How does Wave Energy work ?
Introduction
Till now we have studied about the power sources on a ship namely the diesel marine engines used for propulsive mechanical power, and the auxiliary engines used for providing electric power on various types of ships. This article is a little different in that it deals with harnessing energy from the waves of the oceans through the use of special devices known as OWCs and how these can be used to supply energy to the land or any installation for electric power supply purposes.
Renewable Energy Sources are going to change the way energies are being procured and put to use till now. They are a promising alternate source not only because they are available freely but also because they produce zero amount of pollution. Among all the various renewable resources, wave energy is considered as the most reliable one as it is available continuously ( i.e day and night) unlike solar and wind energies.
There is a huge deficit of energy in the world today and new ways and methods for procuring energy from the renewable sources are continuously being looked for. Ocean is considered to have a massive deposit of energies. It has been predicted that if only 0.1% of renewable energy of oceans is converted into electricity, it would fulfill the present need of energy more than five times over.
Among all the harnessing techniques that are used to tap energy from the waves, Oscillating Water Column system is considered to be the most reliable one as not only it is economically viable but is also simple in construction and operation. In the following sections we will see how does wave energy work in context of osscilating water column systems
Construction
The OWC system consists of an air tight rectangular chamber with a pyramidal top. The pyramidal top is not pointed at the apex in order to accommodate a conical duct through which the air moves into and outside the chamber as and when waves inside the chamber moves. A special turbine known as the Wells turbine is fixed on the conical duct. Wells turbine is a low pressure turbine which eradicates the use of valve system which is used to rectify the valve stream. Also, the turbine is do designed that it moves only in one direction irrespective of the direction of the airflow. The turbine is coupled with a alternator/generator that produces electricity.
Working
The main part of the system is the water tight chamber which is open to the sea, at the bottom. There is already air inside the chamber which compresses and decompresses as the wave inside the chamber moves. Due to the continuous difference in motion inside the chamber a high velocity air is generated which in turn generates highly pressurised air. This pressurised air flows to the turbine through the conical duct. As the turbine generator moves in the same direction irrespective of the direction of air flow, the turbine keeps on turning continuously as the wave level inside the chamber rise and fall alternatively. The turbine thus drive the generator to produce electricity.
References
University of Michigan Wave Device Project
Image credits
https://www.rise.org.au/info/Tech/wave/image002.gif
https://peswiki.com/images/4/48/Oscillating_water_column_npower_renewables.jpg
https://celebrating200years.noaa.gov/magazine/wave_energy/water_column.html
University of Michigan Wave Device Project
