Ocean Power also comes in 3 other forms:

• Wave Energy
• Tidal Energy
• Current Flow Energy

The ocean is a huge reservoir for storing the energy of the sun that is incident on the earth. How huge is huge?

Incident flux on ocean surface area is 10¹⁷ Watts or 100000 Terrawatts The planet is currently a 10 TW planet.

Major currents are shaped by:

• Temperature differences (driven mostly by tilt of earth's axis)
• Prevailing wind patterns interacting with the surface waters (again driven mostly by tilt of earth's axis)
• the rotation of the earth the Coriolis Force
• shorelines of continental masses

Tapping the Current for Energy:

• Gulf current has 1000 times the flow of the Mississippi River(!)
• Current averages about 5 mph
• Density of water is higher as well
• Its always there - no intermittency problem no need for energy storage
• Build Turbines for underwater use
• Anchor a foundation to the ocean floor
• hundreds of miles long rigged with turbines
• cables on ocean floor to shore deliver the electricity

• An engineering challenge but there are few bad side effects from producing energy this way
• Obviously the capital costs are huge in this case but this does represent a Large Scale Solution

Wave Energy From the Oceans:

Tidal Energy from the Ocean

Extracts energy from the kinetic energy of the earth-moon-sun system.

Variations in water level along coastlines can be used to drive turbines technology is the same as low-head hydro power

Vertical tides on US coast range from 2 feet in Florida to more than 18 feet in Maine

To enhance efficiency of turbines driven by tidal currents, it is desireable to build a damlike structure across the mouth of a tidal basin in order to direct the flow to a turbine

Turbines designed for work at both high and low tide (inflow or outflow)

Intermittent tidal flow is major problem. Tidal facility produces about 1/3 the electrical energy of a hydro facility of the same peak capacity

Two tidal plants in the world:

• 1 MW facility on the White Sea in Russia (1969)
• 240-MW on the Rance River, St. Malo France (1967) has 750 meter long dike to impound tides that can be as high as 13 meters (!)
  

  

Proposed New Facilities:

• Phillipines
• A serious commercial venture
• Large Scale production in the UK

Potential Sites in the US

• Alaska ( Cook Inlet)
  

  

• Bay of Funday (US-Canadian Border; NE Coast of US) most favorable site in the World would produce about 30,000 MW in total (1/2 for the US)
  Tidal difference in Bay of Fundy
  

• A 1 MW demonstration plant has been built here - near Annapolis, Nova Scotia
• Locally (New England) this is a potential important source of power but on national scale is just a few percent of our (insatiable) need for power

Bottom Line: There aren't many favorable sites in the world for tidal power and the estimated capacity is 50 times smaller than the world's hydroelectric power capacity.