Performance of materials under hyperthermal solar exposure

The Georgia Institute of Technology has been evaluating materials that can withstand high fluxes of concentrated solar radiation. Researchers have been testing a variety of refractory materials commonly used in extreme temperature environments and for extended periods of time. Two test facilities located on the Georgia Tech campus have been used. One facility uses a heliostat field surrounding a central tower, and the other uses a paraboloid dish concentrator on a horizontal axis. Materials found to be the most satisfactory for solar thermal receiver windows are transparent fused quartz and 96% silica glass. Although the results were preliminary, several possible differences were noted in the samples that may result from fundamental differences between solar and furnace thermal exposures to the “same” temperatures. These effects can produce very different surface and bulk property changes in selected materials that would not be seen as a result of conventional thermal processing.