How do solar panels work? - Richard Komp

譯者: Ann Chen 審譯者: Max Chern

The Earth intercepts a lot of solar power:

地球截獲很多太陽能：

173 thousand terawatts.

173000 兆瓦 （10 的 12 次方瓦）

That's ten thousand times more power than the planet's population uses.

比地球全人類的用電量多一萬倍

So is it possible that one day

所以是否可能有一天

the world could be completely reliant on solar energy?

全世界會完全依賴太陽能呢？

To answer that question,

要回答這問題

we first need to examine how solar panels convert solar energy to electrical energy.

我們需要先來研究太陽能板 如何將太陽能轉為電能

Solar panels are made up of smaller units called solar cells.

太陽能板是由許多 所謂「太陽能電池」小單位所組成

The most common solar cells are made from silicon,

最常用的太陽能電池是用「矽」所做成

a semiconductor that is the second most abundant element on Earth.

它是一種半導體， 是地球第二豐富的元素

In a solar cell,

太陽能電池裡面

crystalline silicon is sandwiched between conductive layers.

結晶矽被夾在兩個導電層中間

Each silicon atom is connected to its neighbors by four strong bonds,

每個矽原子以四個強鍵 與周圍原子連接

which keep the electrons in place so no current can flow.

固定住電子，因而沒有電流流動

Here's the key:

關鍵就在這裡：

a silicon solar cell uses two different layers of silicon.

矽基太陽能電池採用兩層不同的矽

An n-type silicon has extra electrons,

n 型矽層有多餘的電子

and p-type silicon has extra spaces for electrons, called holes.

p 型矽層有多餘的空位 可接納電子，稱為「電洞」

Where the two types of silicon meet,

在不同兩層矽的會合處

electrons can wander across the p/n junction,

電子可流過「p/n 接面」

leaving a positive charge on one side

導致一邊形成正電荷

and creating negative charge on the other.

而另一邊則形成負電荷

You can think of light as the flow of tiny particles

你可把光想成是極細粒子的流動

called photons,

稱為「光子」

shooting out from the Sun.

從太陽發射出來

When one of these photons strikes the silicon cell with enough energy,

當其中一個具有足夠能量的光子 撞擊到太陽能電池

it can knock an electron from its bond, leaving a hole.

它可從結合鍵中撞出一個電子， 而留下一個電洞

The negatively charged electron and location of the positively charged hole

帶負電的電子及 帶正電的電洞位置

are now free to move around.

現在可以四處自由移動了

But because of the electric field at the p/n junction,

但由於在 p/n 接面的電場

they'll only go one way.

使得它們只能走單一方向

The electron is drawn to the n-side,

電子被吸往 n 型區

while the hole is drawn to the p-side.

而電洞則往 p 型區移動

The mobile electrons are collected by thin metal fingers at the top of the cell.

可移動的電子被收集到 電池頂層的一個薄金屬橋廊

From there, they flow through an external circuit,

由此，再流經一個外電路

doing electrical work,

做了電的功

like powering a lightbulb,

如：提供燈泡電力

before returning through the conductive aluminum sheet on the back.

再經電池底層的導電鋁片， 回到 p 型區

Each silicon cell only puts out half a volt,

每個矽基電池只能製造 1/2 伏特

but you can string them together in modules to get more power.

但你可將它們串成模組（太陽能板） 得到更多電力

Twelve photovoltaic cells are enough to charge a cellphone,

12 個光伏電池（太陽能電池） 就可讓一支手機充電

while it takes many modules to power an entire house.

而需要許多太陽能板 才足夠供電給一整棟房屋

Electrons are the only moving parts in a solar cell,

電子是太陽能電池 唯一可活動的部份

and they all go back where they came from.

它們都會回到原來的出發點

There's nothing to get worn out or used up,

不會被耗損掉或被用完

so solar cells can last for decades.

因此太陽能電池可持續使用數十年

So what's stopping us from being completely reliant on solar power?

那麼是什麼原因使我們不能 完全依賴太陽能發電呢？

There are political factors at play,

有許多是政治因素影響

not to mention businesses that lobby to maintain the status quo.

更別提商業界遊說大眾維持現狀

But for now, let's focus on the physical and logistical challenges,

不過現在，讓我們專注在 物理及邏輯的挑戰

and the most obvious of those

這其中最明顯的

is that solar energy is unevenly distributed across the planet.

就是太陽能並非平均地遍佈全球

Some areas are sunnier than others.

有些地區比其他地區陽光充足

It's also inconsistent.

但它也常反覆多變

Less solar energy is available on cloudy days or at night.

陰天或晚上時，可用的太陽能就較少

So a total reliance would require

所以要完全依賴太陽能

efficient ways to get electricity from sunny spots to cloudy ones,

需要有效的方法 將電從陽光充足區送到多雲區

and effective storage of energy.

以及電力有效的儲存

The efficiency of the cell itself is a challenge, too.

電池本身的效率也是一項挑戰

If sunlight is reflected instead of absorbed,

如果陽光是被反射出去 而不是被吸收進來

or if dislodged electrons fall back into a hole before going through the circuit,

或被撞出的電子在流入電路前 就落回電洞

that photon's energy is lost.

那麼光能也就流失了

The most efficient solar cell yet

現在最有效率的太陽能電池

still only converts 46% of the available sunlight to electricity,

也僅能將可用日光的 46% 轉為電

and most commercial systems are currently 15-20% efficient.

多數商用裝置現在的效率是 15-20%

In spite of these limitations,

僅管有這些限制

it actually would be possible

其實是有可能

to power the entire world with today's solar technology.

以現在太陽能的技術 供電給全球

We'd need the funding to build the infrastructure

我們需要經費來建立基本設施

and a good deal of space.

還需要許多空間

Estimates range from tens to hundreds of thousands of square miles,

估計約要數萬到數十萬平方英里

which seems like a lot,

聽起來好像很多

but the Sahara Desert alone is over 3 million square miles in area.

但光撒哈拉沙漠的面積 就已超過三百萬平方英里了

Meanwhile, solar cells are getting better, cheaper,

同時，太陽能電池愈來愈好，也愈價宜

and are competing with electricity from the grid.

足以和需要高壓輸電網的電力競爭

And innovations, like floating solar farms, may change the landscape entirely.

許多創新 ─例如漂浮式太陽能場─ 能使景象完全改變

Thought experiments aside,

先別想這是否可行

there's the fact that over a billion people

事實上超過十億的人

don't have access to a reliable electric grid,

沒有穩定的電力網可使用

especially in developing countries,

尤其是開發中國家

many of which are sunny.

而它們許多是陽光充足的

So in places like that,

所以在這些地區

solar energy is already much cheaper and safer than available alternatives,

太陽能要比其他可用的方式 便宜和安全許多（例如煤油）

like kerosene.

For say, Finland or Seattle, though,

可是，就例如芬蘭或西雅圖

effective solar energy may still be a little way off.

有效的太陽能可能 還是一段遙遠的距離

翻譯：Ann Chen