被動式太陽能除鹽（passive solar-powered desalination）程序因具有節省能源與環境友善等特點，已廣被注意。為求達到最佳的太陽能轉換效率，此程序中的太陽能吸收層應該要在物理與化學特徵上都被妥善設計，然而，發泡或鹽析之類的傳統加工方法並不容易控制太陽能吸收層的結構。在本研究中，我們使用光固化型3D列印精細地設計並製備太陽能吸收層的孔洞結構，探討吸收層構型對能量轉換的影響，此外，也討論石墨烯添加所造成的效應。
在第一部分的研究中，我們設計了數種多孔結構，包括直管狀、圓錐狀、鋸齒狀與輪狀結構，各具有受控制的孔洞直徑、孔隙度與線徑，並調整石墨烯的添加量。根據列印結果，含石墨烯的光固化樹脂在光固化列印中具有高精細度，誤差小於5%，顯示石墨烯/樹脂的混成物有高度可列印性。我們所列印的各種多孔層在自然狀態中可以維持結構與漂浮性超過十七天，代表這些3D列印的光吸收層可以被長時間的使用於除鹽程序中。
我們在一個太陽光照的強度下進行揮發測試，結果顯示添加石墨烯能有效促進水揮發效率。比較不同孔洞結構造成的影響，高孔洞曲折度能最有效地提高揮發速率，就本實驗設計的結構而言，錐體結構提升揮發的效果最大，可達到的最高太陽能熱轉化效率達90%。此外，我們也在70oC 與濕度95%的狀態下進行揮發測試，發現多孔光吸收層能維持相同的揮發效率至少24小時，代表在一般環境中可維持其狀態約52天。本研究證實了多孔結構在揮發除鹽效應中的影響，對製備高效率的太陽能吸收裝置具有相當的幫助。

The passive solar-powered desalination attracted much attention due to its energy-saving and environmental-friendly functions. The transfer of solar energy to heat is the most crucial issue in this process. Thus, the properties of the solar-energy absorbing layer must be well designed and tailored. However, it was not easy to control the porous structures of the solar-energy absorbing layer just by using conventional processes, such as foaming or porogen leaching. In this research, the porous absorbers were precisely designed and fabricated using a photo-curing 3D printer, allowing us to investigate the structural effects on energy transferring efficiency. The graphene additive was also applied in the porous layer for further enhancement of heat generation.
In the first part, several porous structures, including straight channels, cone, zigzag, rhombus and wheel-shaped channels with various intersection grooves, were fabricated for the energy transferring layer. The pore size, porosity, and wire diameter were controlled, followed by the adjustment of graphene amounts. According to the design sketch and images of printed products, the errors of porous structures were less than 5%. The results proved that the structures created in this research were highly accurate, which was achieved by a DLP 3D printer. More importantly, the resin with graphene additive was highly printable. The floatability of the porous layer was longer than 17 days under natural conditions, revealing the stability of this solar-energy absorbing layer for long-term operation.
The evaporation tests were performed under 1 sun irradiation. The results showed that the addition of graphene promoted water evaporation significantly. The temperature of the porous layer was increased by 54.05% with the addition of 20% graphene. Comparing evaporation from different porous structures, the evaporation rate greatly improved with the light reflection from the structure of pores. Thus, the cone structures in this research caused higher evaporation than the others did, where the highest solar thermal efficiency was about 90%. Besides, the evaporation rates of all absorber were not decreased for at least 24 hours under 70oC and 95% humidity, which was identical to the stability for 52 days in actual environment. This study identified the effects of porous structures systematically, which was crucial in producing a highly effective solar-energy absorbing layer for the desalination process.

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