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?

[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.

[paulcole]

> People would have to become politically astute enough not to fall for stupid Trumpian divisive tactics.

Not insulting them would be a good place to start.