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Wearing Smaller Shoes Leaves a Smaller Footprint

November 1, 2008
By Anonymous

Solar energy is produced by harnessing radiation from the sun. Solar radiation is channeled into energy using three different methods: Photovoltaic cells, solar troughs, and solar power towers (Solar Energy). Photovoltaic cells are made out of semiconducting materials, such as silicon, which make up solar panels. They produce electricity by absorbing photons present in solar radiation. These photons knock loose the electrons in the cell material and the flow of these electrons produces a direct current of electricity (Solar Cell).

Benefits of using PV cells are minimal environmental impact and user accessibility. PV cells produce no carbon dioxide or any other greenhouse gas emissions and are an entirely renewable source of energy because it uses sunlight as its only fuel. Some of the drawbacks are cost and sunlight distribution related. PV cells are expensive to produce and because of the small market they are even more expensive for consumers. Solar Panels also cost more because they are only roughly 15 percent efficient, which is more efficient than solar troughs but less so than power towers. These costs can be somewhat offset by lower electricity bills and net metering, where excess electricity is sold back to the power company. The other shortcoming of PV cells is their inability to produce electricity at night and during especially cloudy days (Photovoltaics).

Unlike photovoltaic cells, solar troughs utilize the heat produced by the sun to generate electricity. Solar troughs are often called parabolic troughs because of their parabolic shape which focuses the sunlight on a tube located at the focal point. Inside this tube is a heat transfer fluid, which is heated by the concentrated sunlight. The troughs are made from aluminum or silver and act as mirrors to reflect the light onto the Dewar tubes which usually contain oil. The oil or heat transfer fluid then flows to heat a standard turbine energy generator (Parabolic Trough).

Currently, solar troughs are the least-cost solar energy, which makes them an attractive option along with the jobs that solar trough plants create and their ability to produce electricity at a high capacity. A drawback to solar trough plants is that they require a large amount of land that cannot also be used for other purposes. To meet production levels during peak periods, the plants need to use fossil fuels which produce greenhouse gas emissions. So while troughs produce much less emissions that coal plants, they are not emission free lie PV cells. Solar troughs are also less efficient than PV cells, running at only 13.8% efficiency (Parabolic Trough Solar...).

The solar power tower is similar to the solar trough in that it uses mirrors to focus sunlight on a collection tower in order to produce heat. The heat from this concentrated sunlight is stored in a material with a high heat capacity like sodium for later use. The heat from the capturing substance is then transferred to water, which is boiled to produce steam. This steam powers a turbine which is used to produce electricity (Solar Power Tower).

Solar power towers have many benefits, especially when compared to other solar options. They require the smallest amount of land and have the highest efficiency at 16.2%. The solar tower produces no fossil emissions, but is produces slightly more expensive energy than solar troughs (Solar Power Towers).

The author's comments:
Mr. Joneschild's Envi Sci class. Yay!

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