屋頂型光伏太陽能板對局部環流與對流潛在的影響

Abstract

本研究探討屋頂型光伏太陽能板對局部環流與對流潛在的影響。在擁擠的都市地區，屋頂型光伏太陽能提供了一個有效率的空間使用方案。然而隨著裝設的規模愈來愈大，對於環境可能會造成意料之外的影響。太陽能板會改變地表的輻射收支，進而可能會增強或減弱都市熱島效應，又都市熱島效應已有不少研究指出，會對台灣的午後對流產生影響，因此，太陽能板所造成的溫度改變可能也會進一步的影響局部環流與對流。本研究以都會區台北市為例，以數值模擬實驗測試不同的太陽能轉換效率對環境可能產生的影響。結果顯示，光伏太陽能會在台北市產生冷島效應，增加台北市與南方山區的溫度梯度，進而有較強的氣流沿著山脈爬升，導致在較高海拔較早開始產生對流，進而使降雨區往山區移動。在都市方面，因為冷島效應提供較穩地的大氣環境，進而產生一阻擋效應，使對流較不易移入台北市，因此在台北市有較強的降雨減少訊號。太陽能的轉換效率愈高，冷島效應也會愈強，降雨的改變也愈明顯。

This study investigated the potential impact of rooftop solar photovoltaic (PV) installation on local circulation and convection in the urban area. The rooftop solar PV system is a space-efficient option to deploy renewable energies in the crowded urban area. However, as the installation scale increases, the unintentional impact on local climate may emerge. In particular, PV array deployment can change the surface radiative balance and thus enhance or reduce the urban heat island (UHI) effect. The UHI effect has been implicated to influence afternoon thunderstorm activities in the tropical island, Taiwan. Therefore, temperature change due to PV installation may also alter the local circulation and convection. This research takes the Taipei City, which is a metropolitan area in northern Taiwan, for a case study. Citywide rooftop solar PV installation experiments are conducted by using the Weather Research and Forecasting (WRF) Model coupled with an urban canopy model. Different PV conversion efficiency scenarios, including current and future technology levels, are simulated to evaluate the potential impact of solar PV installation. The results show that solar PV would cause a cold island effect (CIE) in the Taipei City. The CIE would increase the temperature gradient between the Taipei City and the mountains south of the Taipei Basin. This circulation change results in a stronger upslope flow such that the heavy-rainfall region shifted upslope, which can trigger the convection to occur earlier at higher altitudes. On the city side, the strength of heavy precipitation decreased because of the blocking effect of colder air, which causes a more stable environment over the Taipei City. Such effects are stronger for higher PV energy conversion efficiency, including a stronger CIE and more obvious precipitation change.