抄録
The objective of this research is to improve efficiency of conventional evacuated solar collector by simulation. To achieve this, the upper half of vacuum tube consists of Non-imaging Fresnel lens. Non-imaging Fresnel lens consists of many prisms and has acceptable half-angle. The vacuum tube is designed by changing parameters, for example, a position of heat collector, the radius o f the vacuum tube and the number of prisms. The optical efficiency is calculated by ray tracing. As a result, parameters, which affect optical efficiency greatly, are number of prisms and the distance between heat collector and center of vacuum tube. The greatest optical concentration ratio was about 3.0 when parameters of vacuum tube changed.
