Lab2 - FAMU-FSU College of Engineering Department of...

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FAMU-FSU College of Engineering Department of Mechanical Engineering EML 4930/5930: Energy Conversion Systems II Dr. A. Krothapalli Lab 2: Photovoltaic Panels: Tracking vs. Stationary Spring 2006 Introduction Photovoltaic cells convert sunlight into direct current electricity. Sunlight is made of photons, and these photons contain energy. When these photons land on the solar panels, the individual photovoltaic (PV) cells on the panel absorbs them. With an abundance of energy, the electron is freed from its position within that atom, thus leaving a hole to be filled by another electron. This becomes part of the current in an electrical circuit. The PV cells have two separate semiconductors, a negative and a positive, which generate excess electrons and excess holes. When the two semiconductors are ‘sandwiched’ together, they create an electric field at the junction where they meet. This field is what allows the electrons to travel from the semiconductor to the surface and then into the electrical circuit. There are three main types of solar cells available. These different types of cells are a result of the different techniques used to produce the silicon material that the cell is manufactured with. The three types of cells consist of: single-crystalline silicon (most expensive and most efficient), polycrystalline silicon (cheaper and less efficient), and amorphous silicon (cheapest and least efficient). Single-crystalline Single-crystalline PV cells are unique because the silicon used in them is made by growing it from a single crystal seed. In this process, silicon is melted and reformed to fit the pattern of a single crystal seed. Thus the molecular structure of the silicon is a replica of the initial silicon crystal. The repeating pattern or uniform structure of the silicon allows for extremely efficient transferring of electrons through the silicon. This uniform structure is what makes the single-crystalline PV cells the most efficient. Polycrystalline
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Lab2 - FAMU-FSU College of Engineering Department of...

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