利用生命週期評估比較不同矽晶太陽能板之前處理

Abstract

在永續發展的浪潮下，再生能源已成為炙手可熱的議題，太陽能板安裝數量成指數性上升，其中又以矽晶太陽能電池為主流，其使用壽命在20至25年，若未妥善處置將造成環境汙染。矽晶太陽能板回收的前處理流程可大致分為物理處理、化學處理以及熱處理，其中熱處理可獲得完整電池片且無廢溶劑產生，但乙烯/醋酸乙烯酯(Ethylene-Vinyl Acetate, EVA)封裝膠和背板裂解過程會產生廢氣，而關於廢氣所造成的環境影響討論甚少。近年來關於太陽能板的生命週期評估研究與日俱增，但卻鮮少討論太陽能板資源化流程，若有也幾乎是引用數據而非真實數據。

本研究目的為使用實際實驗數據對「傳統裂解」、「兩階段裂解」和「微波裂解」三種不同前處理流程進行生命週期評估，兩階段裂解前處理嘗試在高溫裂解前去除背板，接著進行背板材料分析、裂解廢氣分析，最後利用生命週期評估軟體SimaPro 9.2以ReCiPe 2016 Endpoint評估模式量化潛在衝擊，以便未來建立具永續性的太陽能板資源化流程。

兩階段裂解第一階段在150 ℃持溫5分鐘，去除部分背板，第二階段在480 ℃持溫20分鐘去除剩餘背板與EVA封裝膠。利用化學溶劑法獲得背板後，使用FTIR分析背板材料，分析結果本研究所使用之背板為不含氟背板，外層與核心層使用PET材料，內層使用EVA材料。

生命週期評估結果環境衝擊由大至小為微波裂解>兩階段裂解>傳統裂解，單點得分結果得分最高的衝擊類別分別為Fine particulate matter formation和Global warming, Human health，根據生命週期評估結果能源、耗材使用與背板裂解所產生的微粒是導致環境衝擊的最大原因，若撇除耗材使用環境衝擊由大至小為兩階段裂解>傳統裂解>微波裂解，此結果表明未來可朝這些方向去減少前處理流程所造成的環境衝擊。本研究雖僅為實驗室規模，然而使用真實數據、討論背板裂解氣體皆是目前較缺少的研究，可作為未來建立永續太陽能板資源化流程之參考。

In the wave of sustainable development, renewable energy has become a significant topic, leading to an exponential increase in the installation of solar panels. Among these, crystalline silicon solar cells dominate the market. These cells have a lifespan of 20 to 25 years of lifespan, and improper disposal can result in environmental problems. The pre-treatment process for recycling silicon crystal solar panels can be divided into physical, chemical, and thermal treatments. Thermal treatment can yield complete solar cells without generating waste solvents, but the pyrolysis of Ethylene-Vinyl Acetate (EVA) and the backsheet produces emissions, which have been limitedly discussed regarding their environmental impact. In recent years, life cycle assessment (LCA) studies on solar panels have increased, but discussions on the recovery processes for solar panels are rare and often reference data rather than utilizing actual data.

The purpose of this study is to use empirical data to conduct a life cycle assessment on three different pre-treatment processes: "traditional pyrolysis," "two-stage pyrolysis," and "microwave pyrolysis." The study begins with the two-stage pyrolysis pre-treatment, attempting to remove the backsheet before high-temperature pyrolysis, followed by an analysis of the backsheet material and pyrolysis emission. Finally, the potential impacts are quantified using the ReCiPe 2016 Endpoint assessment model in the life cycle assessment software SimaPro 9.2, to establish the most sustainable solar panel resource recovery process for the future.

In the first stage of the two-stage pyrolysis, the temperature was maintained at 150°C for 5 minutes to remove part of the backsheet. In the second stage, the temperature was maintained at 480°C for 20 minutes to remove the remaining backsheet and EVA. After obtaining the backsheet using a chemical solvent method, the backsheet material was analyzed by FTIR. The analysis results indicated that the backsheet used in this study was a fluorine-free backsheet, with the outer and core layers made of PET and the inner layer made of EVA.

The life cycle assessment results indicated that the environmental impacts, from highest to lowest, were as follows: microwave pyrolysis > two-stage pyrolysis > traditional pyrolysis. The single score results' highest impact categories were Fine Particulate Matter Formation and Global Warming, Human Health. According to the LCA results, the major causes of environmental impact were energy, material consumption and the fine particulates produced during backsheet pyrolysis. Excluding material consumption, the impact result was two-stage pyrolysis > traditional pyrolysis > microwave pyrolysis. This suggests that future efforts should focus on reducing the environmental impacts associated with pretreatment processes. Although this study was limited to a lab-scale, it used real data and discussed backsheet pyrolysis emission, which were areas currently lacking in research, providing a reference for establishing sustainable solar panel resource recovery processes moving forward.