Wave energy
Energy captured from the motion of ocean surface waves using devices such as point absorbers, oscillating water columns and attenuators; still at pre-commercial stage.
Waves are concentrated wind energy, transported across ocean basins with little loss. The power per metre of wave crest in deep water is:
with Hs the significant wave height (m) and Te the energy period (s). A sea state with 3 m waves and 9 s period carries about 40 kW per metre of crest.
Mean annual resource is 20–40 kW/m on many mid-latitude western coasts and 60–100 kW/m off Ireland, Scotland, southern Chile, southern Australia and South Africa. The global theoretical resource is often quoted at about 2–3 TW (roughly 29,500 TWh/yr gross, IPCC SRREN), with the technically exploitable part much smaller.
Main device families:
- Point absorbers: heaving buoys (CorPower, Carnegie CETO)
- Oscillating water columns: air chamber with a Wells or impulse turbine (Mutriku breakwater, Spain, about 300 kW, operating since 2011)
- Attenuators: long articulated floating structures (the former Pelamis)
- Oscillating surge converters: hinged flaps near shore (the former Oyster)
- Overtopping devices
Unlike wind or solar, no design has converged. The core challenge is surviving storm loads up to 100 times average conditions while capturing energy efficiently in normal seas. Pre-commercial LCOE estimates typically exceed EUR 300/MWh (JRC). Wave output is more persistent and less variable hour to hour than wind, which gives it system value if costs fall.
Related terms
All terms →- Tidal stream power
Electricity generated by underwater turbines placed in fast tidal currents, analogous to wind turbines but driven by water about 800 times denser than air.
- Tidal range power
Electricity generated from the height difference between high and low tide, by impounding water behind a barrage or lagoon and releasing it through low-head turbines.
- OTEC (Ocean Thermal Energy Conversion)
Power generation from the temperature difference between warm tropical surface seawater and cold deep water, typically about 20 to 25 °C, using a heat engine cycle.
- 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.
- 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.