Mr. Mansour's List: Solar and Wind

• Solar Energy Can Be Used for Heat and Electricity
• Photovoltaic (PV devices) or “solar cells” change sunlight directly into electricity.
• Concentrating Solar Power Plants generate electricity by using the heat from solar thermal collectors to heat a fluid which produces steam that is used to power the generator.
• wo drawbacks of solar energy are:
• When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. 
• the electrons naturally migrate to the surface. 
• When many electrons, each carrying a negative charge, travel toward the front surface of the cell, the resulting imbalance of charge between the cell's front and back surfaces creates a voltage potential like the negative and positive terminals of a battery. 
• Weather Affects Photovoltaics
• Photovoltaic cells, like batteries, generate direct current (DC), which is generally used for small loads (electronic equipment).  When DC from photovoltaic cells is used for commercial applications or sold to electric utilities using the electric grid, it must be converted to alternating current (AC) using inverters, solid state devices that convert DC power to AC.
• The first practical photovoltaic (PV) cell was developed in 1954 by Bell Telephone researchers examining the sensitivity of a properly prepared silicon wafer to sunlight. Beginning in the late 1950s, PV cells were used to power U.S. space satellites.

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• The mirror focuses the sunlight to strike the pipe, and it gets so hot that it can boil water into steam. That steam can then be used to turn a turbine to make electricity.
• The light is reflected back to the top of the tower in the center of the circle where a fluid is turned very hot by the sun's rays. That fluid can be used to boil water to make steam to turn a turbine and a generator.
• Solar cells are also called photovoltaic cells - or PV cells for short
• When sunlight strikes the solar cell, electrons (red circles) are knocked loose. They move toward the treated front surface (dark blue color). An electron imbalance is created between the front and back. When the two surfaces are joined by a connector, like a wire, a current of electricity occurs between the negative and positive sides.

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