邁向公路淨零排放:臺灣機車車隊模型發展與應用

Towards Net-Zero Road Transport: Taiwan Scooter Fleet Model Development and Application

張綜桁(Tsung-Heng Chang)

指導教授 ： 謝依芸

國立臺灣大學/工學院/土木工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202203432

摘要

為衡量2050淨零排放目標下機車於運輸部門之減碳成果，本研究建立一個包含機車持有預測、以及以燃料生命週期為基礎的能源需求與溫室氣體排放模型。在機車持有方面，過去的研究指出機車無法使用傳統常用來描述汽車擁有數的S型曲線來呈現；取而代之，隨著所得增加，機車的持有反而呈現U型反轉的情況。本論文提出以Gamma分布函數為基礎的機車持有率模型，發現加入常數項的模型在數學上更能詮釋台灣的機車持有機率，暗示機車持有在我國具有基本的需求。研究中也引入拔靴法用以評估模型參數本身的不確定性，進而呈現機車持有(率)數、能源需求、溫室氣體排放預測的信賴區間。本研究指出，全國機車持有率將於2035年達到每100人持有59.15輛的高峰，接著U型反轉下降至2050年達每100人58.72輛。然而全國人口的急遽下降，使機車持有數將於2024年提前達到高峰，約13.82百萬輛，並於2050年達約11.96百萬輛。另外，燃油與電動機車每公里的燃油生命週期(即油井到輪子階段；WTW)溫室氣體排放，是以本研究的GREET-Taiwan模型以及電網排碳係數推估結果，作為後續推估整體排放的基礎。本研究設計三種情境，分別是基準情境(BASE)、推行電動機車情境(ESC)、推行電動機車以及電網改善情境(ESC-GRID)，採用從油井到輪子(WTW)分析法來衡量2050淨零排放政策規劃下是否能有效達到所設定目標，並了解各情境的減碳成果。研究發現，在2050年，ESC-GRID情境的生命週期排放將會降至1.37 百萬公噸，且該情境2020至2050的累積生命週期溫室氣體排放量約188百萬公噸—低於ESC情境的196百萬公噸以及BASE情境的265百萬公噸。在2050淨零排放政策下(2040年機車銷售全面電動化)，電動機車在2050年佔整體機車將達約85%(即燃油機車佔約15%)，卻仍將造成0.91百萬公噸的溫室氣體直接排放，高於政策所預期的0.41百萬公噸。但若2050年電動機車保有量佔比達93.3%，或是機車每年平均行駛里程降低55%，則該目標將有機會達成。綜上所述，本研究由下而上開發的機車車輛至生命週期的能源消耗與溫室氣體排放模型，將有助於我國未來評估車輛電動化以及能源轉型政策。

關鍵字

機車持有 ； 機車電動化 ； 溫室氣體 ； 淨零排放 ； 生命週期分析 ； 拔靴法信賴區間

並列摘要

Taiwan has recently published“Taiwan’s Pathway to Net-Zero Emissions in 2050” with a clear timeline for vehicle electrification. With the world's highest density of two-wheeler ownership highest density of two-wheeler ownership in the world, Taiwan’s scooter fleet turnover should be carefully studied for understanding long-term fleet trends and greenhouse gas (GHG) emissions under various policies. This thesis, therefore, develops a bottom-up model for Taiwan’s scooter fleet to examine scooter fleet turnover pace, future energy demand, and GHG emissions from a life cycle perspective. Based on the household survey data, it is found that the propensity to own a scooter would grow during the beginning stages as the income increases; but instead of approaching a saturation level like private cars, scooter ownership would start declining once a threshold level is exceeded. Consequently, this thesis proposes using Gamma distribution (i.e., inverse U shape) to simulate scooter ownership patterns. After adding a constant term to the gamma distribution, the mathematical model gives the better curve fitting (R2 = 0.83) results, suggesting that scooters are widely considered a necessity in Taiwan. Moreover, the bootstrap method is adopted to characterize this inherent uncertainty and establish the confidence intervals for vehicle stock forecasting. The model results indicate that Taiwan’s scooter stock will reach the peak at 13.82 million (95% CI: 13.58 – 13.96 million) around 2024 and then decrease to 11.96 million (95% CI: 11.54 – 12.15 million) in 2050. Scenario analysis is conducted to explore the potential GHG emissions reduction by scooter electrification alone and the deployment synergy between electric scooters and the decarbonization in power sector. Under the 2050 Net-Zero Pathway (i.e., ESC-GRID scenario; electric scooters with cleaner power grid), the battery-powered scooters will account for nearly 85% of the scooter stock by 2050, and the direct (i.e., pump-to-wheel; PTW) carbon emission will be 0.91 Mt per year, which is still 0.5 Mt more than the net-zero emissions target for scooters. Based on the scooter fleet model, as long as 93.3% of the on-road scooters are electric in 2050, the decarbonization target could be achieved.

並列關鍵字

Scooter ； Motorcycle ； Scooter electrification ； GHG ； Net-Zero Emission ； Life-cycle analysis ； Bootstrap confidence interval

參考文獻

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