Image above: Detail of M. C. Escher drawing of perpetual motion waterfall turning a millwheel.
From (http://www.notjohnchow.com/not-john-chow-discovers-perpetual-motion-recycle-those-old-posts)
By John Michael Greer on 24 February 2010 in The Archdruid Report -
(http://thearchdruidreport.blogspot.com/2010/02/energy-follows-its-bliss.html)
Industrial civilization is a complicated thing, and its decline and fall bids fair to be more complicated still, but both rest on the refreshingly simple foundations of physical law. That’s crucial to keep in mind, because the raw emotional impact of the unwelcome future breathing down our necks just now can make it far too easy to retreat into one form or another of self-deception.
Plenty of the new energy technologies discussed so enthusiastically on the internet these days might as well be poster children for this effect. I think most people in the peak oil community are aware by now, for example, that the sweeping plans made for ethanol production from American corn as a solution to petroleum depletion neglected one minor but important detail: all things considered, growing corn and turning it into ethanol uses more energy than you get back from burning the ethanol. It’s not at all surprising that this was missed, for the same variety of bad logic underlies an astonishing amount of our collective conversation about energy these days.
The fundamental mistake that drove the ethanol boom and bust seems to be hardwired into our culture. Here’s an example. Most bright American ten-year-olds, about the time they learn about electric motors and generators, come up with the scheme of hooking up a motor and a generator to the same axle, running the electricity from the generator back to the motor, and using the result to power a vehicle. It seems perfectly logical; the motor drives the generator, the generator powers the motor, perpetual motion results, you hook it up to wheels or the like, and away you drive on free energy. Yes, I was one of those ten-year-olds, and somewhere around here I may still have one of the drawings I made of the car I planned to build when I turned sixteen, using that technology for the engine.
Of course it didn’t work. Not only couldn’t I get the device to power my bicycle – that was how I planned on testing the technology out – I couldn’t even make the thing run without a load connected to it at all. No matter how carefully I hooked up a toy motor to a generator salvaged from an old bicycle light, fitted a flywheel to one end of the shaft, and gave it a spin, the thing turned over a few times and then slowed to a halt. What interests me most about all this in retrospect, though, is that the adults with whom I discussed my project knew that it wouldn’t work, and told me so, but had the dickens of a time explaining why it didn’t work in terms that a bright ten-year-old could grasp.
This isn’t because the subject is overly complicated. The reason why perpetual motion won’t work is breathtakingly simple; the problem is that the way most people nowadays think about energy makes it almost impossible to grasp the logic involved. Most people nowadays think that since energy can be defined as the capacity to do work, if you have a certain amount of energy, you can do a certain amount of work with it. That seems very logical; the problem is that the real world doesn’t work that way.
In the real world, you have to take at least two other things into account. The first of them, of course, has seen a fair amount of discussion in peak oil circles: to figure out the effective energy yield of any energy source, you have to subtract the amount of energy needed to extract that energy source and put the energy in it to work. That’s the problem of net energy, and it’s the trap that’s clamped tightly onto the tender portions of the American ethanol industry; ethanol from corn only makes sense as an energy source if you ignore how much energy has to go into producing it.
The second issue, though, is the one I want to stress here. It’s seen a lot less discussion, but it’s even more important than the issue of net energy, and it unfolds from the most ironclad of all the laws of physics, the second law of thermodynamics. The point that needs to be understood is that how much energy you happen to have on hand, even after subtracting the energy cost, doesn’t actually matter a bit when it comes to doing work. The amount of work you get out of a given energy source depends, not on the amount of energy, but on the difference in energy concentration between the energy source and the environment.
Please read that again: The amount of work you get out of a given energy source depends, not on the amount of energy it contains, but on the difference in energy concentration between the energy source and the environment.
Got that? Now let’s take a closer look at it.
Left to itself, energy always moves from more concentrated states to less concentrated states; this is why the coffee in your morning cuppa gets cold if you leave it on the table too long. The heat that was in the coffee still exists, because energy is neither created nor destroyed; it’s simply become useless to you, because most of it’s dispersed into the environment, raising the air temperature in your dining room by a fraction of a degree. There’s still heat in the coffee as well, since it stops losing heat when it reaches room temperature and doesn’t continue down to absolute zero, but room temperature coffee is not going to do the work of warming your insides on a cold winter morning.
In a very small way, as you sit there considering your cold coffee, you’re facing an energy crisis; the energy resources you have on hand (the remaining heat in the coffee) will not do the work you want them to do (warming your insides). Notice, though, that you’re not suffering from an energy shortage – there’s exactly the same amount of energy in the dining room as there was when the coffee was fresh from the coffeepot. No, what you have is a shortage of the difference between energy concentrations that will allow the energy to do useful work. (The technical term for this is exergy).
How do you solve your energy crisis? One way or another, you have to increase the energy concentration in your energy source relative to the room temperature environment. You might do that by dumping your cold coffee down the drain and pouring yourself a fresh cup, say, or by putting your existing cup on a cup warmer. Either way, though, you have to get some energy to do the work, and that means letting it go from higher to lower concentrations.
Any time you make energy do anything, you have to let some of it follow its bliss, so to speak, and pass from a higher concentration to a lower one. The more work you want done, the more exergy you use up; you can do it by allowing a smaller amount of highly concentrated energy to disperse, or by allowing a much larger amount of modestly concentrated energy to do so, or anything in between.
One way or another, though, the total difference in energy concentration between source and environment – the total exergy – decreases when work is done. Mind you, you can make energy do plenty of tricks if you’re willing to pay its price; you can change it from one form to another, and you can even concentrate one amount of energy by sacrificing a much larger amount to waste heat; but one way or another, the total exergy in the system goes down.
This is why my great discovery at age ten didn’t revolutionize the world and make me rich and famous, as I briefly hoped it would. Electric motors and generators are ways of turning energy from one form into another – from electricity into rotary motion, on the one hand, and from rotary motion into electricity on the other. Each of them necessarily disperses some energy, and thus loses some exergy, in the process. Thus the amount of electricity that you get out of the generator when the shaft is turning at any given speed will always be less than the amount of electricity the motor needs to get the shaft up to that speed.
This gets missed whenever people assume that the amount of energy, rather than its concentration, is the thing that matters. Post something on the internet about energy as a limiting factor for civilization, and dollars will get you doughnuts that somebody will respond by insisting that the amount of energy in the universe is infinite. Now of course Garrett Hardin was quite right to point out in Filters Against Folly that when somebody says “X is infinite,” what’s actually being said is “I refuse to think about X;” the word “infinite” functions as a thoughtstopper, a way to avoid paying attention to something that’s too uncomfortable to consider closely.
Still, there’s another dimension to the problem, and it follows from the points already raised here. Whether or not there’s an infinite amount of energy in the universe – and we simply don’t know one way or the other – we can be absolutely sure that the amount of highly concentrated energy in the small corner of the universe we can easily access is sharply and distressingly finite. Since energy always tries to follow its bliss, highly concentrated energy sources are very rare, and only occur when very particular conditions happen to be met.
In the part of the cosmos that affects us directly, one set of those conditions exist in the heart of the sun, where gravitational pressure squeezes hydrogen nuclei so hard that they fuse into helium. Another set exists here on the Earth’s surface, where plants concentrate energy in their tissues by tapping into the flow of energy dispersing from the sun, and other living things do the same thing by tapping into the energy supplies created by plants.
Now and again in the history of life on Earth, a special set of conditions have allowed energy stockpiled by plants to be buried and concentrated further by slow geological processes, yielding the fossil fuels that we now burn so recklessly. There are a few other contexts in which energy can be had in concentrated forms – kinetic energy from water and wind, both of them ultimately driven by sunlight; heat from within the Earth, caught and harnessed as it slowly disperses toward space; a handful of scarce and unstable radioactive elements that can be coaxed into nuclear misbehavior under exacting conditions – but the vast majority of the energy we have on hand here on Earth comes directly or indirectly from the sun.
That in itself defines our problem neatly, because by the time it gets through 93 million miles of deep space, then filters its way down through the Earth’s relatively murky atmosphere, the energy in sunlight is pretty thoroughly dispersed. That’s why green plants stockpile only about 1% of the energy in the light striking their leaves; the rest either bounces off the leaves or gets dispersed into waste heat in the process of keeping the plant alive and enabling it to manufacture the sugars that store the 1%. Sunlight just isn’t that concentrated, and you have to disperse one heck of a lot of it to get a very modest amount of energy concentrated enough to do much of anything with it.
All this explains as well why the “zero point energy” people are basically smoking their shorts. The premise of zero point energy is that there’s a vast amount of energy woven into the fabric of spacetime; if we can tap into it, we solve all our energy problems and go zooming off to the stars. They do seem to be right that there’s a huge amount of energy in empty space, but once again, the amount of energy does not tell you how much work you can do with it, and zero point energy is by definition at the lowest possible level of concentration. By definition, therefore, it can’t be made to do anything at all, and any attempt to make use of it belongs right up there on the shelf with my motor-generator gimmick.
The same logic also explains why projects for coming up with a replacement for fossil fuels using sunlight, or any other readily available renewable energy source, are doomed to fail. What makes fossil fuels so valuable is the fact that the energy they contain was gathered over countless centuries and then concentrated by geological processes involving fantastic amounts of heat and pressure over millions of years. They define the far end of the curve of energy concentration, at least on this planet, which is why they are as scarce as they are, and why no other energy resource can compete with them – as long as they still exist, that is.
As concentrated fossil fuel supplies deplete, in turn, a civilization that depends on them for its survival will find itself in a very nasty bind. If ours is anything to go by, it will proceed to make that bind even worse by trying to make up the difference by manufacturing new energy sources at roughly the same level of concentration.
That’s a losing bargain, because it maximizes the amount of exergy that gets lost: you have to disperse a lot of energy to make the concentrated energy source, remember, before you can get around to using the concentrated energy source to do anything useful. Thus trying to fill our gas tanks with some manufactured substitute for gasoline, say, drains our remaining supplies of concentrated energy at a much faster pace than the other option – that of doing as much as possible with relatively low concentrations of energy, and husbanding the highly concentrated energy sources for those necessary tasks that can’t be done without them.
This is where E.F. Schumacher’s concept of “intermediate technology,” which was discussed in last week’s post, can be fitted into its broader context. Schumacher’s idea was that state-of-the-art factories and an economy dependent on exports to the rest of the world are not actually that useful to a relatively poor nation trying to build an economy from the ground up.
He was right, of course – those Third World nations that have prospered are precisely the ones that used trade barriers to shelter low-tech domestic industries, and entered the export market only after building a domestic industrial base one step at a time – but in a future in which all of us will be a good deal poorer than we are today, his insights have a wider value. A state-of-the-art factory, after all, is more expensive in terms much more concrete than paper money; it takes a great deal more exergy to build and maintain one than it does to build and maintain a workshop using hand tools and human muscles to produce the same goods.
My readers will doubtless be aware that such considerations have about as much chance of being taken seriously in the governing circles of American politics and business as a snowball has for a long and comfortable stay in Beelzebub’s back yard. Fortunately, the cooperation of the current American political and executive classes is entirely unnecessary.
In the next few posts, we’ll discuss some of the ways that individuals, families, and local communities can make the switch from economic dependence on highly concentrated energy sources to reliance on much more modestly concentrated and more widely available options. The fact that most of the energy in our highly concentrated energy sources has already followed its bliss into entropic ecstasy puts hard limits on what can be achieved, but there’s still plenty of room to make a bad situation somewhat better.
.
Energy Follows Its Bliss
SUBHEAD: A variety of bad logic underlies an astonishing amount of our collective conversation about energy these days.
Image above: Detail of M. C. Escher drawing of perpetual motion waterfall turning a millwheel.
From (http://www.notjohnchow.com/not-john-chow-discovers-perpetual-motion-recycle-those-old-posts)
By John Michael Greer on 24 February 2010 in The Archdruid Report -
(http://thearchdruidreport.blogspot.com/2010/02/energy-follows-its-bliss.html)
Industrial civilization is a complicated thing, and its decline and fall bids fair to be more complicated still, but both rest on the refreshingly simple foundations of physical law. That’s crucial to keep in mind, because the raw emotional impact of the unwelcome future breathing down our necks just now can make it far too easy to retreat into one form or another of self-deception.
Plenty of the new energy technologies discussed so enthusiastically on the internet these days might as well be poster children for this effect. I think most people in the peak oil community are aware by now, for example, that the sweeping plans made for ethanol production from American corn as a solution to petroleum depletion neglected one minor but important detail: all things considered, growing corn and turning it into ethanol uses more energy than you get back from burning the ethanol. It’s not at all surprising that this was missed, for the same variety of bad logic underlies an astonishing amount of our collective conversation about energy these days.
The fundamental mistake that drove the ethanol boom and bust seems to be hardwired into our culture. Here’s an example. Most bright American ten-year-olds, about the time they learn about electric motors and generators, come up with the scheme of hooking up a motor and a generator to the same axle, running the electricity from the generator back to the motor, and using the result to power a vehicle. It seems perfectly logical; the motor drives the generator, the generator powers the motor, perpetual motion results, you hook it up to wheels or the like, and away you drive on free energy. Yes, I was one of those ten-year-olds, and somewhere around here I may still have one of the drawings I made of the car I planned to build when I turned sixteen, using that technology for the engine.
Of course it didn’t work. Not only couldn’t I get the device to power my bicycle – that was how I planned on testing the technology out – I couldn’t even make the thing run without a load connected to it at all. No matter how carefully I hooked up a toy motor to a generator salvaged from an old bicycle light, fitted a flywheel to one end of the shaft, and gave it a spin, the thing turned over a few times and then slowed to a halt. What interests me most about all this in retrospect, though, is that the adults with whom I discussed my project knew that it wouldn’t work, and told me so, but had the dickens of a time explaining why it didn’t work in terms that a bright ten-year-old could grasp.
This isn’t because the subject is overly complicated. The reason why perpetual motion won’t work is breathtakingly simple; the problem is that the way most people nowadays think about energy makes it almost impossible to grasp the logic involved. Most people nowadays think that since energy can be defined as the capacity to do work, if you have a certain amount of energy, you can do a certain amount of work with it. That seems very logical; the problem is that the real world doesn’t work that way.
In the real world, you have to take at least two other things into account. The first of them, of course, has seen a fair amount of discussion in peak oil circles: to figure out the effective energy yield of any energy source, you have to subtract the amount of energy needed to extract that energy source and put the energy in it to work. That’s the problem of net energy, and it’s the trap that’s clamped tightly onto the tender portions of the American ethanol industry; ethanol from corn only makes sense as an energy source if you ignore how much energy has to go into producing it.
The second issue, though, is the one I want to stress here. It’s seen a lot less discussion, but it’s even more important than the issue of net energy, and it unfolds from the most ironclad of all the laws of physics, the second law of thermodynamics. The point that needs to be understood is that how much energy you happen to have on hand, even after subtracting the energy cost, doesn’t actually matter a bit when it comes to doing work. The amount of work you get out of a given energy source depends, not on the amount of energy, but on the difference in energy concentration between the energy source and the environment.
Please read that again: The amount of work you get out of a given energy source depends, not on the amount of energy it contains, but on the difference in energy concentration between the energy source and the environment.
Got that? Now let’s take a closer look at it.
Left to itself, energy always moves from more concentrated states to less concentrated states; this is why the coffee in your morning cuppa gets cold if you leave it on the table too long. The heat that was in the coffee still exists, because energy is neither created nor destroyed; it’s simply become useless to you, because most of it’s dispersed into the environment, raising the air temperature in your dining room by a fraction of a degree. There’s still heat in the coffee as well, since it stops losing heat when it reaches room temperature and doesn’t continue down to absolute zero, but room temperature coffee is not going to do the work of warming your insides on a cold winter morning.
In a very small way, as you sit there considering your cold coffee, you’re facing an energy crisis; the energy resources you have on hand (the remaining heat in the coffee) will not do the work you want them to do (warming your insides). Notice, though, that you’re not suffering from an energy shortage – there’s exactly the same amount of energy in the dining room as there was when the coffee was fresh from the coffeepot. No, what you have is a shortage of the difference between energy concentrations that will allow the energy to do useful work. (The technical term for this is exergy).
How do you solve your energy crisis? One way or another, you have to increase the energy concentration in your energy source relative to the room temperature environment. You might do that by dumping your cold coffee down the drain and pouring yourself a fresh cup, say, or by putting your existing cup on a cup warmer. Either way, though, you have to get some energy to do the work, and that means letting it go from higher to lower concentrations.
Any time you make energy do anything, you have to let some of it follow its bliss, so to speak, and pass from a higher concentration to a lower one. The more work you want done, the more exergy you use up; you can do it by allowing a smaller amount of highly concentrated energy to disperse, or by allowing a much larger amount of modestly concentrated energy to do so, or anything in between.
One way or another, though, the total difference in energy concentration between source and environment – the total exergy – decreases when work is done. Mind you, you can make energy do plenty of tricks if you’re willing to pay its price; you can change it from one form to another, and you can even concentrate one amount of energy by sacrificing a much larger amount to waste heat; but one way or another, the total exergy in the system goes down.
This is why my great discovery at age ten didn’t revolutionize the world and make me rich and famous, as I briefly hoped it would. Electric motors and generators are ways of turning energy from one form into another – from electricity into rotary motion, on the one hand, and from rotary motion into electricity on the other. Each of them necessarily disperses some energy, and thus loses some exergy, in the process. Thus the amount of electricity that you get out of the generator when the shaft is turning at any given speed will always be less than the amount of electricity the motor needs to get the shaft up to that speed.
This gets missed whenever people assume that the amount of energy, rather than its concentration, is the thing that matters. Post something on the internet about energy as a limiting factor for civilization, and dollars will get you doughnuts that somebody will respond by insisting that the amount of energy in the universe is infinite. Now of course Garrett Hardin was quite right to point out in Filters Against Folly that when somebody says “X is infinite,” what’s actually being said is “I refuse to think about X;” the word “infinite” functions as a thoughtstopper, a way to avoid paying attention to something that’s too uncomfortable to consider closely.
Still, there’s another dimension to the problem, and it follows from the points already raised here. Whether or not there’s an infinite amount of energy in the universe – and we simply don’t know one way or the other – we can be absolutely sure that the amount of highly concentrated energy in the small corner of the universe we can easily access is sharply and distressingly finite. Since energy always tries to follow its bliss, highly concentrated energy sources are very rare, and only occur when very particular conditions happen to be met.
In the part of the cosmos that affects us directly, one set of those conditions exist in the heart of the sun, where gravitational pressure squeezes hydrogen nuclei so hard that they fuse into helium. Another set exists here on the Earth’s surface, where plants concentrate energy in their tissues by tapping into the flow of energy dispersing from the sun, and other living things do the same thing by tapping into the energy supplies created by plants.
Now and again in the history of life on Earth, a special set of conditions have allowed energy stockpiled by plants to be buried and concentrated further by slow geological processes, yielding the fossil fuels that we now burn so recklessly. There are a few other contexts in which energy can be had in concentrated forms – kinetic energy from water and wind, both of them ultimately driven by sunlight; heat from within the Earth, caught and harnessed as it slowly disperses toward space; a handful of scarce and unstable radioactive elements that can be coaxed into nuclear misbehavior under exacting conditions – but the vast majority of the energy we have on hand here on Earth comes directly or indirectly from the sun.
That in itself defines our problem neatly, because by the time it gets through 93 million miles of deep space, then filters its way down through the Earth’s relatively murky atmosphere, the energy in sunlight is pretty thoroughly dispersed. That’s why green plants stockpile only about 1% of the energy in the light striking their leaves; the rest either bounces off the leaves or gets dispersed into waste heat in the process of keeping the plant alive and enabling it to manufacture the sugars that store the 1%. Sunlight just isn’t that concentrated, and you have to disperse one heck of a lot of it to get a very modest amount of energy concentrated enough to do much of anything with it.
All this explains as well why the “zero point energy” people are basically smoking their shorts. The premise of zero point energy is that there’s a vast amount of energy woven into the fabric of spacetime; if we can tap into it, we solve all our energy problems and go zooming off to the stars. They do seem to be right that there’s a huge amount of energy in empty space, but once again, the amount of energy does not tell you how much work you can do with it, and zero point energy is by definition at the lowest possible level of concentration. By definition, therefore, it can’t be made to do anything at all, and any attempt to make use of it belongs right up there on the shelf with my motor-generator gimmick.
The same logic also explains why projects for coming up with a replacement for fossil fuels using sunlight, or any other readily available renewable energy source, are doomed to fail. What makes fossil fuels so valuable is the fact that the energy they contain was gathered over countless centuries and then concentrated by geological processes involving fantastic amounts of heat and pressure over millions of years. They define the far end of the curve of energy concentration, at least on this planet, which is why they are as scarce as they are, and why no other energy resource can compete with them – as long as they still exist, that is.
As concentrated fossil fuel supplies deplete, in turn, a civilization that depends on them for its survival will find itself in a very nasty bind. If ours is anything to go by, it will proceed to make that bind even worse by trying to make up the difference by manufacturing new energy sources at roughly the same level of concentration.
That’s a losing bargain, because it maximizes the amount of exergy that gets lost: you have to disperse a lot of energy to make the concentrated energy source, remember, before you can get around to using the concentrated energy source to do anything useful. Thus trying to fill our gas tanks with some manufactured substitute for gasoline, say, drains our remaining supplies of concentrated energy at a much faster pace than the other option – that of doing as much as possible with relatively low concentrations of energy, and husbanding the highly concentrated energy sources for those necessary tasks that can’t be done without them.
This is where E.F. Schumacher’s concept of “intermediate technology,” which was discussed in last week’s post, can be fitted into its broader context. Schumacher’s idea was that state-of-the-art factories and an economy dependent on exports to the rest of the world are not actually that useful to a relatively poor nation trying to build an economy from the ground up.
He was right, of course – those Third World nations that have prospered are precisely the ones that used trade barriers to shelter low-tech domestic industries, and entered the export market only after building a domestic industrial base one step at a time – but in a future in which all of us will be a good deal poorer than we are today, his insights have a wider value. A state-of-the-art factory, after all, is more expensive in terms much more concrete than paper money; it takes a great deal more exergy to build and maintain one than it does to build and maintain a workshop using hand tools and human muscles to produce the same goods.
My readers will doubtless be aware that such considerations have about as much chance of being taken seriously in the governing circles of American politics and business as a snowball has for a long and comfortable stay in Beelzebub’s back yard. Fortunately, the cooperation of the current American political and executive classes is entirely unnecessary.
In the next few posts, we’ll discuss some of the ways that individuals, families, and local communities can make the switch from economic dependence on highly concentrated energy sources to reliance on much more modestly concentrated and more widely available options. The fact that most of the energy in our highly concentrated energy sources has already followed its bliss into entropic ecstasy puts hard limits on what can be achieved, but there’s still plenty of room to make a bad situation somewhat better.
.
Image above: Detail of M. C. Escher drawing of perpetual motion waterfall turning a millwheel.
From (http://www.notjohnchow.com/not-john-chow-discovers-perpetual-motion-recycle-those-old-posts)
By John Michael Greer on 24 February 2010 in The Archdruid Report -
(http://thearchdruidreport.blogspot.com/2010/02/energy-follows-its-bliss.html)
Industrial civilization is a complicated thing, and its decline and fall bids fair to be more complicated still, but both rest on the refreshingly simple foundations of physical law. That’s crucial to keep in mind, because the raw emotional impact of the unwelcome future breathing down our necks just now can make it far too easy to retreat into one form or another of self-deception.
Plenty of the new energy technologies discussed so enthusiastically on the internet these days might as well be poster children for this effect. I think most people in the peak oil community are aware by now, for example, that the sweeping plans made for ethanol production from American corn as a solution to petroleum depletion neglected one minor but important detail: all things considered, growing corn and turning it into ethanol uses more energy than you get back from burning the ethanol. It’s not at all surprising that this was missed, for the same variety of bad logic underlies an astonishing amount of our collective conversation about energy these days.
The fundamental mistake that drove the ethanol boom and bust seems to be hardwired into our culture. Here’s an example. Most bright American ten-year-olds, about the time they learn about electric motors and generators, come up with the scheme of hooking up a motor and a generator to the same axle, running the electricity from the generator back to the motor, and using the result to power a vehicle. It seems perfectly logical; the motor drives the generator, the generator powers the motor, perpetual motion results, you hook it up to wheels or the like, and away you drive on free energy. Yes, I was one of those ten-year-olds, and somewhere around here I may still have one of the drawings I made of the car I planned to build when I turned sixteen, using that technology for the engine.
Of course it didn’t work. Not only couldn’t I get the device to power my bicycle – that was how I planned on testing the technology out – I couldn’t even make the thing run without a load connected to it at all. No matter how carefully I hooked up a toy motor to a generator salvaged from an old bicycle light, fitted a flywheel to one end of the shaft, and gave it a spin, the thing turned over a few times and then slowed to a halt. What interests me most about all this in retrospect, though, is that the adults with whom I discussed my project knew that it wouldn’t work, and told me so, but had the dickens of a time explaining why it didn’t work in terms that a bright ten-year-old could grasp.
This isn’t because the subject is overly complicated. The reason why perpetual motion won’t work is breathtakingly simple; the problem is that the way most people nowadays think about energy makes it almost impossible to grasp the logic involved. Most people nowadays think that since energy can be defined as the capacity to do work, if you have a certain amount of energy, you can do a certain amount of work with it. That seems very logical; the problem is that the real world doesn’t work that way.
In the real world, you have to take at least two other things into account. The first of them, of course, has seen a fair amount of discussion in peak oil circles: to figure out the effective energy yield of any energy source, you have to subtract the amount of energy needed to extract that energy source and put the energy in it to work. That’s the problem of net energy, and it’s the trap that’s clamped tightly onto the tender portions of the American ethanol industry; ethanol from corn only makes sense as an energy source if you ignore how much energy has to go into producing it.
The second issue, though, is the one I want to stress here. It’s seen a lot less discussion, but it’s even more important than the issue of net energy, and it unfolds from the most ironclad of all the laws of physics, the second law of thermodynamics. The point that needs to be understood is that how much energy you happen to have on hand, even after subtracting the energy cost, doesn’t actually matter a bit when it comes to doing work. The amount of work you get out of a given energy source depends, not on the amount of energy, but on the difference in energy concentration between the energy source and the environment.
Please read that again: The amount of work you get out of a given energy source depends, not on the amount of energy it contains, but on the difference in energy concentration between the energy source and the environment.
Got that? Now let’s take a closer look at it.
Left to itself, energy always moves from more concentrated states to less concentrated states; this is why the coffee in your morning cuppa gets cold if you leave it on the table too long. The heat that was in the coffee still exists, because energy is neither created nor destroyed; it’s simply become useless to you, because most of it’s dispersed into the environment, raising the air temperature in your dining room by a fraction of a degree. There’s still heat in the coffee as well, since it stops losing heat when it reaches room temperature and doesn’t continue down to absolute zero, but room temperature coffee is not going to do the work of warming your insides on a cold winter morning.
In a very small way, as you sit there considering your cold coffee, you’re facing an energy crisis; the energy resources you have on hand (the remaining heat in the coffee) will not do the work you want them to do (warming your insides). Notice, though, that you’re not suffering from an energy shortage – there’s exactly the same amount of energy in the dining room as there was when the coffee was fresh from the coffeepot. No, what you have is a shortage of the difference between energy concentrations that will allow the energy to do useful work. (The technical term for this is exergy).
How do you solve your energy crisis? One way or another, you have to increase the energy concentration in your energy source relative to the room temperature environment. You might do that by dumping your cold coffee down the drain and pouring yourself a fresh cup, say, or by putting your existing cup on a cup warmer. Either way, though, you have to get some energy to do the work, and that means letting it go from higher to lower concentrations.
Any time you make energy do anything, you have to let some of it follow its bliss, so to speak, and pass from a higher concentration to a lower one. The more work you want done, the more exergy you use up; you can do it by allowing a smaller amount of highly concentrated energy to disperse, or by allowing a much larger amount of modestly concentrated energy to do so, or anything in between.
One way or another, though, the total difference in energy concentration between source and environment – the total exergy – decreases when work is done. Mind you, you can make energy do plenty of tricks if you’re willing to pay its price; you can change it from one form to another, and you can even concentrate one amount of energy by sacrificing a much larger amount to waste heat; but one way or another, the total exergy in the system goes down.
This is why my great discovery at age ten didn’t revolutionize the world and make me rich and famous, as I briefly hoped it would. Electric motors and generators are ways of turning energy from one form into another – from electricity into rotary motion, on the one hand, and from rotary motion into electricity on the other. Each of them necessarily disperses some energy, and thus loses some exergy, in the process. Thus the amount of electricity that you get out of the generator when the shaft is turning at any given speed will always be less than the amount of electricity the motor needs to get the shaft up to that speed.
This gets missed whenever people assume that the amount of energy, rather than its concentration, is the thing that matters. Post something on the internet about energy as a limiting factor for civilization, and dollars will get you doughnuts that somebody will respond by insisting that the amount of energy in the universe is infinite. Now of course Garrett Hardin was quite right to point out in Filters Against Folly that when somebody says “X is infinite,” what’s actually being said is “I refuse to think about X;” the word “infinite” functions as a thoughtstopper, a way to avoid paying attention to something that’s too uncomfortable to consider closely.
Still, there’s another dimension to the problem, and it follows from the points already raised here. Whether or not there’s an infinite amount of energy in the universe – and we simply don’t know one way or the other – we can be absolutely sure that the amount of highly concentrated energy in the small corner of the universe we can easily access is sharply and distressingly finite. Since energy always tries to follow its bliss, highly concentrated energy sources are very rare, and only occur when very particular conditions happen to be met.
In the part of the cosmos that affects us directly, one set of those conditions exist in the heart of the sun, where gravitational pressure squeezes hydrogen nuclei so hard that they fuse into helium. Another set exists here on the Earth’s surface, where plants concentrate energy in their tissues by tapping into the flow of energy dispersing from the sun, and other living things do the same thing by tapping into the energy supplies created by plants.
Now and again in the history of life on Earth, a special set of conditions have allowed energy stockpiled by plants to be buried and concentrated further by slow geological processes, yielding the fossil fuels that we now burn so recklessly. There are a few other contexts in which energy can be had in concentrated forms – kinetic energy from water and wind, both of them ultimately driven by sunlight; heat from within the Earth, caught and harnessed as it slowly disperses toward space; a handful of scarce and unstable radioactive elements that can be coaxed into nuclear misbehavior under exacting conditions – but the vast majority of the energy we have on hand here on Earth comes directly or indirectly from the sun.
That in itself defines our problem neatly, because by the time it gets through 93 million miles of deep space, then filters its way down through the Earth’s relatively murky atmosphere, the energy in sunlight is pretty thoroughly dispersed. That’s why green plants stockpile only about 1% of the energy in the light striking their leaves; the rest either bounces off the leaves or gets dispersed into waste heat in the process of keeping the plant alive and enabling it to manufacture the sugars that store the 1%. Sunlight just isn’t that concentrated, and you have to disperse one heck of a lot of it to get a very modest amount of energy concentrated enough to do much of anything with it.
All this explains as well why the “zero point energy” people are basically smoking their shorts. The premise of zero point energy is that there’s a vast amount of energy woven into the fabric of spacetime; if we can tap into it, we solve all our energy problems and go zooming off to the stars. They do seem to be right that there’s a huge amount of energy in empty space, but once again, the amount of energy does not tell you how much work you can do with it, and zero point energy is by definition at the lowest possible level of concentration. By definition, therefore, it can’t be made to do anything at all, and any attempt to make use of it belongs right up there on the shelf with my motor-generator gimmick.
The same logic also explains why projects for coming up with a replacement for fossil fuels using sunlight, or any other readily available renewable energy source, are doomed to fail. What makes fossil fuels so valuable is the fact that the energy they contain was gathered over countless centuries and then concentrated by geological processes involving fantastic amounts of heat and pressure over millions of years. They define the far end of the curve of energy concentration, at least on this planet, which is why they are as scarce as they are, and why no other energy resource can compete with them – as long as they still exist, that is.
As concentrated fossil fuel supplies deplete, in turn, a civilization that depends on them for its survival will find itself in a very nasty bind. If ours is anything to go by, it will proceed to make that bind even worse by trying to make up the difference by manufacturing new energy sources at roughly the same level of concentration.
That’s a losing bargain, because it maximizes the amount of exergy that gets lost: you have to disperse a lot of energy to make the concentrated energy source, remember, before you can get around to using the concentrated energy source to do anything useful. Thus trying to fill our gas tanks with some manufactured substitute for gasoline, say, drains our remaining supplies of concentrated energy at a much faster pace than the other option – that of doing as much as possible with relatively low concentrations of energy, and husbanding the highly concentrated energy sources for those necessary tasks that can’t be done without them.
This is where E.F. Schumacher’s concept of “intermediate technology,” which was discussed in last week’s post, can be fitted into its broader context. Schumacher’s idea was that state-of-the-art factories and an economy dependent on exports to the rest of the world are not actually that useful to a relatively poor nation trying to build an economy from the ground up.
He was right, of course – those Third World nations that have prospered are precisely the ones that used trade barriers to shelter low-tech domestic industries, and entered the export market only after building a domestic industrial base one step at a time – but in a future in which all of us will be a good deal poorer than we are today, his insights have a wider value. A state-of-the-art factory, after all, is more expensive in terms much more concrete than paper money; it takes a great deal more exergy to build and maintain one than it does to build and maintain a workshop using hand tools and human muscles to produce the same goods.
My readers will doubtless be aware that such considerations have about as much chance of being taken seriously in the governing circles of American politics and business as a snowball has for a long and comfortable stay in Beelzebub’s back yard. Fortunately, the cooperation of the current American political and executive classes is entirely unnecessary.
In the next few posts, we’ll discuss some of the ways that individuals, families, and local communities can make the switch from economic dependence on highly concentrated energy sources to reliance on much more modestly concentrated and more widely available options. The fact that most of the energy in our highly concentrated energy sources has already followed its bliss into entropic ecstasy puts hard limits on what can be achieved, but there’s still plenty of room to make a bad situation somewhat better.
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