Published in 2014

What is the raw material that composes a photovoltaic module?

Have you ever wondered what is the structure of a photovoltaic module and what are the main materials?
There are many solutions available on the market and many raw materials that can be found, but the philosophy for manufacturing a solar panels is the same for everyone.
If we try to describe in a few words the structure, we could say that a photovoltaic panel is composed by a series of photovoltaic cells protected by a glass on the front and a plastic material on the rear. The whole of it is vacuum encapsulated in a polymer as transparent as possible.
Let’s focus now on the single components more thoroughly:

• Photovoltaic solar cell
  Cells are the main component and have the function to capture the sunlight and convert it into electricity.
  Crystalline cells can be monocrystalline or polycrystalline, according to their manufacturing process.
  This however does not affect the PV module production process. The main technical characteristics are: size, color, number of bus-bar and above all the conversion efficiency.
  The latter is the main parameter affecting the power output of the panel. In this period the most common cells are the polycrystalline ones with an efficiency of about 17.6%, which originate a 250W photovoltaic module with 60 cells. The cells are interconnected with each other by a thin copper tape coated with a tin alloy, called ribbon;
• Front glass
  The front glass is the heaviest part of the photovoltaic module and it has the function of protecting and ensuring robustness to the entire photovoltaic module, maintaining a high transparency. The thickness of this layer is usually 3.2mm but it can range from 2mm to 4mm depending on the type of glass chosen. It is important to pay attention to features such as quality of hardening, spectral transmittance and light transmittance. For photovoltaics, some special glasses have been studied with a special pattern on their surface ensuring a greater degree of light trapping. Choosing carefully the glass, checking these features or adding antireflective layers, can bring an overall improvement of the efficiency of the module;
• Back-sheet
  The term backsheet literally means the sheet on the back. It is made from a plastic material that has the function to electrically isolate, protect and shield the PV cells from weather and moisture. This particular sheet is usually white in color and is sold in rolls or sheets. There are particular versions that can be different in thickness, in color and in the presence of particular materials for a greater shielding or for a higher mechanical strength;
• Encapsulant material
  One of the most important materials is the encapsulant, which acts as a binder between the various layers of the PV panel. The most common material used as an encapsulant is EVA – Ethylene vinyl acetate. It is a translucent polymer sold in a roll. It must be cut in sheets and deposited before and after the photovoltaic cells. When subjected to a thermal process of vacuum cooking, this particular polymer becomes similar to atransparent gel and incorporates the photovoltaic cells. The quality of this process, called lamination, ensures a high service life to the module itself, while the encapsulant quality affects the light transmission, the process speed and the resistance to yellowing due to UV rays.
• Frame
  One of the last parts to be assembled is the frame. It is normally made of aluminum and has the function to ensure robustness and a practical and safe coupling to the photovoltaic module. Together with the frame, also a layer of sealant is deposited around the walls of the panel as a moisture barrier. For this purpose the most widely used material is silicon, although sometimes a special sealing tape is used.
  For special applications, also frameless modules or special plastics solutions are available. These solutions usually involve the use of supports glued in the rear side and modules with glass-glass technology.
• Junction box
  The junction box has the function of bringing the electrical connections of the PV module outside.
  It contains the protection diodes for shadows and the cables for the connection of the panels in the field. In choosing the Junction box we pay attention to the quality of plastic, the goodness of sealing, the type of connection of the ribbon and the quality of by-pass diodes. In these years also boxes with special low-loss diodes or integrated with micro inverters were born. The price of these solutions has not yet allowed a mass distribution, although the potentiality is interesting.

The structure and materials used in the PV panel manufacturing process are very similar independently from the different types of solution. That is why a fundamental role is played by the manufacturing process, research and experience in order to achieve quality photovoltaic modules.
The assembly process of a solar panel is concerned to best integrate each raw material adopting all the optimizations necessary to improve the quality of the final product. It can use dedicated equipment for each step of the pv module production with different levels of automation.
Contact us to develop your project together. Thanks to Ecoprogetti equipment, you will quickly be able to start manufacturing photovoltaic modules with very high efficiency and quality.