Ocean Energy

Kim Cobbwith slides from Dr. Alam, MIT

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

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

-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 energy800 TWh/yr for tidal current energy2,000 TWh/yr for salinity gradient energy10,000 TWh/yr for ocean thermal energy

World’s electricity consumption 17,000 TWh/yr

Source of Ocean Wave Energy

Wave Energy Extraction TechnologiesPoint Absorber(OPT,Finavera)

Oscillating Water Column (Energetech/Oceanlinx)

Attenuator, Pelamis WP Overtopping, Wave Dragon

Power From Ocean Waves

kW/m crest length

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.

Point absorber buoys: most common

Ocean Power Technology buoy, to best tested this month off Oregonwill power 50 homes. Federal permit obtained for grid-connection.

capacity = 150 kW

Oscillating Water Column Installations: LAND

NOTE: Plant Bowen (Georgia Power) operates at 3,200,000 kW

Oscillating Water Column Installations: OCEAN

“Overtopping” Wave Energy

“Sea Snake” Wave Energy

121m long, 3.5m tall!

Tidal Energy Conversion

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

Ocean Thermal Energy Conversion

210 kW OTEC test plant, 1993-1998, Hawaii

Future OTEC plant: grow food and fuel?

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

Ocean Energy: PROS and CONS?