How Feasible Is Green Hydrogen?

The world is on the cusp of a global energy transition, the likes of which has not been seen since the industrial revolution in the 1800s.

While natural gas, oil, and coal still account for over 77 percent of the world's primary energy consumption, new energy storage solutions are gaining momentum.

And one such solution is green hydrogen.

Based on current trajectories, green hydrogen could be a feasible, widespread energy source within the next decade. By weight, it is three times more energy dense than gasoline and can be produced from renewable energy sources.

Hydrogen-powered delivery trucks, cars and buses are already being trialed across the U.S., and the Department of Energy has committed to making hydrogen a cost competitive energy solution within the next decade.

Preliminary tests with green hydrogen-powered fuel networks have shown promising results—so what needs to happen before green hydrogen can enter the mainstream?

What Is Green Hydrogen?

Hydrogen is the most abundant element in the universe, although it rarely exists as a pure gas on Earth.

Instead, it is usually found combined with other elements, for example with oxygen in water, H₂O. Separating it from these other elements requires energy, and energy is released when they come back together.

"When hydrogen is used as a fuel, it combines with oxygen to form water, emitting no carbon dioxide," Molly Gilson, Director of Media Relations at the National Grid, told Newsweek. "Hydrogen doesn't contain carbon, which means that it doesn't emit carbon monoxide or carbon dioxide [and] when hydrogen is used as an energy source, it [only] emits water vapor."

Hydrogen is also a denser source of energy than batteries, meaning that hydrogen-powered vehicles would weigh a lot less than those running on a lithium batteries.

Producing Green (And Other Colored) Hydrogen

To produce green hydrogen, electricity from renewable sources—like solar and wind—is used to split water into its constituent parts: hydrogen and oxygen, via a process called electrolysis.

"Clean hydrogen is valuable because it can store energy from renewable sources such as solar and wind, either for using directly as a fuel or for generating clean power at another time," Gilson said.

To be classified as "clean hydrogen" the Department of Energy specifies that fewer than two kilograms of carbon dioxide can be produced for every one kilogram of hydrogen.

Green hydrogen is produced using carbon-free sources of energy, so theoretically should not produce any carbon dioxide during its manufacture. However, there are other colors of hydrogen that do produce carbon dioxide but can still be considered "clean."

Blue hydrogen is hydrogen produced from natural gas through a method called steam methane reforming. In this process, natural gas is mixed with very hot steam and usually a nickel catalyst.

A chemical reaction occurs which produces hydrogen and carbon monoxide, and this carbon monoxide is later converted to carbon dioxide, and more hydrogen by the addition of water.

If this carbon dioxide is released, hydrogen produced by this method is termed "gray hydrogen." However, if efforts are made to capture the carbon and store it underground, the process is considered to be carbon neutral and is classified as "blue hydrogen."

Other colors of hydrogen also exist, such as pink hydrogen, which refers to hydrogen produced by electrolysis powered by nuclear fission, and yellow hydrogen, which refers to hydrogen produced from electrolysis powered by the energy grid, which is usually a mix of fossil fuels and renewables.

To avoid confusion, the DOE and others in the space tend to refer to it as "clean" hydrogen.

When Was Green Hydrogen Discovered?

Green hydrogen is no different to any other hydrogen molecule. It is the method by which it is produced that determines whether it is "green" or not.

To be classed as green hydrogen, the energy source for the electrolysis process must be a clean, renewable energy source, sch as solar or wind.

Electrolysis was first formally discovered and categorized in 1800 by English scientists, William Nicholson and Anthony Carlisele. Three decades later, Michael Faraday provided a mathematical explanation for this phenomenon in his "two laws of electrolysis."

The process involves using an electric current to drive an otherwise non-spontaneous reaction—in other words, a reaction that requires an energy input.

This is not exclusive to splitting water: electrolysis is also used in the extraction and refinement of metals, such as aluminum, from their ores.

By 1938, the first hydrogen fuel cell was developed to generate electricity, and by 1960, hydrogen fuel cells were being used to power spaceships in the Apollo and Gemini space missions.

Is Green Hydrogen the Future of Clean Energy?

Today, the DOE has estimated that 10 million metric tons of hydrogen are produced in the U.S. every year. There are also over 1,600 miles of hydrogen pipeline in the U.S. and large production facilities exist in almost every state.

However, most of this hydrogen is in the form of gray hydrogen and is used in petroleum refining and fertilizer production.

"Interest in green hydrogen is increasing as a critical piece of the clean energy future," Gilson said. "The Inflation Reduction Act was a major milestone for progressing hydrogen as a clean energy technology. Tax credits in the new law, combined with funding from the 2021 Bipartisan Infrastructure Law indicate hydrogen might be finally catching on."

One major stumbling block for the acceptance of green hydrogen is its safety. Hydrogen is non-toxic, but it is also highly flammable and can ignite more easily than natural gas and gasoline. Therefore, ventilation and leak detection are essential to ensure safe hydrogen infrastructure.

Luckily, hydrogen is already safely used for a range of applications.

"Hydrogen is used safely in a wide array of settings across the U.S. and globally, including in gas networks, and is safely transported and stored in both compressed gas and liquid forms," Gilson said.

"In terms of what needs to happen, there will need to be a widespread acceptance of uses from hydrogen blending in existing gas networks to use in industrial settings, and acceptance and infrastructure for long haul transportation uses, to fueling power plants.

"We will also need transportation methods, so hydrogen can travel from where it is less expensive to produce to high density geographies."

Can Green Hydrogen Be Used As A Fuel In The Future?

Companies in the U.S. are already working to introduce hydrogen into the energy mix through existing gas delivery networks.

HyGrid is one of these projects, set up by the National Grid in Long Island, which plans to create a blend of up to 20 percent green hydrogen with natural gas to distribute through existing distribution systems. The pilot demonstration will be used to heat approximately 800 homes in the region and power 10 municipal vehicles.

"Numerous studies and projects have demonstrated hydrogen blending across the globe," Gilson said. "We have conducted rigorous scientific studies on how hydrogen behaves, which have shown that blends of up to 20 percent hydrogen in natural gas are safe in our system.

"Prior to the advent of natural gas in the 1950s, some systems had approximately 50 percent hydrogen blend flowing in the system. Over the years, the materials used in the distribution network, as well as innovations in end use appliances, has changed significantly.

"In this regard, National Grid has invested significantly in evaluating the material compatibility and safety of its system as well as customer appliances to ensure the safety and reliability of the system for the clean energy transition."

Hydrogen-powered vehicles have been successfully trialed across the U.S., including hydrogen fuel cell delivery and parcel trucks in California and New York, fuel cell-powered forklifts, and hydrogen-powered buses.

Pilot projects such as HyGrid will continue to test the safety and efficacy of green hydrogen, and the DOE has launched a collaboration called H2USA to focus on advancing hydrogen infrastructure to support the transportation and storage of hydrogen fuel.

Today, green hydrogen is more expensive than natural gas but, as the volume of hydrogen production increases, this cost is expected to come down.

The world's largest producer of electrolyzers, NEL, believes green hydrogen production could reach cost parity with fossil fuels as early as 2025, and the DOE has laid out plans to reduce the cost of hydrogen to $1 per 1 kilogram within the next decade.

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