因應全球性的能源危機，尋求再生能源成為目前最熱門的研究之中。在所有再生能源中，太陽能儼然成為最具有廣泛應用潛力的能源選項。而為了完善利用太陽能並減少能量的損耗，我們的團隊已耗費數年致力於以日光創造健康的照明環境之研究，並設計出一系列的相關產品，稱之為自然光照明系統。在此系統中，收集陽光之光學元件稱為集光器，而導光管接於集光器之後，並負責傳輸光線之使用，然而若是集光器與導光管之間沒有使用耦合器作銜接時，會產生大量的損失，所以耦合器之設計在此自然光照明系統也扮演著重要的角色，但是以往的耦合器用於銜接一個集光模組與一根導光管，是以一對一方式作銜接，其中如何將多個集光模組整合至一根傳光元件之中，是許多耦合器研究所忽略之問題。
因此，本文提出一個耦合設計概念，透過自由曲面反射與折射之設計搭配，使得耦合模組與傳光元件產生高度之位差，避免前者阻擋後者光線傳輸，將多個集光模組整合至一導光管。此一耦合模組之效率為82%，本文亦提出新型導光管之設計供此耦合模組作傳輸使用，並提出在堆疊數量下對應之效率模擬數據。最後將此耦合模組應用與傳統自然光照明系統作比較，使用耦合器時，效率雖然相較遜色並隨著堆疊數量增加而下降，但是能量密度比會隨著堆疊數量增加而凸顯其優勢。在成本的比較上，隨著堆疊數量的增加，使用耦合器的情況所需的導光管及透鏡數量遠比一般情況少，這也表示其成本優勢。透過模組堆疊化方式，可大量減少自然光照明系統之建造面積、導光管數量、成本，進而提升該系統之優勢。

In response to the energy crisis, renewable energy became one of the most popular issues. Among all renewable energy sources, solar energy was a widely used potential energy source. In order to minimize energy expenditure and create a healthy illumination, our team has designed a Natural Light Illumination System that can transfer natural light into indoor illumination.
This paper presented a freeform reflector coupler designed for a daylighting system. This freeform coupler module was composed of a reflector and a refractor, the former is used to control input rays from the collector to a freeform refractor, then the later collimates reflected light for later transmission via light guides. The efficiency of a freeform coupler module is 82%, and we got the stacked number corresponding to efficiency. We also find the best designed lightguide with Fresnel lens were focal length 1200mm, lens space 600mm and the radius of the lens were 120mm. The design allowed freeform coupler modules to be stackable, which means light transmitted from the previous module would not be blocked by the next module and could be well transmitted. In other words, it decreased number of light guides used in the daylighting system and reduces the difficulty of the cascade implementation.

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