Alternative Forms of Generating Electrical Energy: Wind, Solar and Fuel Cell Power Essay Example

Pages: 11 (4205 words) Published: June 5, 2006
The societal demands for electrical energy have drastically increased in the past number of years. The sharp escalation of fuel consumption caused the demand for fossil fuels, which generate electrical energy, to increase as well. Almost 80% of domestic electricity use is used for space and water heating. To reduce the amount of energy produced by fossil fuels, the amount of electricity used must be lessened, and other renewable methods of electrical energy generation must be found. Research in the field of electrical energy generation in the past years has revealed several viable sources for potentially generating electricity in the near future, which include wind turbines, solar cells and fuel cells, all of which are forms of renewable sources of energy.

Wind power is a renewable resource that offers clean and affordable energy, but can be unreliable. All renewable sources of energy ultimately come from the sun, which radiates approximately 1.37 kW/m on the surface of the spherical Earth, which has the sun as its centre and the average radius of the Earth's orbit. The power reaches a circular area, with an area of about 1.27 x 1014 m. Therefore, the power that reaches the Earth is 1.744 x 1017 W every hour. Approximately one to two percent of this energy is converted into wind energy. This process occurs when the energy from the sun heats the air, which constitutes the Earth's atmosphere. The air at 0° latitude receives a greater portion of the energy, due to its closer proximity to the source of energy, the sun. As the air around the equator is less dense, due to its increased temperature, it rises roughly 10 km up and then moves towards either of the Earth's poles. Due to the rotation of the Earth, this air is diverted counter-clockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere. This effect is called the Coriolis force, after French mathematician, Gustave Gaspard Coriolis (1792-1843). The wind rising up from the equator that moves towards the north and south poles is prevented by the Coriolis force from moving any great distance farther, which occurs at around 30° latitude. The force causing the wind to sink creates a lower pressure area around the equator and a higher-pressure area around the poles, which causes prevailing winds. Areas where these prevailing winds are unobstructed are ideal locations for wind turbines, where they will receive maximum wind energy. Turbines harness a natural force, wind, and convert the power of the wind into a torque, or turning force, which in turn, acts upon the rotor blades, producing a useful, useable energy: electricity. The kinetic energy that can be obtained from the wind, a moving body, is proportional to its mass. Therefore, the kinetic energy of the wind is dependent on the density of the air. The greater density of the air, the greater the volume of energy produced by the turbine. At approximately 101.325 kPa and 15°C, typical atmospheric air weighs around 1.23 kg/m3; however, density decreases slightly with increased levels of humidity. The typical 1000 kW wind turbine has a rotor diameter of 54 metres, which indicates a rotor area of 2290.22 m2. The rotor area indicates an approximation of the amount of energy a wind turbine can harvest from the wind. However, a wind turbine could never fully capture all the wind energy due to deflection by the wind turbine itself. The wind must be slowed down as it passes by the wind turbine rotors, in order to convert the kinetic energy of the wind into rotational energy of the turbine. The air entering the turbine must be equal to the air exiting the turbine, yet, it moves at a slower speed, taking up a larger area behind the rotor. The wind speed is vital to determining the amount of wind energy a turbine can convert to electricity. The average wind speed varies with the kinetic energy with the third power, which means that if the wind speed were to be twice as high, it would...
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