[Question] Could waste heat become an environment problem in the future (centuries)?

I have won­dered about this sce­nario for a while, and would like to know what is your opinion about it. Its as­sump­tions are quite spe­cific and prob­a­bly won’t be true, but they do ap­pear re­al­is­tic enough for me.

(1): As­sume that nu­clear fu­sion be­comes an available en­ergy source within a cou­ple cen­turies, it will provide a cheap, plen­tiful, emis­sion-free, and long last­ing source of en­ergy for hu­man ac­tivi­ties.

(If this as­sump­tion is wrong, we are prob­a­bly in trou­ble)

(2): As­sume that con­tinued eco­nom­i­cal/​tech­nolog­i­cal de­vel­op­ment re­quires in­creas­ing en­ergy con­sump­tion in­definitely.

(This is prob­a­bly wrong if we util­ise com­pletely new physics in the fu­ture, but I don’t think this as­sump­tion is un­likely)

(3): As­sume that the gen­er­a­tion of waste heat dur­ing en­ergy gen­er­a­tion/​con­sump­tion can­not be dra­mat­i­cally low­ered in the short-term fu­ture.

(This is also prob­a­bly wrong. But it will hold true if we still have to use ma­chines/​en­g­ines/​gen­er­a­tors based on the same de­sign prin­ci­ples as we do to­day, and I don’t see that hap­pen­ing too soon)

The log­i­cal con­clu­sion from the above three as­sump­tion:

At some point af­ter the im­ple­men­ta­tion of nu­clear fu­sion, hu­man­ity’s en­ergy con­sump­tion might reach a level so high that the waste heat we re­lease into the at­mo­sphere will be al­ter­ing the Earth’s cli­mate sys­tem not un­like what our car­bon emis­sions are do­ing to­day.

(Since the source of any fu­ture fu­sion plant is likely hy­dro­gen in sea­wa­ter, for Earth it prob­a­bly acts as an ex­tra heat source in­de­pen­dent of the sun)

The Earth is func­tion­ally a gi­ant space­craft, and space­crafts usu­ally have very so­phis­ti­cated heat man­age­ment sys­tems to pre­vent them from over­heat­ing, so per­haps we have to work with that as well.

I haven’t done too much num­ber crunch­ing yet, I might have got­ten the figures wildly wrong.

We know to­day the amount of so­lar en­ergy the Earth re­ceives per year is about ~5000 times the amount of en­ergy hu­man­ity con­sumes.

If hu­man­ity’s en­ergy con­sump­tion in­creases 100 times, and 50% of the en­ergy is re­leased into the at­mo­sphere as waste heat, then we are re­leas­ing ~1% of so­lar en­ergy into the at­mo­sphere as heat.

That might have some se­ri­ous cli­mate im­pli­ca­tions if last­ing for a long time, but I’m not cer­tain about that yet.

Pos­si­ble solu­tions:

(1): Geo­eng­ineer­ing, that seems to be ob­vi­ous. We try to re­duce the so­lar en­ergy in­put on Earth when the heat we re­lease is too much. But that prob­a­bly will nega­tively im­pact the bio­sphere a lot due to pho­to­syn­the­sis is­sues.

(2): Set “en­ergy con­sump­tion tar­gets” for coun­tries/​firms/​etc like cur­rent cli­mate policy.

Prob­lem: while coun­tries can con­tinue to de­velop their econ­omy and tech­nol­ogy with­out in­creas­ing car­bon emis­sion (by adopt­ing clean en­ergy, etc), a limit on en­ergy con­sump­tion seems be a hard cap on a coun­try’s de­vel­op­ment that can­not be worked with. So, prob­a­bly no one would be com­pli­ant with such an agree­ment...

(3): Colon­is­ing other planets/​so­lar systems

Each colony would also have to face that prob­lem.

The Earth (and any other planet/​moon we colon­ise) seems to be func­tion­ally the same as a gi­ant space sta­tion. And space sta­tions need so­phis­ti­cated main­te­nance sys­tems, in­clud­ing man­age­ment of waste heat.

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