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Comment by scrumbledober | Hacker News Reader

PV just doesn't scale in the same way. There's only so much surface area to cover in panels. The power density of fusion is so many orders of magnitude larger that even with cheap reliable solar panels I think there will always be a use for working fusion

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PV scales fine. Do the math, please. There is far more than enough land onto which we can put PV farms. And the cost/W for solar (of which the cost of land is small fraction) is two order of magnitude below current fusion machines.

So hypothetically, if all developed countries suddenly decided that it was worth whatever the cost, could we get to 100% renewable in say.. 10 years? How much of our activity would need to be directed at this? Not even research, if the plan was just make as much renewable energy as we can with current methods as fast as we can.

Of course this would never actually happen and we're in all likelihood gonna continue to trash the place, but is this possible even in theory?

Then there's the ocean.

I'm imagining the solitary life of a caretaker living in a little ship that travels the canals between acres of floating cross-linked solar panels, fixing wiring and washing off salt deposits.

Poetically, it would be a tale of isolation out in the middle of the Pacific, but I suppose you'd need to stay close enough to shore that you can transmit the power using wires, unless it's batched up in chemical storage.

If you perform electrolysis of sea water the main products given off would be hydrogen and bleach, both of which could be piped or shipped (if you filled an oil tanker with hydrogen, would it be lighter than air?) back to shore. Although a leak of bleach into the ocean may not be very good, it's probably no worse than the damage done from oil.

I like the poetry. :)

We already have offshore wind power.

If nothing else, it could be useful for portability. You can't make a solar powered aircraft carrier. You might be able to make a fusion-powered one.

Fusion has very bad power density compared to fission, so a fusion-powered ship would be idiotic.

Fission has this radioactive waste and nuclear proliferation problem. A fission-powered ship would be idiotic if a fusion powered ship was an option.

Fusion has proliferation problems too. In some ways this is easier than using fusion for energy production. A Q = 0.1 DD burning reactor, for example, would be useless as a power producer, but would produce plenty of neutrons (at lower, less damaging energies) to make plutonium in a subcritical natural uranoium blanket. And it would not need to breed tritium.

You can always make it 10x times as big and if that is not enough then make it 10x times bigger still.

Yeah, let's make our ship 100x bigger for a given engine power! How could the customer paying for this POSSIBLY object?

Please don't be absurd.

you say that like its a bad thing

Don't know why this got downvoted. It's true.

PV might take us the next 100 years. Fusion might be necessary for the following 100.

It got downvoted because it is not true. PV scales so well that people are voluntarily throwing panels on their roofs to reduce their energy bills. It scales so well that even with current single junction cells, we could cover just 1% of the Sahara with panels and meet the entire world's energy needs. When multi junction gets cheaper, it's basically end game for power generation. And you're probably going to say that storage is a problem, but again storage is something that scales so well people and utilities are buying battery systems all over the place while multiple giga-scale battery factories are coming online in the next 5 years to push prices even lower. Plus High voltage DC power transmission can get power thousands of miles with surprisingly low losses.

And why do you think fusion might be necessary for the following 100 years? Energy use per capita has been dropping in developed countries for years. Fusion really only makes sense as a "must have" technology for space exploration, which current reactor designs are so far away from it's basically a joke.

I wonder if working fusion utility power generation, by the time it is working fusion utility power generation, might end up being more expensive than putting solar in space and beaming the power, given the potential for launch costs to drop and the possibility of even doing the panel manufacturing up there using asteroids as raw materials in the long run, so avoiding the gravity well cost. Economies of scale can get very big in space and if we are comparing to fusion research we should look at the medium to long run.

The simple fact we make nuclear ships supports this.

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