自來水系統碳排放熱點及抽水機能效之分析

Abstract

分析水廠碳排放熱點(hot spot)是節能減碳之關鍵，大多數國內傳統處理水廠之碳排放熱點為輸配水系統抽水機用電，因此抽水機節能對於水廠節能減碳十分重要。輸配水系統抽水機節能最大之困難點在於水廠抽水機能耗及效率隨供水量變動而改變，操作人員無法準確地調整抽水機組合至最佳效率點運作(best efficiency point)同時又滿足用戶需水量。本研究旨在了解傳統處理水廠之碳排放情形，依據碳足跡計算準則PAS 2050以板新給水廠為例評估自來水碳足跡，碳足跡評估範疇包括取水、淨水及輸配水階段，並分析板新給水廠碳排放熱點。此外，分別以不同抽水機能耗數據(固定揚程能耗、抽水機效率及單位出水能耗)評估板新給水廠及寶山給水廠之抽水機能效。 研究結果顯示，100年板新給水廠自來水碳足跡為0.39 kg CO2e/m3，碳排放熱點為輸配水系統抽水機用電，佔總碳排放量65%。當淨水場抽水機運作數據只含揚程及能耗時，固定揚程之能耗可作為評估抽水機操作能耗與額定能耗是否相符之參數，讓操作人員得以檢修或汰換低能效抽水機。當抽水機運作數據含揚程、功率及系統總流量之連續值時，實測分析抽水機效率(%)及單位出水能耗(kW/Q)之關係可作為水廠判斷不同供水量下抽水機運作最適能效組合之方法。

Evaluation of carbon emission hot spot for water treatment plant (WTP) is crucial to the reduction of carbon emission. For conventional WTP, the major carbon emission is energy used from pumping in water supply. Thus, pumping energy saving is very important in reducing carbon emission of WTP. The pumping efficiency and energy consumption are significantly affected by flow rate. It is difficult to operate the pump at the best efficiency point through properly adjusting the combination of pump meanwhile satisfy the requirement of potable water for user. This study aims to analyze the data of carbon emission in the operation of Bansin WTP following the PAS 2050 guideline for carbon footprint evaluation. The boundary of inventory and assessment includes the intake, the purification, and the distribution stages. In addition, pumping efficiency, power consumption per pump lift and specific energy consumption were used to estimate the potential of energy reduction in pumping for Bansin and Baoshan WTPs. The study results revealed that carbon footprint of Basin WTP is 0.39 kg CO2e/m3 in 2011. In addition, pumping energy used is carbon emission hot spot responsible for 65% total carbon emission. When WTP only contains the data of pump lift and power, the power consumption per pump lift can be used to evaluate the difference between rated power and operational power of pump and provide information for operator to replace or maintain the less efficiency pump. When WTP has the data of continuous values of pump lift, flow rate and power, the relationship between pumping efficiency (%) and specific energy consumption (kW/Q) can be used as an index to identify the optimum pump combinations which operate at the best efficiency point under different water supply.