How do solar panels work? - Richard Komp

翻译人员: Elvis Liu 校对人员: Tom Liu

The Earth intercepts a lot of solar power:

地球接收了很多太阳能：

173 thousand terawatts.

173000太瓦。

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

这一数字是地球上人类 所使用能源总和的一万倍。

So is it possible that one day

那么有没有可能有一天

the world could be completely reliant on solar energy?

我们的世界会完全依赖太阳能？

To answer that question,

为了回答这一问题，

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

首先我们需要明白太阳能板 是怎样将太阳能转化为电能的。

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

太阳能板由更小的单位构成， 称为太阳能电池。

The most common solar cells are made from silicon,

最常见的太阳能电池原料是硅。

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

硅是一种半导体， 也是地球上储量第二的物质。

In a solar cell,

在一个太阳能电池单元里，

crystalline silicon is sandwiched between conductive layers.

晶体硅像是三明治夹心一样 被夹在两个导电层之间。

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

每个硅原子通过四个强键 和其他硅原子连接，

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

能够固定电子， 因此不会产生电流。

Here's the key:

工作原理如下：

a silicon solar cell uses two different layers of silicon.

一个硅太阳能电池 有着两个不同的硅层。

An n-type silicon has extra electrons,

包括一层有着额外电子的n型硅层，

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

和拥有能存储额外电子的空隙的 p型硅层。

Where the two types of silicon meet,

在两种硅层交界处

electrons can wander across the p/n junction,

电子可以在p-n的连接处移动，

leaving a positive charge on one side

在一个硅层上产生正电荷，

and creating negative charge on the other.

在另一个硅层上产生负电荷。

You can think of light as the flow of tiny particles

你可以把光线想象成从太阳发射出的

called photons,

由微小的

shooting out from the Sun.

光子构成的粒子束。

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

当其中一些光子带着足够的能量 撞击太阳能电池时，

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

它可以将一个电子撞离束缚它的强键， 形成空隙。

The negatively charged electron and location of the positively charged hole

带有负电荷的电子 和带有正电荷的空隙

are now free to move around.

现在可以自由移动了。

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

但是由于p型和n型硅层 交界处存在电场，

they'll only go one way.

它们只会向一个方向移动。

The electron is drawn to the n-side,

电子被吸引至n型硅层处，

while the hole is drawn to the p-side.

空隙则跑到p型硅层处。

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

这些自由电子被太阳能电池 顶部的细小金属导体收集。

From there, they flow through an external circuit,

从那里开始，它们留过一个外部电路，

doing electrical work,

以电流的形式做功，

like powering a lightbulb,

比如点亮一盏电灯，

before returning through the conductive aluminum sheet on the back.

然后从背面的铝制 导体薄片返回。

Each silicon cell only puts out half a volt,

每个硅太阳能电池只能产生 半伏特的电压，

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

但你可以将它们组装成模块 来获得更多的能量。

Twelve photovoltaic cells are enough to charge a cellphone,

十二个光电太阳能电池 可以为手机充电，

while it takes many modules to power an entire house.

但是为一个房间提供电能 需要许多太阳能板。

Electrons are the only moving parts in a solar cell,

电子是太阳能电池中 唯一的移动单元，

and they all go back where they came from.

而且它们工作后会沿原路返回。

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

没有组件会遭受磨损和损伤，

so solar cells can last for decades.

因此太阳能电池可以使用几十年。

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

那么是什么限制了我们 完全依赖太阳能提供能源呢？

There are political factors at play,

这里有着政治因素在起作用，

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

更不要说商人为了维持利润现状 而四处游说（反对使用太阳能）。

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

但现在，我们只研究物理和 后勤方面的障碍，

and the most obvious of those

其中最主要的原因是

is that solar energy is unevenly distributed across the planet.

太阳能不是均匀地分布在 这颗星球上的。

Some areas are sunnier than others.

其中一些地区比其他地区更晴朗。

It's also inconsistent.

而且阳光也不是持续性的。

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

在多云天气或是晚上 太阳能供给量就会下降。

So a total reliance would require

所以对太阳能的完全依赖

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

需要依赖从晴朗地区将电能转移 到多云地区的快捷方法，

and effective storage of energy.

以及有效的能量储蓄技术。

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

太阳能电池本身的效率 也是一大障碍。

If sunlight is reflected instead of absorbed,

如果阳光被反射而不是被吸收，

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

或是失去束缚的电子在进入电路前 掉进了空隙中，

that photon's energy is lost.

这时光子的能量就损失掉了。

The most efficient solar cell yet

迄今为止最高效的太阳能电池

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

也只能将阳光能量的46% 转化为电能，

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

而目前大多数商业化的太阳能系统 只有15-20%的转化效率。

In spite of these limitations,

即使面临着这些障碍，

it actually would be possible

使用现如今的太阳能技术

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

为全世界提供能量依然是可行的。

We'd need the funding to build the infrastructure

我们只需要制造设施的资金

and a good deal of space.

和足够的空间。

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

估计需要几万 至几十万平方英里的土地，

which seems like a lot,

这看起来很多，

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

但光是撒哈拉沙漠 就有三百万平方英里的土地。

Meanwhile, solar cells are getting better, cheaper,

与此同时，太阳能电池正 变得越来越高效，经济，

and are competing with electricity from the grid.

而且正和输电网进行竞争。

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

像水上太阳能农场之类的创新设计 可能会完全改变当今的（能源）格局。

Thought experiments aside,

这不是异想天开，

there's the fact that over a billion people

事实上超过十亿民众

don't have access to a reliable electric grid,

还没有可靠的输电网供给，

especially in developing countries,

尤其是在发展中国家，

many of which are sunny.

其中许多国家阳光很充足。

So in places like that,

因此在这些地方，

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

太阳能比起煤油等其它能源来说已经

like kerosene.

十分经济和安全了。

For say, Finland or Seattle, though,

但至于芬兰和西雅图 （这些阴雨连绵的地方），

effective solar energy may still be a little way off.

有效的太阳能应用 可能还有很长的路要走。