【翻译】为何电动车高速费电?

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啊峰
08-08 14:43


开过车都知道,车子跑高速更省油,但是在新兴的纯电动车里面,这个理论却是相反的——跑高速比跑市区更耗电。这种完全相反的事实让很多人心生怀疑。撇开数据是否虚标不说,今天我们就来说下为什么电动车跑高速更耗电。



在国外知乎Quora上,也有类似的问题。



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为什么在市区行驶的电动车续航里程会比在高速行驶的高?



以下是阅读数最高的一个回答,来自Brian Feldman,一位创意顾问以及机器人专家。



There are three main things that consume energy in a car - rolling resistance, aerodynamic resistance, and accessories (such as heating and air conditioning).



一辆车的功耗跟三个方面相关:滚动阻力,空气阻力,以及车内电气部件。



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Very simply, the efficiency of an electric powertrain doesn’t vary much once you get moving above a few mph.Your accessory loads are mostly a function of time, and are generally low compared to the energy it takes to keep the car moving. Rolling resistance doesn’t change much with speed. The factor that does make a big difference, however, is your aerodynamic drag. Your aerodynamic drag (wind resistance) is proportional to the square of the speed of your car, and thus the electric car consumes more energy to travel the same distance at a higher speed than a lower one because the aerodynamic drag will (at highway speeds) greatly outweigh the energy used to overcome rolling resistance or accessory loads.



很简单,电动车在行驶的时候的电子传动系统效率的变化并不大。电器能耗一般随着使用时间增长而增大,而且相比于车子行驶所需能量,这一点功耗不值一提。滚动阻力并不会随着车速变化太多,而随着车速变快,改变最大的还是空气阻力。空气阻力的变化增长速度是车速增长速度的平方,这就导致,在驾驶电动车行驶同样距离的情况下,速度更快功耗更大。在高速行驶下,克服空气阻力做功的能耗会远远大于克服滚动阻力的能耗或者电器能耗。



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In a typical gasoline engine car the same rules apply, but during the city driving cycle the engine is often running in a much less efficient state (low power or idling, as opposed to higher load on the highway) and much of the energy in an urban environment is wasted due to braking. This is why a gasoline engine vehicle will typically do worse in the city as compared to the highway. 



理论上来说,跑高速比低速行驶更耗能,这点在汽油车上一样适用。但是为什么汽油车却是反过来的呢?这是因为在市区低速行驶的时候,发动机经常处于低效率运转的状态(比如低功率或者怠速状态,跟高速行驶相反),同时在市区行驶的时候,大量能量在频繁的刹车中被浪费了。这就是为什么普遍汽油车在市区行驶会比高速耗油。



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In an electric car if the car is stopped the motor won’t be using any energy (even in a low-power state they’re very efficient) and energy from braking can often be recaptured through regenerative braking, which eliminate the two largest inefficiencies that a gasoline engine has in a city. At the low speeds in a city the aerodynamic drag will be much less than you’d encounter on a highway, meaning for a given distance you’ll need less energy to move the car in the city.



在电动车上,如果它是静止不动的,那它基本上不会有能量消耗(即便是在低速行驶下也会非常省电),而制动能量损耗则会被回收系统吸收,重复利用。这两个点刚好是汽油车在市区行驶的“高能耗大户”。在市区行驶的时候,空气阻力,这个最影响功耗的因素,肯定会比你在高速行驶下更小,这就意味着电动车在市区行驶能够更省电。



总的来说,撇开动力单元的差别来说,一个移动的物体,高速行驶状态下肯定比低速行驶更加耗能。但是为什么汽油车是相反的呢?归根到底就是因为汽油车在低速行驶下有两个致命缺点:



一是能量转化率低。汽油车是通过汽油燃烧,将热能转换成机械能。汽油发动机的能量转化率一般在30%左右(当然现在某些品牌的发动机转换率会更高,但是不会超过50%)。而在低速行驶下,发动机的效率会更低。这也就导致油耗的增长。



另一方面,制动带来的能量损耗也不容小觑。市区走走停停,制动是常规操作。但是制动就是一个将动能转换成为热能的过程,也就是说这一部分能量被“浪费”了。电动车上能够将动能重新回收成为电能,汽油车则没办法将动能从新提炼成为汽油,只能够让这些多余的动能白白浪费。






最新评论 (11)
    头像
    dv-G
    g3什么价位
    08-15 10:07
    头像
    红色
    想问小鹏表现如何?
    08-14 22:33
    头像
    sing
    终于懂了
    08-14 12:56
    头像
    马里丂丂
    get
    08-14 09:46
    头像
    youbinbin0
    充电多久能?能跑多少公里? 还有中途没有电怎么办?
    08-14 00:24
    头像
    聪000
    中途没电了插上充电宝继续开
    08-14 10:15
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    黄药师
    涨姿势,学习了
    08-13 17:25
    头像
    nbdjacky
    厉害
    08-13 15:26
    头像
    caxa
    为什么现在电动车还要跟燃油车一样配置12v铅蓄电池?
    08-08 22:46
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    电动智能
    想问一问题,电池在高温和低温环境中寿命会变的更短吗?衰减更快吗?
    08-08 14:52
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    啊峰
    好问题,下次我直接来一篇科普文,感谢你的问题(•̀ω•́)
    08-08 15:43
    没有更多了~