电动汽车热泵全生命周期气候性能评估模型与环保制冷剂减排分析

Life cycle climate performance(LCCP)evaluation model for electric vehicle heat pumps and emission reduction analysis of low-GWP refrigerants

为满足我国“双碳”(碳达峰、碳中和)目标和《<蒙特利尔议定书>基加利修正案》的要求,采用低全球变暖潜能值(global warming potential,GWP)的热泵系统有助于从直接和间接两个方面全面减少新能源汽车碳排放.然而,目前对于采用何种低GWP工质尚无定论,几乎所有研究仅仅采用GWP值来衡量制冷剂的环保性能,对低GWP工质热泵系统全生命周期气候性能(life cycle climate performance,LCCP)的认识明显不足,同时也缺少适用于新能源汽车热泵的LCCP评估模型.为此,本文基于7个城市的气候数据、当地供电特性、真实世界驾驶循环、乘员舱冷热负荷与舒适性、热泵系统台架测试等,新开发了适用于电动汽车热泵的完整LCCP模型.基于该模型,对传统高GWP工质R134a和R410A、低GWP工质CO_(2),以及先前开发的新型高效环保工质CO_(2)/R41(GWP为49)、M2(非共沸混合物,GWP为137)在电动汽车热泵中的全生命周期环境影响作了评估.结果表明,建立的LCCP模型对热泵系统性能系数(coefficient of performance,COP)的预测精度在±6.5%.LCCP中的直接排放主要与制冷剂的GWP相关,几乎不受气候影响,而间接排放主要受气候、制冷剂类型以及发电碳排放强度的影响.在本文所研究的制冷剂中,CO_(2)/R41电动汽车热泵系统LCCP最低,其LCCP值相比R134a系统减少了5%~42%,相比CO_(2)系统减少了1%~21%.本文所建立的模型与计算结果可为电动汽车热泵制冷剂替代政策的制定提供决策依据.

With the proposal of China’s carbon neutrality target and the official entry into force of the Kigali Amendment to the Montreal Protocol,the green and efficient development of the new energy vehicle heat pump is imperative,since China has the largest number of new energy vehicles in the world.The environmental-friendly heat pump with low global warming potential(GWP)is increasingly essential for the electric vehicle(EV)to save energy consumption and extend the driving range,it is beneficial to achieve the carbon neutrality from reducing both direct and indirect carbon emissions.The longused R134a has a great climate impact due to its high GWP,researchers have been investigating heat pump systems with low-GWP refrigerants.Previously,the life cycle climate performance(LCCP)was a widely accepted metric to evaluate the carbon footprint of mobile air conditioning systems“from cradle to grave”for the classical engine vehicle,however,the new energy vehicle heat pump has significant differences from the mobile air conditioning systems,which makes the LCCP developed for MAC systems no longer applicable for the NEV heat pump system.Such LCCP analysis about EV heat pumps can hardly be found.To facilitate the EV industry and policymakers better understand the environmental impacts of those low-GWP refrigerants,this study provides a comprehensive LCCP analysis for the EV heat pumps based on the heat pump system bench test results,local climates(six cities:Beijing,Shanghai,Guangzhou,Phoenix,Fargo,and Chicago),local power supply characteristics,real-world driving patterns,vehicle cabin thermal sensation,and climate control load.Three low-GWP refrigerants,i.e.,CO_(2),binary blends of CO_(2)and R41(with GWP value of 49),M2(R410A substitute with GWP value of 137),were compared against R410A and R134a.Results show that the system COPs in the energy consumption model are estimated within±6.5%;In most regions,the heat pump can save 36%–69%of electricity for heating on electric vehicles compared to the conventional PTC heater system;The direct emissions depend on the refrigerant GWP and are almost unaffected by the climate.The indirect emissions are influenced by the climate,refrigerant type and the carbon intensity;among the indirect emissions,manufacturing and EOL disposal account for only 5%or so,while the major part is the emissions due to system operation;The R410A heat pump shows higher levels than R134a in both direct and indirect emissions,with 11%–36%increase in total;although M2 shows 2%–27%higher indirect emissions than R134a,it reduces 90%of the direct emissions.In general,it shows 3%–35%less total emissions compared to R134a for EV heat pump application;the direct emissions of the CO_(2)heat pump can be neglected while the CO_(2)system can reduce7%of the indirect emissions only in cold climates such as Fargo.Thanks to its low direct emissions,the total LCCPs of the CO_(2)heat pump are reduced by 6%–27%relative to R134a except in Shanghai(+20%);among the selected refrigerants,CO_(2)/R41 shows the lowest LCCP,reducing 5%–42%of total emissions relative to R134a in various climates,and 1%–21%less than the CO_(2)system.