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PV System Components
The typical PV system is made up of the following parts:
- PV panel: This is made of cells that help to convert energy from the sun directly into electricity. The cells are made of silicon and are connected to form modules which may be either in series, parallel or both. The modules should be durable and be able to withstand temperature variations and humidity. There are three main types of solar cells as below:
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- Mono-crystalline: These are cells made from pure mono-crystalline silicon with a single thin crystalline structure. They are very efficient; however the cost of production is high as it is energy and labour intensive. This would be useful for small installations or areas with very limited mounting space.
- Poly-crystalline: These are made from small grains of mono-crystalline silicon. They are cheaper and easier to manufacture but are also found to be less efficient than their mono-crystalline counterpart.
- Amorphous Silicon: These are cells made from thin films of silicon in a form known as amorphous silicon. Here the silicon structures are in less order than the crystal lattice structure of the mono crystalline and the poly crystalline. Its production method though complex, is not as energy intensive as crystalline cells; however its efficiency is low. This technology is most often used in smaller applications such as calculators, or garden lights. It is also often found in multi-layer technology which increases cost, performance and efficiency typically to crystalline levels.
- Inverters: PV systems generate electricity in direct current (DC), however most appliances found in the home operate on alternating current (AC). Transformation of the DC to AC is done by the inverter, and they come in various sizes depending on the user’s energy needs. Battery powered devices also work on DC whilst the mains is supplied through 230 volts AC. The inverter also has several important safety features which protect electricians and householders from electrical dangers.
- Storage batteries: These are used to store excess energy produced by the system which can be used at night when the system can’t produce energy. Alternatively, excess energy stored here can be exported to the grid. If the grid is available, it is always preferable to use grid-connected PV circuits.
How They Work
Sunlight is made of a stream of photons which are absorbed by the cells of the PV panels. These photons interact with electrons found in the cells to ‘upgrade’ the electrons to a higher energy level which can be exploited as an electric current. These currents are conducted by wires to the electrical system of the building to be used for a range of appliances; directly to the grid or to batteries for storage purposes.