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Comment by f0e4c2f7 | Hacker News Reader

Ctrl+f fusion.

> "Fusion is therefore a complicated and not particularly cheap way to generate electricity. Meanwhile, we are not running terribly short on renewable ways to produce electricity: solar; wind; hydroelectric; geother- mal; tidal."

Fusion is the key to long term success for humanity. It paves the way to essentially unlimited cheap burstable power.

In the even longer term plasma fusion offers a way to create the heavier elements that we are running out of here on earth. Forged in a manmade nuclear furnace.

These pesky climate problems can be solved. We just have to mine ideas out of nature now instead of minerals.

If you're trying to think about humanity's long term prospects fusion should be the crown jewel, not an after thought you handwave away. I believe today we spend somewhere on the order of 1% of what we should be spending on fusion research.

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In the even longer term plasma fusion offers a way to create the heavier elements that we are running out of here on earth. Forged in a manmade nuclear furnace.

The only heavy element that we actually "use up" to any significant degree is uranium, which is consumed for energy, but if we had cheap fusion energy uranium consumption would plummet. Even if we could make artificial uranium it would be a net-energy-losing process to make artificial uranium with fusion power instead of using fusion power directly.

>The only heavy element that we actually "use up" to any significant degree is uranium

Helium would like a word with you.

The only heavy element. Helium is the second lightest of all elements. I didn't think that the post I responded to meant helium because it said heavy elements (plural) and it referred to the far future, after mastering fusion as an energy source.

> These pesky climate problems can be solved.

The thing is, it's not just climate that's the problem. The "pesky" problem is that we've crossed or are soon crossing most planetary boundaries[1] at the same time.

Fusion doesn't stop and reverse biodiversity loss, chemical pollutants, land-system change, biochemical flows, ocean plastic buildup and ocean acidification.

To stop the ecological collapse, the necessary condition is that the global North drastically reduces material flows and energy consumption. With less energy use, fusion also becomes less critical.

[1] https://en.m.wikipedia.org/wiki/Planetary_boundaries

disagree essentially because I believe we'd get into a situation where the problem becomes heat dissipation.

the problem is the human psique, not technological capabilities.

If we find a cheap new way to generate orders of magnitude more energy, we'll use orders of magnitude more energy.

And you're right. We're only a bit over two hundred years away at 2.3% annualized growth in energy use from noticeably raising Earth's surface temperatures just from a thermodynamic perspective. And that's completely ignoring the effects of greenhouse gases.

You and parent project this in some theoretical universe where these effects would be ignored. Why on earth do you think so? With semi-unlimited energy at our palms, we can do serious geoengineering. We can put these furnaces into high orbits, or moon and beam down just raw output energy with lasers. Or whatever, even the sky isn't a proverbial limit.

Unlimited energy doesn't free us from the consequences of thermodynamics. Geoengineering doesn't help us. Where we generate the energy doesn't change anything if it's used here on this planet.

There are literal physical limits here that can't just be handwaved away by space magic. Higher energy use in a finite spherical volume fundamentally results in increased temperatures when your only way of getting rid of that heat is radiation (and not convection or conduction). And we can't just beam that heat away with space magic either thanks to entropy.

Thermodynamics gives us no tools to deal with this problem outside of increasing the spherical volume of Earth (and therefore its surface area).

Fusion isn't magic, more energy doesn't suddenly obviate the burden of practical engineering constraints, we won't be "geoengineering" our way out of climate change for the foreseeable future.

A world where energy consumption increases by a factor of 10,000 is a far fetched fantasy. If we're starting with such premises, should they not be followed?

A world where energy consumption increases by a factor of 10,000 would already be a world where the surface is lava thanks to basic thermodynamics. Earth can only radiate so much heat into space, and its ability to do so will not outpace energy production for much longer.

A world where energy consumption increases fiftyfold is a century and a half away and would be brushing up against the point where we are noticeably increasing the equilibrium temperature of Earth sans any greenhouse gases. Hitting the thermodynamic limits of Earth's ability to radiate heat into space isn't a far-fetched fantasy, it's terrifyingly close.

This is very wrong. Humans produce about 30 TW of heat. The sun imparts 10 trillion times this amount. If we increased our production by 10,000 then we need to put a small umbrella in space to slightly dim the sun the smallest amount to maintain power balance.

Feel free to do the math yourself. You’ll forgive me for trusting in the calculations of UCSD professor of physics Tom Murphy, who’s written about this extensively.

Edit: Also, your numbers are quite simply incorrect. The 70% of sunlight that doesn’t bounce back into space is about 35,000TW, far from the hundreds of trillions of terawatts you claim. At 2.3% energy growth for the next 275 years, we’ll be adding 7,000TW to this number. That is easily enough to noticeably increase Earth’s equilibrium temperature, and far less than this will be necessary to do so given greenhouse gases which reduce our ability to radiate heat into space.

https://dothemath.ucsd.edu/2011/07/galactic-scale-energy/

Sorry the 13 trillion number was from the total power output of the sun (10^26 W).

The Earth receives 340 W / m^2 on average (not accounting for albedo) [1]. The surface area of the Earth is 510 trillion m^2. Humans release 160,000 TWh / year (18.5 TW) [2]. That means the input power from the sun is 9350x what humans release into the atmosphere. If wind and solar play a larger role in the energy mix then the picture looks even better. I can't see how humans could increase power consumption by multiple orders of magnitude without solving so many other (more difficult) problems. Even if we did, playing games with albedo and/or orbital sunshades are on the table with the comparatively meager means we have today. Any future society using that much power surely could address these issues with ease.

Also, expecting constant growth for the next 275 years isn't really a good projection of current trends. We're already seeing negative 2nd derivatives in energy production and population. There is nowhere left to expand in to. The world has become very small very fast.

1. https://earthobservatory.nasa.gov/features/EnergyBalance/pag...

2. https://www.e-education.psu.edu/egee102/node/1925

> If wind and solar play a larger role in the energy mix

The whole point of this debate was that fusion will not unleash a new era of unlimited cheap energy. My argument is that not only will it not, it can not. Will we have more energy available to us than before? Certainly. But all it will do is push us closer to fundamental thermodynamic limits of the Earth's ability to radiate excess heat into space.

Replacing 18.5TW of current power generation with 185TW (10x!) of fusion capacity will already start putting us frighteningly close to those limits. 10x on top of what we have today sounds like a lot, but nearly 90% of the global population today lives in poverty. Bringing them up to a developed-world standard of living will likely eat up well over 100% of that additional budget. Can we augment that with solar? Certainly! But this is hardly "unlimited" energy. A 10-fold increase in energy output will buy us maybe 150 more years of growth.

You may not be happy with it it, but this is the graph of Earth's equilibrium temperature given a consistent 2.3% annual increase in (non-solar) power generation:

https://dothemath.ucsd.edu/wp-content/uploads/2011/07/tmp.pn...

I encourage you to run the numbers yourself. They are correct. And this is treating the Earth as a perfect blackbody which it is not. These numbers are worse when you consider greenhouse gases, even if we manage to somehow go back to pre-industrial levels of carbon in our atmosphere.

That is an overwhelmingly good problem to have. We would have truly mastered the planet for that to be a concern. As it stands, keeping society above water for the next hundred years seems like the grand challenge to accomplish. Do not assume victory is given. Nothing is a given. We are always on the edge.

I agree. I don't think humanity is happier given more resources, above a certain relatively small amount. But humanity's desires are limitless. If we are able to invent a free energy machine we'll just use it so much that it causes new problems.

It's still sort of a gamble.

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