Breakthrough Furnace Can Cut Solar Costs
October 21, 2011
The cavity inside the Solar Optical Furnace glows white hot during a simulated firing of a solar cell.
Credit: Dennis Schroeder
Solar cells, the heart of the photovoltaic industry, must be tested for mechanical strength, oxidized, annealed, purified, diffused, etched, and layered.
Heat is an indispensable ingredient in each of those steps, and that's why large furnaces dot the assembly lines of all the solar cell manufacturers. The state of the art has been thermal or rapid-thermal-processing furnaces that use radiant or infrared heat to quickly boost the temperature of silicon wafers.
Now, there's something new.
A game-changing Optical Cavity Furnace developed by the U.S. Department of Energy's National Renewable Energy Laboratory uses optics to heat and purify solar cells at unmatched precision while sharply boosting the cells' efficiency.
The Optical Cavity Furnace (OCF) combines the assets that photonics can bring to the process with tightly controlled engineering to maximize efficiency while minimizing heating and cooling costs.
NREL's OCF encloses an array of lamps within a highly reflective chamber to achieve a level of temperature uniformity that is unprecedented. It virtually eliminates energy loss by lining the cavity walls with super-insulating and highly reflective ceramics, and by using a complex optimal geometric design. The cavity design uses about half the energy of a conventional thermal furnace because in the OCF the wafer itself absorbs what would otherwise be energy loss. Like a microwave oven, the OCF dissipates energy only on the target, not on the container.
http://www.nrel.gov/news/features/fe...eature_id=1629