Energy and the Environment Ocean Energy Energy and the Environment

Tidal Energy Tides are caused by the gravitation pull on the oceans caused by the moon (and to a small amount the Sun) “Spring Tides” are extra big since they occur when the Sun and moon are in alignment.

Tidal Energy Early 1960’s France constructed a barrage across La Rance tidal estuary. At 240 MW it is the largest tidal energy facility in the world. Second is 18 MW and is located in Annapolis Royal, Canada.

Annapolis Royal Tidal Power Plant

Tidal Energy

Tidal Energy: Future Potential Optima sites are scarce, only about two dozen location around the world Only Maine and Alaska in the USA have sufficient tide oscillations to be effective. Proposed project in the UK, Severn Estuary, 8640 MW, 5% on the UK power consumption in 2002

Tidal Energy: Future Potential Benefits Drawbacks Emission free Predictable Reliable Once built, energy source is free. Remote and limited global distribution of the tidal resource. Produce electricity intermittently High capital costs Environmental concern are similar to conventional hydroelectric energy

Wave Energy Waves are created by the movement of the wind over the ocean. Since the Sun causes wind, wave energy is a form of solar energy. It has been estimated that wave technology could feasibly fulfill 10% of the global electricity supply if fully developed.

Wave Energy Waves lose 60% of their energy by the time they reach the shore But offshore energy production requires sub-sea transmission lines to distribute the electricity. This is very costly

Example of Wave Systems Pacific Northwest Generating Cooperative Magnets are secured to the ocean floor, copper coils move up and down with the waves.

Example of Wave Systems Pelamis Wave Energy Converter Pressurized oil drives a hydraulic ram which turns a generator Prototype in Scotland and in Portugal, but now offline.

Example of Wave Systems Seabased AB system Generator anchored to the seabed and a floating buoy rises and falls with the waves

Example of Wave Systems Oyster wave energy converter by Aquamarine power Testing being done in the UK and Scotland

Example of Wave Systems Waves move a turbine and generator by forcing a column of air up and down.

Wave Energy: Future Potential The US has a great deal of wave potential, but Europe has taken the lead in wave energy.

Wave Energy: Future Potential Benefits Drawbacks Generally predictable and constant Waves have much more kinetic energy than wind due to its density Emission free Currently more expensive Eyesore and may disrupt the natural movement of sediment.

Marine Current Systems Lunar gravitation as well an thermal differences and water density influence TIDAL STREAMS or strong marine currents Systems resembled wind turbines but underwater. Rotating blades are used to convert the kinetic energy in water currents into electricity Can be floating or anchored to the seabed

Marine Current Systems: Future Potential 2003 Norway completed the world’s first commercial power plant using marine current technology.

Marine Current Systems: Future Potential Benefits Drawbacks Predictable in both timing and quantity Virtually non intermittent, only in some places ceasing during the turning of the tides. Since they are modular, they can be scaled up when more capital becomes available Little “eyesore” factor Early studies show little environmental or ecological footprint Still more expensive than using fossil fuels Harsh marine environment makes maintenance both difficult and necessary.

Ocean Thermal Energy Conversion The ocean stores way more energy from the sun than we use on a daily basis If we could harness just a fraction of that energy we would be able to offset fossil fuel use substantially Must be a temperature differential of 36oF Much potential in tropical and island locations

Closed Cycle: Ammonia

Open-Cycle

Can be land based or floating

OTEC: Future Potential

OTEC: Future Potential Benefits Drawbacks Could serve as ideal base load energy source. Provide other attractive services such as desalination of sea water and air conditioning. Little notable impact on marine ecosystem Only certain places have a large enough temperature gradient for it to be efficient Same challenges as other marine technologies – susceptible to extreme weather. Technology is still far from being cost effective