In the North Sea, 14 to 20 km off Denmark's west coast, Horns Rev 1 was assembled from 80 Vestas V80 turbines to a total capacity of 160 MW — four times the capacity of the largest offshore wind farm built before it.

Behind its now-familiar silhouette lies a genuine first: an offshore installation method, monopile foundations driven into open sea at repeatable scale, that had no large-scale precedent to draw on when construction began.

80
Vestas V80 turbines
160 MW
Total capacity
2002–2003
Construction period
14–20 km
Distance offshore
Stage 1
Monopile driving
A single large steel pile was driven into the seabed at each of the 80 turbine positions — a simpler foundation than the multi-legged jacket structures common in offshore oil and gas at the time, chosen specifically because it could, in principle, be repeated at scale.
Stage 2
Transition piece and tower erection
A transition piece was fitted above each monopile to correct for verticality deviation, followed by tower sections stacked and bolted in sequence — a repeatable erection cycle across all 80 positions in open sea conditions.
Stage 3
Nacelle and rotor installation
Nacelle and rotor assemblies were lifted into place to complete each turbine. Installation, carried out by Danish offshore services provider A2SEA, brought the final turbine online on 11 December 2002.
Installation note

No offshore wind installation industry existed to draw expertise from before Horns Rev 1. Vessels, foundation methods, and erection sequencing were adapted largely from oil-and-gas offshore experience rather than validated on any prior wind project.

Horns Rev 1 wasn't scaling up a known method — it was establishing one, at a capacity four times anything built before it.

Horns Rev 1 is now jointly owned by Vattenfall and Ørsted, and remains operational more than two decades after commissioning. Its lasting contribution is methodological: the monopile foundation approach it proved at scale became the offshore wind industry's standard foundation type, still recognizable in projects many times its size.

For further reading, see Heavy Lift Engineering for Offshore Wind, which places monopile installation in a wider sector context.

Related case studies: Hywind Tampen · Dogger Bank · Vindeby

Sources: Vattenfall — operator's account of the monopile and offshore-substation firsts; Tethys (Pacific Northwest National Laboratory) — project record; Horns Rev. Horns Rev 1 is described as the first large-scale offshore wind farm; Vindeby (1991) was the first offshore wind farm of any size.