Wave EnergyWinds Turbulent Air Flow

Wind Flow on Upwind Wave Faces

Shear Stress on Surface of Water

Solar Radiation Wind Waves

Wave Size Factors1. Wind Speed2. Wind Duration3. Distance Over Which Wave Travels

Wave Energy

The energy resource available:

(W per m of crest)

= density of water T = period of wave (s)H = wave height (m)

Swells formed by storms can travel great distances. Power is lost when water depth < 200 m. Wave has 1/3 of original power when water depth reaches 20 m.

32

22THgPower

Wave Energy

Magnitude of the Resource:• In U.S., approximately 2,100 TW-hr is

available at a depth of 60 m offshore.• Current U.S. electrical use 11,200 TW-hr

Technologies• Terminators – Perpendicular to waves• Attenuators – Parallel to waves • Point Absorber – Small floating device• Overtopping – Reservoir (above avg.

ocean level) filled by waves, turbines

Wave Energy

Oscillating Water Column (OWC)

Wave Energy

The 500 kW LIMPET OWC, New Zealand

Wave Energy

Wave Energy

Pelamis (Sea Snake)

Hydraulic Rams Pump High Pressure Fluid

Accumulated Fluid Drives Turbines, Generators

Wave Energy

The 750 kW Pelamis Wave Energy Converter, Portugal

Wave Energy

Wave Energy

Wave Energy

Wave Energy

Environmental Considerations• Visual appearance• Reduction in wave height• Marine habitat• Toxic releases – hydraulic fluids• Conflict with other sea space users –

Shipping, fishing, recreational boating• Installation, decommissioning

Wave Energy

Benefits• Waves = Concentrated Solar Energy• Demand in Phase with Availability (Winter)• Low/No Chemical Pollution• Low Visual Pollution (Offshore)• Large Potential Resource

Challenges• Electricity Transmission• Immature Technology• Potential Shipping, Boating Accidents