在自然光照明系統中的集光器為一靜態式集光器，且此集光器需要太陽光準直的入射在集光器上才能具有它高效率的表現，但由於集光器不進行追日導致只有在正午時刻能具有功能，所以需要定日鏡的輔助，本文提出一個定日鏡由九個拋物面鏡及九個自由曲面鏡組成，利用拋物面將光線聚焦壓縮，再利用自由曲面將光線均勻輸入到集光器，使光線準直入射在集光器上，且提升集光器收到的能量。透過這兩個結構的搭配也可以引導太陽光到因大樓擋住而無法受光的地方使其可架設自然光照明系統。此定日鏡可使整體太陽光照明系統日均效率達到原本的2.94倍，可將日均能量提升到原的25.7倍。

A daylighting system collects outdoor sunlight and then transmits it inside for indoors illumination. In general, the system has maximum efficiency when the sunlight is vertically impinging on the collection part of the system, while oblique incidence on the collector causes the efficiency to decline rapidly. To overcome the problem, this paper presents a heliostat design to redirect sunlight, to vertically imping on the collector. The heliostat is composed by paraboloid and free-form reflection surfaces, which is different from the traditional heliostat by merely using mirrors. The paraboloid reflector is used to concentrate more power on the collector to improve the total power. The new design increases the average daily efficiency of daylighting system’s 2.94 times, and average daily power 25.7 times.

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