Offshore wind
Wind turbines installed in seas or large lakes, usually on fixed foundations in water up to about 60 m deep, exploiting stronger and steadier winds than onshore sites.
Offshore wind benefits from low surface roughness, low shear and few siting constraints on turbine size. Mean wind speeds of 9–10.5 m/s at hub height are common in the North Sea, giving capacity factors of 40–50% for new projects, against about 25–40% for typical onshore wind (IRENA, Ember).
Foundation types depend on water depth:
- Monopiles: the dominant type, now 8–11 m in diameter, for depths up to about 40–50 m
- Jackets: lattice structures for 30–60 m or heavy turbines
- Gravity bases and suction buckets: site-specific
- Floating: beyond about 60 m, see floating offshore wind
Global installed capacity passed roughly 75–80 GW by 2024 (GWEC), led by China, the United Kingdom and Germany. Turbines of 12–15 MW are standard in Europe, with 18–26 MW prototypes in China.
Costs are higher than onshore because of foundations, installation vessels, export cables and offshore substations; projects far from shore use HVDC connections. IRENA reported a global weighted LCOE around USD 75–80/MWh for 2023 projects, about double onshore wind. From 2022 to 2024 inflation, interest rates and supply-chain constraints led to cancelled US and UK contracts, showing sensitivity to financing costs. Large arrays also face growing wake interactions between neighbouring projects.
Related terms
All terms →- Floating offshore wind
Wind turbines mounted on buoyant platforms moored to the seabed, enabling wind farms in water deeper than about 60 m where fixed foundations become uneconomic.
- Wake effect
The reduced wind speed and increased turbulence downstream of a wind turbine, which lowers the output and raises the fatigue loads of turbines located behind it.
- Capacity factor
The ratio of the energy a power plant actually produces over a period to the energy it would produce running at full nameplate capacity for the whole period.
- HVDC (High-Voltage Direct Current)
Transmission technology that carries bulk power as direct current, with lower losses over long distances and the ability to link asynchronous grids.
- Contract for Difference (CfD)
A support scheme or contract in which a generator receives the difference between a fixed strike price and a market reference price, paying back when prices exceed it.
- Hub height
The height of a wind turbine's rotor centre above ground or sea level; taller hubs reach stronger, steadier winds and are a main driver of rising capacity factors.