The news report I read said that the energy comes only from windmill type of generators not previously connected to the national grid.
It's a bit ironic that Holland, once famed for its attractive windmills to grind corn etc, now returns to this means of power for energy.
One of the objections to wind power for energy is the necessity for tall towers for the blades which some people find ugly. Where I live in Kent, there used to be several windmills locally a century ago. One residential road is called Windmill St, which is on top of a very steep hill. There's always a wind blowing there. Would residents find it more acceptable if an old style windmill was put at the cul-de-sac end? Could smaller versions of the modern windmill be put on the roofs of high-rise blocks? Bearing in mind how my extractor fan is blown by the wind (when "off"), could a wall of smaller rotating blades be erected on a multi-storey building?