Solar Photo Voltaic Panel is the key part of a solar photo voltaic power generation system. This articles briefs on the various components of a solar photo voltaic panel.
The solar photo voltaic panels are kept outside facing the sunlight. The PV panel converts the sunlight in to DC electricity. The solar photo voltaic panel is generally of three types 1. Poly Crystalline solar panel 2. Mono Crystalline solar panel and 3. Thin Film panel. The crystalline panels are made of crystalline silicon while the thin film panels are made of technologies such as cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and amorphous thin-film silicon (a-Si, TF-Si).
A typical crystalline solar panel has the following components
- Solar Cells
- Back Sheet
- Front Glass
- Bus bar
- Aluminum Frame
- Junction Box and Diodes
Solar cells are made of silicon in case of crystalline panels. In case of Mono crystalline panels, the solar is made from a single large block of silicon. The large block is cut into small wafers. While, the efficiency of mono crystalline solar panels are high, the production process is labor intensive and expensive. The poly or multi crystalline solar cells are made of melting several silicon crystals together. The production process is simpler and cost effective. The efficiency is lesser than that of the mono crystalline panel.The solar cells are arranged in an array. Each of the cells is connected to other cells, which together constitute the solar pv panel.
Back Sheet and EVA
The back sheet is the last, but important layer of the solar PV panel. It is made of polymer and protects the solar pv panel from UV rays, humidity, moisture, wind, dust, etc. The back sheet should be of good quality as it has to last through out the life time of the solar PV panel. The EVA (Ethylene Vinyl Acetate) is a thermoplastic placed on the either side of the solar cells to encapsulate the solar cells.
The glass plays a crucial part in the solar PV panel as it is the front end and allows sunlight to fall on the solar panels. The glass is usually made of Toughened or tempered glass. These toughened glasses are made through chemical and heating process. The toughened glasses are usually thicker, while some thin toughened glasses have also been introduced. However, care must be taken, as some low quality manufacturers may use very thin glasses, posing to be a toughened glass.
The solar cells are inter connected through bus bars. Higher capacity solar PV panels have three bus bars, while the lower wattage solar PV panels have two bus bars. The bus bars are attached to the solar cells through soldering. First soldering flux is applied on the solar cells to remove oxide. Silver color ribbons are placed on the solar cells and they are soldered with the soldering rod. The soldering temperature is usually in the range of 300 to 450 degree Celsius. Since over heating can make the solar cell vulnerable, it is advisable not to place the soldering rod for too long on the solar cell.
The assembled solar cells which are mounted on the back sheet are enclosed in an aluminum frame. The aluminum frame protects the solar panel from any external damage and can help in keeping the solar panel intact in the solar panel mounting structure.
The junction box is located at the back side of the solar pv panel. The connections from the solar cells ends at the junction box. The box is made to with stand the temperature and the external forces for the entire life time of the solar panel. The junction box encloses diodes to make sure that the power flow is uni directional i.e, from the panels to the external connection. It also prevents power flowing in to solar panels during the night-time.
DC cables are present in larger size solar PV panels (250Wp and above). Lower wattage solar PV panels do not have cables attached to it. The cables are teminated by MC4 connectors.