Ocean Tides and Tidal Energy

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Questions and Answers

What percentage of the Earth's surface is covered by oceans?

70%

60%

71.4%

71% (correct)

Why do high tides form on the opposite side of the Earth?

Because the solid Earth is pulled away from the water surface (correct)

Due to the gravitational pull of the moon on the water surface

Due to the movement of the Earth around the sun

Due to the rotation of the Earth

What is the approximate time it takes for a high tide to form due to the moon's gravitational pull?

24 h and 5 min

12 h

24 h

12 h and 25 min (correct)

What is the ratio of the gravitational pull of the moon to that of the sun?

2.2:1 Signup and view all the answers

What is the minimum tidal range required to drive a turbine coupled with a generator to produce electricity?

5-15 m Signup and view all the answers

What is the time it takes for the moon to complete a rotation on its axis?

24 h and 50 min Signup and view all the answers

What is the reason for the solar tides moving in and out of phase with lunar tides?

Due to the difference in the periods of the Earth's rotation around the sun and the moon's rotation Signup and view all the answers

What is the resulting effect of the gravitational pull of the moon on the Earth's surface?

Formation of high tides Signup and view all the answers

What is the minimum tidal range required for the working of a tidal power plant?

5 m Signup and view all the answers

What is the primary source of energy in a tidal power plant?

Difference in water levels between high and low tides Signup and view all the answers

Why are sluiceways provided in a tidal power plant?

To control water flow into the basin Signup and view all the answers

What is the purpose of a dam or dyke in a tidal power plant?

To form a barrier between the sea and the reservoir Signup and view all the answers

What is the function of turbines in a tidal power plant?

To generate electricity Signup and view all the answers

What is the type of tidal energy generation possible during both high and low tides?

Two-way generation Signup and view all the answers

What is the output of a tidal power plant?

Electrical energy Signup and view all the answers

What is the name of the phenomenon where the sun, earth, and moon are aligned?

Spring tides Signup and view all the answers

What is the duration of one tidal cycle?

12 hours and 25 minutes Signup and view all the answers

What is the name of the process where water is pumped into the reservoir during high tides and used for power generation during low tides?

Pumping and turbining Signup and view all the answers

What is a necessary requirement for the construction of an OTEC plant?

Building it on floats Signup and view all the answers

What is a potential environmental impact of an OTEC plant's operation?

Destruction of marine life due to water circulation Signup and view all the answers

Why may an OTEC plant affect the ecosystem and coral?

Because of the plant's water circulation Signup and view all the answers

What is released into the atmosphere in an open-cycle OTEC plant?

Carbon dioxide Signup and view all the answers

What is a potential consequence of releasing cold water into a warmer environment?

Adverse effect on marine life Signup and view all the answers

What is the primary consideration for selecting a site for a tidal power plant?

Safety from high wave action during storms Signup and view all the answers

What is a major advantage of tidal energy over other forms of energy?

It is free from pollution Signup and view all the answers

What is a limitation of tidal energy?

The power output varies with the lunar cycle Signup and view all the answers

What type of tidal plant system uses reversible turbines to generate power during both filling and emptying of the basin?

Double cycle system Signup and view all the answers

What is the primary reason for the high transmission cost of tidal power?

The distance between the tidal power plant and the load centers Signup and view all the answers

What is the purpose of the sluice valves in a single basin tidal plant?

To regulate the flow of water into the basin Signup and view all the answers

What is a major disadvantage of tidal energy?

The construction period of a dam is long Signup and view all the answers

What is the purpose of the turbines in a tidal power plant?

To drive the generators to produce power Signup and view all the answers

What is the effect of the corrosive nature of sea water on tidal power equipment?

It reduces the life of the equipment Signup and view all the answers

What is the purpose of the basin in a tidal power plant?

To store water during high tides Signup and view all the answers

What is the primary limitation of the single basin system?

Continuous power generation is not possible Signup and view all the answers

In a double basin system, what is the purpose of the dam between the upper and lower basins?

To allow turbines to generate power Signup and view all the answers

What is the minimum temperature difference required for ocean thermal energy conversion?

20°C Signup and view all the answers

What is the primary advantage of ocean thermal energy conversion?

It is an indirect method of utilizing solar energy Signup and view all the answers

What is the purpose of the upper water layer in ocean thermal energy conversion?

It acts as a heat storage reservoir Signup and view all the answers

What is the primary reason for the temperature difference between the surface and deep water in the ocean?

The absorption of solar radiation according to Lambert's law of absorption Signup and view all the answers

What is the typical temperature of the heat source in ocean thermal energy conversion?

27°C Signup and view all the answers

What is the primary requirement for a site to be suitable for tidal power development?

High tidal range Signup and view all the answers

What is the purpose of the dam between the sea and the basin in a tidal power plant?

To allow water to flow from the sea to the basin Signup and view all the answers

What is the typical temperature of the heat sink in ocean thermal energy conversion?

4°C Signup and view all the answers

What is the primary principle behind the OTEC system?

Conversion of thermal energy into mechanical work Signup and view all the answers

What is the purpose of the flash evaporator in the open cycle OTEC plant?

To evaporate warm water into low pressure steam Signup and view all the answers

What is the advantage of using a closed cycle OTEC plant over an open cycle plant?

More compact size and lower cost Signup and view all the answers

Which country has planned a 10 MW closed cycle OTEC plant in the Caribbean or Pacific ocean?

United Kingdom Signup and view all the answers

What is one of the useful by-products of an OTEC plant?

Desalinated water Signup and view all the answers

What is a major limitation of OTEC plants?

Low temperature difference between warm surface water and cold deep water Signup and view all the answers

What is the purpose of the condenser in an OTEC plant?

To cool the steam into water Signup and view all the answers

What is a major challenge in the design of OTEC plants?

All of the above Signup and view all the answers

What is a major drawback of OTEC plants in terms of their location?

Requirement for long-distance cable to transmit power to shore Signup and view all the answers

What is the primary advantage of OTEC plants in terms of power supply?

Ability to supply steady power without fluctuation in all weather conditions Signup and view all the answers

Study Notes

Tides and Tidal Energy

Tides are produced by the gravitational attraction of the moon and sun acting on the rotating Earth.
The periodic rise and fall of the water level in the oceans creates a large amount of potential energy, which can be harnessed to generate electric power.
The tidal range, which is the difference in water level between high and low tides, can be used to drive turbines coupled with generators to generate electric power.

Origin of Tides

The gravitational pulls of the moon and sun cause the formation of high and low tides.
The moon's gravitational pull is about 2.5 times stronger than the sun's.
The rotation of the Earth and the orbit of the moon result in the formation of two high tides and two low tides per day.

Spring and Neap Tides

Spring tides occur when the Earth, sun, and moon are aligned, resulting in maximum tidal heights.
Neap tides occur when the sun and moon are perpendicular to the Earth, resulting in minimum tidal heights.
Spring and neap tides occur twice in a lunar month.

Tidal Energy

Tidal energy is generated by harnessing the difference in water levels between high and low tides.
The potential energy of water is converted into kinetic energy, which is used to drive turbines and generate electricity.
The minimum tidal range required for economic power production is 5 meters.

Modes of Operation of Tidal Power Plants

Ebb generation: generate power during low tides by allowing water to flow out of the reservoir.
Flood generation: generate power during high tides by allowing water to flow into the reservoir.
Two-way generation: generate power during both high and low tides.
Pumping and turbining: use pumps to fill the reservoir during high tides and turbines to generate power during low tides.

Components of Tidal Power Plants

Dam or dyke: forms a barrier between the sea and the reservoir.
Sluiceways: allow water to enter and exit the reservoir.
Powerhouse: contains turbines, generators, and other equipment.

Feasibility of Tidal Power Plants

Factors affecting feasibility: tidal range, cost, shipping traffic, safety, and silt content.

Merits and Limitations of Tidal Energy

Merits: free from pollution, inexhaustible, and can be used for fish farming.
Limitations: limited to suitable sites, transmission costs are high, operation is uneven, and construction is costly.

Classification of Tidal Plants

Single basin system: uses one basin to store water.
Double basin system: uses two basins at different levels.

Site Requirements

High tidal range, short length of dam, nearness to load location, protection from high waves, and no hindrance to shipping traffic.

Tidal Power Development in India

Suitable sites: Gulf of Kutch, Gulf of Khambhat, Sundarbans delta, Gulf of Cambay, and Pitts Creek.

Ocean Thermal Energy

Created by solar energy absorbed by ocean water.
Temperature gradient between surface and deep water can be used to generate power.

Working Principle of Ocean Thermal Energy Conversion

Uses a heat engine to convert heat into mechanical energy.
Requires a minimum temperature difference of 20°C between the surface and deep water.

Ocean Thermal Energy Conversion Systems

Open cycle: uses warm surface water to evaporate low-pressure steam.
Closed cycle: uses a low-boiling-point refrigerant to generate energy.

Status of OTEC Plants

Many countries are actively involved in research and development of OTEC plants.
Examples of planned and launched plants: France, Japan, UK, Netherlands, and others.

Merits and Demerits of OTEC Plants

Merits: steady power supply, no seasonal variation, and useful by-products.
Demerits: low efficiency, design and operation difficulties, and environmental impacts.

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Description

Learn about the formation of tides, tidal energy, and how it can be harnessed to generate electricity. Understand the gravitational forces behind tides and their potential for power generation.