How much renewables expansion is needed for a global green hydrogen economy?

And is a massive wind and solar build-out of that scale even feasible?

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Hydrogen is increasingly being touted as the molecule of choice for the energy systems of the future. It has a vast range of potential applications, from heating to long-distance transportation to steel production, and green hydrogen” can be produced with renewable energy.

But using solar or wind power to split water into hydrogen and oxygen is not exactly energy efficient. So how much renewable energy would we need to meet hydrogen projections for 2050 with green hydrogen?

The answer, based on a Canary Media analysis of data provided by Siemens Gamesa Renewable Energy and other sources, is a lot — but probably not so much as to make the whole concept unviable.

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The outlook for green hydrogen growth, as with many aspects of the energy transition, is riddled with unknowns. As a result, there is no consensus about hydrogen demand by 2050,” according to Siemens Gamesa senior specialist Antonio Palacios.

Estimates vary by a factor of almost 10, from 61 million metric tons (MT) per year in Shell’s 2018 Sky Scenario to 546 MT per year in the Hydrogen Council industry consortium’s 2019 Hydrogen Scaling Up forecast.

The wide range of estimates is due to varying assumptions about hydrogen demand and technology penetration in hard-to-electrify sectors like maritime shipping, long-haul road transportation, aviation and the steel and chemical industries, Palacios said.

But given that many countries have yet to announce hydrogen plans, the final demand figure probably will be more aligned with Hydrogen Council expectations of around 550 MT,” he said.

The big question for hydrogen boosters is how much of this can be delivered in the form of green hydrogen.

The International Renewable Energy Agency’s new World Energy Transitions Outlook, which lays out a scenario to keep global warming below 1.5 degrees Celsius, calls for two-thirds of hydrogen production to be green and one-third to be blue,” or made via natural gas coupled with carbon capture and storage.

But if we aim for 100 percent green production, how much renewable energy would be needed to power the electrolyzers that convert electricity and water into hydrogen?

A green hydrogen economy would require a whole lot of wind and solar

Here again, a lot depends on your assumptions.

Key variables include the efficiency of electrolysis, which Palacios said currently ranges between 72 percent and 74 percent but could rise to 79 percent by the end of the decade. But they also include the type of carbon-free energy used.

The most efficient sources of energy are those that can run electrolyzers continuously, which is why hydropower and even nuclear power have been proposed as potentially ideal power supplies for green hydrogen.

In practice, however, cost and siting constraints mean green hydrogen hubs will likely be powered by wind or solar. And because wind and solar each have a lower capacity factor (the measure of a generation resource’s output over the course of a year) than hydro or nuclear, a lot more generation would need to be installed to meet a given electrolyzer output target.

If we were to use solar power alone to generate 550 MT of green hydrogen a year, that would require around 13 terawatts of PV, according to a rough calculation by Palacios. That assumes an optimistic 24 percent capacity factor for solar, along with an electrolyzer efficiency of almost 79 percent. That’s around 18 times the almost 714 gigawatts of solar power that the International Renewable Energy Agency estimates had been installed worldwide as of the end of 2020.

Powering electrolysis entirely with wind energy would improve the picture because of wind’s somewhat higher capacity factor. Based on a still optimistic 50 percent capacity factor, Palacios calculates that 550 MT of green hydrogen production could be powered with 6.2 terawatts of wind. That is almost eight times the 800 gigawatts of installed wind that the Global Wind Energy Council expects will be reached this year.

It is a massive amount of new generation capacity that would be needed, whether it’s wind, solar or a combination. Is it even feasible to build this much?

A whole lot of land too

Purely from a land-use perspective, it seems so. Although the amount of land needed for wind power varies greatly by location and technology, research suggests the average is probably around 0.75 acres per megawatt. So 6.2 terawatts of wind would take up roughly 7,265 square miles, or a little more than the land area occupied by Kuwait in the Middle East. For comparison, the world’s urban areas cover around 250 times more land than that. In practice, of course, most of this capacity would likely be installed in remote areas and at sea.

Even powering electrolyzers purely with solar power is not beyond the realm of possibility in terms of land use. Based on various sources, solar requires an average of around 4 acres per megawatt. So building out 13 terawatts would require around 81,250 square miles. That is bigger than many countries, including Greece, Nepal and Uruguay.

But it also represents just 2.3 percent of the land in the Sahara Desert, one of several open, arid and sunny locations appropriate for solar-based hydrogen production.

Naturally, all of these calculations are highly speculative, and they don’t include the wind and solar capacity that will be needed for direct production of electricity. The true outlook for green hydrogen will depend as much on political will and investment attractiveness as on matters such as renewable capacity and land use.

And a big question mark still remains as to whether green hydrogen will live up to the hype. Not everyone is convinced, including some of the groups that might be expected to back the kind of renewables build-out that hydrogen could trigger.

The European wind energy association WindEurope, for example, favors only a limited role for hydrogen because of its low efficiency compared to electrification.

Surely there’s a role for hydrogen in the future energy system,” said Christoph Zipf, WindEurope’s press and communications manager. But most sectors will run on electricity, either mostly or 100 percent.”

(Lead photo: Fueling a fuel-cell electric car with hydrogen at the new Apex Energy Hydrogen power plant in northern Germany. Photo by Bernd Wüstneck/​picture alliance via Getty Images.)

Jason Deign reports on global trends in climatetech, energy storage and wind. He is based in Barcelona, Spain.