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Thermal and PV System Lauren Masseria Jenny Bishop Bryan Picard Solar Photovoltaic Photo=light Voltaic=electricity The conversion of solar energy directly into electricity Brief History • Discovery credited to French physicist Edmund Becquerel in 1839 – ‘Wet Cell’ Battery • 1883 the first PV cell was created • 1950 at the Bell Laboratory, New Jersey – Research on silicon semiconductors • 1960’s-70’s Orbiting satellite usage • 1970’s Rise in residential and commercial usage – Energy crisis • 1980’s Consumer electronic devices Why Solar? • Reliable • Long term cost benefits • Environmentally friendly • Remote Locations (grid unavailability) • State, federal and private incentives • Socially responsible • Positive public image Panels & Cells • A cell consists of sliced up crystals, connected with wire, and placed in a module • Life expectancy = over 30 years • There is nothing exhausted in the silicon cells, and theoretically, if well packaged and protected from moisture they could produce electricity indefinitely. • PV cells are a junction between two thin layers of • • • dissimilar semi-conduction materials known as ‘p’ and ‘n’ type semi conductors Most cells made from silicon, a semiconductor, and the second most abundant element in the earth’s crust Sets up an electric field when joined Photons (sun energy) hit this electric field and transfer energy to the p and n semi conductors creating a reverse electric field and an electric current Types of Cells Three types of PV cells Monocrystalline Polycrystalline Amorphous Monocrystalline Silicon with a single crystal lattice structure with no impurities and virtually no defects most efficient at 16% – most expensive – longest life span Polycrystalline Consists of many small grains of connected monocrystalline silicon – 15% efficiency – typically less expensive than monocrystalline Amorphous / Thin Film Silicon are much less ordered than in the mono and polycrystalline cells – 8% efficiency – least expensive – Most flexible models, ex rolls – Take the most space – Are being phased out