High performance solar collector amenable to mass production

The high temperature thermal performance of a mass producible evacuated tube solar collector (ETC) has been significantly improved by shaping the outer glass envelope into the profile of a nonimaging Compound Parabolic Concentrator (CPC). Placing the reflector surface in a vacuum eliminates degradation of the mirror's reflectance. The transparent part of the glass vacuum also functions as a window and thus eliminates the need for an external cover glazing. This paper describes the design, fabrication, and preliminary test results for a panel of prototype tubes based on this concept. A schematic illustration of the prototype design is shown. Optical and thermal performance, for several parameters, are measured. The performance curve shows efficiencies greater than 40% across the full range of temperature.