Tidal Energy

TIDAL ENERGY

PRESENTED BY GROUP #1

OVERVIEW Renewable Energy Historical Aspects Tidal Types Of Tidal Energy Tidal Power How Electricity can be produced by tides? How power can generated? Types of Turbine Future Expansion of Tidal Turbines Advantages And Disadvantage Conclusions

Alternative Energy Sources?? 

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Need to move away from fossil fuels

 Need safe and clean energy sources that don’t create significant amounts of waste.

Renewable Energy Sources offer this.

Renewable Energy 

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Renewable energy sources capture their energy from existing flows of energy, from on-going natural  processes, such as sunshine, wind, flowing water (hydropower), biological processes, and geothermal heat flows.

Examples of Renewable Energy Sources: Wind

Solar

Hydroelectric

Historical Aspects 

Tidal power is not a new concept and has been used since at least the 11th Century.

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During the Roman occupation at England, tide mills were built to grind grain and corn

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These tide mills operated by storing water behind a dam during high tide. As the tide moves,the water was slowly let out from behind the dam in order to power the mill.

Global Primary Energy Sources 2002

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TIDES

Definition

What is tidal power? Tidal power is a means of electricity generation achieved by capturing the energy contained in moving water mass due to tides. Essentially caused by interaction of moon, earth, and sun centrifugal forces

The Tides

Tidal energy comes from the gravitational forces of the Sun and the Moon on the Earth’s bodies of  water, water, creating periodic shifts in these bodies of  water. These shifts are called tides. •

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TYPES OF TIDAL ENERGY Two types of tidal energy can be extracted:

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Kinetic energy of water due the tides Potential energy from the difference in height (or head) between high and low tides.

Tidal Hydrokinetic Power Like a wind turbine…

…but underwater

001,09-11-09,WEI.ppt

Tidal Power 

Obviously requires large bodies of water nearby.

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Tidal power generators derive their energy from movement of the tides.

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Has potential for generation of very large amounts of  electricity, or can be used in smaller scale.

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There are a number of places around the world that have adopted pilot projects for different types of tidal generators

How Electricity can be produced by tides? 

As usual, the electricity is provided by spinning turbines.

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The potential energy contained in a volume of water is

 E = xMg where x is the height of the tide, M is the mass of water and g is the acceleration due to gravity. 

Therefore, a tidal energy generator must be placed in a location with very high-amplitude tides. Suitable locations are found in the former USSR, USA, Canada, Australia, Korea, the UK and other countries

The Worldwide Distribution of Tidal Energy

Grey areas in the ocean have the most intense tidal energy.

BASIC PRINCIPLE OF TIDAL TURBINE 

Water flows due to tides, strikes with blades of turbine , it rotates and tidal energy is converted into mechanical energy.

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This mechanical energy is further converted into electrical energy with generators.

DIFFERENT METHODS TO HARNESS TIDAL ENERGY

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Tidal Turbines

Tidal turbines operate on similar similar principles to that of wind turbines. Like wind turbines, turbines, tidal tidal turbines can either be horizontal axis turbines or vertical axis turbines. While the operating principles of tidal tidal turbines and wind turbines are very similar.

Bulb Turbine

Bulb Type

In systems with a bulb turbine, water flows around the generator, making access for maintenance difficult in generator. •

Rim type

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Rim turbines reduce these problems as the generator is mounted in the barrage, at right angles to the turbine blades.

Tubular turbines

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In this configuration, the blades are connected to a long shaft and orientated at an angle so that the generator g enerator is sitting on top of the barrage.

Deeper Water Current Turbine

Oscillating Tidal Turbine 

Oscillates up and down

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150 kW prototype operational (2003)

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Plans for 3 – 5 MW prototypes

SeaGen

Strangford commercial  prototype  prototype

 16

m diameter ( x2)

 1.4

MW @ 2.5 m/s

Evolution of Turbine Types 

Waterwheel Waterwheel turbines were used in tidal mills Undershot

Overshot

Ebb Generation System 

The simplest generating system for tidal plants, known as an ebb generating system, involves a dam, known as a barrage across an inlet.

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Alternatively, flood-generating systems, which generate power from the incoming tide are possible, but are less favored than ebb generating systems.

How power can generated? Sluice gates on the barrage allow the tidal basin to fill on the incoming high tides and to exit through the turbine system on the outgoing tide (known as the ebb tide). The generation of electricity from tides is very similar to hydroelectric generation, except that water is able to flow in both directions and this must be taken into account in the development of the generators.

Ebb Generation 

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.

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The cycle repeats itself.

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Ebb generation (also known as outflow generation) takes its name because generation occurs as the tide ebbs. Ebb generating system with a bulb turbine

Different Generator Types 

Tidal Fences

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Tidal Lagoons

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Tidal Turbines

Future Expansion of Tidal Turbines 

Tidal Farms. Sets of up to hundreds of tidal turbines working in conjunction.

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Potential for giga-watts of  power

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Marine Current Turbine (MCT) created SeaFlow (300kW), is following up with SeaGen (1MW), which will expand to a 5 turbine tidal farm that will provide 5MW.

Proposal By The Rawalpindi Chamber of  Commerce and Industry. 

Tidal energy is profitable than wind energy and solar power. In Pakistan, which has over 700 kilometers of Shoreline, the vision of  using tidal power has yet to be analyzed.

Advantages of Tidal Turbines 

Low Visual Impact 

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Low Noise Pollution 

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Sound levels transmitted are very low

High Predictability 

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Mainly, if not totally submerged.

Tides predicted years in advance, unlike wind

High Power Density 

Much smaller turbines than wind turbines for the same power

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Disadvantages of Tidal Turbines 

High maintenance costs

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High power distribution costs

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Needs a suitable site, where waves are consistently strong.

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Disturbance or destruction of marine life.

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Conclusions 

Tidal power is a renewable, potentially zero emission (during operation) energy source.

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Tides have the advantage of being completely predictable, unlike solar and wind power.

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Different types of Tidal Generators suit different areas and energy needs.

QUESTIONS?