Tidal powerTidal power

• This is the power achieved by This is the power achieved by capturing the energy contained in capturing the energy contained in moving water mass due to tides. moving water mass due to tides.

• There are two types: Kinetic energy There are two types: Kinetic energy and Potential Energy.and Potential Energy.

• One method of extracting tidal One method of extracting tidal energy involves building a barrage energy involves building a barrage and creating a tidal lagoon. and creating a tidal lagoon.

• The largest of this type of tidal power The largest of this type of tidal power has been working on the Rance River has been working on the Rance River (Bretagne, France) since 1967 and (Bretagne, France) since 1967 and produces 600 million KWh annually. produces 600 million KWh annually.

Modes of OperationModes of Operation

• Ebb GenerationEbb Generation

• Flood GenerationFlood Generation

• PumpingPumping

• Two basin schemesTwo basin schemes

• Tidal ‘wind farms’Tidal ‘wind farms’

Disadvantages of tidal Disadvantages of tidal powerpower• They do not produce energy 24 hours a They do not produce energy 24 hours a

day, but for more like 6-12 hours each day, but for more like 6-12 hours each day. day.

• The tide cycle is based on the moon and The tide cycle is based on the moon and changes daily. The demand for changes daily. The demand for electricity is based on the rotation of the electricity is based on the rotation of the earth- so the energy production cycle earth- so the energy production cycle will not always be the same as the will not always be the same as the demand cycle. demand cycle.

Environmental ImpactsEnvironmental Impacts

• Tidal Energy Efficiency- 80%Tidal Energy Efficiency- 80%

• Turbidity and Salinity DecreasesTurbidity and Salinity Decreases

• Sediment MovementsSediment Movements

• Pollutants less efficiently displacedPollutants less efficiently displaced

• FishFish

Tidal Power case studiesTidal Power case studies

• Rance tidal power plant built over a period Rance tidal power plant built over a period of 6 years from 1960 to 1966 at La Rance, of 6 years from 1960 to 1966 at La Rance, France. It has 240MW installed capacity and France. It has 240MW installed capacity and was the first tidal power plant in the world. was the first tidal power plant in the world.

• The first (and only) tidal power site in North The first (and only) tidal power site in North America is the Annapolis Royal Generating America is the Annapolis Royal Generating Station, Annapolis Royal, Nova Scotia, which Station, Annapolis Royal, Nova Scotia, which opened in 1984 on an inlet of the Bay of opened in 1984 on an inlet of the Bay of Fundy. It has 20MW installed capacity Fundy. It has 20MW installed capacity

Wave PowerWave Power

• refers to the energy of ocean surface refers to the energy of ocean surface waves and the capture of that energy waves and the capture of that energy to do useful workto do useful work

• Wave power generation is not a Wave power generation is not a widely employed technology, with widely employed technology, with only a few experimental sites in only a few experimental sites in existence. existence.

A simplified electricity generator

Waves!Waves!

• Generally large waves are more powerfulGenerally large waves are more powerful• Wave size is determined by wind speed Wave size is determined by wind speed

and fetch and by the depth and and fetch and by the depth and topography of the seafloor (which can topography of the seafloor (which can focus or disperse the energy of the focus or disperse the energy of the waves). waves).

• Wave motion is highest at the surface, Wave motion is highest at the surface, and diminishes exponentially with depth.and diminishes exponentially with depth.

Challenges of wave powerChallenges of wave power

• Efficiently converting wave motion Efficiently converting wave motion into energyinto energy

• Constructing devices that can survive Constructing devices that can survive storm damage and saltwater storm damage and saltwater corrosioncorrosion

• Low total cost of electricity. Low total cost of electricity.

Potential Potential • Wave power could yield much more Wave power could yield much more

energy than tidal powerenergy than tidal power• The energy potential of waves is certainly The energy potential of waves is certainly

greater, and wave power can be exploited greater, and wave power can be exploited in many more locations.in many more locations.

• Countries with large coastlines and strong Countries with large coastlines and strong prevailing winds (notably, Ireland and the prevailing winds (notably, Ireland and the UK) could produce five percent or more of UK) could produce five percent or more of their electricity from wave power. their electricity from wave power.

• Excess capacity (a problem common with Excess capacity (a problem common with intermittent energy sources) could be intermittent energy sources) could be used to produce hydrogen or smelt used to produce hydrogen or smelt aluminium aluminium

Wave Power case studiesWave Power case studies

• The first commercial power plant was The first commercial power plant was opened in 2000 on the island of Islay, opened in 2000 on the island of Islay, Scotland Scotland

• Provides 500kW of energy for the Provides 500kW of energy for the Island and the national GridIsland and the national Grid