No matter how you run the numbers, offshore wind — seen by many as an experimental technology just a few years ago — is going to be central to our planet-saving efforts in the coming decades. As the International Energy Agency (IEA) spelled out in its first stand-alone report on the sector, the build-out under way now could balloon 15-fold in the next 20 years, from the current 23GW installed to 340GW, with a longer-term potential that the IEA’s chief modeller called “mind-blowing”.

By the IEA’s calculus, which was based on geospatial analysis that maps out wind speed along hundreds of thousands of kilometres of coastline around the globe, seaborne winds could generate 36,000TWh a year for turbines in water depths of less than 60 metres within 60km of land. The current global electricity demand stands at 23,000TWh. The maths are plain.

Wade out farther from shore into the deeper waters that cover three quarters of the world’s surface, and add floating wind plants to the ranks, and the industry could unlock enough power to meet global electricity demand 11 times over by 2040.

In Europe alone, offshore wind could become the largest single source of electricity by then as the engine of a carbon-neutral energy system. Imagine what this could mean to the energy transition of the world’s two biggest CO2 emitters: China, which is dashing to have well over 100GW installed in the next 20 years; and the US, just now leaving harbour on a mission to build about 40GW by 2040.

One more number: $1trn. That is the expected investment that will come in the next two decades with this construction boom: from the de-mothballed offshore oil & gas fabrication yards, to the reborn ports, to the maritime vessel fleets that will be used in installation and servicing of the wind farms and transmission infrastructure.

Offshore wind could unlock enough power to meet global electricity demand 11 times over by 2040

This doesn’t take into account the economic impact of the shipping, aquaculture and other industries that will increasingly be powered by offshore wind in the future Blue Economy.

The sobering reality behind these heady prospects is that offshore wind today accounts for only 0.3% of global power supply, still a long way behind the generation from the 600GW land-based fleet, although already accounting for 40% of new projects in pre-construction.

The speed of the energy transition in many ways hinges on the old industrial incumbents, the oil & gas companies still spending single-digit percentages of their capital budgets on renewable energy projects, the heavy-emitting construction conglomerates that can shift offshore wind up the gears into true mass-production mode.

Two developments might inform cautious optimism here. Shell’s takeover of French offshore developer Eolfi is a new sign of the petro-giant’s appetite for the sector; and the tie-up between Tokyo construction behemoth Taisei and floating wind technologist Ideol, which is targeting an Asian offshore market that is foreseen as soon eclipsing Europe’s.

There is also courage to be taken from an unlikely source: “emerging” markets, with a report from the World Bank and International Finance Corporation spotlighting nations from South Africa to Sri Lanka as among the plays that could add a staggering 3TW to the global fleet in the coming years.

While there is life, as Cicero said, there is hope.