Advanced module technologies such as half-sheet, multi-grid, and stacked tile, which optimize the module design structure. And change the module manufacturing process to achieve the purpose of improving module power, are currently receiving widespread attention. In fact, the effect of optimizing module auxiliary materials on power improvement should not be underestimated. Most of the component auxiliary material efficiency improvements are achieved by optimizing the component optical solution. The current module auxiliary material efficiency improvement technologies include reflective welding tape, reflective film, white EVA/POE, coated glass, etc.
The cell gap of the conventional module accounts for about 3% of the module area. And the area covered by the welding tape accounts for about 2-3% of the module area. Usually the direct sunlight to this part can not be used by the panel, resulting in a waste of light energy. If this part of the invalid light can be used, it will effectively increase the module power.
Light Reflective Busbar
The front side of the reflective busbar is embossed with a groove-like knot along the length of the tape. This structure reflects the light incident on the solder strip at an angle to the inner surface of the glass layer of the module. And projects it back to the cell surface after total reflection at the glass-air interface. The captured light allows the module to produce additional increased power.
In May 2018, Frontier Technologies introduced its patented technology “Stealth Enhanced Metallization Interconnection” (SEMI). Its data show that SEMI modules can significantly improve the utilization of incident light. And it reduces module power loss, and improve module power generation power 10W-20W. The biggest difference between the SEMI technology and the conventional technology is that the cross-sectional area of the solder tape is triangular.
SEMI’s triangular-shaped solder tape reflects sunlight directly onto the cell surface, except for a small area at the top, reducing the loss of light caused by solder tape shading. At the same time, the contact area between the bottom of the welding tape and the main grid line is large, the series resistance is small. And the welding strength is high, which solves the problem that the flat welding tape has a large shading area and the resistance loss is difficult to take into account and balance.
Reflective film can be attached to the photovoltaic welding tape to achieve the reflective effect. And the sunlight through the glass incident to the reflective film surface. Total reflection occurs on the surface of the reflective film. Light is reflected to the lower surface of the photovoltaic glass. And light is then reflected from the lower surface of the glass to the cell. It reduces the loss of light at the solder strip. Reflective film can also be applied to the cell gap to achieve the same effect. It is said that the reflective film needs to be used with the high-grain EVA front film to achieve the best effect.
3M redirecting reflective film (light redirecting film, LRF), with microstructure on the surface. The sunlight irradiated at the location of the welding strip is deflected and reflected. And then irradiated to the solar cell through the secondary reflection of the coated glass for secondary use. So that the sunlight at the location of the interconnection strip shading can be used twice to improve the light energy utilization per unit area. 3M says its LRF with EVA technology can increase module power by 1.5-2%.
The white encapsulation material has extremely high light reflectivity. It can help improve light utilization and thus increase module output power.
White EVA/POE is used as the backside encapsulation material of the module to reflect the light leakage between cells back into the module. Thus increasing the module power. In double-glass modules, the use of white EVA for encapsulation can increase the module power by 7-10W. In single glass modules, the use of white EVA can increase the power of pure backsheet reflective modules by 1.2-3.5W.
High reflection backsheet/back glass
The backside of the module uses high reflective backsheet/backside glass, which enhances the module power by the same principle as white EVA. And the reflectivity can be increased from 80% to over 90%. Reflectivity can be increased from 80% to over 90%, and module power gain can be up to 0.5%. The appearance and reliability of the modules with high reflective backsheet/back glass is better. And there are no difficulties in the use of white EVA, such as turning over the layers.
Front side anti-reflective coated glass
AR coating (antireflection coating) reduces the reflectivity and increases the transmittance of sunlight in the spectral response range of solar cells. The front glass of the module is coated with antireflective film, and about 90% of PV modules use AR coated PV glass.
Self-cleaning coated glass
In addition to improving the light transmission of glass, photovoltaic glass has a second research direction to enhance the self-cleaning and anti-fouling effect of glass. So that it becomes self-cleaning glass.
Self-cleaning glass can effectively reduce the module power decay caused by the external environment. And over time, the power generated by self-cleaning modules will be increasingly larger than that of ordinary modules.