Green hydrogen and its derivatives will play a vital role in the decarbonisation of Europe — mainly for use in aviation, shipping, chemicals, steel and industrial heat — according to an academic study modelling the most “cost-optimised” path to net-zero emissions by 2050.

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The “central element is power-to-X in this future energy system”, says the study, entitled Reflecting the Energy Transition from a European Perspective and in the Global Context. Power-to-X refers to the use of electricity to produce hydrogen and H2 derivatives — also known as “e-fuels” or “e-chemicals” — such as ammonia, methanol and synthetic kerosene.

In the most cost-effective future net-zero energy system “electricity is used for heat supply, in heat pumps and direct power-to-heat conversion in electric boilers; for mobility in battery-electric road vehicles, trains, ferries and first short-haul flights; and for e-fuels and e-chemicals, in e-hydrogen, e-methane/LNG and e-liquids”, the paper explains.

“The most important energy carrier is electricity from renewable sources, and the second most important energy carrier is hydrogen — but less for final energy supply and mainly for conversion in e-fuels and e-chemicals, which are needed for long-distance marine and aviation transportation, and [in the] chemicals [industry].”

The study adds that high-temperature industrial process heat would “largely be provided by direct electricity use, but also some fuel combustion in future, mainly e-hydrogen or renewable methane”.

Less than a quarter of all hydrogen produced would be utilised directly as H2, with more than three quarters used to produce derivatives.

The authors explain that the “Power-to-X economy” would use battery storage and electrolyser operation to “effectively balance” variable renewable energy (VRE) generation — alongside demand-side response and perhaps smart electric vehicle charging and vehicle-to-grid — while playing down fears that not enough wind and solar power would be available in winter to meet electricity demand.

“Grids for regional balancing, battery storage for temporal balancing and power-to-X technologies for demand balancing provide the necessary flexibility to the energy system, while the role of flexible generation like biomass power plants or hydropower dams is very low,” they write.

The paper adds that the so-called “dark doldrums” — periods in winter where there is little wind or solar power on the grid — are actually far less frequent than people might imagine. A detailed investigation into this phenomenon, carried out as part of the study, found that the longest periods of these “dark lulls” modelled would be just 17 hours — short enough for it to be weathered by battery storage, grid interconnection and the flexible demand of power-to-X technologies.

This means that the production of hydrogen-based fuels and chemicals can be ramped up and down according to how much wind and solar power is available on the network, thus helping to balance the grid. (That may not be the most cost-effective method of producing those products, but it is part and parcel of the academics’ “cost-optimised” energy system.)

While the study suggests that there would be no role for hydrogen in the heating of buildings, “some” H2 (and e-methane) would be used for industrial heat from 2040 onwards — and there would also be a role for hydrogen on the roads, with 7% of total hydrogen production used directly in road transport (although the quantity of H2 that this proportion represents is not clear).

The paper adds that solar power would provide 61-63% of all electricity in Europe by 2050 “mainly driven by its least cost nature and ubiquitous resource availability”.

“The central energy system components are solar PV, wind power, batteries, electrolysers and CO2 direct air capture for carbon capture and utilisation [to produce e-fuels containing carbon such as methanol for shipping and e-kerosene for aviation].”

The study, which was published last month in the journal Progress in Photovoltaics, was led by academics at the LUT University in southeast Finland, with contributions from Finnish utility Fortum, trade association SolarPower Europe, the Renewable Energy Institute in northeast Italy, the Brussels-based Becquerel Institute, and the European Commission’s Joint Research Centre in northwest Italy.