State of the art wind turbines with a diameter bigger than the London Eye are being assembled at Belfast Harbour.
The 32 turbines are destined for the sea off Liverpool.
Once running, they will generate enough electricity for a city twice the size of Belfast - about 230,000 homes.
The component parts have been shipped to a purpose-built facility in the docks, built several years ago at a cost of £50m.
They are being put together and fitted out, before being shipped out horizontally on a specialist vessel to the 40sq km site in Liverpool bay.
At peak operation each turbine can produce the same amount of energy in one day as contained in 22,600 barrels of oil.
Joe O'Neill of Belfast Harbour said a second, bigger project would follow the current one.
He said there was a significant spin-off for the economy of Northern Ireland with local firms supplying plant and other services to the company, MHI Vestas Offshore Wind, which is developing the turbines.
Company spokesman Peter Clusky said advances in technology meant more power could be generated by fewer, more efficient turbines.
Government subsidies for onshore wind have been stopped, leading to the shelving of many projects.
But financial support remains for off-shore projects, with developers promising to cut costs through technology and lower the amount of subsidy needed.