Hourly electricity matching is the only reliable way to reduce emissions from green hydrogen: study
Annual correlation of additional renewable power can push green H2 carbon intensity above that of blue hydrogen made with abated fossil gas, say German researchers
Hydrogen: hype, hope and the hard truths around its role in the energy transition
The study, which is yet to be peer-reviewed, found that “annual matching” (when the grid-sourced renewable power supply for an electrolyser is balanced with operational hours on an annual basis) would push up the carbon emissions intensity of green hydrogen.
This is because under annual matching rules, hydrogen producers are more likely to operate during times of low renewable power supply, incentivising more coal-fired power generation and pushing up emissions elsewhere in the system, the researchers noted, as well as putting up electricity prices across the board.
In fact, the additionality rule is so critical, that failing to use it could actually make green hydrogen three times’ more polluting than grey hydrogen made with fossil gas, the study found.
The only time when annually-matched green hydrogen saw a reduction in emissions in the TUB model is when the electrolyser was operated during real-time renewable power generation.
And the emissions intensity of monthly matching is almost identical to that of annual, said the trio, adding that, in the event that the grid failed to adapt quickly to new electrolyser capacity, monthly and annual matching could also have the effect of pushing up electricity prices by 45% and 43% respectively.
Hourly matching additional capacity with electrolyser operation, on the other hand, incentivises green hydrogen producers to operate only when the wind is blowing or sun is shining, bringing emissions to zero, and has no effect on electricity prices.
However, this could lead to more expensive green hydrogen, the researchers admitted, especially if there was no cheap storage available in either underground caverns or steel tanks.
A final decision on the content of the EU's Delegated Acts (DAs), which will regulate the definition of green hydrogen, is due any day.
Trade association Hydrogen Europe has warned that hour-by-hour rules would have been technically difficult, requiring hundreds of thousands of gigawatt hours of battery storage — which chief policy officer Daniel Fraile has said would be an “impossible” task for developers when the largest systems built today are only 2-3GWh.
But one of the report’s authors, TUB professor of digital transformation of energy systems, Tom Brown, suggested that the EU could afford to be flexible with the regulation in the short term.
“Given that volumes will be small initially and we do not want to burden the first hydrogen projects, there could be a case for lax rules now, enforcing stricter rules in 2027-2035, then relaxing them afterwards (if renewable targets and coal phase-outs happen on time),” he said on Twitter.
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