How Are Waves Formed?
We have seen that waves form in the ocean, and they hit the shore with a large force and a loud noise.
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These waves originate in the ocean and destroy on the shore.
So, what makes these waves?
Wind energy transfers its energy to the surface water of the ocean, and hence waves are formed.
The formation of the waves is an endless phenomenon, so they keep on forming in the ocean and keep on destroying on the shore.
These waves have enormous potential.
It is calculated that if the potential of these waves is completely exploited then, they can fulfill 40% of the world’s total energy needs.
The advantage of wave energy is that it is an incessant source of energy.
What is Wave Energy?
Wave energy is one of the forms of the ocean or sea wave energy.
Unequal solar heating of the earth generates wind and wind blowing over the surface of water generates waves.
So, the energy possessed by the ocean and sea waves is called the wave energy.
The Advantages of the Wave Energy Are
Non-polluting
Renewable source of energy
Disadvantages
Variable output
Affects marine life
Expensive
Ocean Wave Energy
The water of the oceans of the world is almost always in motion. The uninterrupted waves breaking at the coastlines are sometimes strong and sometimes weaker.
These waves have tremendous potential energy round the clock and are free-of-charge.
If the potential of these waves is fully utilized. They can satisfy 40% of the worldwide power demand and this output is equal to 700 to 800 nuclear power stations.
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The point hydroelectric chain is developing technologies to transform this inexhaustible into electric power without the emission of the harmful greenhouse gases.
Wave Energy System
Wave energy stems from wave motion and its power is related to the wave height and period.
Deep-water sea waves generate large energy fluxes under predictable conditions over the periods of days.
The power is given by:
P = (1/64)(ρg2/π)(Hs^2Te^2)
Here, P = Power per unit width of a wavefront measured in W/m
ρ = Density of seawater in Kgm-3,
g = Acceleration due to gravity in ms-2,
Hs =The significant wave height in m, and
Te = The wave period in s-1.
What is Wave Power?
Let’s understand how we can generate electricity from the ocean waves.
Let’s talk about the wave power station, its principle, and working on how to generate power.
The principle of a wave power station is pretty simple.
An enclosed chamber has an opening underground sea level that allows water to flow from the sea to the chamber and back.
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The water level in the chamber rises and descends with the rhythm of the wave.
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The air is pushed forward and backward through the turbine connected to the upper opening in the chamber.
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As this turbine is compressed and decompressed, the airflow has sufficient power to run the Wells turbine.
It is an attribute of Wells turbine (named after its inventor Prof. Alan Arthur Wells) that if it is driven in the same direction by both forward and backward airflow through the turbine.
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Even the weaker airflow can produce sufficient airflow that can keep the turbine rotating, and to generate energy.
As long as there are waves, we can get electrical energy from the wave power station anytime.
The world’s first commercial wave power station was activated on the Hebridean island of Islay and has been feeding power to the grid ever since.
India’s first wave power station named Vizhinjam wave energy plant (located at Vizhinjam, the city in Thiruvananthapuram, Kerala) was set up in 1991.
It is the world’s first wave power plant that works on the Oscillating Water Column (OWC) technology.
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Power plant working on OWC technology
Examples of Wave Energy
Wave energy is also known as the Ocean energy or sea wave energy which is harnessed from the ocean or sea waves.
The rigorous vertical movement of surface ocean currents comprises a lot of kinetic energy that is captured by wave energy technology to do needful tasks.
The captured energy is used to fulfill various tasks such as:
Generation of electricity
Desalination of water, and
Powering the plants or pumping of water into reservoirs.
Example of Wave Energy Conversion
The wave energy is converted into power or wave power and a machine that makes the most use of wave power is a Wave Energy Convertor or simply WEC.
This Wave power captures the energy of wind waves to do useful works such as electricity generation or pumping the water.
Such an example of WEC is Wind Activated Bodies or WAB. They are very compact and light-weighted.
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Here Are Some Examples of Wave Energy Conversions
Ocean wave energy conversion
Resonant wave energy conversion
Buoy-type wave energy conversion
FAQs on Wave Power
1. What is wave power?
Wave power, also known as ocean wave energy, is a form of renewable energy derived from the kinetic energy of wind-generated waves on the surface of the ocean. This energy is captured by specialised devices called Wave Energy Converters (WECs) and is transformed into useful forms, primarily electricity. It originates from the wind transferring its energy to the water's surface.
2. How is electricity generated from ocean waves?
The fundamental principle for generating electricity from waves involves converting their motion into mechanical energy, which then drives a generator. A common method is the Oscillating Water Column (OWC) technology. In this system:
- Waves enter a partially submerged chamber, causing the water level inside to rise and fall.
- This movement alternately compresses and decompresses the air trapped above the water.
- The rushing air is channelled through a special turbine, like a Wells turbine, which is designed to rotate in the same direction regardless of the airflow's direction.
- The spinning turbine powers a generator to produce electricity.
3. What are the main advantages of using wave power?
Wave power offers several significant advantages as an energy source:
- Renewable: As long as the wind blows over the ocean, waves will be generated, making it an inexhaustible resource.
- Environment-Friendly: It produces no greenhouse gases or other air pollutants during operation.
- High Energy Density: Waves contain a large amount of energy in a small area compared to solar or wind energy.
- Predictable: Wave patterns are generally more predictable than wind patterns, allowing for more reliable energy forecasting over several days.
4. Why isn't wave power more widely used despite its huge potential?
Despite its immense potential, the large-scale adoption of wave power faces several challenges. The primary reasons include the high cost of building and deploying durable wave energy converters, the technical difficulties of operating equipment in harsh and corrosive saltwater environments, and potential negative impacts on marine ecosystems and navigation routes. The technology is still developing and has not yet achieved the economic competitiveness of solar or wind power.
5. How is the power of a sea wave mathematically estimated?
The power available in a wave front can be estimated using a formula that relates it to the wave's physical characteristics. The power (P) per unit width of a wavefront is given by the equation: P = (1/64)(ρg²/π)(H_s²T_e). In simple terms, this means the power of a wave is directly proportional to the density of seawater (ρ) and, most importantly, to the square of the significant wave height (H_s²) and the wave energy period (T_e). This explains why taller, longer-period waves are so much more powerful.
6. How does wave power technology impact marine ecosystems?
The impact of wave power technology on marine life is a critical consideration. Potential negative effects include underwater noise from turbines which can disrupt the communication and navigation of marine mammals, and the physical structures altering local water flow and sediment transport. However, these structures can also have a positive effect by acting as artificial reefs, creating new habitats that attract fish and other marine organisms, thereby potentially increasing local biodiversity.
7. What are some examples of different types of Wave Energy Converters (WECs)?
There are several different designs for Wave Energy Converters, each capturing wave motion in a unique way. Key examples include:
- Point Absorbers: These are floating buoy-like structures that absorb energy from the up-and-down motion of waves.
- Attenuators: These are long, multi-segmented devices that float parallel to the direction of the waves and capture energy from the flexing of their joints.
- Oscillating Water Columns (OWC): As seen in India's Vizhinjam plant, these devices use wave action to compress and decompress air to spin a turbine.
8. How does wave energy differ from tidal energy?
While both are forms of ocean energy, they have different origins. Wave energy is generated by wind moving across the ocean's surface, resulting in kinetic energy in the waves. In contrast, tidal energy is generated by the gravitational pull of the moon and sun, which causes the sea level to rise and fall. Wave power is more continuous but can be inconsistent in intensity, whereas tidal power is highly predictable and cyclical but is only available for a limited number of hours each day.
9. What are the main components of a wave power station?
A typical wave power station based on the Oscillating Water Column (OWC) principle consists of three primary components:
- A capture chamber that is partially submerged, allowing waves to enter and exit from below.
- A turbine, often a specialised Wells turbine, placed in an opening at the top of the chamber.
- A generator that is connected to the turbine and converts its rotational mechanical energy into electrical energy.
