Energy Harvesting Dissertation Example | Topics and Well Written Essays - 2000 words

Energy Harvesting - Dissertation Example Energy harvesting, therefore, can be defined as â€Å"The process in which energy is captured from a system’s environment and converted into usable electric power† (Maxim, 2011). The law of conservation of energy is the basis for energy harvesting. Energy can be converted from one form to another and the total amount of energy in an isolated system remains the same (Clark, 2004). Therefore, energy whether in form of wind, kinetic, chemical and others can be converted to electrical energy. 2. METHODS OF HARVESTING ENERGY Energy harvesting produces electric energy from ambient energy sources, present in large and small systems. Recovering a fraction of this energy can have a significant economic and environmental impact. These systems widely vary in sizes. On the macro scale, hydro electricity, tidal power, solar panels and wind turbines can produce MegaWatts. On a smaller scale, immediately available energy such as vibration, heat and light energy can be used to produce milliWatts. A typical energy harvesting system converts energy from the source and stores that energy. Capacitors are used in large scale systems, whereas, batteries are used in small scale systems for storage of energy. ... Photovoltaic cells, which are made up of silicon are used to convert solar energy into electricity. Most of these photovoltaic cells operate at an efficiency of less than 15 % (Asimov, 1969). The maximum theoretical efficiency attainable, however, is only 32.3 % (Clark, 1974). Solar energy is also indirectly used to produce electricity by concentrated solar power plants. The solar collectors are used to concentrate or focus sunlight onto a receiver that heats a liquid to produce steam, which in turn is used to produce electricity in the same way coal or fossil fuel plants do. 2.2 Wind Energy Wind turbines are used to harvest electrical energy from the wind. The wind passes over the blades of wind turbines, which in turn produces a turning force. The rotating blades turn the shaft which passes through the gearbox. The gearbox increases the rotational speed for the generator. The generator uses magnetic fields to convert the rotational energy harvested from the wind into electrical ene rgy. Wind farms, which are clusters of wind turbines, are used to harvest electrical energy from wind. The minimum wind speed for generating electricity is 4-5 m/s and the theoretical maximum power that can be extracted from the wind is 59.3 %. In reality this figure is usually around 45 % maximum for a large turbine. Wind energy has great potential for energy harvesting in the future and even smaller turbines (50-150 watts) are available for household connection (Golding, 1976). Energy harvested from the wind largely depends on siting of the wind farm. 2.3 Hydroelectric Hydroelectric systems create energy by harvesting energy by force of water. Water is collected in a dam or a reservoir. The water near the bottom of the reservoir is forced by the pressure of the water above it to be