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Fusion reactors: Not what they’re cracked up to be

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Re: Fusion reactors: Not what they’re cracked up to be

#111

Post by sfifs »

theptip wrote: post #81
short_sells_poo wrote: post #40

Earlier quoted context omitted.

How exactly do you propose to get that electricity from the desert to say Finland? Furthermore, you need to plaster a vast area in the desert with solar plants, which brings along all sorts of concentrated security risks. The alternative is to have many smaller plants dispersed, which results in a big loss of efficiency. I'm all for clean energy, but you seem to be handwaving away pretty huge issues as "thought exerc…

> How exactly do you propose to get that electricity from the desert to say Finland? High voltage DC transmission works fine for this problem. All of the engineering challenges have been credibly worked out and priced ( https://en.wikipedia.org/wiki/Desertec ). The main problems with this approach are political, in that it requires massive cooperation between many countries over very long time scales (decades). Why i…

The danger is political risk, not necessarily theft or vandalism. Any dependency on territory not under your own societal control can be used to hold you hostage and cannot be depended upon.

Forget the solar farm, easiest is to cut power lines. (explosives?)

Re: Fusion reactors: Not what they’re cracked up to be

#112

Post by DennisP »

dkirtley wrote: post #69
DennisP wrote: post #44

Earlier quoted context omitted.

Another option is to simply breed He3 with pure deuterium fusion; the output of the D-D reaction is He3 half the time, and otherwise tritium, which decays into He3 with a 12-year half-life. D-D produces neutrons but at normal fission energies, not the really high energy of D-T neutrons. Fusion startup Helion, which is funded by YCombinator, is attempting a hybrid D-D/D-He3 reactor, saying the combined reaction would…

6% is about the best we can do with a closed cycle. Extra-terrestrial sources could push those numbers even lower by running up to a pure D-He3 reaction.

Yep. I think 6% is pretty good...it's enough so you don't need a heat cycle to extract electricity, and dealing with the neutron damage is easier than going to Uranus. But working fusion reactors probably also means working fusion rockets, and if we find ourselves going to Uranus anyway, all the better.

If we get really good at fusion we could also use boron fusion. It uses the most common isotope of boron, which is plentiful on Earth, plus regular hydrogen, and the main reaction is aneutronic. There'd be some minor side reactions but it'd be under 1% of energy as neutron radiation, probably better than you'd get with deuterium in the mix.

Re: Fusion reactors: Not what they’re cracked up to be

#113

Post by Arizhel »

jandrese wrote: post #105
Arizhel wrote: post #97

Earlier quoted context omitted.

So you think northern African nations are going to let European nations station troops there and take over a big chunk of their land? That doesn't seem realistic, and seems rather imperialistic actually. Letting the northern African nations provide the security is just plain folly, and also makes Europe completely dependent on these economically backwards and frequently hostile nations.

Why wouldn't an African nation want to charge rent to some European country for vast amounts of land that are otherwise literally worthless[1]? It's not like they're strangers to private company security forces that are basically just extrajudicial mercenaries. History says any company that wants to do this just needs to apply some bribes to the appropriate officials. [1] In the sense that nobody is willing to buy it…

Yeah, I'm sure it'll look just great that Germany or whoever is stationing the Wehrmacht in northern Africa, and no one will complain about that... /s

You really think that's a viable way to maintain the electric power supply for all of Europe? "What could possibly go wrong?!"

Re: Fusion reactors: Not what they’re cracked up to be

#114

Post by opo »

Retric wrote: post #107
opo wrote: post #103

Earlier quoted context omitted.

You are handwaving away huge issues here. As Bill Gates said in the same interview I quoted from before: >"...It’s kind of ironic: Germany, by installing so much rooftop solar, has it that both their coal plants and their rooftop solar are available in the summer, and the price of power during the day actually goes negative—they pay people to take it. Then at night the only source is the coal, and because the energy…

Coal and nuclear are huge steam engines. They cool down when you turn them off which causes thermal stress and you then need to heat them up again before they can generate power. Thus Germany's problem is they have coal power plants in the first place. Gas turbines also have thermal stress, but they are designed for this and they loose vastly less power when you turn them off. With enough of them you can have zero st…

On the plus side, the CO2 from burning natural gas is less than coal and it doesn't emit mercury or the other particulates and doesn't have a waste issue like coal does. Unfortunately for those who care about climate change, (and if you don't, you should) there are inevitable methane releases from fracking and from distribution of natural gas and those are now known to be much worse than previously thought:

>...Back in August, a NOAA-led study measured a stunning 6% to 12% methane leakage over one of the country’s largest gas fields — which would gut the climate benefits of switching from coal to gas. We’ve known for a long time that methane is a far more potent greenhouse gas than carbon dioxide (CO2), which is released when any hydrocarbon, like natural gas, is burned. But the IPCC’s latest report, released Monday (big PDF here), reports that methane is 34 times stronger a heat-trapping gas than CO2 over a 100-year time scale, so its global-warming potential (GWP) is 34. That is a nearly 40% increase from the IPCC’s previous estimate of 25. ...The IPCC reports that, over a 20-year time frame, methane has a global warming potential of 86 compared to CO2, up from its previous estimate of 72. Given that we are approaching real, irreversible tipping points in the climate system, climate studies should, at the very least, include analyses that use this 20-year time horizon. Finally, it bears repeating that natural gas from even the best fracked wells is still a climate-destroying fossil fuel. If we are to avoid catastrophic warming, our natural gas consumption has to peak sometime in the next 10 to 15 years, according to studies by both the Center for American Progress and the Union of Concerned Scientists.

https://thinkprogress.org/more-bad-news-for-fracking-ipcc-wa...

As we use more and more natural gas, we can expect more and more methane disasters like the leak from Aliso Canyon in CA which was the largest leak in US history. This released over 100,000 tons of methane into the atmosphere and required 11,000 residents to be evacuated.

http://www.bbc.com/news/science-environment-35659947

Re: Fusion reactors: Not what they’re cracked up to be

#115

Post by Robotbeat »

cucucfudud wrote: post #110
short_sells_poo wrote: post #40

Earlier quoted context omitted.

How exactly do you propose to get that electricity from the desert to say Finland? Furthermore, you need to plaster a vast area in the desert with solar plants, which brings along all sorts of concentrated security risks. The alternative is to have many smaller plants dispersed, which results in a big loss of efficiency. I'm all for clean energy, but you seem to be handwaving away pretty huge issues as "thought exerc…

i read an article that the nordics actually gets as much sun as southern europe, if you count the whole year. Its as good a place for solar as anywhere else. The summers are sunny all day and night. The problem becomes how to store the energy until the dark winter months. (There are solar panels that doesnt need heat just light) Edit: http://www.nordicenergy.org/article/solar-power-at-the-arcti...

The seasonal variation of solar power is a big problem if you want to rely mostly on solar power, though. Seasonal storage is insanely expensive with any of the usual methods. I mean, let's say to get daily storage, you need 8 hours of batteries. To get 4 or 5 weeks of storage, you need more like 800 hours of batteries. It's literally 100x the cost.

So yeah, if you want to run on natural gas for half the year, then solar in the nordics isn't bad.

But luckily the nordics have lots of hydro and don't need any gas or even solar.

But on the equator, the seasonal variation is small. The Global South will have a big energy cost advantage as solar costs keep dropping.

Re: Fusion reactors: Not what they’re cracked up to be

#116

Post by Panoramix »

short_sells_poo wrote: post #63
labcomputer wrote: post #58

Earlier quoted context omitted.

> Furthermore, you need to plaster a vast area in the desert with solar plants, which brings along all sorts of concentrated security risks This sentence seems to be at odds with itself. How does needing a large area concentrate security risks? If anything it seems to disperse them. Unlike a coal or nuclear plant, you can't just walk up to a critical part of a solar farm and blow it up. Any part that you damage is re…

Sorry I worded that sentence poorly. Let's assume two scenarios: a) We create a 200 square mile solar field in the Sahara, from which cables run to Europe to supply electricity. To take this plant out, one just cuts the cables. There, you just plunged Europe into darkness. b) We create a 20x 10 square mile solar fields in the Sahara, all dispersed over a very large area. Well, this is an engineering and construction…

"just cut the cables"

Not that easy. Furthermore, it's the same for any large power plant of any type. This is a very poor argument against solar. It's also a stretch to imagine that Europe would rely on a single power plant for its sustenance.

Re: Fusion reactors: Not what they’re cracked up to be

#117

Post by Robotbeat »

jcranmer wrote: post #96
Robotbeat wrote: post #71

Earlier quoted context omitted.

I'm the classic US-centric American. Northern Europe can solve its own problems, they have all the tools (nuclear, hydro, wind, geothermal). The rest of the world (i.e. the vast majority of people) is closer to the equator and doesn't need a cable running to the Sahara.

About a decade ago, there was a book written which looked at the ability of Great Britain to become self-sufficient entirely in renewable energy ( https://www.withouthotair.com/ looks to be the URL). It concluded that there is literally not enough renewable energy potential in Great Britain (e.g., cover every square millimeter of space with solar panels) to do so at then-current energy consumption rates. It also poin…

"It concluded that there is literally not enough renewable energy potential in Great Britain (e.g., cover every square millimeter of space with solar panels) to do so at then-current energy consumption rates."

That is false, though. Just a little math shows why.

The UK is 242,500 km². Nameplate solar capacity on that would be on the order of 150MW/km², so 36 Terawatts. UK average electrical consumption is 32 /Giga/watts. Assume solar produces 1/4 of that 36TW on average when it's sunny during equinox, so 9TW. Even on a pretty cloudy day on the winter solstace in London, you're still going to produce at least 1/10th to 1/20th of that much, so worst case of worst cases (cloudy day on solstice) you're looking at 450GW average if you cover the entire UK in solar panels. That's still over ten times the UK's average electrical consumption.

(I used UK instead of Great Britain, but that doesn't make much difference.)

I mean, the overall point that you wouldn't want to power the UK on solar alone is totally and completely valid (and I fully support the Hinkley Point C nuclear power plant, by the way), but the idea that it's literally not possible is BS.

Re: Fusion reactors: Not what they’re cracked up to be

#118

Post by erikgrinaker »

jandrese wrote: post #106
erikgrinaker wrote: post #23

Much of the (valid) criticism in this article relates to the deuterium-tritium fuel cycle. This is the easiest reaction to accomplish on Earth, so most experimental reactors are designed with this fuel in mind, and we're certainly having a hard enough time making even this work. However, I've always considered D-T fusion an intermediate step on the path to aneutronic fusion, such as Helium-3 or proton-Boron reactions…

Billion Kelvin operating temperatures make me super skeptical about the practicality of that solution in my lifetime. It's just so many orders of magnitude beyond where our materials science is.

It's very high, but not as bad as it sounds. There is less than 1 gram of fuel in the reactor at any given time, so it's extremely diffuse, and mostly contained by magnetic fields. Much of the energy can also be radiated away by facilitating ion-electron recombination before the plasma reaches any materials.

The current design for ITER, operating at 150 million Kelvin, focuses the exhaust plasma onto a dedicated divertor surface with an estimated peak heat flux of 20 MW/m2. Experiments show that tungsten handles this fairly well, although with some cracks appearing after many cycles, but this is an active area of research.

Re: Fusion reactors: Not what they’re cracked up to be

#119

Post by jcranmer »

Robotbeat wrote: post #117
jcranmer wrote: post #96

Earlier quoted context omitted.

About a decade ago, there was a book written which looked at the ability of Great Britain to become self-sufficient entirely in renewable energy ( https://www.withouthotair.com/ looks to be the URL). It concluded that there is literally not enough renewable energy potential in Great Britain (e.g., cover every square millimeter of space with solar panels) to do so at then-current energy consumption rates. It also poin…

"It concluded that there is literally not enough renewable energy potential in Great Britain (e.g., cover every square millimeter of space with solar panels) to do so at then-current energy consumption rates." That is false, though. Just a little math shows why. The UK is 242,500 km². Nameplate solar capacity on that would be on the order of 150MW/km², so 36 Terawatts. UK average electrical consumption is 32 /Giga/wa…

Energy consumption here does not mean just current electricity usage. It also includes things like fueling cars and planes. Also, the 150MW/km² is apparently roughly the summer expected solar insolation; year-round average insolation comes out to ~100MW/km² per the book's numbers.

The total chart at the end came out to " rel="nofollow">https://www.withouthotair.com/c18/page_103.shtml>, with solar making up about 68 kWh/d per person.

Re: Fusion reactors: Not what they’re cracked up to be

#120

Post by prewett »

spdionis wrote: post #67
Robotbeat wrote: post #42

Earlier quoted context omitted.

That all looks trivial compared to the challenges of fusion power, though.

Are you sure? This is a recurring theme in your arguments but I don't necessarily agree with you. What are the reasons for you to think that?

We already have things that float in the ocean for long periods of time (ships, oil rigs) and which withstand ocean storms, so it seems like a solved problem compared to fusion.
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