中空式綠屋頂降溫實驗分析

Abstract

建築物設置綠屋頂可降溫節能，但傳統綠屋頂由於一些問題，因而不易在國內推廣。本研究因而建立接受度較高且成本效益較佳的中空水盆式綠屋頂。該綠屋頂建置校內建築的屋頂上，且留一半裸屋頂作為比較。並以儀器連線監測日照、溫度、熱通量、水盆水位等數據。再依據所收集資料比較二個屋頂間屋頂表面及室內等溫度及熱通量等之差異及進行相關數據分析。且參考ISO9869及使用LORD模式估算中空式綠屋頂熱傳係數U-value值，亦以之前研究所建立環工館EnergyPlus模式推估該中空式綠屋頂的節能效益。也建立一個能量平衡模式分析中空綠屋頂的熱能變化。 依實測結果，夏天時中空綠屋頂及裸屋頂表面溫差超過20度，降低屋頂表面熱脹冷縮，可保護屋頂表面。兩屋頂下之室內溫度差約2-4度。中空綠屋頂依材質所估算的U-value在假設中空層較通風與不通風情形下分別約為0.79及0.86W/m2K；依實測值估算U-value，雖然在裸屋頂部分尚可接受，但中空綠屋頂因動態變化無法得到收斂的結果，LORD模式亦因而無法得到收斂結果。節能效益依EnergyPlus模擬結果，若在實驗裸屋頂上設中空綠屋頂則每年約可節電為9.71-9.81kWh/m2，若在傳統裸屋頂上則由於原來的隔熱效果已較好約為5.71-5.83kWh/m2。中空綠屋頂能量平衡分析結果，潛熱約占77%，可感熱約占4%，綠屋頂藉由植物調節之蒸發散作用，將屋頂表面部分可感熱和儲熱轉換部分潛熱釋放，可有效隔熱。

Covering building with green roof can reduce roof temperature and result in energy-saving. However, due to some problems associated with the conventional green roof, green roof is not widely promoted in this country. Therefore, this study has established a hollow type of green roof (HGR), which is expected to be publicly acceptable and cost-effective. To carry out this study, a green roof was installed on half of a campus building roof, and the remaining conventional half building roof (CR) without green roof as a comparison. Data such as solar radiation, temperature, heat flux, and water level were monitored. Based on the data collected, the differences between two roofs for surface temperature, interior temperature and heat flux were compared and analyzed. According to ISO 9869 and the LORD model, the U-value of the HGR was estimated based on monitored data. Also, the energy saving of applying the HGR on the other campus building was simulated and estimated by the EnergyPlus model. Finally, an energy balance model was established to analyze the thermodynamic transmission of the HGR. According to experimental results, the surface temperature difference between two roofs during summer is more than 20 degree Celsius. The HGR can decrease roof surface thermal expansion and contraction, and subsequently protect the roof surface. For interior temperature, the differences between the rooms under two roofs are about 2-4 degree Celsius. The U-value of the HGR was estimated to be 0.79 W/m2 under ventilation assumption or 0.86W/m2 under poor ventilation assumption. Although the U-value estimated by measured data is acceptable for the CR, the values estimated for the HGR does not converge due to dynamic microclimate fluctuation. For the same reason, the LORD model cannot obtain a converged result either. The annual HGR energy saving simulated by the EnergyPlus model for the experimental roof with the HGR is approximately 9.71-9.81 kWh/m2. For the conventional roof with a better insulated layer, the annual energy saving is approximately 5.71-5.83 kWh/m2. From the energy balance analysis for the HGR, the latent and sensible heats are about 77% and 4 %, respectively, of the net radiation. The proposed HGR can significantly reduce roof surface sensible and storage heat flux by releasing the latent heat through the plant and water evaporations instead.