Comment by strainer | Hacker News Reader

Comment by strainer | Hacker News Reader

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Nuclear fusion and fission are both exceptionally complicated ways to boil water, and even if given an ideal water boiler, turbine and cooling plants still need to be built for them and situated somewhere that about 3 times as much heat energy can be released into the local environment. This is known as thermal pollution:

"ultimately, when heat waves are extreme enough, power plants will need to draw down their power output."[1]

Here [2] is a study which shows anthropogenic heat emissions from energy consumption are a pressure on global climate. If we put out another 200%+ of whatever energy we consume, in the form of thermoelectric cooling (heat) then quite surely that will amount to a bigger problem.

Also, "Thermoelectric power use has a significant impact on water resources and the power sector is highly dependent on these water resources; the United States Geological Survey (USGS) estimated on a national level that 41% OF ALL FRESHWATER WITHDRAWALS in the United States in 2005 were for thermoelectric power operations, primarily for cooling needs (Kenny et al 2009)."[3]

I believe the real game changers are plainly solar and wind. These have shown the most rapid improvements from investment. On similar timescale to developing fission or secure nuclear, floating oceanic wind and solar combined with hydrogen generation rigs (and even ocean plastic filtering) are possible...

[1] https://www.sciencedirect.com/topics/earth-and-planetary-sci...

[2] https://link.springer.com/article/10.1007/s10584-017-2092-z

[3] https://iopscience.iop.org/article/10.1088/1748-9326/7/4/045...

> 3 times as much heat energy can be released into the local environment

Or used for desalination, hydrogen, syngas, ammonia, methanol, ethanol production [1] etc.

http://www.world-nuclear.org/information-library/non-power-n...

Also, your estimation is incorrect. The thremal rated power of a nuclear reactor doesn't mean it releases 3x as much heat in the environment. At least 1/3 of the thermal energy is converted to electricity, and part of what remains is fed into a new cycle. The overall efficiency of a nuclear reacor is 33-37%. Gen IV reactor projected efficiencies are above 45%.

Waste heat cant simply be used for this and that, or else we would see all existing thermo-electric powerplants already doing so. Efforts to make thermo-electric plant more efficient and use waste heat are ongoing, but full use of waste heat would be a more game changing development than practical fission reactors !

Its rather rhetorical for us to quibble with my statement "about 3 times.." But in my readings on the matter 33-37% is the theoretic optimal running efficiency of most existing nuclear plants (depends on the kind and expense of turbine cycle and cooling system employed).

Combined heat and power (CHP) is a thing, though mostly in colder climates where there's a need for heating in the winter.

In principle you could do the same with nuclear, but there's challenges in siting a reactor close enough to a big city, and also current reactors tend to be too big. SMR's might help, and there's active research in this area.

SMRs likewise require generators and cooling plant, 2 or 3 times as much cooling as electricity produced, perhaps even more if its to be done most economically. So if CHP is justification for such release of heat into cool environments - they should be categorized as mainly a source of heating, not high value electrical energy. An ability to make continuous heat on this planet is not a futuristic energy supply in its own right, it falls well short of the "game changer" goal.

Thermal nuclear reactors have their MWt rating 3x of their MWe. All of them produce heat.

Generators? Cooling Plant? I don't know about others, but NuScale Power's SMR has natural circulation an passive cooling.

https://www.nuscalepower.com/about-us/faq

That's internal passive cooling which they mention briefly in their faq (transferal of heat from their reactor to their output loop). These units take in water and output steam, and they need attached to thermo-electric plant to produce electricity. They are water boilers.

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