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The fundamental currency of our Universe is energy.
It lights our homes,
grows our food,
powers our computers.
We can get it lots of ways:
burning fossil fuels,
splitting atoms
or sunlight striking photovoltaics.
But there's a downside to everything.
Fossil fuels are extremely toxic,
nuclear waste is... well, nuclear waste,
and there are not enough batteries to store sunlight for cloudy days yet.
And yet, the Sun seems to have virtually limitless, free energy.
Is there a way we could build a sun on Earth?
Can we bottle a star?
The Sun shines beacuse of nuclear fusion.
In a nutshell - fusion is a thermonuclear process,
meaning that the ingredients have to be incredibly hot, so hot,
that the atoms are stripped of their electrons,
making a plasma where nuclei and electrons
bounce around freely.
Since nuclei are all positively charged, they repell each other.
In order to overcome this repulsion
the particles have to be going very, very fast.
In this context, very fast means very hot:
millions of degrees.
Stars cheat to reach these temperatures.
They are so massive, that the pressure in their cores
generates the heat to squeeze the nuclei together
until they merge and fuse,
creating heavier nuclei and releasing energy in the process.
It is this energy release
that scientists hope to harness
in a new generation of power plant:
the fusion reactor.
On Earth, it's not feasible to use this brute-force method
to create fusion.
So if we want to build a reactor that generates energy from fusion,
we have to get clever.
To date, scientists have invented two ways of making plasmas
hot enough to fuse:
The first type of reactor uses a magnetic field
to squeeze a plasma in a donut-shaped chamber
where the reactions take place.
These magnetic confinement reactors, such as the ITER reactor in France,
use superconducting electromagnets cooled with liquid helium
to within a few degrees of absolute zero.
Meaning they host some of the biggest temperature gradients in the known Universe.
The second type, called inertial confinement,
uses pulses from superpowered lasers
to heat the surface of a pellet of fuel,
imploding it,
briefly making the fuel hot and dense enough to fuse.
In fact,
one of the most powerful lasers in the world
is used for fusion experiments
at the National Ignition Facility in the US.
These experiments and others like them around the world
are today just experiments.
Scientists are still developing the technology.
And although they can achieve fusion,
right now, it costs more energy to do the experiment
than they produce in fusion.
The technology has a long way to go
before it's commercially viable.
And maybe it never will be.
It might just be impossible to make a viable fusion reactor on Earth.
But, if it gets there it will be so efficient,
that a single glass of sea water
could be used to produce as much energy as burning a barrel of oil,
with no waste to speak of.
This is because fusion reactors would use hydrogen or helium as fuel,
and sea water is loaded with hydrogen.
But not just any hydrogen will do:
specific isotopes with extra neutrons, called deuterium and tritium,
are needed to make the right reactions.
Deuterium is stable and can be found in abundance in sea water,
though, tritium is a bit trickier.
It's radioactive and there may only be twenty kilograms
of it in the world, mostly in nuclear warheads
which makes it incredibly expensive.
So, we may need another fusion body for deuterium instead of tritium.
Helium-3, an isotope of helium, might be a great substitute.
Unfortunately,
it's also incedibly rare on Earth.
But here the Moon might have the answer.
Over billions of years,
the solar wind may have built up huge deposits
of helium-3 on the moon.
Instead of making helium-3, we can mine it.
If we can sift the lunar dust for helium,
we'd have enough fuel to power the entire world
for thousands of years.
One more argument for establishing a moon base,
if you weren't convinced already.
Okay, maybe you think building a mini sun
still sounds kind of dangerous.
But they'd actually be much safer than most other types of power plant.
A fusion reactor is not like a nuclear plant
which can melt down catastrophically.
If the confinement failed,
then the plasma would expand and cool and the reaction would stop.
Put simply, it's not a bomb.
The release of radioactive fuel like tritium
could pose a threat to the environment.
Tritium could bond with oxygen, making radioactive water
which could be dangerous as it seeps into the environment.
Fortunately, there's no more than a few grams of tritium
in use at a given time,
so a leak would be quickly diluted.
So we've just told you
that there's nearly unlimited energy to be had,
at no expense to the environment
in something as simple as water.
So, what's the catch?
Cost.
We simply don't know if fusion power will ever be commercially viable.
Even if they work, they might be too expensive to ever build.
The main drawback is that it's unproven technology.
It's a ten billion dollar gamble.
And that money might be better spent on other clean energy
that's already proven itself.
Maybe we should cut our losses.
Or maybe,
when the payoff is unlimited, clean energy for everyone,
it might be worth a risk?
Subtitles by the Amara.org community
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核聚變,解構未來或是失敗? (Fusion Power Explained Future or Failure)

618 分類 收藏
valkyrja 發佈於 2017 年 3 月 26 日
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