Offshore Wind Fundamentals
Prerequisites
Wind over the ocean is faster, steadier, and more consistent than wind over land. Offshore turbines achieve 40-55% capacity factors versus 25-45% onshore. The trade: 2-3x the capital cost per megawatt, because everything is harder when your construction site is underwater.
Offshore wind uses three foundation types depending on water depth. Fixed-bottom monopiles (steel tubes driven into the seabed) work to about 30 meters. Jacket foundations (lattice structures) extend to 50-60 meters. Floating platforms (moored to the seabed with cables) can operate in 60-1,000+ meter depths, unlocking vast deep-water resources off the US West Coast, Japan, and the Mediterranean.
Compare the economics. Onshore wind LCOE: $25-50/MWh. Fixed-bottom offshore: $60-100/MWh. Floating offshore: $100-200/MWh (early projects). Higher capacity factors partially offset higher capital costs, but offshore wind remains more expensive per kilowatt-hour.
If offshore wind is more expensive, why are countries investing tens of billions in it?
The value proposition beyond LCOE. Offshore wind resources are close to coastal population centers (where electricity demand is highest). Onshore wind's best resources are often in remote, sparsely populated areas requiring long transmission lines. Offshore wind also faces less public opposition than onshore wind or new transmission corridors. For densely populated coastal nations (UK, Northeast US, Northern Europe), offshore wind may be the only large-scale renewable resource within reach.
Offshore wind achieves 40-55% capacity factors versus 25-45% for onshore wind. This advantage comes from:
Open ocean has minimal surface roughness. Wind is less turbulent, more consistent, and faster at hub height. Since power scales with wind speed cubed, even modest speed increases produce substantially more energy.
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