Sunday, November 18, 2007

There Ain't No Such Thing As A Free Lunch

Some friends and I have been talking about peak oil and the implications of actually finding a cheap, plentiful alternative energy source.

I'm not a global warming expert (although I have stayed at a Holiday Inn Express), but the role greenhouse gasses play is that they increase the retention of the ambient heat that we generate. Instead of letting it be emitted as infrared into space, they reflect it back or store it as heating and emit it back. The CO2 itself doesn't generate any heat itself, it just traps the heat we create (hence the name "greenhouse" gas). So global warming is an issue of ambient heat generation AND our inability to dissipate it because of greenhouse gasses.

The role that energy production and its use plays in heat generation is covered in the second law of thermodynamics which deals with entropy. All energy is, over time, broken down into unusable heat, because the entropy (disorder) of all physical systems increase over time. Meaning: every single bit of energy we generate and use eventually turns into heat. It may be a multi-step process, but as you drive your car down the road, your engine (electric or gasoline) generates heat; your tires generate heat from friction with the road; your car generates heat from friction with the air; the refinery that made the gasoline generated heat in its production. It all becomes heat. You can't get around this: it's the way the Flying Spaghetti Monster built the universe in his/her/its/their infinite wisdom. "Heat death" is pretty much the ultimate end of everything. When we're dead and buried, as we rot we generate heat, as our bodies release their stored chemical energy.

If we have some form of really cheap, really easily had energy, such that our energy production and use really increases, our heat generation rises by exactly that same amount. Greenhouse gasses in the atmosphere means that heat gets trapped instead of being radiated away as IR. But even if we didn't have any greenhouse gasses in the atmosphere, there is a physical limit to how much heat can be generated away per unit time. Basically, cheap available energy means we eventually cook ourselves to death. Literally.

Are there ways around this? It's been seriously suggested we build giant lasers that would somehow (this part is really unclear to me) radiate waste heat into space. I can imagine an SF story where we fry some passing alien craft and start an interplanetary war.

This has been proposed even for space craft with large power plants, since the only way to get rid of heat in space is by radiation; neither convection nor conduction works because there's no material to which to convect or conduct, like air or water. This is one of the reasons the Space Shuttle has big honking radiators built into the cargo bay doors and why they have to open them up when in orbit, even if they're not using the cargo bay. Their waste heat has no where else to go. This also places a physical limit to how much energy the Shuttle can expend, and how big a Shuttle we can build.

Quoting Robert Heinlein: TANSTAAFL. Cheap energy means increased heat production. In a way it just moves the problem somewhere else.

If you think about it, what is oil or coal? It's stored chemical energy. Where did the energy come from? From plants, and maybe some dinosaurs, that lived, ate, and grew millions of years ago. Because no system is 100% efficient, those plants (and dinosaurs) consumed a LOT more stored chemical energy, in the form of plants, dinosaurs, and soil and chemicals that once was plants and dinosaurs and rocks, than they created. Today we're taking advantage of a process that began millions of years ago, and that we cannot replicate. We can't make more oil because, besides the fact that we're impatient and can't wait millions of years (hence we invade small middle eastern dictatorships), the natural resources that went into making the oil, the incredibly rich biosphere, doesn't exist anymore. It went into making the oil that we DO have right now. Pretty much a one-way process.

Just like entropy and heat death.


Jon said...

"Cheap energy means heat production"? I think that energy, cheap or dear, means heat production... heat is energy, no matter how much you paid for it.

Agreed, entropy, aka time's arrow, is a one-way process. But I suspect that a change in a small portion of the sun's energy being retained makes a much larger difference in the net heat gain of the earth than does liberating the bonds holding some hydrocarbons together.

Okay, some math - the earth receives an estimated 174 Petawatts of solar power from the sun...

And total world energy consumption is something like 15 terawatt.

So we're consuming energy equivalent to about 0.0086% of the energy that's coming in.

So I think that how much of the sun's energy we're trapping or releasing is much more important than the energy relased by burning fossil fuels or the like. (In other words, the atmospheric CO2 created by burning fossil fuels has a much greater effect than does the heat released by that burning.)

I think that the bottome line is, if we want to travel, eat, live, and other such nice things, we're going to have to use energy... so we'll have to find a way to deal with the effects of that. I believe we will.

Didn't Krakatoa (sp?) lower global temps by more than 1 degree C? So we could always do something like that, spread lots of little particles in the air and block out the sun for a while...I've seen that suggested somewhere. I suspect the engineers will figure a technical way out. (and then upper management will demand a "wow" feature which reduces the solution's potency by half.)

Chip Overclock said...

Much of the sun's energy is used to drive the weather. Okay, that sounds kinda obvious, but it takes a lot of energy to move massive quantities of air and water around. The sun's energy is neither created nor destroyed, but converted into other forms. That includes kinetic energy that drives weather.

But I get your point. The point I'm was trying (probably unsuccessfully) to make is that the laws of physics mean that there's no such thing as a free lunch... any solution to virtually any problem has its downside, and that includes "cheap energy" (whatever the form in which it may come).

Thanks for the comment!

Anonymous said...

I see Jon beat me to the clarification that energy humans "generate" is small compared to that received daily from the sun.
That is exactly the problem with greenhouse gases: a larger percentage of the sun's energy is trapped, instead of reradiated.

As Jon's numbers show, a very small percentage increase in trapped solar energy dwarfs anything we could create.


Chip Overclock said...

My concern with heat production really started years ago when it looked like fusion power might become a reality. Recent articles on "cheap" nuclear power raise similar concerns. Finally, I think the argument that we can't produce as much heat as solar heating hides the issue. If the heating was distributed globally, as one might argue the heating from the sun is, that would be true. But any motorcyclist -- or anyone living in Phoenix Arizona -- can tell you, heating is a localized phenomenon (at least initially). Since energy use and heat production tends to be concentrated in urban areas, heating from energy production is I believe a very serious issue. The fact that the global average temperature is just a fraction of a degree higher doesn't help you when the average temperature of your city block has risen 20F. Your comments on greenhouse gasses are of course exactly why it's so serious an issue.