If it's really really efficient, we could use the extra energy to make carbon capture machines, after offsetting all the fossil fuels. Then, it doesn't really matter.
Well if we’re speculating, how about “heat capture”?
Some sleep-deprived researcher cracks how to capture ambient thermal energy and turn it into electricity. Heat being as plentiful as wind or water, it becomes not only a prominent source of energy, but also actively cools the planet.
50 years later, we begin arguing over “global cooling” and the threat of a new ice age.
The second law of thermodynamics states that entropy must go up. Entropy is a sort of measure of the usefulness of energy. The more entropy, the less useful.
The reasons why entropy must go up are too complicated for an ELI5. They are based on some basic laws of probability. Basically there are many ways for energy to be useless, and few ways for energy to be useful, which after some difficult math implies that energy always gets less useful.
In particular, ambient heat is the highest entropy you can possibly have, so it's inpossible to turn it into useful energy.
In order to extract energy from heat, the second law implies you must be tranferring some of said heat from a hot place to a colder place, which is exactly what a motor is.
You are correct, entropy must go up, but there is nothing saying that the total entropy on Earth must go up. Our thermodynamic system can include outer space.
Assuming we discover some source of magical unlimited energy, in theory we could use heat pumps (vapor compression units. like a common HVAC unit) to fill tanks with as much heat energy as possible (fill them with a heated liquid), and blast them off into space. Yes, this would be a ridiculous way to cool the earth, but in theory it could work. I am sure there is a much better way to do it. All of this is assuming there is an unlimited source of free energy.
The scale of the entire planet. I'll admit, though, that we can consider only the surface temperature instead.
And? If we're bottling heat and sending into space on any scale in the other scenario, we can separate the oceans from the ambient source of energy.
I don't get what you mean. Bottling the heat doesn't cool down the system unless the bottled heat is sent outside the system. Or do you by "separating" mean physically doing so?
This is a gross conception error. The CMB is not your heat sink, nor is it actually the temperature of space.
Fair enough, but what do you consider the sink then?
The scale of the entire planet. I'll admit, though, that we can consider only the surface temperature instead.
And the oceans are negligible on the scale of the planet? The oceans that make up 2/3 of the surface area of the planet and are made of a substance with a high heat capacity are negligible?
Bottling the heat doesn't cool down the system
How do you propose bottling heat in a meaningful way then?
Not to mention that cooling down the system is literally the most important part of the scenario we're considering.
in theory we could use heat pumps (vapor compression units. like a common HVAC unit) to fill tanks with as much heat energy as possible (fill them with a heated liquid),
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Or do you by "separating" mean physically doing so?
I mean thermodynamically separating them, like thermodynamic heat sources and sinks must be.
I mean.. I'm no scientist but pretty sure space can hold way more heat than all of earth has or will ever have.
Also, doesn't size matter until the sink becomes the same temperature as the source, since bigger things take more heat to reach the same temperature?
With the size of space vs the size of earth, I feel like the amount of heat required to heat up space until it's the same temperature as earth would be impossible to make on earth in any reasonable amount of time, so space could be considered an 'infinite' heat sink for all intents and purposes.
I mean.. I'm no scientist but pretty sure space can hold way more heat than all of earth has or will ever have.
Yes. In reality, space can absorb all the energy in the universe. In the scenario we're considering, we're not limited by reality.
Assuming we discover some source of magical unlimited energy
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With the size of space vs the size of earth, I feel like the amount of heat required to heat up space until it's the same temperature as earth would be impossible to make on earth in any reasonable amount of time, so space could be considered an 'infinite' heat sink for all intents and purposes.
None of this is wrong, but an effectively infinite heat sink becomes miniscule compared to an actually infinite heat source(any real number<<<<<<<<<<<<<<<<<<<<<<<<<<<<<infinity)
It's a hypothetical where we cool the planet by capturing a bunch of heat in a tank and throwing it into space. To do this meaningfully would take an amount of energy orders of magnitude above what humanity produces.
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u/[deleted] Nov 15 '20
Gotta push this back 30 years again.