VENDORVIEW
The RFS-D version of the fast firing system can be combined with a dryer for simultaneous drying of the pastes. Controllable, variable conveyor speeds allow for ideal matching of the process parameters to the paste requirements, and assure a throughput rate of 3000 solar cells per hour – compared to 1500 on the single-lane variant. The compact design of the two-lane system also safeguards valuable production floor space.
Firing System
The RFS system’s process chamber is subdivided into burning and fast firing sections, which are equipped with IR radiators from top to bottom. Eight individually adjustable heat zones allow for flexible temperature profiling while burning section zones vary to accommodate various paste requirements.
The RFS process chamber consists of a multilayer ceramic insulation which creates a metal-free interior. An advanced air ducting system has been integrated into the design, which serves to preheat the flow of gas and cool the insulation.
Energy consumption is thus reduced while the system’s exterior covering is kept at low temperatures (
The chamber can be opened automatically for maintenance purposes (see fig 4). The IR radiators are embedded in ceramic seals in the chamber wall, reducing heat loss and allowing for tool-free radiator replacement, taking only four minutes! Standard process temperatures of 200 to 600°C are reliably reached in the burning zone while the firing zone is laid out for a maximum system temperature of 1100°C.
Cooling Zone and Conveyor System Cooling works on the basis of the forced convection principle; the entire cooling tract is designed as a closed system. Air is exhausted from the process chamber with high-performance blowers, and is subsequently fed to the filtering system.
Afterwards, the air flows through cooling units and around the solar cells before being exhausted. Cooling power is adjustable while the top of the cooling tract can be manually opened up for maintenance purposes.
The conveyor system for the two-lane conveyor has a width of 500mm for cells with edge lengths of up to 210mm, and a width of 440mm for solar cell sizes of up to 156 mm.
Vibration-free transport assures highly accurate positioning of the solar cells and minimal breakage rates. Belt return is underneath the process chambers while conveyor speeds are individually adjustable up to 6.8 meters per minute. Transport is accomplished by means of a separate belt system.
Using a separate conveyor system in the cooling zone has two fundamental advantages: cooling power requirements can be reduced by 2kW, and solar cells are cooled to much lower outlet temperatures.
With single belt operation, outlet temperatures of just under 100°C are possible, whereas less than 50°C is achieved with a separate belt. Fig 5 shows a comparison of solar cell temperature curves using different conveyor concepts.
Fig 3: Schematic Diagram of the Firing System
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Fig 4: RFS-D Fast-Firing System, Partially Open
www.solar-pv-management.com Issue VI 2010
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