| 摘要: | 鑒於近年風能技術日趨進步以及都市密度快速增加，加上台灣地狹人稠使得陸域大型風場發展受到限制的特性，除了離岸風能外，都市風能有機會成為台灣綠色能源中相當有潛力的一項發展目標。本研究以台中市的都市風能潛力評估為例，首先以模式模擬來得到良好的都市風場，接著根據風場資料評估都市風能，然後討論評估都市風能的經濟效益以及在供電系統上所能扮演的角色。
本研究模擬2017年四季代表月份1月、4月、7月、10月期間的台中市風場，首先針對WRF模式進行敏感度測試，包括都市粗糙度長度、四維資料同化(Four-Dimensional Data Assimilation, FDDA)、Urban Canopy Model(UCM)、Building Effect Parameterization (BEP)、Building Energy Modeling (BEM)三種都市參數化修正，發現整體來說以FDDA加上BEP參數化在台中市模擬風場表現最佳，尤其在市中心建築密度較高區域有明顯的改善，然後將這組模擬風場作為CALMET風場診斷模式的初始猜測場，並結合分布在台中市區域的二十個觀測站資料進行最後修正，由模擬結果可以看到藉由耦合WRF/FDDA/BEP和CALMET能夠將模擬場更加接近觀測場，特別是在地形變化較大的都市郊區。。
本研究接著分析都市風速及風能密度的分布，應用2.5kW屋頂型小型風機架設在清水、梧棲、龍井及沙鹿區4樓以上建築(平均風速2~6 m s-1)，年發電量達5500~12000度，或北屯、西屯、市中心及南屯區120公尺以上大樓(平均風速3~5 m s-1)，年發電量達4500~9000度。15kW地面型小型風機則適合架設在清水、梧棲、龍井及沙鹿區的空曠處(平均風速2~6 m s-1)，年發電量達38000~72000度。
根據目前台灣能源局再生能源躉購政策，本研究所有小型風機地點年發電量皆高於年售電量上限(1650度/kW)，因此投資回收期皆為13年。若在無售電上限的情況下，投資回收期可縮短為6~12年，以經濟投資的立場來說，前述提及的地點皆非常有開發價值。供電方面，以年的角度來看，對服務業、公家機關或大專院校等建築用途，2.5 kW屋頂型小型風機發電量僅能支持部分照明或部分負載項目用電量，較適合做為推廣綠能的用途，而15 kW地面型小型風機可以支持服務業、公家機關或大專院校等照明用電的35%以上，具有發展潛力。小型風機發電量對於供應住宅用電則具有相當大的貢獻，15 kW小型風機的年發電量能夠支持5至10戶住宅用電，2.5 kW屋頂型小型風機則能完全支持1戶住宅年用電量。在季節上，2.5 kW屋頂型小型風機在秋、冬季月份(一月及十月)發電量能完全支持住宅用電，但在春、夏季月份(四月及七月)發電量則較為不足(月發電量為秋、冬季的一半以下)，需要其他供電系統的支持才能穩定供應住宅用電。而從小時來看，一天中發電量與用電量分布相反，即使在本研究中發電量最高的地點，在住宅尖峰用電的18時至凌晨1時之間，亦僅能堪達到完全支持用電，對於供電系統的調節有較大的挑戰，因此調配電力供給、搭配良好的儲能技術以維持供電穩定性會是小型風機開發及運用的關鍵。
;In addition to the large-scale onshore and offshore wind farms, urban wind energy has gradually drawn attention among green energy resources because of creative wind energy technology and rapid increase of urban development in recent years. In order to assess the potential of urban wind energy, this study first compared various wind field correction methods in WRF model and combines CALMET wind diagnostic model to obtain the best final wind field. Then, we assessed urban wind energy based on final wind farm data and discussed the economic benefits and the demand/supply of power system.
This study took Taichung City as an example and simulates wind field during the January, April, April, and October 2017. First, the sensitivity test was conducted for the WRF model, including adjustment of urban roughness length in land use data, Four-Dimensional Data Assimilation. (FDDA), urban parameterization in WRF such as Urban Canopy Model (UCM), Building Effect Parameterization (BEP), and Building Energy Modeling (BEM). We found that the overall performance of FDDA plus BEP parameterization is the best in the test and significantly improved the simulated wind field in areas where building density is high in the city center. Then we used the WRF/BEP derived wind field as the initial guess and combined the observation data for the CALMET diagnosis modeling. The coupling WRF/BEP and CALMET can strongly pull simulations toward observations, especially in the suburban area with relatively high terrain complexity nearby.
This study then analyzed the distribution of urban wind speed and wind energy density. It is found that the 2.5kW rooftop small wind turbine is suitable for building above 4th floor in Chingshuei, Wuchi, Longjing and Shalu districts (Average wind speed 2~6 m s-1, annual power generation 5500~12000 kWh), or the buildings above 120 meters in Bei Tun, Si Tun, Tai Jhong and Nantun districts (Average wind speed is 3~5 m s-1, annual power generation 4500-9000 kWh). The 15 kW ground type small wind turbine is suitable in the open area of Chingshuei, Wuchi, Longjing and Shalu districts (average wind speed is 2~6 m s-1, annual power generation 38000~72000kWh). According to the renewable energy procurement policy of the Bureau of Energy in Taiwan, the annual power generation of all small wind turbine locations in this study is higher than the annual sales cap (1650kWh/kW), so the payback period is 13 years. If there is no electricity sales cap, the payback period can be shortened to 6~12 years. From the standpoint of economic investment, all the locations mentioned above are very valuable for wind energy development.
From the perspective of power supply, 2.5 kW rooftop small wind turbine can only support a small amount of lighting or small-load project power consumption for construction purposes such as service industry, public institutions, or colleges. It implied the 2.5 kW rooftop small wind turbine is suitable for promoting green energy. The use of 15kW ground-type small wind turbines can support more than 35% of lighting power in service industries, public institutions or educational organizations. The power generation of the 15kW ground-type small wind turbines can supply the residential electricity. The annual power generation of 15kW small wind turbines can also support the electricity consumption of 5 to 10 households, as well as the 2.5kW rooftop small wind turbines can fully support the annual electricity consumption of 1 household. From the perspective of seasonal changes, 2.5kW rooftop small wind turbines can fully support residential electricity consumption in the autumn and winter months (January and October). However, in spring and summer months (April and July) the power generation is insufficient (The monthly power generation is less than half of that in autumn and winter). It needs the support of other power supply systems to stabilize the supply of residential electricity. The main challenge of the 2.5kW rooftop small wind turbine is that the trend of its hourly generation is opposite to the electricity consumption. For the spots with the highest power generation, the residential power consumption peaks between 6 p.m. to 1 a.m. and nearly meets the power generation. Therefore, the deployment of power supply and intellectual energy storage technology to maintain power supply stability will help the operation of small wind turbines in urban area. |
