By: Meg Xu
Newton’s first law of thermodynamics states that energy can neither be created or destroyed. Despite such facts constructing the basis of modern day physics, the entropy of a system increases with each conversion of energy. Thus an issue commonly faced by scientists is the preservation of harnessable energy. Among the most efficient are tidal power plants.
Tidal generators commonly rely on the movement of tides through a turbine to generate electrical energy. A turbine, connected to a barrage, is spun by the movements of the water from high to low tides. This turbine contains a generator made of magnets and a coil of wire. As the blades of the turbine turn, the loop of wire between the magnet also turns. Flux is calculated by the equation =BA (dot product of magnetic field and area). Such an equation can be re-written as =|B||A|cos(). Thus as the angle formed by the plane of area created by the loop and the magnetic field shifts with the turning of the loop a change in flux will occur. Consequently, by Lenz’s law, a current will be induced, creating a magnetic field opposite to the change in flux. As a result a current will be induced in the loop(s) of wire. However, the current will not be constant and will switch directions throughout the rotation.
The energy which powers the turbine initially starts with the moon. The gravitational field of the moon pulls on the tides resulting in gravitational potential energy. This GPE is then converted into kinetic energy as the waters of the ocean move around. As the water passes through the turbines, the kinetic energy of the water is transferred to the kinetic energy of the spinning blades of the turbine. The generator then converts the kinetic energy of the turbine and loop of wire into electrical energy. The generator's change in flux induces current, subsequently causing the movement of electrically charged particles through the loop of wire.
Like many other sources of energy, tidal generators have a plethora of both advantages and disadvantages. As water is “a hundred times denser than air”, tidal energy is more efficient then both wind and solar power, generating more usable energy per the same amount of total energy input. In addition tidal generators produce “no greenhouse gasses or other waste” making it an attractive, sustainable source of renewable energy. Contrary to other sources of energy, tides are mostly continuous and cyclic, making them easy to predict and utilize. Despite this, tidal energy technology is both costly and slow to develop. As a result it has proved challenging for any tidal energy companies to emerge as market leaders, with cost-efficient products. Furthermore, geographic limitations and marine life further restrict the usage of tidal energy. Not all coasts are suitable for tidal generators as both the spinning turbine blades and electromagnetic fields have the potential to wreak havoc on more sensitive marine species.
Bibliography:
Pacific Northwest National Laboratory, https://www.pnnl.gov/explainer-articles/tidal-energy, “Tidal Energy”, accessed April 6th, 2024
Selin, Tidal Power, Britannica, Mar 20th 2024
