Energy from Ocean: Tides and Potential Energy

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Questions and Answers

What is the alignment of the earth, sun, and moon during the production of spring tides?

In a straight line (correct)

At a 90-degree angle

In a perpendicular direction

At random angles

What is the minimum tidal range required for a tidal power plant to be economically viable?

10 meters

7 meters

5 meters (correct)

3 meters

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

To allow water to enter and exit the basin (correct)

To construct the dam

To control the water level

To generate electricity

What is the term for the energy harnessed from the difference in water levels between high and low tides?

Tidal energy Signup and view all the answers

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

To generate electricity using turbines and generators Signup and view all the answers

What is the mode of operation where water is made to flow through turbines during both high and low tides?

Two-way generation Signup and view all the answers

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

71% Signup and view all the answers

What is the difference in the level between the high and the low tide called?

Tidal range Signup and view all the answers

How often is a high tide formed at a place due to the moon's gravitational pull?

Twice a day Signup and view all the answers

What is the approximate ratio of the moon's gravitational pull to the sun's gravitational pull?

2.2:1 Signup and view all the answers

Why is a corresponding high tide formed on the opposite side of the Earth?

Due to the solid earth being pulled away from the water surface Signup and view all the answers

What is the time period for the formation of a high tide due to the moon's gravitational pull?

12 hours and 25 minutes Signup and view all the answers

What is the main limitation of the single basin system for tidal power generation?

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

What is the primary function of the upper basin in a double basin tidal power plant?

To fill up with sea water at high tides Signup and view all the answers

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

20°C Signup and view all the answers

What is the primary source of energy for ocean thermal energy conversion?

Solar energy Signup and view all the answers

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

To separate the upper and lower basins Signup and view all the answers

Which of the following is a suitable location for tidal power development in India?

Gulf of Kutch Signup and view all the answers

What is a major consideration when selecting a site for a tidal power plant?

Minimum cost of construction Signup and view all the answers

What is an advantage of tidal energy compared to other forms of energy?

It is free from pollution Signup and view all the answers

What is a limitation of tidal energy?

It can be harnessed only if natural sites are available Signup and view all the answers

What is a characteristic of the single ebb cycle system of tidal power generation?

Power generation is intermittent Signup and view all the answers

What is a drawback of using tidal energy?

The equipment is affected by the corrosive nature of sea water Signup and view all the answers

What is a benefit of using tidal energy?

The site of the plant can be generally dam at bays and its construction does not uproot the villages Signup and view all the answers

What is the primary basis of an OTEC system?

The conversion of ocean thermal energy into mechanical work Signup and view all the answers

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

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

What is the advantage of a closed cycle OTEC plant compared to an open cycle OTEC plant?

It is more compact in size and less costly Signup and view all the answers

What is one of the disadvantages of OTEC plants?

The plant has to withstand severe ocean conditions and storms Signup and view all the answers

Which country has built a 5 MW OTEC shore plant in Tahiti?

France 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 necessary maintenance task for an OTEC plant?

Removing algae growth Signup and view all the answers

Why are large diameter and length pipes required for an OTEC plant at shoreline?

To handle a large volume of water Signup and view all the answers

What is a potential environmental impact of constructing an OTEC plant?

Affecting the ecosystem and impacting coral Signup and view all the answers

Why is the equipment installed at a great depth in an OTEC plant?

To reach the cold water level Signup and view all the answers

What is a consequence of releasing a large quantity of cold water into the warmer surface environment?

Adversely affecting marine life Signup and view all the answers

What is a potential impact of an OTEC plant on the atmosphere?

Releasing carbon dioxide into the atmosphere Signup and view all the answers

Why is the whole plant constructed on floats?

To enable the plant to operate in shallow water Signup and view all the answers

What is a potential impact of the water circulation in an OTEC plant on marine life?

Destroying marine life Signup and view all the answers

What is a potential impact of an OTEC plant on ocean currents?

Influencing ocean currents and climate Signup and view all the answers

What is a characteristic of an OTEC plant's construction?

It is constructed on floats 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 tides, their causes and effects on ocean water levels, and the potential energy stored in them. Understand the role of moon and sun's gravitational attraction on the rotating earth.