Analysis and Experimental Tests of a High-Performance Evacuated Tubular Collector

A high-performance collector based on the use of all-glass, evacuated tubular collector elements is described and analyzed, and supporting experimental data presented. The collector operates with excellent efficiency at temperatures high enough to drive existing air conditioning units, and shows good performance under diffuse light and low insolation conditions. collector efficiency is insensitive to operating temperature, ambient temperature, and wind speed. In addition, air as well as liquid can be used as the heat transfer fluid, with no significant performance penalty. While the equations governing the useful energy produced can be cast in a form similar to that for flat plate collectors, several important parameters are unique in a number of respects.