Tides are periodical rise and fall of sea levels seen in seas and oceans caused by the combined gravitational forces of Sun and Moon and the rotation of the Earth. The gravitational pull of the moon causes the oceans to bulge out in the direction of the Moon. There is also a bulge on the opposite side because the Earth is also being pulled towards the Moon and away from the water bodies. As the earth is also rotating along with the interaction of the Sun and the Moon, two tides happen each day, a high tide and a low tide. The spring tides are strong tides and they occur when the Earth, Sun, and the Moon are in line and the Sun and the Moon are in the same direction. The combined gravitational pull of both Sun and the Moon produces this tide. The spring tides occur during full Moon and new Moon. Neap tides are weak tides and they occur when the gravitational forces of the Sun and the Moon perpendicular to each other in regard to the Earth. Neap tides occur during quarter Moon and half Moon.
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The tidal zone is the region along the shoreline where the sea level rises and falls.
The stages of tidal flow are:
1. Seal level rises over several hours to cover the intertidal zone, also called as flood tide.
2. The level of water rises to its highest level, also called as high tide.
3. Seal level falls over several hours to reveal the intertidal zone, also called as ebb tide.
4. The sea level stops falling to a limit, also called as low tide.
Tidal stream is the oscillating currents produced by the tides.When the tidal current cease, it is called as slack tide. The tide reverses direction and return which is called as the turning tide.
Tide causes the water level to rise in the oceans and seas and travel towards the rivers, canals systems, and lagoons along the coastline. Some shorelines experience about two almost equal high tides and two equal low tides every day, which is called as semi-diurnal tide, whereas other locations experience only one high tide and one low tide each day, called as the diurnal tide. Generally, the time lag between high tide and low tide is about 6 hours. The time and amplitude of the tides at a location are influenced by the alignment of the Sun, Moon, pattern of tide formation in the deep ocean, shape of the coastline, and local geography and topography of the ocean floor and shorelines. Other than tidal fluctuations in sea level, other types of sea level fluctuations occur due to forces such as wind and barometric pressure changes during storms etc.
Tidal Energy Generation:
Tidal energy is the power produced by capturing the energy contained in moving tides and ocean currents. There are two types of energy systems that can be harnessed to get energy from the tides:
1. The kinetic energy of moving waters of rivers, tides, and open ocean currents. Underwater turbines and generators are used to produce electricity. Does not cause much harm to the environment.
2. The potential energy from the difference of height between high and low tides. Massive barrages and dams are built around the coastal sites to collect the tidal waters to sustain the running of generators in a power house. Potentially destructive to the environment.
Tidal Stream:
The tidal stream energy is the kinetic energy of moving waters in tidal streams and tidal lagoons. it is a constant and stable source of energy due to the regular phase of moon and flow of tidal waters. Turbines are placed in the fast moving streams of water in tidal streams around river estuaries, tidal lagoons etc. and harness energy retained in them. The generators produce electricity that is stable and more environmentally friendly. Turbines can be constructed on shallow waters, which produce more electricity. Individual turbines can be placed in places without affecting the flora or fauna.
Photo credit: www.esru.strath.ac.uk
Advantages:
This is an environmentally friendlier way of tidal energy generation because it does not affect the movement or livelihood of the marine creatures or fish.
The turbine blades are rotating free in the water and so the chances of sea creatures to get injured due to the blades are decreased.
Disadvantages:
Comparatively less amount of power is produced as it is constructed only on a few selected places spread out, which harnesses only the kinetic energy of waves.
Tidal Barrage:
Tidal barrage uses the potential energy due to the difference in height between high and low tides. A tidal barrage is a large dam like barrier which is constructed across rivers, bays, tidal estuaries etc. These are dams essentially spreading across entire length of the estuary. There will be spillways inside the barrage for the water to pass through. Turbines placed on the spillways allows the generation of electricity. During high tides, the barrage gates are opened letting the tidal water into the estuary or basin. The water level in the tidal basin continues to increase in the collecting basin holding a higher amount of potential energy. When the tides recede the water flows through the spillways generating electricity.
Photo credit: climatekids.nasa.gov
Advantages:
Higher amount of tidal water potential energy can be stored in dams and basins and greater amount of electricity can be generated.
The kinetic energy as well as potential energy of the waves are utilized for energy production.
Disadvantages:
It is environmentally destructive due to the need for construction of large barrage across the estuary or basins which are the thriving ground for a variety of sea flora and fauna.
The barrage inhibits the free travel of fish and marine creatures into and out of the tidal basin, which mostly get trapped.
The salinity of the tidal basin lowers, which changes the the type of organisms that are able to live in those waters.
Turbines move fast and so marine animals can be caught in the blades which injures those animals.
The birds and other fauna need to migrate to other regions to catch their prey.
Tidal Lagoon:
It is also called as the dynamic tidal power (DTP), where both the kinetic and potential energy of the tidal waves are utilized to generate power. This involves the construction of tidal lagoons in normal coastline where tidal water can be stored. An artificial lagoon is created along a normal tidal coastline rather than an estuary or a lagoon. Long dams are built from the coast to coast in the open ocean to create an artificial lagoon, which helps to retain the water during tides. The retained Tidal potential difference as well as the kinetic energy stored in the tidal waves are harnessed using this technique. This is more suitable in coasts where there is much greater tidal variation and flow.
Advantages:
It can produce large amount of electricity due to utilization of both kinetic and potential energy of the waves.
It provides a constant supply of electricity.
Environmental impact of the tidal lagoons are minimal.
It creates a natural lagoon where marine flora and fauna can thrive and smaller animals can swim around the structures.
Large predators will be kept away which allows for small fishes to thrive and that will increase the number of birds that flock around the lagoon.
The tidal lagoon can be constructed of natural materials such as rock or other natural materials.
It acts as a sea wall that decreases the impact of the heavy tidal surge during stormy weather.
Disadvantages:
If tidal lagoon is constructed utilizing artificial materials that could be hazardous for the marine animals and endanger their life.
Excessive human activity around these structures may cause disruption of natural ecosystem and harm marine life.
The tidal zone is the region along the shoreline where the sea level rises and falls.
The stages of tidal flow are:
1. Seal level rises over several hours to cover the intertidal zone, also called as flood tide.
2. The level of water rises to its highest level, also called as high tide.
3. Seal level falls over several hours to reveal the intertidal zone, also called as ebb tide.
4. The sea level stops falling to a limit, also called as low tide.
Tidal stream is the oscillating currents produced by the tides.When the tidal current cease, it is called as slack tide. The tide reverses direction and return which is called as the turning tide.
Tide causes the water level to rise in the oceans and seas and travel towards the rivers, canals systems, and lagoons along the coastline. Some shorelines experience about two almost equal high tides and two equal low tides every day, which is called as semi-diurnal tide, whereas other locations experience only one high tide and one low tide each day, called as the diurnal tide. Generally, the time lag between high tide and low tide is about 6 hours. The time and amplitude of the tides at a location are influenced by the alignment of the Sun, Moon, pattern of tide formation in the deep ocean, shape of the coastline, and local geography and topography of the ocean floor and shorelines. Other than tidal fluctuations in sea level, other types of sea level fluctuations occur due to forces such as wind and barometric pressure changes during storms etc.
Tidal Energy Generation:
Tidal energy is the power produced by capturing the energy contained in moving tides and ocean currents. There are two types of energy systems that can be harnessed to get energy from the tides:
1. The kinetic energy of moving waters of rivers, tides, and open ocean currents. Underwater turbines and generators are used to produce electricity. Does not cause much harm to the environment.
2. The potential energy from the difference of height between high and low tides. Massive barrages and dams are built around the coastal sites to collect the tidal waters to sustain the running of generators in a power house. Potentially destructive to the environment.
Tidal Stream:
The tidal stream energy is the kinetic energy of moving waters in tidal streams and tidal lagoons. it is a constant and stable source of energy due to the regular phase of moon and flow of tidal waters. Turbines are placed in the fast moving streams of water in tidal streams around river estuaries, tidal lagoons etc. and harness energy retained in them. The generators produce electricity that is stable and more environmentally friendly. Turbines can be constructed on shallow waters, which produce more electricity. Individual turbines can be placed in places without affecting the flora or fauna.
Advantages:
This is an environmentally friendlier way of tidal energy generation because it does not affect the movement or livelihood of the marine creatures or fish.
The turbine blades are rotating free in the water and so the chances of sea creatures to get injured due to the blades are decreased.
Disadvantages:
Comparatively less amount of power is produced as it is constructed only on a few selected places spread out, which harnesses only the kinetic energy of waves.
Tidal Barrage:
Tidal barrage uses the potential energy due to the difference in height between high and low tides. A tidal barrage is a large dam like barrier which is constructed across rivers, bays, tidal estuaries etc. These are dams essentially spreading across entire length of the estuary. There will be spillways inside the barrage for the water to pass through. Turbines placed on the spillways allows the generation of electricity. During high tides, the barrage gates are opened letting the tidal water into the estuary or basin. The water level in the tidal basin continues to increase in the collecting basin holding a higher amount of potential energy. When the tides recede the water flows through the spillways generating electricity.
Advantages:
Higher amount of tidal water potential energy can be stored in dams and basins and greater amount of electricity can be generated.
The kinetic energy as well as potential energy of the waves are utilized for energy production.
Disadvantages:
It is environmentally destructive due to the need for construction of large barrage across the estuary or basins which are the thriving ground for a variety of sea flora and fauna.
The barrage inhibits the free travel of fish and marine creatures into and out of the tidal basin, which mostly get trapped.
The salinity of the tidal basin lowers, which changes the the type of organisms that are able to live in those waters.
Turbines move fast and so marine animals can be caught in the blades which injures those animals.
The birds and other fauna need to migrate to other regions to catch their prey.
Tidal Lagoon:
It is also called as the dynamic tidal power (DTP), where both the kinetic and potential energy of the tidal waves are utilized to generate power. This involves the construction of tidal lagoons in normal coastline where tidal water can be stored. An artificial lagoon is created along a normal tidal coastline rather than an estuary or a lagoon. Long dams are built from the coast to coast in the open ocean to create an artificial lagoon, which helps to retain the water during tides. The retained Tidal potential difference as well as the kinetic energy stored in the tidal waves are harnessed using this technique. This is more suitable in coasts where there is much greater tidal variation and flow.
It can produce large amount of electricity due to utilization of both kinetic and potential energy of the waves.
It provides a constant supply of electricity.
Environmental impact of the tidal lagoons are minimal.
It creates a natural lagoon where marine flora and fauna can thrive and smaller animals can swim around the structures.
Large predators will be kept away which allows for small fishes to thrive and that will increase the number of birds that flock around the lagoon.
The tidal lagoon can be constructed of natural materials such as rock or other natural materials.
It acts as a sea wall that decreases the impact of the heavy tidal surge during stormy weather.
Disadvantages:
If tidal lagoon is constructed utilizing artificial materials that could be hazardous for the marine animals and endanger their life.
Excessive human activity around these structures may cause disruption of natural ecosystem and harm marine life.
