摘要
太陽光電熱能系統可在有限屋頂面積下同步產生電能與熱能，提升太陽能的整體利用效率。為評估奈米碳球作為此類系統集熱材料之可行性與效益，本研究建置並驗證以奈米碳球為吸熱層之太陽光電熱能系統。奈米碳球與 EVA 經加熱混合製成 CNC 集熱膜層；結構分析結果顯示 CNC 與 EVA 可於膜層中共存，但隨膜厚增加，可能出現 CNC 於厚度方向分布不均或成分梯度之現象。當膜厚 ≥ 0.9 mm 時，CNC 膜層光吸收率>70%，方能滿足太陽光電熱能系統基本需求。我們採用厚度 2.5 mm、面積 0.3 m²（其上配置 0.125 m² 太陽能電池）的 CNC 集熱膜層製造太陽光電熱能系統，在戶外 9 小時自然光照測試下，可讓水溫提升 11.8℃。測量時間內太陽光入射能量為 1217.2 Wh，水體獲得熱能 823 Wh，對應熱轉換效率 67.6%；同時太陽能電池輸出電能 62.08 Wh，使系統整體轉換效率達72.7%。未來可由膜厚、電池面積佔比與有效受光面積進行參數最佳化，以提升熱、電輸出效益。
關鍵詞：奈米碳球、太陽光熱光電、集熱膜、能量轉換
Abstract
Photovoltaic–thermal (PVT) systems enable the simultaneous generation of electricity and heat within limited rooftop space, thereby improving the overall utilization efficiency of solar energy. In this study, we developed a PVT system using carbon nanocapsules (CNCs) as the photothermal absorbing material to evaluate its feasibility and performance. Photothermal collectors were fabricated by thermally mixing CNCs with ethylene-vinyl acetate (EVA). Structural analyses confirmed the coexistence of CNCs and EVA; however, increased film thickness resulted in non‑uniform CNC distribution and potential through‑thickness compositional gradients. Films with thickness ≥ 0.9 mm exhibited optical absorptance exceeding 70%, satisfying basic PVT application requirements. A prototype PVT system employing a 2.5 mm-thick CNC film (collector area: 0.3 m²) coupled with photovoltaic cells (total PV area: 0.125 m²) was evaluated under outdoor conditions over a 9-h period. The system increased the water temperature by 11.8 °C. With a total incident energy of 1217.2 Wh, the system produced 823 Wh of thermal energy, corresponding to a thermal efficiency of 67.6%, and 62.08 Wh of electrical energy, yielding an overall energy conversion efficiency of 72.7%. These results demonstrate the potential of CNC-based PVT systems for efficient solar energy harvesting. Future work will focus on optimizing film thickness, PV area fraction, and effective illuminated area to further enhance system performance.
Keywords: Carbon nanocapsules, Photovoltaic-thermal system, Thermal collector, Energy conversion