Hypothetical and vague solution to global warming/energy crisis

[redacted]

Heat is energy, yeah? So if we could figure out a way to use heat around us as an energy source, it would kill two birds with one stone -- deal with climate change and give us more energy to use.

I have no idea how this could be practically applied, but doesn't it seem like a logical solution? Is there something I'm missing? I'd like to hear anyone's thoughts on practical problems here.

 

[ygolo]

It is an interesting idea, but we have to contend with the second law of thermodynamics:

It is impossible to convert heat completely into work.

That is, it is impossible to extract energy by heat from a high-temperature energy source and then convert all of the energy into work. At least some of the energy must be passed on to heat a low-temperature energy sink. Thus, a heat engine with 100% efficiency is thermodynamically impossible.

Source:
Second law of thermodynamics - Wikipedia, the free encyclopedia

So if we are using the ambient heat as the source, what would be our low temprature energy-sink (which would of-course become higher in temperature over time)?

 

[redacted]

The efficiency is not a problem, though, as part of the goal is to just waste heat energy, making the environment colder.

 

[ygolo]

Actually, the point I was making was not about the efficiency per say, but about the need for a cooler energy sink.

Where do we get one big enough?

 

[ajblaise]

I think we have a better chance of harnessing energy from the cold ocean depths. Scientists are talking about doing this.

 

[Jack Flak]

1. The crisis is make believe.
2. As stated, flawed plan.

 

[ygolo]

hopefully I did this right

Ignoring the "doing work" part and focusing on the heat transfer:

 

[redacted]

1. The crisis is make believe.

I'm not saying it's a crisis or anything. I'm just saying, if the world is too hot, for whatever reason, it seems like there should be a way to use that heat for energy, killing two birds with one stone.

Actually, the point I was making was not about the efficiency per say, but about the need for a cooler energy sink.

What is a sink?

Also, I can't follow your math unfortunately. I also know very little science.

I think we have a better chance of harnessing energy from the cold ocean depths. Scientists are talking about doing this.

I'm not talking about a solution to finding energy. I'm talking about a solution that would cool down the world and utilize energy at the same time.

 

[ygolo]

What is a sink?

Also, I can't follow your math unfortunately. I also know very little science.

An energy sink takes in energy from its environment and goes nowhere else in consideration. The energy usually becomes heat inside the sink.

The think the math is saying, is that compared to desity ratios, and specific heat ratios, the ratio of volumes is overwhelming. In essense, whatever you try to use to cool the environment will in become as hot as the environment while the environment stays about the same.

 

[redacted]

So would it literally change the average temperature by zero?

Hmm. I guess the only way to get rid of the energy would be to somehow take it off the planet.

Meh, it was just a thought.

 

[ygolo]

So would it literally change the average temperature by zero?

Zero for practical purposes. Negligibly small. Unless you can get something cold that is increadibly dense, and has very high spefic heat (like a mini-blackhole jk).

 

[redacted]

Ah. Well that was the point of me posting this. To get someone to tell me why it wouldn't work. If it would, I'm sure someone else would have talked about it by now...

Thanks man.

 

[ygolo]

I think it was a satisfactory explanation of why we'd have trouble cooling the environment by directly extracting heat.

But I didn't really give an explanation on the work aspect.

No engine using heat can be more efficient than a Carnot Engine. The maximum efficiency is (1-Tc/Th), where Tc is the temperature of our cold resevoir (energy sink), and Th is the temperature of the environment.

Lets optimistically say that our magical heat engine can "pay" its temperature change cost only after it has done all its work, and that the heat capacity of our cold reservoir is C.

The amount of work our cold reservoir can sink C(Th-Tc) in heat. But since our heat engine is only (1-Tc/Th) efficient, the maximum amount of work done is C(Th-Tc)(1-Tc/Th)=(C/Th)(Th-Tc)^2.

The heat capacity C is in-turn directly proportional to the specific heat, density, and volume of our cold reservoir.

So you can extract work from the environment, but considering how relative cold our environment is, running of our more convention engines has bee better.

...you know I wonder if we can create "cold-running" engines. How similar would these be to fuel cells?

 

[The_Liquid_Laser]

We could use outer space as a heat sink. It's plenty big and also cold enough.

 

[runvardh]

The problem with space is that your only means of disposing of eat would be through radiation as there is nothing out there to help with the conduction or convection that we enjoy the use of while in an atmosphere with all our other neat toys. Its the reason why, even though it's approaching absolute zero out there, a person with no suit in space would die from suffocation first before hypothermia sets in.

 

[ygolo]

rundvah has the space idea covered.

Beside the radiation is already in play.

 

[The_Liquid_Laser]

rundvah has the space idea covered.

Beside the radiation is already in play.

Heh, my space comment was meant as a joke. I.e. the problem with global warming is that it traps too much heat in the atmosphere and not enough dissipates into space.

 

[Jack Flak]

Heh, my space comment was meant as a joke. I.e. the problem with global warming is that it traps too much heat in the atmosphere and not enough dissipates into space.

Perhaps we could just use a fan, and a series of tubes, to send part of our atmosphere to the Moon.

 

[ptgatsby]

The problem with space is that your only means of disposing of eat would be through radiation

*shrug* Point a laser at the sun.

 

[ygolo]

Heh, my space comment was meant as a joke. I.e. the problem with global warming is that it traps too much heat in the atmosphere and not enough dissipates into space.

Ah. That's what the wink was for. I've had bad luck interpreting ENTP winks lately. Still, it lead to an interesting idea.

*shrug* Point a laser at the sun.

Laser cooling - Wikipedia, the free encyclopedia

[...] laser cooling, in which photons are used to pump heat away from a material (normally a solid) and thus cool it. The phenomenon has been demonstrated via anti-Stokes fluorescence, and both electroluminescent upconversion and photoluminescent upconversion have been studied as means to achieve the same effects.

Although, the other versions of laser cooling are intersting too.

Laser cooling is a technique that uses light to cool atoms to a very low temperature. It was simultaneously proposed by Wineland and Dehmelt and by Theodor W. Hänsch and Arthur Leonard Schawlow in 1975, and first demonstrated by Letokhov, Minogin and Pavlik in 1976. One conceptually simple form of laser cooling is referred to as optical molasses, since the dissipative optical force resembles the viscous drag on a body moving through molasses. Steven Chu, Claude Cohen-Tannoudji and William D. Phillips were awarded the 1997 Nobel Prize in Physics for their work in laser cooling.