The Earth intercepts a lot of solar power.
地球截获了大量的太阳能。
01 / READ
Transcript
173,000 terowatt.
173,000太瓦。
That's 10,000 times more power than the planet's population uses.
这比全球人口使用的能量多出10,000倍。
So, is it possible that one day the world could be completely reliant on solar energy?
那么，世界有一天完全依赖太阳能吗？
To answer that question, we first need to examine how solar panels convert solar energy to electrical energy.
要回答这个问题，我们首先需要研究太阳能电池是如何将太阳能转换为电能的。
Solar panels are made up of smaller units called solar cells.
太阳能电池板由称为太阳能电池的小单元构成。
The most common solar cells are made from silicon, a semiconductor that is the second most abundant element on Earth.
最常见的太阳能电池是由硅制成的，硅是一种半导体，是地球上第二丰富的元素。
In a solar cell, crystallin silicon is sandwiched between conductive layers.
在太阳能电池中，结晶硅夹在导电层之间。
Each silicon atom is connected to its neighbors by four strong bonds which keep the electrons in place so no current can flow.
每个硅原子通过四个强键与其邻居相连，这使电子保持在位，因此电流不能流动。
Here's the key.
这是关键。
A silicon solar cell uses two different layers of silicon.
硅太阳能电池使用两种不同层的硅。
An N type silicon has extra electrons and ptype silicon has extra spaces for electrons called holes.
N型硅有额外的电子，而P型硅则有称为孔的电子空位。
where the two types of silicon meet, electrons can wander across the PN junction, leaving a positive charge on one side and creating negative charge on the other.
在这两种硅相遇的地方，电子可以穿越PN结，导致一侧带正电，并在另一侧产生负电。
You can think of light as the flow of tiny particles called photons shooting out from the sun.
你可以把光看作是从太阳发射出的微小粒子，称为光子。
When one of these photons strikes the silicon cell with enough energy, it can knock an electron from its bond, leaving a hole.
当这些光子用足够的能量撞击硅电池时，它可以从其键中击出一个电子，留下一个孔。
The negatively charged electron and location of the positively charged hole are now free to move around.
带负电的电子和带正电的孔的位置现在可以自由移动。
But because of the electric field at the PN junction, they'll only go one way.
但是由于PN结的电场，它们只会朝一个方向移动。
The electron is drawn to the N side while the hole is drawn to the P side.
电子被吸引到N侧，而孔则被吸引到P侧。
The mobile electrons are collected by thin metal fingers at the top of the cell.
活动的电子被收集在电池顶部的细金属指上。
From there, they flow through an external circuit, doing electrical work like powering a light bulb before returning through the conductive aluminum sheet on the back.
然后，它们通过外部电路流动，进行电力工作，比如为灯泡供电，然后通过后面的导电铝片返回。
Each silicon cell only puts out half a volt, but you can string them together in modules to get more power.
每个硅电池只能输出半伏特，但你可以将它们串联在模块中以获得更多的电力。
12 photovalttaic cells are enough to charge a cell phone, while it takes many modules to power an entire house.
12个光伏电池就足够为手机充电，而为整个房屋供电需要许多模块。
Electrons are the only moving parts in a solar cell, and they all go back where they came from.
电子是太阳能电池中唯一的活动部件，它们都会回到它们来的地方。
There's nothing to get worn out or used up, so solar cells can last for decades.
没有任何东西会磨损或耗尽，因此太阳能电池可以持续数十年。
So, what's stopping us from being completely reliant on solar power?
那么，是什么阻止我们完全依赖太阳能？
There are political factors at play, not to mention businesses that lobby to maintain the status quo.
有政治因素在起作用，更不用说一些游说维持现状的企业。
But for now, let's focus on the physical and logistical challenges.
但现在，我们来集中讨论物理和后勤挑战。
And the most obvious of those is that solar energy is unevenly distributed across the planet.
其中最明显的问题是，太阳能在地球上的分布不均匀。
Some areas are sunnier than others.
某些地区比其他地区更阳光明媚。
It's also inconsistent.
它也是不稳定的。
Less solar energy is available on cloudy days or at night.
在阴天或晚上，可用的太阳能较少。
So, a total reliance would require efficient ways to get electricity from sunny spots to cloudy ones and effective storage of energy.
因此，完全依赖太阳能将需要有效的方式将电力从阳光明媚的地方输送到多云的地方，并有效储存能量。
The efficiency of the cell itself is a challenge too.
电池本身的效率也是一个挑战。
If sunlight is reflected instead of absorbed, or if dislodged electrons fall back into a hole before going through the circuit, that photon's energy is lost.
如果阳光被反射而不是被吸收，或者如果被取出的电子在通过电路之前掉回了一个孔，那么那个光子的能量就会损失。
The most efficient solar cell yet still only converts 46 % of the available sunlight to electricity,
迄今为止，最有效的太阳电池仍然只能将46%的可用阳光转化为电能，
and most commercial systems are currently 15 to 20 % efficient.
而大多数商业系统目前的效率为15%到20%。
In spite of these limitations, it actually would be possible to power the entire world with today's solar technology.
尽管存在这些限制，实际上用今天的太阳能技术为整个世界供电是可能的。
We'd need the funding to build the infrastructure and a good deal of space.
我们需要资金来建设基础设施和相当大的空间。
Estimates range from tens to hundreds of thousands of square miles, which seems like a lot, but the Sahara Desert alone is over 3 million square miles in area.
估计范围从数万到数十万平方英里，这似乎很多，但仅撒哈拉沙漠的面积就超过300万平方英里。
Meanwhile, solar cells are getting better, cheaper, and are competing with electricity from the grid.
与此同时，太阳能电池在性能、价格上都有所提高，并正在与电网电力竞争。
and innovations like floating solar farms may change the landscape entirely.
像漂浮太阳能农场这样的创新可能完全改变景观。
Thought experiments aside, there's the fact that over a billion people don't have access to a reliable electric grid,
抛开思想实验不谈，事实上超过十亿人无法获得可靠的电网，
especially in developing countries, many of which are sunny.
特别是在许多阳光充足的发展中国家。
So in places like that, solar energy is already much cheaper and safer than available alternatives like kerosene.
所以在这样的地方，太阳能已经比可用的替代品如煤油要便宜和安全得多。
For say Finland or Seattle though, effective solar energy may still be a little way off.
然而，对于芬兰或西雅图来说，有效的太阳能可能仍然还有一段距离。
02 / UNDERSTAND
A closer look
IN THIS CONTEXT ·0:08
The Earth intercepts a lot of solar power.
地球截获了大量的太阳能。
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