Introduction+to+solar+technology

Three key elements in a solar cell form the basis of its manufacturing technology:

1) **Semiconductor** - absorbs light and converts it into electron-hole pairs 2) **Semiconductor junction** - separates the the photo-generated carriers (electrons and holes) 3) **Contacts** (front and back of cell) - allows the current of electrons to flow to the external circuit

2 main categories of technology are defined by the choice of semiconductor - either Crystalline Silicon (wafer form) or thin film Solar Cells

1) **Crystalline Silicon or c-Si** (80-90% market share) - historically used in most PV, even though it is a relatively poor absorber of light and is thick (several hundred microns.) Convenient because it yields stable solar cells with good efficiency (15-17%, or about 1/3 of theoretical maximum power production.) Of the several types of c-Si cells, the industry trend is towards multicrystalline technology cells. Each cell generates about 0.5V, and are combined together to create the panel. Generally last about 25 years.

2) **Thin film solar cells**(10-20% market share) - Because of the high cost of c-Si cells, a move towards cheaper technology has resulted in development of thinner solar cells to reduce cost(only about 1 micron thick.) Example materials: amorphous silicon (a-Si) -degraded over time by the sun- cadmium telluride (CdTe), copper indium (gallium), and diselenide (CIS or CIGS). These compounds can be spread to a thickness of 1 micron, which allows for high volume manufacturing.

Developing Technology: Unlike conventional flat plate PV arrays, concentrator systems require direct sunlight, and will not operate under cloudy conditions. They generally follow the sun's path through the sky during the day by use of a tracking mechanism.


 * **Concentrators**: Solar cells operate more efficiently under concentrated light, therefore a push in innovation has started to use mirrors and lenses to concentrate light onto specifically designed cells.
 * **Heat Sinks**: active cooling of the cells, have also been used to dissipate the large amount of generated heat


 * Batteries:** Rechargeable batteries are the most effective storage mechanism available. Remaining capacity can be used up by the electrochemical conversion process of the battery


 * Charge Controllers:**used to prevent over- and under-charging of the battery. Monitoring current and voltage throughout the system is important for safety and overall system performance. A voltmeter will monitor the performance of the battery, while an ammeter monitors the output of the solar modules.

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In addition, be careful not to confuse solar panel efficiency with the efficiency of the PV module as a whole.