Tidal Power Generation Systems

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.