Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Danube's record low levels force shutdown of Hungary's only nuclear plant

bbc.com

Post reply on HN
Print view View original

231–240 of 252 posts

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#231

Post by inigyou »

noduerme wrote: post #42
wongarsu wrote: post #29

Earlier quoted context omitted.

Fully closed loop is probably not viable. But I suspect that's not the extreme GP might have meant. If for the sake or discussion we simplify cooling to four options: 1: just passing river water through a heat exchanger for cooling 2: ingesting river water, using it for cooling, then passing it through a cooling tower before returning it to the river 3: pass the water output from the cooling tower directly back in th…

How do these things, whose sole purpose is to turn heat into electricity, end up with so much extra heat that it takes more energy than they produce to disperse it? Can't the excess heat in a closed loop system be captured and used to power the cooling? Sorry, maybe this is a stupid question.

The laws of thermodynamics don't allow it. Energy usually comes with entropy attached, which can't be destroyed and has to be dumped somewhere. At a colder temperature you need less energy to raise the entropy, which allows for energy and entropy to be split into a cold part (containing most of the entropy and some energy) and a hot part (containing low entropy) at specific ratios. Electricity is low-entropy energy, which is why it's so useful.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#232

Post by inigyou »

slow_typist wrote: post #133
dredmorbius wrote: post #91

Earlier quoted context omitted.

Thermodynamics, specifically the Carnot Cycle. Heat engines do turn heat into mechanical energy (motion). What they don't do is do this with infinite efficiency. In practice , Carnot engines (heat engines) tend to operate at efficiencies between about 20 to 50%, with an average close to 30% percent. This means that most thermal electrical generation produces roughly three times as much heat as it does electricity. Th…

Wouldn’t a Carnot engine with 33% efficiency produce 2 J of heat per 1 J of mechanical work? With 40% efficiency 1.5 J of heat? Efficiency of the generator should be better than 90 % so I think the 3x estimate is a bit off.

Yes, that's right.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#233

Post by inigyou »

noduerme wrote: post #219
Tade0 wrote: post #52

Earlier quoted context omitted.

The heat is spread out to a much larger volume. Heat engines are most efficient when the temperature difference between the hot and cold side is high, so you need to keep it that way to extract energy. A nuclear power plant achieves this by converting extreme heat from a small, but very angry rock to a huge lake of slightly warmer water. There exist reactor designs which operate at higher temperatures, thus increasin…

okay but to maybe beat a dead horse, if you have these enormous cooling towers spewing out steam, is the steam coming out the top of those just not economically viable to use to run smaller generators or something?

There are plants with multiple stages of turbines. You really do need high pressure, high temperature steam to make appreciable energy though. What comes off the top of a cooling tower will keep you warm, but it's had 99% of its energy already extracted.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#234

Post by inigyou »

chermi wrote: post #194

I ask once again: why is everyone so convinced that nuclear is the one technology that somehow doesn't get cheaper and better with advancing tech and scale? And don't tell me learning curves are proven to not apply. The preconditions for learning curves are arguably only now being met in China.

Go and invent an awesome nuclear plant then.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#235

Post by inigyou »

bratbag wrote: post #157
pjmlp wrote: post #153

So nuclear isn't the solution after all.

Nuclear without greed is fine. Its only where shortcuts have been taken with cooling that there will be issues.

What do you consider adequate cooling? Remember that for every GW of electricity you need to remove 2-3 GW of heat. That's a lot of heat. Strapping a giant PC radiator fan to the plant won't cut it.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#236

Post by inigyou »

Cthulhu_ wrote: post #20
emsign wrote: post #18

This is what nuclear power enthusists like to ignore when they talk about nuclear power being a solution to energy and climate change.

Is that a fact or are you just trying to spark a debate?

Seems like a fact to me?

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#237

Post by inigyou »

fylo wrote: post #32
emsign wrote: post #18

This is what nuclear power enthusists like to ignore when they talk about nuclear power being a solution to energy and climate change.

Every power source has trade offs, bud. They call solar renewable, but in fact panels have a shelf life, and take valuable finite resources and energy to manufacture. This is what climate change activists like to ignore /s

Glad you added the /s because solar panels only wear out over hundreds of years.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#238

Post by AngryData »

acdha wrote: post #177
bratbag wrote: post #157

Earlier quoted context omitted.

Nuclear without greed is fine. Its only where shortcuts have been taken with cooling that there will be issues.

That seems like a huge disadvantage for nuclear power if you need to guarantee strict ideological commitment to ignore cost-competitiveness not just now but into the future. Renewables and batteries are not only cheaper now but have far less scope for major failures based on some MBA cutting corners in a decade.

You think big battery plants can't have issues with cost cutting?

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#239

Post by Kon5ole »

Hammershaft wrote: post #221
Kon5ole wrote: post #198

Earlier quoted context omitted.

>The harms of radiation are massively overhyped. >Nobody from the Fukushima accident died from radiation sickness or radiation syndrome, and so far there's been no evidence of long term elevated cancer rates either. You say these two things as if the second statement supports the first, but it doesn't. The dangers of radiation are very well known and don't change at all based on what happened at Fukushima. If you fir…

https://ourworldindata.org/grapher/death-rates-from-energy-p... People die from the operation & externalities of every energy source, it's just that Nuclear power has orders of magnitude fewer deaths per kilowatt-hour than the dirtier energy sources these regulations have pushed energy production towards. I'm sure some lives would be lost if Nuclear Power faced the same regulatory costs that other energy sources do,…

>Nuclear power has orders of magnitude fewer deaths per kilowatt-hour

By this logic the minuteman missile is harmless. It hasn’t killed anyone, right?

Nuclear power has the potential to cause orders of magnitude more damage than any other power plant.

Again, what has happened is irrelevant, the risk is all about what could happen.

Re: Danube's record low levels force shutdown of Hungary's only nuclear plant

#240

Post by blitzar »

cozzyd wrote: post #223
peterashford wrote: post #217

Earlier quoted context omitted.

So, larger batteries, then. Or produce hydrogen from excess wind power in the summer as a chemical battery.

yes, people (some of whom I know) have looked at this of course: https://www.sciencedirect.com/science/article/pii/S136403212... but it's somewhat risky, since if the power goes out in winter, to first order, everyone dies. I think you'd always keep the generator on at low load, just in case. Note that wind turbines at pole have not historically been very successful, maybe that will improve.

I presume the optimal solution is solid oxide fuel cells + renewables. Not complete science fiction, but not quite ready to do away with the diesel backup.
Post reply on HN