Most photovoltaic panels are made from silicon wafers. Silicon is a very valuable resource for our planet as it is available in abundance. The manufacturing process of photovoltaic cells is described in detail in a previous articles.
How are photovoltaic panels made?
The solar panels are made from six main components. They are assembled in advanced manufacturing facilities with extreme precision to minimise the risk of manufacturing defects.
The six main components of the solar panel:
- Photovoltaic cells
- Toughened glass - thickness 3 to 4 mm
- Extruded aluminium frame
- Airtightness - EVA film layers
- Rear polymer layer
- Junction box - diodes and connectors
Photovoltaic module construction
PRODUCTION STEPS FOR PHOTOVOLTAIC PANELS
The first step in manufacturing a solar panel is to extract and purify the silicon.
Cylinders of pure silicon, known as ingots, are cut into paper-thin discs or wafers and then trimmed into rectangles or hexagons. This method allows a perfect fit to the module frame.
The treatment of polysilicon with boron and phosphorus results in a positive and negative charge. This P/N junction is where the electric current is created. Wires connect the tiny semiconductors to the metal, creating pathways for electricity.
GLASS
The front glass protects the photovoltaic cells from the weather and airborne debris. The glass is usually toughened with high strength and a thickness of 3.0 to 4.0 mm. It is characterised by high resistance to mechanical loads and extreme temperature changes. To increase performance, manufacturers use high-permeability glass, which has a very low iron content and an anti-reflective coating on the back side to reduce losses and improve light transmission.
ALUMINIUM FRAME
The aluminium frame plays a key role. It protects the edges of the laminate section that houses the cells and provides a solid structure to mount the solar panel in place. The extruded aluminium sections are designed to be extremely light, rigid and resistant to the extreme stresses and strains caused by strong wind and external forces.
ENCAPSULATION - LAYERS OF EVA FILM
EVA, or 'ethylene vinyl acetate', is a specially designed polymeric, highly transparent layer that is used to encapsulate cells and hold them in place during production. The EVA material needs to be extremely durable and resistant to extremes of temperature and humidity, as it plays a key role in long-term performance by preventing the ingress of moisture and dirt.
The lamination on both sides of the photovoltaic cells provides cushioning and protection of the cells and connecting wires against vibrations and sudden impacts from hail and other objects. A high-quality EVA film with a high degree of so-called 'cross-linking' can determine the long service life.
REAR POLYMER LAYER
The back layer is the rearmost layer of standard solar panels that acts as a moisture barrier, providing both mechanical protection and electrical insulation. The backing layer material is made from a variety of polymers or plastics, including PP, PET and PVF, which provide different levels of protection, thermal stability and long-term UV resistance.
JUNCTION BOX
This is a small, weatherproof enclosure located at the rear of the panel. It is necessary to securely fix the cables required to connect the panels. The junction box is important because it is the central point where all the cell sets connect and must be protected from moisture and dirt.
Bypass diodes
There are also bypass diodes in the junction box to prevent reverse currents that occur when the cells are shaded or dirty. The diodes only allow current to flow in one direction and a typical 60-cell panel is divided into three groups of 20 photovoltaic cells.
MC4 solar connectors
The solar panels are connected to each other using special weatherproof plugs and sockets called MC4 connectors. The term MC4 stands for a multi-pin connector with a diameter of 4 mm. Due to the extreme weather conditions, the connectors must be very robust, UV resistant and maintain a good connection with minimal resistance at both low and high voltages up to 1000V. The connectors are designed for use with standard, double-insulated 4mm or 6mm DC solar cable with a multi-conductor tinned copper core for minimum resistance and increased durability. A special crimping tool is used to properly assemble the connectors, which crimps the multi-conductor cable to the inner end, which is then inserted and snapped into the MC4 housing.
