WAVE ENERGY

INTRODUCTION

Introduction  Waves are created by the gravitational action of sun and the moon and also by the interaction of wind with the surface of the sea. Wave power is practically inexhaustible and classified as a renewable energy source. Wave energy can be extracted and converted into electricity by wave power machines. They can be deployed either on the shoreline or in deeper waters offshore.

Introduction Wave energy fluxes in open sea or against coasts may vary from a few watts to kilowatts per metre. In favourable locations, wave energy density can average 65 megawatts per mile of coastline. The total power of waves breaking on the world's coastlines is estimated at 2 to 3 million megawatts. They are smallest in summer and greatest in winter.(Westerlies and the Trade winds.)

Introduction Wave motion consists of both vertical and horizontal movement of water. Individual particles of water undergo almost a circular motion, moving up as the crest approaches, forward at the crest, down as it recedes, and backward in the trough.

APPROACHES TO CAPTURE WAVE ENERGY

1.Float or Pitching Device or buoyant moored device The device floats on or just below the surface of the water and is moored to the sea floor. A wave power machine needs to resist the motion of the waves in order to generate power: part of the machine needs to move while another part remains still. In this type of device, the mooring is static and is arranged in such a way that the waves motion will move only one part of the machine. Electricity is generated from the bobbing or pitching action of a floating object which can be mounted to a floating raft or to a device fixed on the ocean floor.

2.Oscillating Water Columns (OWC) An oscillating water column is a partially submerged, hollow structure that is installed in the ocean. It is open to the sea below the water line, enclosing a column of air on top of a column of water. Waves cause the water column to rise and fall, which in turn compresses and depresses the air column.

Oscillating Water Columns (OWC).. This trapped air is allowed to flow to and from the atmosphere via a Wells turbine, which has the ability to rotate in the same direction regardless of the direction of the airflow. The rotation of the turbine is used to generate electricity.

3.Hinged contour device Here, the resistance to the waves is created by the alternate motion of the waves, which raises and lowers different sections of the machine relative to each other, pushing hydraulic fluid through hydraulic pumps to generate electricity. A hinged contour device is able to operate at greater depths than the buoyant moored device.

Hinged contour device… These shoreline devices, also called "tapered channel" systems, rely on a shore-mounted structure to channel and concentrate the waves, driving them into an elevated reservoir. Water flow out of this reservoir is used to generate electricity, using standard hydropower technologies. The main problem with wave power is that the sea is a very harsh, unforgiving environment.

Hinged contour device An economically-viable wave power machine will need to generate power over a wide range of wave sizes, as well as being able to withstand the largest and most severe storms and other potential problems such as algae, barnacles and corrosion.

ADVANTAGES & DISADVANTAGES

Advantages A much greater extent of power is concentrated in the motion of waves than in the movement of air. Whereas the power density at a good wind energy site may be of the order of a few square metre, the power density in a corresponding area of wave motion may be up to 100 times greater. It produces no greenhouse gases or other waste. It needs no fuel.

Advantages….. Wave energy has this advantage over wind or solar energy that the energy has been naturally concentrated by accumulation over-time and space and transported from the point at which it was originally present in the winds. Wave power devices do not use up large land masses like solar or wind. It produces electricity reliably. It is free and renewable energy source.

Advantages….. These devices are relatively pollution free, and because they remove energy from the waves, the water is left in a relatively placid(calm) state in their wakes.

Disadvantages The major disadvantage of wave energy, as compared to wind, is that the energy is available in the ocean. Therefore the extraction equipment must operate in a marine environment which will have to be taken into account during its construction and its maintenance ,lifetime and reliability should be considered since the energy may have to be transported through a great distance to the shore.

Disadvantages… There is relative scarcity of accessible sites of large wave activity. Wave energy conversion devices that have been proposed are relatively complicated . Economic factors such as the capital investment, costs of maintenance, repair and replacement as well as problems of biological growth of marine organisms which seem to be very large, are all relatively unknown.

Disadvantages… Wave energy converters must be capable of withstanding very severe peak stresses in storm.

Challenges to Deploy Wave Power Devices

Challenges to Deploy Wave Power Devices Efficiently converting wave motion into electricity; generally speaking, wave power is available in low-speed, high forces, and the motion of forces is not in a single direction. Most readily-available electric generators operate at higher speeds, and most readily-available turbines require a constant, steady flow.

Challenges to Deploy Wave Power Devices… Constructing devices that can survive storm damage and saltwater corrosion; likely sources of failure include seized bearings, broken welds, and snapped mooring lines. Knowing this, designers may create prototypes that are so overbuilt that materials costs prohibit affordable production. High total cost of electricity; wave power will only be competitive when the total cost of generation is reduced.

Challenges to Deploy Wave Power Devices… The total cost includes the primary converter, the power takeoff system, the mooring system, installation & maintenance cost, and electricity delivery costs.

WAVE POWER POTENTIAL ALONG THE INDIAN COASTLINE

Wave power potential along the Indian coastline Location (Non-monsoon) Mean wave height(m) Mean wave period(sec) Wave power (kW/h) 10-15 N and coast 85 E (off Madras) 1.14 5.50 7.00 15-20 N and coast 85 E (off Vishakhapatnam) 1.24 7.10 10.70 20-25 N and 85-95 E (off Calcutta) 1.72 6.51 18.87 10-15 N and 70 E coast (off Cochin) 1.01 5.38 5.37 15-25 N and 70 E coast (off Mumbai) 5.25 5.24 5 -10 N and 75-80 E (off Cape Comorin) 1.29 5.46 8.90

Wave power potential along the Indian coastline…. Location (North-east monsoon) Mean wave height(m) Mean wave period(sec) Wave power (kW/h) 10-15 N and coast 85 E (off Madras) 1.53 5.86 13.44 15-20 N and coast 85 E (off Vishakhapatnam) 1.60 6.28 15.75 20-25 N and 85-95 E (off Calcutta) 1.33 8.01 13.88 10-15 N and 70 E coast (off Cochin) 1.03 5.05 5.25 15-25 N and 70 E coast (off Mumbai) 1.00 5.00 4.90 5 -10 N and 75-80 E (off Cape Comorin) 1.22 5.35 7.80

Wave power potential along the Indian coastline…. Location (South-West monsoon)m Mean wave height(m) Mean wave period(sec) Wave power (kW/h) 10-15 N and coast 85 E (off Madras) 1.71 5.8 16.62 15-20 N and coast 85 E (off Vishakhapatnam) 2.04 8.25 33.65 20-25 N and 85-95 E (off Calcutta) 1.96 7.66 28.84 10-15 N and 70 E coast (off Cochin) 2.03 6.77 27.34 15-25 N and 70 E coast (off Mumbai) 2.63 6.93 46.98 5 -10 N and 75-80 E (off Cape Comorin) 1.78 6.29 19.52

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