Novel Design for Temperature Reduction of Solar Panel Assisted by Energy Storage Material

相變材料輔助太陽能光電板降溫之新穎設計

相變材料因具備可重複使用、高能量儲存密度及價格低廉的特性，十分適合作為能量儲存材料。白晝之際，藉由其巨大的潛熱，降低太陽能晶片溫度，從而提升太陽能光電板效率；夜間時刻，利用溫度較低的溫差效果，散掉白天所吸收儲存的熱量。由於相變材料可回收重複使用，加上製作過程簡單，同時又取得方便且不會造成環境污染，特別適合要求低廉成本的再生能源應用。利用示差掃描熱量儀量測出數種無機鹽類水合物之潛熱值及熔點溫度，篩選出碳酸鈉十水合物作為設計用之相變材料。融化狀態的碳酸鈉十水合物裝填於高密度聚乙烯塑膠袋中，並且置於金屬盒中冷卻固化成型(長20cm×寬20cm×高1cm)，然後以真空封裝成相變材料包。將相變材料包以鋁箔貼布固定於太陽能光電板背面的中間部位，表面溫度可立刻由59~63°C下降至40~49°C，並且可維持數小時，同時於相變材料包貼到太陽能光電板背面之際，以手持式電表量測開路電壓，三分鐘內由16.1V上升至17.0V。此外，透過SolidWorks Flow Simulation 進行有限元素數值分析，模擬結果與Fluke Ti20熱像儀實測值進行比較，發現太陽能光電板中心點表面模擬溫度與實際量測值相差約3°C。

Phase change material can be used as energy storage due to its reusable property, high heat storage density, and inexpensive price. To raise the efficiency of solar panel system, phase change material can be incorporated into solar panel system to reduce the daytime temperature of solar panel system which then can be released during nighttime when the temperature is lower. Because of its reusability, easy accessibility and non-toxicity, phase change material is especially suitable for the renewable energy industries. By utilizing a differential scanning calorimeter to measure latent heat and melting point, Na2CO3.10H2O was chosen as the phase change material for design after several inorganic hydrates were screened. Molten Na2CO3.10H2O was put into a bag of high density polyethylene, and cooled down to complete solidification inside a metallic case. After vacuum sealed, the formed phase change material bank (length 20cm×width 20cm×height 1cm) was fixed on the central backside of solar panel with an aluminum tape. Then, the frontside surface of solar panel was cooled down from 59~63°C to 40~49°C, and could lasted for several hours. Once the phase change material bank was installed, the open circuit voltage read by a portable power meter increased from 16.1V to 17.0V within three minutes. Besides, with the aid of Solidworks Flow Simulation for finite element numerical analysis, we found that the central surface temperature difference of solar panel between the numerically simulated results and the experimental data measured with the Fluke Ti20 thermal imager was about 3°C.