In some ways the answer just boils down to  “climate change” - we need way more renewable  

在某些方面，答案只是歸結為 "氣候變化"--我們需要更多的可再生能源。

energy, so it makes sense that lots and lots  of engineering and economic resources have  

能源，所以，大量大量的工程和經濟資源都在情理之中。

gone into improving and enlarging windmills. But  while “climate change” can explain why windmills  

了改進和擴大風車。但是，雖然 "氣候變化 "可以解釋為什麼風車

have pushed towards really good design, it  doesn't explain what makes a design good.

已經推動了真正的好設計，它並沒有解釋什麼是好設計。

I see three main features to explain: the size,  the number of blades, and the shape of the blades.

我看主要有三個特點來解釋：葉片的大小、葉片的數量、葉片的形狀。

Size is easiest: the bigger the area , the more  wind you can use, and therefore the more wind  

尺寸最簡單：面積越大，可以使用的風量越大，是以風量也越大。

energy you can capture . Plus, the higher up you  go, the less the wind itself is impeded by stuff  

你可以捕捉到的能量 。另外，你越往上走，風本身受到的阻礙就越小。

on the ground, the faster it blows, and therefore  the more wind energy you can capture . So for a  

地面上的風速越快，吹得越快，是以你能捕捉到的風能就越多。所以對於一個

windmill to have access to air with a lot  of energy , it should be giant and tall.

風車要能接觸到空氣，獲得大量的能量，它應該是巨大而高大的。

However, a paradox of windmills is that they need  to capture energy from the wind while also letting  

然而，風車的一個悖論是，它們需要從風中獲取能量，同時也讓

the wind past. If you extracted 100% of the  kinetic energy from the wind, it would stop moving  

風過去。如果你從風中提取100%的動能，它就會停止移動。

and there'd be nowhere for incoming wind to go.  So you have to let some wind through - calculation  

這樣一來，進風就無處可去了。 所以你必須讓一些風通過--計算。

shows that a mathematically ideal windmill can  only extract 59% of the wind's kinetic energy .

顯示，一個數學上理想的風車只能提取59%的風的動能 。

Since windmills can't block the wind  too much, they're faced with a tradeoff:  

由於風車不能太過擋風，所以面臨著取捨。

either have fast-moving blades that cover a small  amount of area, or slow-moving blades that cover  

要麼有快速移動的葉片，覆蓋少量的區域，要麼有緩慢移動的葉片，覆蓋

a large amount of area. This is because, just as  an airplane wing produces more lift the faster the  

大面積。這是因為，就像飛機機翼產生更多的升力一樣，速度越快，升力越大。

plane is moving, a windmill blade “catches” more  of the wind the faster it's moving - so roughly  

飛機在移動，風車葉片在移動速度越快的情況下，就會 "捕捉 "到更多的風--是以，大致上來說

speaking, a fast-moving windmill, like modern  ones, needs correspondingly fewer, thinner blades  

說起來，像現代的風車一樣，快速移動的風車需要相應的更少、更薄的葉片。

in order to not slow the wind too much, while a  slow-moving windmill can have more, wider blades.

以免風速太慢，而慢速的風車可以有更多、更寬的葉片。

Obviously, modern windmills have gone with  the narrow, fast approach. So why modern  

很顯然，現代風車走的是窄而快的路子。那麼，為什麼現代

windmills are designed to spin more quickly than  old windmills - I mean, if slower were better,  

風車的設計是為了比老式風車轉得更快--我是說，如果慢一點更好。

there would be no reason modern windmills  couldn't look like giant high-tech sails!

現代的風車沒有理由不像巨大的高科技風帆!

The answer comes from Newton's third law: just as  the wind pushes the blades sideways to turn them,  

答案來自牛頓第三定律：就像風把葉片推到側面去轉動一樣。

so the blades push back on the wind,  giving the air a reverse twist,  

所以葉片對風的推力，使空氣產生反向扭曲。

and hence some rotational kinetic energy -  which is energy the windmill doesn't capture.  

從而獲得一些旋轉動能--這是風車沒有捕捉到的能量。

So the most efficient windmill will give  the wind the smallest twist possible.

所以最有效的風車會給風以最小的扭轉。

And, you guessed it, the faster a windmill blade  moves, the less rotational energy it gives to the  

而且，你猜對了，風車葉片移動的速度越快，它給風車的旋轉能量就越少。

wind. This might seem a little counter-intuitive,  but a similar thing happens when a ball falls and  

風。這似乎有點違反直覺，但類似的事情會發生，當一個球落下，並。

bounces off an angled block - if the block isn't  moving, conservation of momentum and energy mean  

從有角度的木塊上反彈--如果木塊沒有移動，動量和能量的守恆意味著......。

that the ball bounces to the left and the block  gets pushed right. But if the block starts off  

即球向左彈，擋板向右推。但如果球塊開始時

moving to the right, it's able to absorb more  of the ball's energy when it accelerates.  

向右移動，它在加速時能夠吸收更多的球的能量。

The faster the block moves, the more energy  it extracts from the ball! (You can see this  

球塊移動的速度越快，從球中提取的能量就越多！（你可以看到這一點。(你可以看到這個

because the ball moves less each time). Windmill  blades are a bit more complicated, but it's  

因為球每次移動的次數較少）。)風車葉片比較複雜，但它的

roughly the same idea - for decent efficiency, a  windmill blade should be moving through the air at  

大致相同的想法--為了達到適當的效率，風車葉片應該以以下速度在空氣中移動。

least five times faster than the incoming speed of  the wind… though obviously different parts of the  

至少是風速的五倍......雖然顯然是不同部位的風速。

windmill blade are moving at different speeds and  so the shape varies along the length of the blade.

風車葉片以不同的速度運動，所以形狀沿著葉片的長度變化。

So in summary: an ideal power-generating  windmill is big to capture a lot of wind,  

所以綜上所述：理想的發電風車是大的，可以捕捉大量的風。

tall to capture strong winds, fast-moving  to be most efficient, and narrow-bladed  

高大才能抓住強風，快速移動才能效率最高，窄刃才是王道

because a fast-moving windmill (needs  to have a smaller blade area - aka,  

因為快速移動的風車（需要有較小的葉片面積--也就是。

just a few, narrow blades) to  not slow down the wind too much.

只是幾片，狹長的葉片），以免風速太慢。

This video was created in partnership  with Bill Gates, inspired by his new book  

這段視頻是與比爾-蓋茨合作製作的，靈感來自於他的新書。

“How to Avoid a Climate Disaster.” You can find  out more about how we can all work together to  

"如何避免氣候災難"。你可以瞭解更多關於我們如何共同努力，以

avoid a climate disaster - like how we need  huge development in energy/grid storage in  

避免氣候災難--就像我們需要在能源/電網儲存方面進行大規模開發一樣。

addition to renewable energy generation -  you can find out more in the link below.

除了可再生能源發電--你可以在下面的鏈接中瞭解更多。