The photovoltaic module is an assembly of electrically interconnected solar cells enclosed in a weatherproof package. Modules are manufactured in an assembly line, which contains either stand-alone machines or a fully automated setup. Starting with individual cells, machines take cells and process them into ready-to-mount modules. Several machines contribute to the manufacturing process.
The first is a cell sorter, which arranges photovoltaic cells according to their electrical performance, tested under simulated sunlight. An automated production machine interconnects solar cells by soldering flat metal leads, or tabs, to cell contacts. A photovoltaic module laminator bonds multiple layers of materials together with thermoplastic or thermosetting films, such as ethylene vinyl acetate polymer. The processing chamber of a laminator has temperature, vacuum and atmospheric pressure capabilities which are independently controlled to provide optimum lamination processing conditions for particular materials and configurations. Finally, a sun simulator, or flasher, is critical in both module production lines and testing and certification laboratories. In a production setting, modules must pass an appropriate series of sun simulation tests to be certified and shipped. Simulators provide short- and long-term stability over the life of the tool for spectral, spatial and temporal uniformity.
Some manufacturers use automated production equipment as listed above. Also, there are new companies investing in solar PV in emerging markets for local manufacture of cells and modules. Large manufacturers typically buy best-in-class individual machines. New companies typically invest in turnkey production lines. With proper training, technician-level skills are more than adequate to operate the machines.
In recent years, manufacturing equipment has become more automated with higher throughput, including factory-wide integration with statistical process control and MES systems. The key challenges for these systems are to improve equipment process capability and reliability to produce solar cells and modules, using new materials and process methods, at the highest yields and overall final product quality.
The manufacturing process:
1. Use a cell sorter to test and sort solar cells into performance .
2. Wash, rinse and dry the glass superstrate using a glass washer.
3. Cut EVA using a cut and place station and place it on the glass superstrate.
4. Assemble and interconnect cells with metal ribbons to make cell strings using an
assembler.
5. Align and place cell strings on EVA or glass with an assembler module layup station.
6. Complete the module laminate circuit at the busing station by soldering bus ribbons to connect the strings and provide output leads.
7. Visually inspect and electrically test the module laminate circuit by measuring its dark IV characteristics at an inspection station.
8. Cut EVA, fiberglass and back sheets to length using the cut and place station, and then assemble them with the glass and module circuit using the back sheet layup station, all in preparation for encapsulation.
9. Laminate the assembly and cure the EVA with the laminator.
10. Complete the final assembly, which includes edge trimming, attaching a junction box and by-pass diodes and installing an edge gasket and frame at a frame press station.
11. Measure the module’s performance under simulated sunlight.
12. Perform a high-voltage isolation test to measure the voltage isolation between the cell circuit and the module frame, and test the frame ground continuity.
13. Visually inspect the completed module for quality of materials and workmanship.
By: Peter DiSessa, Vice President of Global Sales at Spire Corporation
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