The transfer window is a dedicated “isolation channel” for the transfer of materials between the clean space and the non-clean area (or areas of different cleanliness levels) in new energy factories. Its core function is to minimize the contamination of the clean area caused by the entry and exit of materials during the material transfer process, and at the same time avoid cross-contamination between different areas. It is a key auxiliary device for ensuring the sealing and cleanliness of the clean space.

In the production of new energy (such as lithium batteries, photovoltaic, hydrogen fuel cells), materials (such as electrode sheets, separators, battery casings, photovoltaic glass, catalysts, etc.) need to frequently flow between the storage area (non-clean) and the production workshop (clean), or between processes of different cleanliness levels. The transfer window is precisely designed to address the “contamination risk during material flow” The specific functions can be broken down into the following four points:
I. Core Function: Block contamination channels and prevent external contaminants from entering the clean area
Particles, dust and microorganisms in the air of non-clean areas (such as raw material warehouses and logistics channels) will directly affect product quality if they enter the clean production area along with the materials (such as short circuits in lithium batteries and a decrease in the light transmittance of photovoltaic modules). The transfer window fundamentally blocks the pollution path through physical isolation and a double-door interlock design.

Double-door interlocking mechanism: The “inner door” (leading to the clean area) and the “outer door” (leading to the non-clean area) of the transfer window are electrically controlled to achieve “interlocking” – that is, when one door is opened, the other door is forcibly locked and cannot be opened simultaneously. This design avoids the direct formation of “air convection” between the clean area and the non-clean area, preventing contaminated air from the non-clean area from directly flowing into the clean area.
Physical isolation space: The transfer window itself is a sealed box structure. Materials are first placed into the transfer window through the outer side door. After the outer side door is closed, the materials are taken out through the inner side door. Throughout the process, the materials remain in the “isolation space” to avoid direct contact with unclean air.
Second, carry out “purification treatment” on the materials to remove the contaminants adhering to their surfaces
Even if the materials are well sealed in the non-clean area, particles and dust (such as packaging debris generated during transportation and environmental dust) may still adhere to their surfaces. If they are directly brought into the clean area, they will become new sources of pollution. Transfer Windows are usually equipped with purification function modules to pre-treat the surface of materials:

UV ultraviolet sterilization: Some transfer Windows are equipped with built-in UV ultraviolet lamps. After the materials are placed in, the outer door can be closed to start the UV lamp to sterilize the surface of the materials for 5 to 15 minutes (mainly killing microorganisms such as bacteria and mold), which is suitable for processes sensitive to microorganisms (such as the production of hydrogen fuel cell membrane electrodes).
Clean air flow purging: High-end transfer Windows will integrate a “clean air spray” system – through the built-in fan and high-efficiency filter (HEPA), high-speed clean air flow (with a wind speed of about 15-20m/s) is sprayed into the transfer window to blow away the particles adhering to the surface of the material, and then the dusty air is discharged through the return air outlet (filtered and then recirculated or discharged externally). This design is particularly suitable for materials such as lithium battery electrode sheets and photovoltaic cell sheets that are extremely sensitive to particles.
Hot air drying (Special Requirements) : In humid environments (such as rainy areas in the south), some transfer Windows can be equipped with hot air modules to dry the materials entering the clean area (such as packaging materials), preventing the materials from entering with moisture and causing the humidity in the clean area to exceed the standard (lithium battery production has extremely high requirements for humidity control, and excessive humidity can easily cause safety risks).

Iii. Maintain the pressure balance in the clean area to ensure the stability of the overall clean environment
The cleanliness of a clean space depends on a stable pressure gradient (generally, the higher the cleanliness level, the higher the pressure: for example, the pressure in ISO Class 5 areas > in ISO Class 6 areas > in non-clean areas), to prevent air from low-cleanliness areas from seeping into high-cleanliness areas. The design of the transfer window can prevent the pressure balance from being disrupted during material transfer.
If there is no transfer window and the door of the clean area is directly opened to transfer materials, it will cause a large amount of clean air to leak out of the clean area and non-clean air to flood in, instantly destroying the pressure and cleanliness of the area. The air conditioning system needs to run for a long time to restore it, which not only consumes a lot of energy but may also affect the continuity of production.
The small-sized isolation space of the transfer window and the double-door interlock design only allow a single door to be opened during material transfer, having a negligible impact on the pressure in the clean area. This ensures that the pressure in the clean area remains consistently stable within the set range (typically a positive pressure of 5-10Pa).
Fourth, adapt to the special needs of the new energy industry and avoid process risks
The material characteristics of new energy production (such as flammability, explosiveness, corrosiveness, and high precision) have special requirements for transfer Windows. Customized transfer Windows can specifically address the pain points of the industry
Explosion-proof design (lithium battery/hydrogen energy) In the production of lithium batteries, the electrolyte and electrode sheets (containing active substances) transferred are flammable and explosive. In the production of hydrogen energy, the catalysts and hydrogen pipe fittings transferred need to be protected from leakage. Therefore, the transfer Windows should be made of explosion-proof boxes (such as stainless steel), explosion-proof glass, and explosion-proof electrical components (switches, UV lamps) to prevent safety accidents caused by static electricity or sparks.
Anti-corrosion design (hydrogen energy/photovoltaic) : In the production of hydrogen fuel cells, acidic electrolytes and hydrogen are encountered. The photovoltaic coating process uses corrosive coating agents (such as silane). The inner walls of the transfer window and the door body need to be coated with 316L stainless steel or PTFE to prevent corrosion damage and avoid metal debris from falling off and contaminating the materials.
Anti-static design (applicable across all industries) : New energy materials (such as separators, photovoltaic films, and electrode sheets) are mostly high-molecular materials, which are prone to generating static electricity and adsorbing particles. The box body, door body and internal bracket of the transfer window will be made of anti-static materials and grounded to eliminate the risk of static electricity accumulation.
Résumé
The transfer window plays the role of a “material contamination firewall” in new energy clean factories – it is not merely a simple “material passage”, but also blocks contamination at the “last meter” of material flow through three core functions: isolation, purification, and pressure protection. At the same time, it meets the special requirements of the new energy industry such as explosion-proof, anti-corrosion, and anti-static It is a key device for ensuring the stability of the production process and the product qualification rate.