Generation Of Electricity Through Tidal Energy Group Members

Generation Of Electricity Through Tidal Energy

Group Members • Asad Saleh Hayat • Umad Zaib • Azmat Ullah • Halim Ullah • Sibghat Ullah

Power Generation 1. 2. 3. 4. 5. 6. 7. Tidal Hydro Wind Solar Nuclear Fuel fossils Geothermal

What are Tides? • The alternate rising and falling of the sea, usually twice in each lunar day at a particular place, due to the attraction of the moon and sun. • Tides originate in the oceans and progress toward the coastlines where they appear as the regular rise and fall of the sea surface. • Tides are one of the most reliable phenomena in the world.

What Is Tidal Power? ? ? • The objective of tidal power is to convert the kinetic energy of the waves of water, flowing in the sea to electric energy via Generator. • Tidal power facilities harness the energy from the rise and fall of tides. • Ideal sites are located at narrow channels and experience high variation in high and low tides. • Extracts kinetic energy from moving water generated by tides.

Energy from the moon • Tides generated by the combination of the moon and sun’s gravitational forces. • Greatest affect in spring when moon and sun combine forces • Bays and inlets amplify the height of the tide. • In order to be practical for energy production, the height difference needs to be at least 5 meters. • Only 40 sites around the world of this magnitude. • Overall potential of 3000 gigawatts from movement of tides.

History of Wave Energy • 1799: First patent of a device designed to use ocean waves to generate power • 1910: First oscillating water column was built by Bochaux-Praceique to power his house • 1940 s: Yoshio Masuda experimented with many concepts of wave power • 2004: Wave power was delivered to an electrical grid for the first time

How it works • First generation, barrage-style tidal power plants • Works by building Barrage to contain water after high tide, then water has to pass through a turbine to return to low tide • Sites in France (La Rance), Canada (Annapolis), and Russia • Future sites possibly on Severn River in England, San Francisco bay, Passamaquoddy

How it works: Tidal Barrages

Tidal Barrage: A series of Water Turbine

Parts of TPS • Barrage • Turbines • Hydro Generator

Barrage • The basin is filled through the sluices and freewheeling turbines until high tide. Then the sluice gates and turbine gates are closed. • They are kept closed until the sea level falls to create sufficient head across the barrage and the turbines generate until the head is again low. Then the sluices are opened, turbines disconnected and the basin is filled again.

Tidal Barrage • Utilize potential energy • Tidal barrages are typically dams built across an estuary or bay. • consist of turbines, sluice gates, embankments, and ship locks. • Two types: • Single basin system • Double-basin system

Wave Power

Some Turbine Types Bulb Type Rim Type • In systems with a bulb turbine, water flows around the turbine, making access for maintenance difficult, as the water must be prevented from flowing past the turbine. Tubular Type • Rim turbines reduce these problems as the generator is mounted in the barrage, at right angles to the turbine blades. Unfortunately, it is difficult to regulate the performance of these turbines and it is unsuitable for use in pumping. • Tubular turbines have been proposed for use some UK projects. In this configuration, the blades are connected to a long shaft and orientated at an angle so that the generator is sitting on top of the barrage.

Tidal Turbines (cont. ) • ‘Sea. Flow, ’ a 300 k. W prototype turbine was the world’s first offshore tidal turbine and was installed off Lynmouth, Devon in May 2003. Cost £ 3. 4 million and was funded by a consortium of private companies and the UK and German governments.

Tidal Multiple Turbines Underwater turbines are by definition out of sight and it is believed that their environmental impact is negligible thanks to their slow rotation rates of just 1030 revolutions per minute 10 times slower than that of ships propellers). In addition, tidal turbines do not affect navigation or shipping and so there are no hidden extra costs to consider.

Different Generator Types • Tidal Fences • Tidal Lagoons • Tidal Turbines

Tidal Fences • Tidal fences are composed of individual, vertical axis turbines which are mounted within the fence structure, known as a caisson. • Kind of like giant turn styles which completely block a channel, forcing all of the water through them. • Unlike barrage tidal power stations, tidal fences can also be used in unconfined basins, such as in the channel between the mainland a nearby off shore island, or between two islands.

Tidal Fences (cont. ) • “A 2. 2 GW tidal fence using the Davis turbine, was being planned for the San Bernadino Strait in the Philippines to be constructed by the Blue Energy company. The project, estimated to cost $US 2. 8 Billion is unfortunately on hold due to political instability” according to Michael Maser a Blue Energy spokesman. ” Davis Hydro Turbine http: //www. bluenergy. com/

Tidal Fences (cont. ) • Since they do not require flooding of the basin, tidal fences have much less impact on the environment, and are significantly cheaper to install. • Unlike barrage generators, tidal fences have the advantage of being able to generate electricity once the initial modules are installed. • Since a caisson structure is still required, which can disrupt the movement of large marine animals and shipping, there are still ecological concerns

Tidal Lagoons • Tidal lagoons are an adaptation of the barrage system. Similar to standard barrage models, tidal lagoons retain a head pond and generate power via conventional hydro -turbines. • The difference is that the conventional barrage designs exploit the natural coast line to minimize barrage length. However, this entails blocking the estuary regardless of how deep it is. This raise the costs considerably. • However, a lagoon, for a low cost can pretty much be built anywhere that there is a high tidal range. • The lagoon has relatively little visual impact, as it is below the high water tide mark and appears like a normal sea wall at low tide.

-Tidal Stream Generators • Very close in concept to traditional windmills • Most popular prototype on the market • Prototype sites include Norway, England, and New York. • In 2007 8 prototype turbines where placed in the East River between Queens and Roosevelt Island. • It is the first major tidal power project in the USA.

Tidal Turbines • Proposed shortly after the oil crisis of the 1970 s, tidal turbines have only become reality in the last decade, when a 10 -15 k. W 'proof of concept' turbine was operated on Loch Linnhe. Resembling a wind turbine, tidal turbines offer significant advantages over barrage and fence tidal systems, including reduced environmental effects. • Tidal turbines utilize tidal currents that are moving with velocities of between 2 and 3 m/s (4 to 6 knots) to generate between 4 and 13 k. W/m 2. Fast moving current (>3 m/s) can cause undue stress on the blades in a similar way that very strong gale force winds can damage traditional wind turbine generators, whilst lower velocities are uneconomic.

Tidal Turbines (cont. ) • • Tidal turbines offer significant advantages over barrage and fence tidal systems (and other renewable energy sources): High energy intensity: A 1 MW tidal turbine can access five to ten times as much energy per square meter of rotor than a 1 MW wind turbine, resulting in a smaller and potentially lower cost machine. Minimal environmental impact: tidal turbines are visible enough to be avoided by mariners but they have a low visual impact on the seascape, they produce no pollution or noise and their slow moving rotors which turn at less than one revolution in four seconds (15 rpm) are considered unlikely to harm marine life. High energy return on energy invested: tidal turbines should offer faster energy payback than most other renewables.

-Comparison to Wind Energy • Tidal Stream generators draw energy in the same basic way wind turbines do • Higher density of water allows a single generator to provide significantly more power • Water speeds of nearly 1/10 the speed of wind can provide the same energy output • Current in water is much more reliable then wind in the air.

Environmental/Ecological Concerns • Tidal power generation can offer significant advantages, including improved transportation due to the development of traffic or rail bridges across estuaries and reduced greenhouse gas emissions by utilizing tidal power in place of fossil fuels. • However there also some significant environmental disadvantages which make tidal power, particularly barrage systems less attractive than other forms of renewable energy. La Rance, France (240 MW)

Tidal Changes • The construction of a tidal barrage in an estuary will change the tidal level in the basin. This change is difficult to predict, and can result in a lowering or raising of the tidal level. This change will also have a marked effect on the sedimentation and purity of the water within the basin. In addition, navigation and recreation can be affected as a result of a sea depth change due to increased sedimentation within the basin. A raising of the tidal level could result in the flooding of the shoreline, which could have an effect on the local marine food chain. Ecological Changes • Potentially the largest disadvantage of tidal power is the effect a tidal station has on the plants and animals which live within the estuary. As very few tidal barrages have been built, very little is understood about the full impact of tidal power systems on the local environment. What has been concluded is that the effect due to a tidal barrage is highly dependent upon the local geography and marine ecosystem. • Wales have been caught in tidal generators. • Fish may move through sluices safely, but when these are closed, fish will seek out turbines and attempt to swim through them. Also, some fish will be unable to escape the water speed near a turbine and will be sucked through.

240 MW La Rance France

-Sea. Gen • World’s first large scale commercial tidal stream generator. • First one was installed in the Strangford Narrows (Ireland) • Generates 1. 2 MW between 18 -20 hours a day • Blades span 16 meters in diameter • http: //www. energysavers. gov/renewable_energy/ocean/index. cfm/mytopic=50009

-Calculations: Tidal Stream Generators- P = the power generated (in watts) ξ = the turbine efficiency ρ = the density of the water (seawater is 1025 kg/m³) A = the sweep area of the turbine (in m²) V = the velocity of the flow *Power equation is based on the kinetic energy of the moving water*

Future Expansion of Tidal Turbines • Tidal Farms. Sets of up to hundreds of tidal turbines working in conjunction. • Potential for giga-watts of power • Marine Current Turbine (MCT) created Sea. Flow (300 k. W), is following up with Sea. Gen (1 MW), which will expand to a 5 turbine tidal farm that will provide 5 MW. • The Norwegian company, Hammerfest Strom, believes that they will have their first tidal farm of over 20 second generation devices operational before the end of 2008. This would be the 3 rd phase of their 'Blue Concept' project and would result in a tidal farm that would produce 10 MW of renewable electricity.

Advantages • No pollution • Renewable resource • More efficient than wind because of the density of water • Predictable source of energy vs. wind and solar • Second generation has very few disadvantages • Does not affect wildlife • Does not affect silt deposits • Less costly – both in building and maintenance

Disadvantages • Presently costly • Expensive to build and maintain • A 1085 MW facility could cost as much as 1. 2 billion dollars to construct and run • Connection to the grid • Technology is not fully developed • Barrage style only produces energy for about 10 hours out of the day • Barrage style has environmental affects • Such as fish and plant migration • Silt deposits • Local tides change- affects still under study

Pros and cons of both tidal power facilities Tidal Barrages • Mature technology that has been around for nearly 50 years. • Reliable energy source. BUT • High costs of construction • Environmental impacts on marine life • Low power output in comparison to other energy source like coal and nuclear power plants Tidal Current Turbines • Able to utilize both ebb and flood tides. • Tidal current turbines are not large massive dam structure. BUT • Tidal current turbine technology is young in its development. • Installation and maintenance challenges. • Environmental impacts are still being tested.

Conclusions • Tidal power is a renewable, potentially zero emission (during operation) energy source. • Tides have the advantage of being completely predictable, unlike solar and wind power. • Different types of Tidal Generators suit different areas and energy needs. • There are environmental concerns that need to be addressed when developing this technology further.