The document summarizes different types of ocean energy resources including wave, tidal, ocean thermal, and salinity gradient energy. It notes that the theoretical global resource of ocean energy is substantial, with wave energy alone estimated at 8,000-80,000 TWh/yr, which exceeds current worldwide electricity consumption of 17,000 TWh/yr. The document also provides examples of different technologies used to extract energy from ocean waves, tides, and thermal gradients and gives updates on the status of grid-connected ocean energy projects around the world.

1. Ocean Energy
Kim Cobb
with slides from Dr. Alam, MIT

2. Overview of Ocean Energy
-ocean energy is replenished by the sun and through tidal influences of the
moon’s and sun’s gravitational forces
-near-surface winds induce wave action and cause wind-blown currents at
about 3% of the wind speed
-tides cause strong currents into and out of coastal basins and rivers
-ocean surface heating by some 70% of the incoming sunlight adds to the
surface water thermal energy, causing expansion and flow
-wind energy is stronger over the ocean due to less drag, although
technically, only seabreezes are from ocean energy

3. How much energy and what types?
-250 Billion barrels of oil worth of energy coming into ocean every day
-80 million barrels of oil per day produced
kinetic
potential

4. -250 Billion barrels of oil worth of energy coming into ocean every day
-80 million barrels of oil per day produced
How much energy and what types?
Theoretical global resource of ocean energy:
8,000-80,000 TWh/yr for wave energy
800 TWh/yr for tidal current energy
2,000 TWh/yr for salinity gradient energy
10,000 TWh/yr for ocean thermal energy
World’s electricity consumption 17,000 TWh/yr

5. Source of Ocean Wave Energy

7. Wave Energy Extraction Technologies
Point
Absorber
(OPT,
Finavera)
Oscillating Water Column
(Energetech/Oceanlinx)
Attenuator, Pelamis WP Overtopping, Wave Dragon

8. Power From Ocean Waves
kW/m crest length

9. Power From Ocean Waves
• Wave energy is strongest on the west coasts and increases toward the poles.
• At approx. 30 kW/mcl in the Northwest (yearly avg.), a single meter (3.3 feet) of wave has the
raw energy to power about 23 homes.

10. Point absorber buoys: most common

12. Ocean Power Technology buoy, to best tested this month off Oregon
will power 50 homes. Federal permit obtained for grid-connection.
capacity = 150 kW

13. Oscillating Water Column Installations: LAND
NOTE: Plant Bowen (Georgia Power) operates at 3,200,000 kW

14. Oscillating Water Column Installations: OCEAN

15. “Overtopping” Wave Energy

16. “Sea Snake” Wave Energy
121m long, 3.5m tall!

18. Tidal Energy Conversion

19. Ocean Renewable Power Company installed first grid-connected tidal
device in Cobbscook Bay, Maine in June, 2012. Powers 25 homes.

21. Ocean Thermal Energy Conversion

22. 210 kW OTEC test plant, 1993-1998, Hawaii

23. Future OTEC plant: grow food and fuel?

24. Ocean Energy: Where are we today?
Wave Energy (grid-connected):
-0.4MW and 0.5MW OWC off the coast of Pico and Islay by 2008
-2.25MW Pelamis off Portugal by 2008
-0.5MW section of Wave Star Energy off Denmark by 2009
-7MW Wave Dragon off Wales by 2010
Tidal:
- barriers: 240MW France in 1966 and 20MW in Canada
-Current: 1.2MW off Ireland by 2009, 1MW France
Thermal:
-0.2MW Hawaii 1993-1998

25. Ocean Energy: PROS and CONS?