Waste heat: the other global warming

May 29, 2009 6:51 AM

The Other Global Warming. Waste heat (second law of thermodynamics) over the next 300 years could add 3 degrees of warming.
posted by stbalbach (41 comments total)

Critics say 300 years is beyond worry and greenhouse gases are the more serious concern. Probably true. But this does present an interesting vision of the future, on this planet or elsewhere. It would be hard to imagine an advanced long-lived civilization that didn't account for waste heat. The only energy source that doesn't add waste heat is solar (which includes wind and wave). Nuclear Fusion may be the "holy grail" of unlimited cheap power, but it stands to reason a few mini-sun's burning away on Earth would heat the planet up and not be sustainable. And if solar is the only reasonable long term power source, will we reach a limit of growth, long term (a figure easily calculable). It's hard to argue with the second law of thermodynamics.
posted by stbalbach at 6:59 AM on May 29, 2009

Waste Heat is decreasing very fast today - I am sure it will be even more so over the next 250 years.

I am an electrician, and we are installing more and more LED lights and fluorescent lights everyday. The old style incandescant lights waste tons of heat, but not LED lights.

Plus, air conditioners and water heaters are becoming increasingly efficient. Don't get me wrong, waste heat is an issue that needs to be dealt with - not only in wasted heat escaping into the environment, but also wasted energy (and greeh-house gases) to produce that wasted heat.

But, I can see first hand in my industry that the issue is being addressed (at least, starting to be addressed)
posted by Flood at 7:03 AM on May 29, 2009

Clarke's 3001: The Final Odyssey featured this. After fusion goes bigtime, we kinda start cooking the planet. Oopsie.
posted by adipocere at 7:04 AM on May 29, 2009

But isn't waste heat only a problem when it's "extra" waste heat? As in, when we convert stored chemical energy (such as fossil fuels) into heat/mechanical/electrical energy? But if we were using heat from the environment (solar, geothermal, wind, etc), we'd actually be *decreasing* waste heat, right? So this is really just part of the same problem: Using up stored energy rather than paying as we go.
posted by DU at 7:22 AM on May 29, 2009

Waste Heat is decreasing very fast today

Those are increases in efficiency, like with lightbulbs, but efficiency doesn't mean less energy use overall. For example, we are much more efficient with energy today than the Roman Empire was, but we still produce much more waste heat overall, mainly because of population and per-capita energy use. Per-capita, we are probably 1000 times or more energy users than a typical Roman, and this trend will only increase in the future since the greater the population, the more complexity (energy) is needed to maintain it.

But isn't waste heat only a problem when it's "extra" waste heat?

My understanding is everything produces waste energy, to some various degree, as measured by "efficiency". The only heat from the environment that would be here regardless of humans is solar (photovoltaic, wind and wave) and a small amount of surface geothermal and perhaps tidal (moon). So those are the only sources that can be tapped without adding new energy (heat) to the system.
posted by stbalbach at 7:30 AM on May 29, 2009

And if solar is the only reasonable long term power source, will we reach a limit of growth, long term (a figure easily calculable).

I'd think any form of renewable energy should work, not just solar. Geothermal energy, wave energy, etc.
posted by Blazecock Pileon at 7:34 AM on May 29, 2009

Guys, it says right in the article that geothermal is part of the problem because it pumps heat into the atmosphere.
posted by adamdschneider at 7:54 AM on May 29, 2009

Waste Heat is decreasing very fast today - I am sure it will be even more so over the next 250 years.

I submit to you Jevon's Paradox (and the even more delightfully named Khazzoom-Brookes Postulate, a derivation of Jevons original observation). Essentially: increases in energy efficiency mean that we use more energy, not less, canceling out any gains in efficiency.

While we will undoubtedly create more energy-efficient devices in the future, we will also use more of them, more frequently. As an example, look at the daily energy use of a typical suburban couple of the 1950's versus today: which do you think used more energy?
posted by Bora Horza Gobuchul at 7:55 AM on May 29, 2009 [1 favorite]

> I submit to you Jevon's Paradox

I came here to post that. Instead I'll just say that I'm sure humanity will dig its way out of this hole, one way or another.
posted by you just lost the game at 7:58 AM on May 29, 2009

Waste Heat is decreasing very fast today

For achieving a particular goal this may be true, e.g. for lighting a room, powering a TV, etc, but in societal terms not really, electrical demand has gone up continuously for decades and is set to continue doing so, while there has been a downward trend in energy intensity, (i.e. GDP against energy use) the overall energy use has gone up, and it is likely that the overall waste heat output has also gone up. Waste heat is set to become more of an issue in terms of wasted resource too hopefully - it is after all a termednous potential resource, hte UK for example, puts enough heat up power station cooling towers to provide all the heat energy for domestic space and water heating in every household in the country. Similar figures are likely to pertain for other western countries. Some countries do use waste heat in district heating systems, but there's a lot more that could be done.

Plus, air conditioners and water heaters are becoming increasingly efficient.

This is a prime example of my previous point, they're becoming more efficient but there are a lot more of them, so the overall energy use for AC has gone up. (There is some potential for renewable cooling by the way but it is an area that is not very far developed.)

As in, when we convert stored chemical energy (such as fossil fuels) into heat/mechanical/electrical energy? But if we were using heat from the environment (solar, geothermal, wind, etc), we'd actually be *decreasing* waste heat, right? So this is really just part of the same problem: Using up stored energy rather than paying as we go.

The article does make it clear that its refering to waste heat associated with burning fossilfuels but that exploiting geothermal and nuclear would also effectively release previously stored heat into the environment. so solving the greenhouse gas problem with improved efficiency and increased renewables would also address the waste heat issue.
posted by biffa at 8:03 AM on May 29, 2009

Using solar will increase waste heat. Why?

Compare the albedo of average groundcover versus that of a solar panel. Those solar panels are awfully dark, aren't they? Rather than reflecting light back into space, the panels absorb it. And it doesn't matter how efficient you are, energy used always winds up as waste heat, it's just that you can get more work out of the energy while it is on its way to being waste heat.

Take a sugar cane plant, grow it, it's stored that solar energy. Cut it down, seal it in a safe, it'll still decay and all of that nice chemical energy will be used to make bacterial goo and be released as waste heat.

Grab some wind in your little turbine? Well, it was once slightly impeded kinetic energy, but it will soon be waste heat and now some stagnant air.

You can't win, you can't break even ... you can't even leave the game.
posted by adipocere at 8:04 AM on May 29, 2009 [5 favorites]

Guys, it says right in the article that geothermal is part of the problem because it pumps heat into the atmosphere.

Only if you pump it into the atmosphere at a greater rate than it is already being pumped there. As a totally made up example, imagine that steam vents and volcanoes were pumping out 1 GW of heat continuously. If our geothermal plants diverted some of that 1 GW and turned 10% of it into electricity (net), we'd actually be reducing the problem. Whereas if we ignored that 1 GW and dug new holes extract 10 MW and then turned 10% of *that* into electricity, we'd be adding to it.
posted by DU at 8:10 AM on May 29, 2009 [2 favorites]

And it doesn't matter how efficient you are, energy used always winds up as waste heat, it's just that you can get more work out of the energy while it is on its way to being waste heat.

But the work you get decreases the waste, which your solar panel albedo argument ignores. You can't just say that the solar panel is reflecting less, therefore the Earth is hotter. A lot of that captured energy is turned into work. Except...wait. If that work is done here on Earth and the energy never leaves Earth after that, then we have increased the total internal energy, i.e. raised the temperature. Hmmm...
posted by DU at 8:13 AM on May 29, 2009

We can all agree that wind and hydro power don't increase waste heat, right? They are just ways of rerouting energy along its path from solar radiation to waste heat. Even if we weren't using the wind or water, all of the energy they have would have eventually become heat anyway.

Solar power should also have a very small effect -- the albedo point is a good one, but we'd need to design very very efficient solar panels, and have a huge number of them, for this to matter.
posted by goingonit at 8:13 AM on May 29, 2009

Waste Heat is decreasing very fast today - I am sure it will be even more so over the next 250 years. ... I am an electrician, and we are installing more and more LED lights and fluorescent lights everyday.

While I'm all for greater efficiency and more CFLs, waste heat is definitely not decreasing. There are more powerplants pumping out more megawatts from fossil sources today than ever before, and the trend doesn't look like it's going to change anytime very soon. The rate of increase may start to slow soon, as we build more solar and wind powerplants instead of new fossil ones, but it won't start to actually decrease until we take the fossil plants off-line.

It's great that people are using the power more efficiently, but they're still using a lot of it, and that's what matters; it's the net amount of energy that you're trying to sink into the biosphere.

Five people each using a 20W CFL is better than five people each using a 100W incandescent, but it's exactly the same from a global-heating perspective as one person with a 100W incandescent. Most conservation and efficiency measures seem to be aimed at allowing us to go from 1 person with the 100W bulb to 5 people with CFLs, particularly as lots of people in the developing world start to consume more energy. In other words, we're doing more with the same or more with less than we'd otherwise need to add, not doing the same with less.
posted by Kadin2048 at 8:16 AM on May 29, 2009

Entropy isn't what it used to be.
posted by exogenous at 8:17 AM on May 29, 2009

Guys, it says right in the article that geothermal is part of the problem because it pumps heat into the atmosphere.

Geothermal vents do this naturally, anyway, don't they? Might as well tap in.
posted by Blazecock Pileon at 8:21 AM on May 29, 2009

I was under the impression that geothermal power generally involves sinking pipes into the ground so that they absorb heat not exposed to the elements, not simply plopping a turbine on top of a steam vent.
posted by adamdschneider at 8:25 AM on May 29, 2009

More on that topic:

World energy use over time, 1965-2005, based on BP data. I am skeptical, based on that chart, that even the rate of increase (first derivative) is decreasing, but it's tough to tell.

Also, according to the DOE:

World net electricity consumption nearly doubles over the projection period, from 13,290 billion kilowatthours in 2001 to 23,072 billion kilowatthours in 2025. Strong growth in electricity use, averaging 3.5 percent per year, is projected for the developing world, where robust economic expansion drives demand for electricity to run newly purchased home appliances for cooking, air conditioning, space and water heating and refrigeration. For the industrialized world and the EE/FSU, where electricity markets are more mature, slower average growth rates of 1.6 percent per year and 2.0 percent per year, respectively, are projected. [...] Coal remains an important component of the world’s electricity markets and is expected to continue to dominate many national electricity markets in developing Asia. Currently, of the coal consumed worldwide, 64 percent is used for electricity generation; and in almost every region of the world, power generation accounts for most of the projected growth in coal consumption (Figure 4).

So maybe there's a slowing of the first derivative in industrialized countries, but it's offset by increased growth in the developing world which is predicted to come in large part from fossil sources, or at least enough from fossil sources so that the total amount of coal burned will actually increase for the foreseeable future.
posted by Kadin2048 at 8:26 AM on May 29, 2009

Why only waste heat? The useful work done by power generation turns into heat, too (except the tiny fraction used to make light and radio waves that get sent into space).

[okay, off to read the article]
posted by fantabulous timewaster at 8:35 AM on May 29, 2009

The paper
posted by fantabulous timewaster at 8:46 AM on May 29, 2009

Geothermal vents do this naturally, anyway, don't they?

The amount of geothermal energy that makes it to the surface into the atmosphere I would imagine is very small. Actually it's very large when one considers plate tectonics with erupting volcanoes (earthquakes?) - but those occur over very long time scales and are not usable by humans.

Also just to clarify - wind is solar energy, so are waves. Tidal energy is a uniqe form since it's gravity-based - I don't know if tidal energy contributes to heating the atmosphere or not, one would think so, the oceans would be cooler without tides?
posted by stbalbach at 8:48 AM on May 29, 2009

There are a couple ways to get rid of extra heat, shade the earth from orbit (large mylar solar shades), reflect sunlight that reaches the earth (same idea, but with mirrors on the ground) or pump it out (generate light that escapes the atmosphere). I wonder how much of an effect outdoor night time lights would have on his calculations (if you can see it from space, that energy has left the planet).
posted by 445supermag at 8:53 AM on May 29, 2009

I submit to you Jevon's Paradox (and the even more delightfully named Khazzoom-Brookes Postulate, a derivation of Jevons original observation). Essentially: increases in energy efficiency mean that we use more energy, not less, canceling out any gains in efficiency.

There has been quite a lot of work done on the rebound effect, sometimes it can approach 100% but is generally less, Greening et al published a useful survey of multiple prior studies in Energy Policy, Volume 28, Issues 6-7, June 2000, Pages 389-401, the gist of which is summarised here. it indicates that the rebound effect only accounts for a fraction of efficiency improvements in most cases related to household energy use.
posted by biffa at 9:02 AM on May 29, 2009 [2 favorites]

stbalbach, lunar tides also deform the earth's crust (as on Io, but less dramatic). My instinct is that these "rock tides" dissipate more energy than ocean tides, perhaps contributing to plate tectonics or other geothermal effects, but I haven't looked quantitatively.
posted by fantabulous timewaster at 9:06 AM on May 29, 2009

I submit to you Jevon's Paradox (and the even more delightfully named Khazzoom-Brookes Postulate, a derivation of Jevons original observation).
posted by Bora Horza Gobuchul at 7:55 AM on May 29 [+] [!]

Educating the natives? Perosteck Balveda would like a word with you.
posted by Durn Bronzefist at 9:27 AM on May 29, 2009 [1 favorite]

Just curious how many predictions made in 1709 you think have come to pass?
posted by one_bean at 10:11 AM on May 29, 2009

Plus, air conditioners and water heaters are becoming increasingly efficient.

Wait, I thought air conditioners produced waste cold?

I kid. This argument might be better framed in terms of the really really really long-term implications of the second law, by which we're REALLY fucked.
posted by 7segment at 10:49 AM on May 29, 2009

To paraphrase James Blish, we're all just local anomalies in the second law of thermodynamics.
posted by sciurus at 10:56 AM on May 29, 2009

Solar power should also have a very small effect -- the albedo point is a good one, but we'd need to design very very efficient solar panels, and have a huge number of them, for this to matter.

All the light that goes into a solar panel (rather then being reflected) comes out as heat or electricity, so all that matters is how dark they are, not how efficient.

Anyway, I doubt that wind and ocean energy would actually increase heat, because those would end up as heat anyway.

Maybe in 300 years global warming will be so under control that we'll be able to offset those 3 degrees.
posted by delmoi at 11:12 AM on May 29, 2009

Related: global warming already causing 300,000 excess deaths per year.
posted by Rumple at 11:14 AM on May 29, 2009

One possible amelioration would be to optimize the temperature of waste heat so that its black body spectrum allows it to radiate into space with minimal absorption by any component of the atmosphere, but here again, carbon dioxide makes things worse by threatening to trap the heat we make the way it does the heat of absorbed solar radiation.

It would also be wiser to produce as much waste heat as possible in regions with no cloud cover.

Big solar installations which use a working fluid to absorb solar energy could have a nearby conventional power installation that pumped heat into them at night to be radiated away into space-- working in reverse, so to speak.
posted by jamjam at 11:42 AM on May 29, 2009

Also just to clarify - wind is solar energy, so are waves.

huh?
posted by Flood at 1:25 PM on May 29, 2009

If exponential growth in energy usage is going to continue for 300 years, I say we let the people (or whatever) on the other side of the singularity worry about this one.
posted by sfenders at 3:06 PM on May 29, 2009

"You can't win, you can't break even ... you can't even leave the game."

...uh.
....mm.
...Raise. *push chips*
*level stare*
posted by Smedleyman at 3:44 PM on May 29, 2009

Always good to curb waste (save money and the planet!)
posted by Catholicgauze at 5:22 PM on May 29, 2009

I've always been a bit skeptical of the greenhouse effect (not global warming, just the mechanics of it) for basically this reason. Because, like, duh.

"Why would the earth be getting hotter?"
"Well, you know all these smoke stacks and chimneys and tailpipes and things? The stuff coming out of them? That's hot."
"But look! The carbon dioxide and carbon monoxide and all this other stuff also kind of traps the heat in once it gets up into the sky and the sun's rays get in and bounce around and--"
"Yeah, but it's hot. Wouldn't that directly heat the atmosph--"
"It's just like an elaborate chemical greenhouse!"
"Maybe so, but that stuff rises into the atmosphere because it's hot."
"Like a greenhouse..."
"Oh, bother."

Even if the problem really is the greenhouse effect, that's all complicated and abstract enough to be dismissed as theoretical hogwash. On the other hand, "hot stuff makes stuff hot" is understandable by even the dimmest of wits. Anyone claiming the contrary couldn't hide behind balonious , "It's just a theory invented by the wacko environmentalist commie nazi atheists!" Because, hey, hot stuff does make stuff hot, doesn't it?
posted by Sys Rq at 7:51 PM on May 29, 2009

fantabulous timewaster: "stbalbach, lunar tides also deform the earth's crust (as on Io, but less dramatic). My instinct is that these "rock tides" dissipate more energy than ocean tides, perhaps contributing to plate tectonics or other geothermal effects, but I haven't looked quantitatively."

If true that is really fascinating.
posted by stbalbach at 8:42 PM on May 29, 2009

Because, hey, hot stuff does make stuff hot, doesn't it?

Uh, yeah. I suppose there are people out there taking this seriously. CO2 is among the largest exhaust gasses by volume (water vapour second, or first?), and it's increased by rather less than 200 parts per million in the atmosphere over 100 years. So take 10ppm for an over-estimate, then make it 100ppm to account for all the other non-exhaust waste heat (though I imagine it's the majority of the heat goes out the exhaust in a car engine for example), and figure it's all at twice the temperature of the atmosphere (400K maybe?) ... and even with this generous estimate we're still talking about raising the temperature by something like .02 degrees, reasonably close to the "100 times less than the greenhouse effect" quoted in the article. The atmosphere will radiate off excess heat until it's in balance, so the effect is not cumulative. To get 3 degrees of warming we'd need to be using hundreds of times more energy than at present, even after the fossil fuels are gone, and be generating that energy from something other than the obvious choice in this techno-utopian future, solar power. Okay, solar power still contributes a bit of heat, but not much compared to the hypothetical alternatives, so in that case make it thousands of times more energy. It's not really likely. It's basically just watching a baby grow at a rate of inches per year and predicting that if this trend continues he'll eventually be a hundred feet tall.
posted by sfenders at 10:08 AM on May 30, 2009

Also just to clarify - wind is solar energy, so are waves.

huh?

Wind is caused by uneven solar heating of the atmosphere. Waves are caused by wind. Basically the point is that any energy source which derives from the sun is energy that would have been in the earth energy system anyway so doesn;tcontribute to heating of the atmosphere. Fossil fuels, nuclear fission and fusion and geothermal are on the planet but effectively 'stored' so do not raise atmpspheric temperatures until they are combusted/released.
posted by biffa at 1:06 PM on May 31, 2009

As fantabulous timewaster points out, waves tap-- to some extent-- the kinetic energy of the spinning Earth. So does wind.

Seems to me I've read that a year contained +400 days just a few hundred million years ago (ah: He also found that 500 million years ago there were 412 days per year;).

Some of the energy of those 50 days went into waves and wind. Wish I had an estimate of how much of the energy content of waves and wind came from this source.
posted by jamjam at 4:01 PM on May 31, 2009