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. 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
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)
Overtopping, Wave Dragon
Attenuator, Pelamis WP
EPRI surveyed, collected information and assessed existing wave energy conversion devices. Sixteen worldwide manufacturers were queried of which 12 provided information of which eight devices passed the initial screening consisting of two factors
Is the device likely to be ready for demonstration in the late 2006 time period?
Has the device manufacturer provided sufficient information to prove the survivability in storm conditions?
The eight devices which passed the initial screen can be grouped into one of four generic types as shown above
AquaEnergy floating point absorber
Ocean Power Delivery Pelamis floating attenuator – the most technologically mature of the devices. A full scale prototype achieved the milestone last summer of being the first offshore wave device to transmit power to an electrical grid
Wave Dragon floating overtopping ramp terminator
Energetech bottom mounted oscillating water column terminator

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

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, 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

25. Ocean Energy: PROS and CONS?