Ocean Energy Prof Park UTI 111 Essex County College Ocean Energy The world s ocean may eventually provide us with energy to power our homes and businesses Right now there are very few ocean energy power plants and most are fairly small But how can we get energy from the ocean There are three basic ways to tap the ocean for its energy We can use the ocean s waves we can use the ocean s high and low tides or we can use temperature differences in the water Let s take a look at each Wave Energy Kinetic energy movement exists in the moving waves of the ocean That energy can be used to power a turbine In this simple example to the right the wave rises into a chamber The rising water forces the air out of the chamber The moving air spins a turbine which can turn a generator When the wave goes down air flows through the turbine and back into the chamber through doors that are normally closed This is only one type of wave energy system Others actually use the up and down motion of the wave to power a piston that moves up and down inside a cylinder That piston can also turn a generator Most wave energy systems are very small But they can be used to power a warning buoy or a small light house Wave Energy Wave Farm The World s First Wave Farm Goes Live in Portugal by Bridgette Meinhold 10 22 08 The world s first commercial wave farm went live at the end of September in Agucadoura located off the coast of northern Portugal Designed by Pelamis Wave Power the farm employs three Wave Energy Converters snakelike semi submerged devices that generate electricity with hydraulic rams driven by waves This first phase of the new renewable energy farm is rated at 2 25 MW with 3 machines and the the second phase will add an additional 25 machines to bring the capacity to 21 MW enough to power 15 000 homes Wave Farm Tidal Energy Another form of ocean energy is called tidal energy When tides comes into the shore they can be trapped in reservoirs behind dams Then when the tide drops the water behind the dam can be let out just like in a regular hydroelectric power plant Tidal energy has been used since about the 11th Century when small dams were built along ocean estuaries and small streams the tidal water behind these dams was used to turn water wheels to mill grains Tidal Energy In order for tidal energy to work well you need large increases in tides An increase of at least 16 feet between low tide to high tide is needed There are only a few places where this tide change occurs around the earth Some power plants are already operating using this idea One plant in France makes enough energy from tides 240 megawatts to power 240 000 homes This facility is called the La Rance Station in France It began making electricity in 1966 It produces about one fifth of a regular nuclear or coal fired power plant It is more than 10 times the power of the next largest tidal station in the world the 17 megawatt Canadian Annapolis station Tidal Energy La Rance Tidal Power Plant Tidal Energy Tidal energy is the utilization of the sun and moon s gravitational forces as the tide is the result of their influences Tidal energy is a type of energy that produces electricity and other forms of power through the use of water Tidal energy is energy that could be obtained from the changing sea levels In other words tidal energy is a direct result of tide shifting from low to high Tidal energy is one of the oldest forms of energy Tide mills in use on the Spanish French and British coasts date back to 787 A D Tide mills consisted of a storage pond filled by the incoming tide through a sluice and emptied during the outgoing tide through a water wheel Tidal Energy The tide moves a huge amount of water twice each day and although the tidal energy supply is reliable and plentiful converting it into useful electrical power is not easy There are two basic theories on how to convert tides into power The first involves converting the power of the horizontal movement of the water into electricity The second involves producing energy from the rise and drop of water levels Severn Barrage Tidal Power The Severn Barrage is a proposed tidal power station to be built across the Bristol Channel Severn Estuary The River Severn has a tidal range of 14 metres the second highest in the world making it perfect for tidal power generation The 20 billion pound US30bn Severn Barrage would involve the construction of a 10 mile long barrage dam between Lavernock Point south of Cardiff Wales and Brean Down in Somerset England The barrage would act as a bridge between England and Wales and will have an operational lifetime of up to 200 years It would be the world s largest ever renewable energy project and the UK s largest engineering project since the Channel Tunnel Severn Barrage Tidal Power Tidal Energy Energy calculations The energy available from a barrage is dependent on the volume of water The potential energy contained in a volume of water is 49 where h is the vertical tidal range A is the horizontal area of the barrage basin is the density of water 1025 kg per cubic meter seawater varies between 1021 and 1030 kg per cubic meter and g is the acceleration due to the Earth s gravity 9 81 meters per second squared The factor half is due to the fact that as the basin flows empty through the turbines the hydraulic head over the dam reduces The maximum head is only available at the moment of low water assuming the high water level is still present in the basin Ocean Thermal Energy Conversion OTEC The idea is not new Using the temperature of water to make energy actually dates back to 1881 when a French Engineer by the name of Jacques D Arsonval first thought of OTEC The final ocean energy idea uses temperature differences in the ocean If you ever went swimming in the ocean and dove deep below the surface you would have noticed that the water gets colder the deeper you go It s warmer on the surface because sunlight warms the water But below the surface the ocean gets very cold That s why scuba divers wear wet suits when they dive down deep Their wet suits trapped their body heat to keep them warm Ocean Thermal Energy Conversion OTEC Power plants can be built that use this difference in temperature to make energy A difference of at least 38 degrees Fahrenheit is needed between the warmer surface water and the colder deep ocean water Using this type of energy source is called Ocean Thermal Energy Conversion or OTEC It is being demonstrated in Hawaii More info on