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Comment by sto_hristo | Hacker News Reader

Sorry. Largest power density is still in the atom. Can't work your magic around this. The only reasonable and sane strategy is to R&D around nuclear. Whoever gets it right will rule, the others will be ruled. Not single bubble kept its integrity; renewables will burst as well.

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You are right about power density,

If only we had an absolutely massive fusion reactor that could passively manage its own containment.

It would be so powerful that one such nuclear reactor would produce millions of times more power than we could ever consume.

The reactor could be designed to run indefinitely. No fuel or decommissioning costs incurred.

We could site the reactor at a large enough distance from population centers that we would not need to deal with its waste.

We could decouple the reactor from power generation. Just use safe EM radiation to freely distribute power wherever it would be needed.

The reactor itself, perhaps funded by some benevolent quadrillionaire, having no operating costs would be literally "too cheap to meter".

I see what you did there.

Read the article. The advantages of the high power density are negated by the inefficiencies of the heat cycle, construction costs etc.

Yes, it makes sense to focus some R&D on nuclear. However after seven decades, it would seem that an alternative to turbines is not so straightforward. The alternatives mentioned in the article are at least a decade (and probably much more) away from commercial use. Even then the other overheads would remain.

As with many engineering problems, an apparently decisive advantage can be overwhelmed by secondary effects.

Why are you choosing a meaningless metric to decide on the technology? Utilities or consumers don't care about energy density of fuels, they care about cost.

High energy density can in principle matter, a lot, from a societal point of view. If you only need a tiny amount of fuel to make the world's energy, then the overall impact on land, minerals, ecosystems, wildlife, etc. can potentially be very small, assuming you deliver the rest of the fuel cycle and reactors with reasonably small footprints as well. The fact that current markets don't yet value these things is more a issue with the current markets than a critique of energy density.

A sackcloth and ashes approach to civilization, where nuclear's low land use is preferred because we're also going to (for example) ban agriculture because it uses land, is a nonstarter. Society has decided that agriculture is ok, because the concerns of people are more important than the putative concerns of unfettered nature. And if agriculture is ok, so is the land use of PV and wind (which produce much more value per unit area than agriculture does.)

(A similar argument applies to materials. Compare the materials used by a renewable energy system to the materials used by industrial society as a whole.)

At global scale, these kinds of things end up mattering a huge amount. This is the basis of Komanoff's "price scales primarily with fleet size" argument. No one remembers that rule, but at planetary scale even seemingly small externalities end up driving costs. Case in point: do you know how many individual anti-wind organizations there are in Germany?

No, they don't. At a global scale, land is enormously available. So are the materials from which renewable energy sources can be built. Are you worried about running out of silicon, iron, or aluminum? If so, stop being silly. Focusing on these is just to ignore the physical realities of what's available to work with.

Considering power density meaningless puts you in direct confrontation with reality. In physics you can't create energy, you can only convert it. So from what you're converting from is the key consideration to take as that also determines the cost.

And while nuclear is expensive at first, its longevity and reliability pays for itself. As it's further developed, that initial tax will only be reduced.

As if you guys don't realize that this "renewable" stuff is pushed by a nuclear reaction that happened thousands of years ago in the core of a plasma ball that is 8 light minutes away? That is not efficient.

What nonsense. I'm not denying power or energy density of nuclear is higher, I'm denying that this bare fact is relevant to any decision that we might make about using nuclear to power civilization.

And no, power and energy density do not determine cost, in general. They might if all else were equal, but all else is NOT equal. Renewable sources can omit entire categories of equipment that thermal power plants require, and have a much lower requirement on reliability (both because the individual units are smaller, and because the consequences of their catastrophic failure are vastly smaller.)

And no, nuclear's longevity and reliability do not pay for themselves. You're engaging in a bit of confrontation with economic reality there.

Pointing to nuclear reactions occurring in the Sun and pretending that justifies using nuclear on Earth is just completely absurd.

> Why are you choosing a meaningless metric to decide on the technology?

Learn to express yourself better. It's like building a house - your first choice is what ground you build it on - quick sands, swamp, or solid rock. If you don't take power density into consideration you're not going to make the right choice and then all your efforts will be meaningless.

Denmark is almost 100% renewable (it imports some). France is 70% nuclear (net exporter). Denmark household pays 170.5% more than french household. https://ec.europa.eu/eurostat/statistics-explained/index.php...

Here's a lecture on nuclear economics https://www.youtube.com/watch?v=cbeJIwF1pVY

Why focus on energy or power density (ostensibly because they affect cost) when you can focus on cost itself? The answer to that is because if you focus on cost, nuclear loses big, so the dishonest nuclear proponent has to obfuscate things and pretend that individual input that indirectly affects cost (along with many other inputs) is somehow dominant.

Wishing doesn't work.

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