Distributed Control and Process Monitoring for Photovoltaic Applications

Distributed process control and monitoring in a multitasking personal computer environment improves the ease of use, reproducibility, and safe operation of photovoltaic solar cell procesing systems. In this paper, we report the experience learned from our recent upgrading of a Tempress high-temperature furnace system at the National Renewable Energy Laboratory (NREL), which is used for processingcrystalline-silicon solar cells in a clean-room environment. The furnace has eight quartz tubes with three temperature zones per tube, for a total of 24 temperature control loops. Customized programs and hardware interface were installed for automated control of the furnace and to provide extensive safety interlocks.