrogen, when it is produced without fossil fuels. It’s a promising idea because the most abundant element in the universe is hydrogen, found in 75 percent of all matter. Moreover, a hydrogen molecule has two paired atoms – Gemini twins that are both non-toxic and highly combustible. Hydrogen’s combustive potential makes it an attractive subject for energy researchers around the world.
That combustive potential and the storage issues are subject to intense research.
At Pacific Northwest National Laboratory (PNNL), a team is investigating hydrogen as a medium for storing and releasing energy, largely by cracking its chemical bonds. Much of their work is linked to the Hydrogen Materials-Advanced Research consortium (HyMARC) at the Department of Energy (DOE).
Hydrogen storage not yet optimized
One PNNL research focus relates to optimizing hydrogen storage, a stubborn issue. To date, there is no completely safe, cost-effective, and energy-efficient way to store hydrogen at large scale.
PNNL researchers recently coauthored a paper that investigates a baking soda solution as a means of storing hydrogen. The study has already been dubbed a “hot paper” by the journal itself, Green Chemistry, published by the Royal Society of Chemistry. That means that it has had a lot of clicks showing interest.
The hydrogen-based storage efforts at PNNL are funded by the DOE’s Hydrogen and Fuel Cell Technologies Office in the Office of Energy Efficiency and Renewable Energy (EERE). The research advances the DOE’s H2@Scale initiative as well as the agency’s Hydrogen Shot.
The new paper’s two main authors are chemist and PNNL Laboratory Fellow Thomas Autrey and his colleague Oliver Gutiérrez, an expert in making chemical reactions speedy and cost-effective.
“You have to be a little creative,” said Autrey, who is amused at how common, cheap, and mild baking soda is as a potential answer to a big problem. “Not every chemical is going to be efficient at storing hydrogen. You have to work with what Mother Nature gives you.”
Clean hydrogen for long-term energy needs
Autrey, Gutiérrez, and others at PNNL see long-duration energy storage as the key to hydrogen’s future as a carrier of renewable energy.
Current battery technology is designed for several hours of storage. In a renewable energy grid, batteries can handle about 80 percent of storage needs.
But “the last 20 percent will take unique approaches,” said Autrey. “We will want to store the excess energy to be prepared for Dunkelflaute.”
Dunkelflaute is a German word describing conditions without enough solar and wind energy potential. During the dark, windless periods of Dunkelflaute, grids need a way to store energy for more than just several hours.
Seasonal storage capability like this is one of hydrogen’s attractions. So is the fact that hydrogen storage can happen anywhere that it is “geographically agnostic,” as experts say. Hydropower, for example, requires differences in elevation to store excess water to make power. Hydrogen storage requires no special conditions related to geography.
In addition, said Autrey, as scales get larger, hydrogen gets more economical. It is cheaper to buy a few additional hydrogen storage tanks than to buy a lot of batteries.
Finding the best way for hydrogen storage
Clean hydrogen has great promise as an energy source. A process called electrolysis, for instance, can split water into hydrogen and oxygen. In the best of worlds, the power for electrolysis would come from renewable energy sources, including solar, wind, and geothermal.
However, there is one stubborn challenge: to produce hydrogen more cheaply.
To address that, in 2021 the DOE announced its Energy Earthshots initiative, a series of six steps to underwrite breakthroughs in clean-energy technology. Introduced first was the Hydrogen Shot, a quest to reduce the cost of hydrogen to from $5 to $1 per kilogram in a decade – an 80 percent reduction.
Beyond getting clean hydrogen production costs down, “you have to figure out how to move and store it,” said Autrey, which are steps that can send prices back up.
But finding the ideal medium for hydrogen storage has been elusive.
Hydrogen can be compressed into a gas, but that requires very high pressures – up to 10,000 pounds per square inch. A safe storage tank would need walls of very thick steel or expensive space-grade carbon fiber.
How about cryogenic liquid hydrogen? This is a proven storage medium but requires getting and keeping something so cold that peripheral energy costs are significant.
What seems to hold…
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