Alternative energyAlternative energy

Tidal power-stationsTidal power-stations

What is a Tide ? What is a Tide ?

• TidesTides are the rising and falling of Earth's are the rising and falling of Earth's ocean surface caused by the tidal forces of ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. the Moon and the Sun acting on the oceans.

What is the Tidal force ?What is the Tidal force ?

• The The tidal forcetidal force is is the vectorial the vectorial difference between difference between the gravitational the gravitational force of the Earth force of the Earth and the and the gravitational force gravitational force of the Moon.of the Moon.

About tidal powerAbout tidal power

• Tidal powerTidal power, sometimes , sometimes called called tidal energytidal energy, is a , is a form of hydropower that form of hydropower that exploits the movement of exploits the movement of water caused by tidal water caused by tidal currents or the rise and fall currents or the rise and fall in sea levels due to the in sea levels due to the tides.tides.

• Although not yet widely Although not yet widely used, tidal power has used, tidal power has potential for future potential for future electricity generation and electricity generation and is more predictable than is more predictable than wind energy and solar wind energy and solar power. power.

History of Tidal power History of Tidal power stationsstations• An early attempt to build a An early attempt to build a

tidal power plant took tidal power plant took place at Aber-Wrac'h in the place at Aber-Wrac'h in the Finistere in 1925, but due Finistere in 1925, but due to financial problems, it to financial problems, it was abandoned in 1930. was abandoned in 1930.

• Tidal millsTidal mills have long have long existed in areas affected existed in areas affected by tides. by tides. In Europe, tide In Europe, tide mills have been used for mills have been used for over a thousand years, over a thousand years, mainly for grinding grains. mainly for grinding grains.

Principle of tidal power Principle of tidal power stationsstations• 1. Barrages make use of the 1. Barrages make use of the potential energypotential energy from the from the

difference in height (or difference in height (or headhead) between high and low tides. ) between high and low tides. Barrages suffer from the problems of very high civil Barrages suffer from the problems of very high civil infrastructure costs, few viable sites globally and infrastructure costs, few viable sites globally and environmental issues. environmental issues.

• 2. Tidal stream systems 2. Tidal stream systems make use of the make use of the kintetic energykintetic energy from from the moving water the moving water currents to power currents to power turbines, in a similar way turbines, in a similar way to wind mills use moving to wind mills use moving air. This method is air. This method is gaining in popularity gaining in popularity because of the lower because of the lower cost and lower cost and lower ecological impact. ecological impact.

Examples of tidal power Examples of tidal power stationsstations• La RanceLa Rance: The first and largest tidal plant in operation is the : The first and largest tidal plant in operation is the

240 MW plant built for commercial production across the La 240 MW plant built for commercial production across the La Rance estuary in north-western France between 1961 and Rance estuary in north-western France between 1961 and 1967. The tidal power plant has 24 bulb-type Kaplan 1967. The tidal power plant has 24 bulb-type Kaplan turbines with a rated capacity of 10 MW each. turbines with a rated capacity of 10 MW each.

• AnnapolisAnnapolis: The second commercially operated tidal power : The second commercially operated tidal power plant built in 1984 in the Western hemisphere is a 18 MW plant built in 1984 in the Western hemisphere is a 18 MW plant at Annapolis Royal on the Nova Scotia coast of the Bay plant at Annapolis Royal on the Nova Scotia coast of the Bay of Fundy in Canada. of Fundy in Canada.

• Other sitesOther sites: Other plants include the 400 kW : Other plants include the 400 kW experimental unit at Kislaya Guna, built in 1968 in experimental unit at Kislaya Guna, built in 1968 in Russia on the Barents Sea, and the 3.4 MW Jianxia Russia on the Barents Sea, and the 3.4 MW Jianxia station built in China between 1980 and 1986. Most station built in China between 1980 and 1986. Most of the technically available tidal resources in Europe of the technically available tidal resources in Europe are in the UK. The site in the Severn estuary in south-are in the UK. The site in the Severn estuary in south-western England represents a potential of 8 GW and western England represents a potential of 8 GW and has been the object of several feasibility studies. has been the object of several feasibility studies. Large potential also exists in northern France, at the Large potential also exists in northern France, at the Cotentin Peninsula in Normandy. Cotentin Peninsula in Normandy.

Advantages of using tidal Advantages of using tidal power:power:• Predictable source of “green" energy during Predictable source of “green" energy during

lifetime of barrage lifetime of barrage • It produces no greenhouse gases or other waste; It produces no greenhouse gases or other waste;

it needs no fuel. it needs no fuel. • Not expensive to maintain. Not expensive to maintain. • Tidal energy has an efficiency of 80% in Tidal energy has an efficiency of 80% in

converting the potential energy of the water into converting the potential energy of the water into electricity electricity

• Vertical-axis tidal generators may be joined Vertical-axis tidal generators may be joined together in series to create a ‘tidal fence’ capable together in series to create a ‘tidal fence’ capable of generating electricity on a scale comparable to of generating electricity on a scale comparable to the largest existing fossil fuelbased, hydroelectric the largest existing fossil fuelbased, hydroelectric and nuclear energy generation facilities and nuclear energy generation facilities

Disadvantages of using tidal Disadvantages of using tidal power:power:• A barrage across an estuary is very A barrage across an estuary is very

expensive to build, and affects a very wide expensive to build, and affects a very wide area - the environment is changed for many area - the environment is changed for many miles upstream and downstream miles upstream and downstream

• it provides power for around 10 hours each it provides power for around 10 hours each day, when the tide is actually moving in or day, when the tide is actually moving in or out, which is not very much out, which is not very much

• Existing ecosystems would be heavily Existing ecosystems would be heavily altered, with new species moving in and altered, with new species moving in and perhaps dominating old species perhaps dominating old species

• Tidal power schemes have a high capital Tidal power schemes have a high capital cost cost

• A tidal power scheme is a long-term source A tidal power scheme is a long-term source of electricity. A proposal for the Severn of electricity. A proposal for the Severn Barrage, if built, has been projected to save Barrage, if built, has been projected to save 18 million tonnes of coal per year of 18 million tonnes of coal per year of operation. This decreases the output of operation. This decreases the output of greenhouse gases into the atmosphere.greenhouse gases into the atmosphere.

• If fossil fuel resource is likely to decline If fossil fuel resource is likely to decline during the 21st century, as predicted by during the 21st century, as predicted by Hubbert peak theory, tidal power is one of Hubbert peak theory, tidal power is one of the alternative source of energy that will the alternative source of energy that will need to be developed to satisfy the human need to be developed to satisfy the human demand for energy.demand for energy.

Global enviromental Global enviromental impactimpact

Made by: Grec MarcelMade by: Grec Marcel

Topliceanu LiviuTopliceanu Liviu