wind past. Unlike a dam, where you extract the  potential energy from the height of the water  

風過。不像大壩，從水的高度上提取勢能。

and so you can lower the water as much as you  want without slowing the flow, with a windmill,  

所以你可以在不放緩流量的情況下，用風車把水降到你想要的程度。

you extract kinetic energy from the *motion* of  the wind, which causes the wind to slow down.

你從風的*運動中提取動能，使風減速。

So how much wind should a windmill mill?

那麼，風車磨應該有多大的風力呢？

Well, the maximum possible amount  of energy you can extract from the  

好吧，你可以提取的最大可能的能量，從你可以提取的

wind is simply the difference between  its initial and final kinetic energy.  

風只是其初始動能和最終動能的差值。

Kinetic energy depends on speed squared,  so if the outgoing wind speed is, say,  

動能取決於速度的平方，所以如果出風速度是，比如。

half of the incoming speed, then the final wind  energy will be a quarter of the initial energy,  

入速度的一半，那麼最終的風能將是初始能量的四分之一。

meaning that three quarters of the energy of the  wind was extracted when it passed the windmill.

意思是說，當風經過風車時，風的四分之三的能量被提取出來。

But then there's the question of how much  of the wind you can actually extract energy  

但還有一個問題，就是你到底能從風中提取多少能量？

from. It turns out that the speed of the  wind at a windmill is halfway between the  

從。原來，風車的風速在一半的時候。

incoming and outgoing wind speeds. So for a  final wind speed of half the incoming speed,  

進風速和出風速。所以對於最終風速為進風速度的一半。

the speed at the windmill will be  three fourths the incoming speed,  

風車的速度將是進風速度的四分之三。

which means only three fourths as much wind  can actually pass the windmill every second.

這意味著每秒鐘只有四分之三的風能真正通過風車。

Combining these two facts means that a  windmill that slows the wind to half its  

將這兩個事實結合起來，意味著一個風車如果將風速減慢到一半，那麼它就會被稱為 "風車"。

initial speed allows three fourths as much  wind to pass and extracts three fourths of  

初始速度允許四分之三的風通過，並提取四分之三的風量。

the energy from that wind, for a total efficiency  of three fourths times three fourths, or 56.25%.

該風的能量，總效率為四分之三乘以四分之三，即56.25%。

Doing the same math for other  possible wind speed reductions,  

對其他可能的風速降低做同樣的計算。

you find that the most efficient windmill possible  slows the wind to a third of its incoming speed.  

你會發現，最有效的風車可能會將風速減慢到其進風速度的三分之一。

Reducing to 1/3 speed achieves a kinetic energy  "efficiency" of v^2-(v/3)^2 equals 88.88% of  

減速到1/3的速度，實現動能 "效率 "v^2-(v/3)^2等於88.88%。

the energy of wind passing the windmill  is extracted. And reducing the wind to  

風經過風車的能量被提取出來。並將風減少到

1/3 speed after the windmill means the wind  passing the windmill is going at 2/3 speed,  

風車後的1/3速度意味著風經過風車的速度是2/3。

so 2/3 as much wind passes through the  windmill. And 88.88% energy extraction  

所以2/3的風通過風車。而88.88%的能量提取

from 2/3 of the wind results in an overall  efficiency of 88.88*2/3 = 59.259 percent.

從2/3的風力中，得出整體效率為88.88*2/3=59.259%。

A windmill that slows the wind down  below 1/3 speed will get a higher  

風車如果將風速降低到1/3以下，將獲得更高的風速。

percentage of the energy but from even less wind,  

能源的百分比，但來自更少的風。

for a lower overall efficiency. And a windmill  that slows the wind down less will get a lower  

以獲得較低的整體效率。而風車的風速減慢，則會得到較低的。

percentage of the energy from somewhat more  wind, again for a lower overall efficiency.

的百分比，同樣是為了降低整體效率。

So how much wind should a windmill mill? 2/3 of  it, for 59% efficiency in extracting the energy.

那麼風車磨的風量應該是多少呢？2/3，提取能量的效率為59%。

Obviously, real world windmills are  far more complicated and have way  

顯然，現實世界中的風車要複雜得多，而且有很多方法可以讓風車更容易地運行。

more engineering considerations, so  the 59% number may not apply exactly.

更多的工程考慮，所以59%這個數字可能並不完全適用。

Ok, Henry here, I've put a bonus video  on Nebula that covers some details I had  

好的，亨利，我在星雲上放了一個額外的視頻，涵蓋了我的一些細節。

to leave out of the main video. Nebula is the  Streamy-award-nominated independent streaming  

要離開主視頻。星雲是獲得Streamy獎提名的獨立流媒體。

service that's the co-sponsor of this video,  built by and for a collection of educational video  

服務，是這個視頻的聯合發起者，由和為收集教育視頻建

creators including Real Engineering, Mike Boyd,  Up and Atom, Jordan Harrod - and me. And Nebula  

包括Real Engineering、Mike Boyd、Up and Atom、Jordan Harrod以及我在內的創作者。還有星雲

has partnered with CuriosityStream, which offers  thousands of documentaries and nonfiction titles,  

已與提供數千部紀錄片和非小說作品的CuriosityStream合作。

to give you access to both platforms in one go...  for just a few dollars a month! I really enjoyed  

讓你一次性訪問這兩個平臺...每月只需幾美元!我真的很喜歡

watching the European Inventor Award episode about  Henrik Stiesdal, who has been intimately involved  

觀看歐洲發明家獎關於亨利克-斯蒂斯達爾（Henrik Stiesdal）的一集，他一直在密切參與歐洲發明家獎的評選。

in the invention and development of modern wind  turbines, building the first offshore wind farm,  

在現代風力發電機的發明和發展中，建立了第一個海上風電場。

and more. Sign up for CuriosityStream using the  link in the description and you'll also get access  

以及更多。使用描述中的鏈接註冊 CuriosityStream，您還可以訪問

to Nebula, including the bonus video that goes  with this one, as well as an ad-free viewing  

到星雲，包括與之配套的獎勵視頻，以及無廣告觀看的

experience across the site. And you'll also get  26% off an annual subscription to CuriosityStream.

整個網站的體驗。而且你還可以享受到26%的優惠，訂閱CuriosityStream的年費。