
Ask HN: How will the world change because of fusion energy? - tsuberim
The internet made the cost of information zero. Fusion promises to make the cost of energy production negligible. What do you think is currently impractical due to high energy usage that is going to be enabled by the advent of fusion energy?
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PaulHoule
Physics seems to require that a practical fusion reactor be very large.
Complex technology is involved, it is hard to believe it is going to beat
solar, hydrocarbons, fission, geothermal. etc. in economics. The problem is
like that with fission -- uranium and uranium processing, and even plutonium
processing are not expensive, but the reactor is.

For a Deuterium-Tritium cycle, half of the fuel will be in the form of Lithium
because you will breed Tritium from it in the reactor blanket. Lithium is a
relatively rare element in the universe because it gets burned up in stars.
It's not clear that the Lithium resource is bigger than the Uranium-in-
seawater resource or the terrestrial Thorium resource.

Another issue is thermal dissipation. It is already challenging to get rid of
2-3 GW worth of heat from a nuclear power plant. You could dissipate that heat
by evaporating a modest amount of water, but that water could then condense
and cause dangerous fog and icing on nearby roads, for instance.

If fusion plants are scaled much bigger, say 50 GW thermal, getting rid of the
heat is more difficult (most practically it could be disposed of in the
ocean.) The plants have to be cited further away from cities, power has to be
sent further, all that adds to the cost.

It would be beautiful if fusion could support human life beyond the "frost
line" where small bodies are rich with volatiles such as water, ammonia,
carbon monoxide, etc. Imaginably you could cut up something like Pluto into
small ringworlds that provide more living area than the Earth.

At some distance solar energy gets weak but a practical fusion cycle (possibly
D-D based) might make it possible to hop to the nearest star from comet to
comet over a time scale of 20,000 years or so.

The trouble is that people used to the Oort Cloud lifestyle probably won't be
too interested in stars if they've managed to live that way for 20,000 years.

~~~
tsuberim
So you think fusion reactors will be too expansive and hard to extract energy
from to be economically competitive with coal? Then why are people investing
huge amounts of money in it?

~~~
PaulHoule
"Beating coal" is not the goal because we can't burn enough coal to increase
human energy consumption without sinking our coastal real estate.

What you have to beat is both current-day sources of carbon neutral energy and
also emerging sources. For instance if you drill a hole down a few miles into
bedrock you might be able to withdraw heat for a century or more, possible
advanced nuclear fuel cycles involving plutonium and thorium, space solar
energy, etc.

Much research in fusion energy is driven by national security or pride
interests. For instance the laser fusion facilities run by the US let the US
develop nuclear weapons without nuclear testing. Projects like ITER are
cultural "stretch goals" like the International Space Station; a lot of risk
is involved but maybe there is a reward in 20+ years. Some people have always
thought they could make an end run to a fusion reactor but so far it has not
panned out. That doesn't mean it won't for somebody.

------
hluska
I live in a Canadian province that is blessed with many sources of renewable
energy. We have enough potential hydro in the north to power much of Canada,
and extremely favourable conditions for solar and wind energy. Despite all of
these benefits, our power is still almost wholly generated by coal fired power
plants (and our ruling party predictably opposes any attempts at a carbon
tax).

Because of that, I believe that if fusion were to become viable, at least in
my part of the world, it would have to start with a serious shift in
worldview. People would have to become politically astute enough not to fall
for stupid Trumpian divisive tactics. And, we would have to adopt a stance in
which the far future is as important as our present.

I really wonder what kind of advancements a species like that would want to
make. My suspicion is that a species like that would invest much of the
savings into completely eliminating the very concept of poverty.

I know that eliminating poverty isn't a terribly sexy answer, but I think it's
the most likely big change.

~~~
Someone
_If_, as stipulated, fusion energy will become as good as free, people will
switch away from coal not because of the environment, but because it’s
cheaper. That doesn’t require a shift in world view.

On the other hand, we would really need that shift in world view. Without it,
global warming would be avoided, but I fear we would destroy the world even
faster than we do now.

Free energy makes anything produced automatically free. That means we could
afford more disposable junk, more and bigger houses, more and bigger cars,
likely even flying ones, with many flying supersonic.

Increased mobility would mean less pristine wilderness (if energy is free, any
group of people could afford to do a mini burning man anywhere in the States)

Also, we would also scrape the ocean floor for minerals, destroying the ocean.

Finally, I am more cynical w.r.t. poverty. We already could have solved it,
but didn’t. Why would that change?

~~~
hluska
In my province's system, you would still need political will to build a fusion
plant. That would require some serious political will, since it would
dramatically change a very wealthy/highly conservative city's economy. That
type of political will would tend to come out of a longer term, more global
point of view.

