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Find out the principal factors that can influence the efficiency of a photovoltaic module during its production process.
The efficiency of a module is given by the relation between the energy that the module is able to produce and the energy received by the sun. In standard conditions it’s assumed that the sun illuminates the modules with a radiation equal to 1000 W/ m², therefore a module with an area of 1,52 m² of 250 W presents an efficiency of 16,4%. This is the same calculation that the sun simulator machine do after the STC measurement of a PV module.
But which are the factors that can influence on the efficiency during the production process of the photovoltaic module?
- Cell efficiency: The photovoltaic cell is the element that generates energy and is the base from where to start when calculating the efficiency of a photovoltaic module. Cells with higher efficiency consent to produce a more performing module. But is has to be considered that the final value is not only the mathematic calculation : Pcell * Number of cells but there are many factors to be considered that play an important role in this calculation.
- Glass: The light that strikes the cells pass through the glass and must therefore be optimized to consent this transit. Fundamental parameters are the spectral band, the light transmittance and the superficial processing. The superficial processing of the glass can help the cells to capture the light reducing the losses or even permit to improve the performance of the cells. Anti-reflective coatings are also available.
- Positioning on the glass: A factor that not often is considered is how the cells are disposed on the module surface. If from one side the necessary space, from cell to border, which guarantees a correct electrical insulation reduces the overall efficiency as not the entire area is used, from the other side a strategic spacing between the cells together with a white back sheet, allow to catch in a better way the light reflected by the cells increasing like this the total efficiency.
- Quality of the soldering: The soldering quality of the solar cells and of the ribbon influences in a direct way on the series resistance of the photovoltaic module. Using a suitable ribbon thickness and monitoring the quality of the soldering guarantee a constant performance of the production process. The use of automatic machines with continuous soldering consent to reduce the series resistance of the photovoltaic module. For this we recommend a production process with:
- A continuous soldering of the photovoltaic cell to reduce the series resistance
- Constant monitoring of the peel strength of the soldered ribbon
- Breakages in the module: Analyzing and monitoring the breakages in the photovoltaic module permit to limit the losses and to guarantee a higher reliability of the module. Small micro-cracks can influence modestly on the power measured by the sun simulator, but potentially they can create bigger breakages that can reduce the efficiency during the life of the module. Typical breakages can be created by: manual work, dirt residuals created during the soldering process, transport and movement of the product, components of bad quality etc.. A control that permits an analysis of these breakages can be performed by making an electroluminescence test of the photovoltaic modules.
- Cables and junction box connection: You can estimate that the loss caused by inner wiring and cables has a value around 1-3%. This is why a careful choice of cables, ribbon, junction boxes and way of making the connections can make a difference for the final power of the pv module.
A correct and careful supervision of the assembly process is the key to obtain efficient and high quality products.
The success of the module manufacturing company is strongly linked with the choice of partners. Ecoprogetti, with a background of more than 25 years in this industry, is able to guide the customer in the right direction to choose the correct equipment, materials, assembly process and custom made supervision solutions.