Energy concentration revisited
For those watching current affairs with an eye sharpened by history, it’s been quite a week since the last Archdruid Report post came out. For starters, American politicians and pundits have gone in for another round of China-bashing, insisting that China’s manipulation of its currency is unacceptable to us. Since the US is manipulating its own currency at least as shamelessly, the strength of their case is open to question; one gathers that the real grievance is that China’s manipulations have been rather more successful than ours. The tone of this latest flurry of denunciation may be gathered from a recent headline: “China Using Trade Agreements For Its Own Advantage.” Er, did anyone think that the Chinese would use those agreements solely for our advantage?
As it happens, my reading material over the last few days has included historian Donald Kagan’s magisterial On The Origins Of War, which anatomizes what generally happens when a declining empire jealous of its privileges collides with a rising power impatient for its own place in the sun. (The title of Kagan’s book offer a hint, if one is needed, about what the consequences usually are.) The slow approach of conflict between America and China has all the macabre fascination of a train wreck in the making; it’s uncomfortably easy, knowing the historical parallels, to see how a few more missteps that each side seems quite eager to make could back both nations into a position where the least either side can accept is more than the most either side can yield. The flashpoint, when it comes, is likely to lie some distance from either country’s borders; look at the parts of the world where Chinese overseas investment is shouldering aside longstanding American interests, and it’s not hard to imagine how and where the resulting struggle might play out.
Meanwhile the Obama administration has decided to give Congress back to the Republicans in the upcoming elections. I can think of no other way of describing Obama’s fixation on ramming through a health care bill that is not merely deeply unpopular, but one of the most absurd pieces of legislation in recent memory as well. How else to describe an attempt to deal with the fact that half the American people can’t afford health insurance by requiring them, under penalty of law, to pay for it anyway? In the process, this bill promises to take tens of billions of dollars a year out of the pockets of American families – during the worst economic conditions since the 1930s, mind you – to benefit a health insurance industry that already ranks as one of the most greedy and corrupt institutions in American public life. You’d think that a party that has ridden into power twice now on a wave of protest would know better than to adopt the most unpopular policies of the party it ousted, and then fritter away its remaining political capital on a disastrously misconceived notion of health care reform. Yet Clinton did that, and Obama’s repeating his mistake; since he’s doing it in the midst of an economic debacle on the grand scale, he’s unlikely to wriggle out of the consequences as adeptly as his predecessor.
Those of my readers who live in America thus might want to consider pressuring their elected representatives to put a brake on either or both of these disasters in the making. Those of my readers who live elsewhere might want to consider hiding under their beds until the rubble stops bouncing; barring exceptionally good luck, the first blasts are unlikely to be long delayed. Still, these cheerful reflections aren’t the theme of this week’s Archdruid Report. No, the theme of this week’s Archdruid Report delves further into the issue at the center of the last several essays, the vexed relationship between thermodynamics, energy resources, and economics in an age of decline.
I’m quite sure that some of my readers would prefer that I talk about something more immediately topical. Still, fundamental issues of the sort I want to pursue just now have immediate practical consequences. The economic debacle that’s among the major forces pushing America and China toward an armed conflict from which neither will benefit, for example, didn’t just happen by chance; it became inevitable once the political classes of the industrial world embraced certain fashionable but direly flawed ideas about economics, and convinced themselves that money was the source of wealth rather than the mere measure of wealth it actually is. Decades of bad policy that encouraged making money at the expense of the production of real wealth followed from those ideas. The result was the transformation of a vast amount of paper “wealth” – that is, money of one kind of another – into some malign equivalent of the twinkle dust of a children’s fairy tale; and the fallout includes economic stresses of the kind that so often push international conflicts past the point of no return.
In the same way, I’m convinced, certain widespread misunderstandings about how energy interfaces with economics are causing a great deal of alternative energy investment to go into schemes that are going to offer us very little help dealing with the end of the age of cheap fossil fuels, while other options that could help a great deal – and there are quite a few of those – are languishing for want of funds. That was the theme of last week’s post; the response was one of the largest these essays have yet fielded, and it helped me clarify the differences between the ways that certain kinds of energy can be used in practice, and the ways that a great deal of current thought assumes they can be used.
That same lesson could have been drawn from history. Solar energy, the most widely available alternative energy source, is not a new thing. Life on earth has been using it for something like two billion years, since the first single-celled prokaryotes figured out the trick of photosynthesis. Human beings were a little slower off the mark, since we had to evolve first, but passive solar heating was in widespread use in ancient Greece and imperial China; the industrial use of solar power in the West dates back to the late Middle Ages, when enterprising alchemists learned to use dished mirrors to focus heat on glass vessels; the first effective solar heat engine had its initial tryout in 1874. One solar energy proponent who commented on last week’s blog argued that human flight had progressed from Kitty Hawk to breaking the sound barrier in sixty years, and therefore solar power could be expected to make some similar leap; he apparently didn’t know that solar power was a working proposition decades before Kitty Hawk, and the leap never happened.
At least, the leap that my commenter expected never happened. Solar power has in fact been hugely successful in a wide range of practical applications. Solar water heaters, a central theme of an earlier post, were in common use across the American Sun Belt for more than half a century before cheap electrical and gas water heaters drove them out of the market in the 1950s. Passive solar household heating has proven itself in countless applications, and so have many other technologies using solar energy as a source of modest amounts of heat. Given that well over half the energy that Americans use today in their homes takes the end form of modest amounts of heat, this is not a minor point, and it directs attention to a range of solar technologies that could be put to work right now to cushion the impact of peak oil and begin the hard but necessary transition to the deindustrial age.
Yet it’s at least as instructive to pay attention to what hasn’t worked. The approach central to today’s large-scale solar plants – mirrors focusing sunlight onto tubes full of fluid, which boils into vapor and runs an engine, which in turn powers a generator – was among the very first things tried by the 19th century pioneers of solar energy. As discussed in last week’s post, these engines work after a fashion; that is, you can get a very, very modest amount of electricity out of sunlight that way with a great deal of complicated and expensive equipment. That’s why, while solar water heaters spread across rooftops on three continents in the early 20th century, solar heat engines went nowhere; the return on investment – measured in money or energy – simply didn’t justify the expenditure.
Now of course we’ve improved noticeably on the efficiency of some of the processes involved in those early solar engines. Still, a good many of the basic limits the 19th and early 20th century solar pioneers faced are not subject to technological improvement, because they unfold from the difference central to last week’s post – the difference between diffuse and concentrated energy.
This difference or, rather, the language I used to discuss that difference, turned out to be the sticking point for a number of scientifically literate readers last week. Some insisted that “exergy,” the term I used for the capacity of energy to do work in a given system, didn’t mean that – though, oddly enough, others who appeared to have just as solid a background in the sciences insisted that it did indeed mean that. Others insisted that I was overgeneralizing, or using sloppy terminology, or simply wrong.
Now I’m quite cheerfully ready to be told that my use of scientific terminology is incorrect. I’m not a physicist, and I don’t even play one on TV; my background is in history and the humanities, and my knowledge of science, with a few exceptions (mostly in ecology and botany), comes from books written for intelligent laypeople. Still, there’s a difference between a misused term and an inaccurate concept, and two things lead me to think that whether or not the former is involved here, the latter is not. The first is the history of alternative energy technologies, of which the trajectory of solar energy traced above is only one part. The second is that I heard from quite a few people who depend on the diffuse energy available from the Sun in their own homes and lives, and thus have a more direct understanding of the matter, and all of them grasped my point instantly and illustrated it with examples from their own experience.
Several additional examples of the same distinction also turned up as I researched the subject. Back most of thirty years ago, when I was studying appropriate technology in college, one of the standard examples the professors used to explain thermodynamic limits was ordinary geothermal heat. This is the sort of thing you get in a place where there isn’t any underground magma close enough to the surface to set off geysers and make commercial geothermal electric plants an option; it’s the gentle heat that filters up through the Earth’s crust from the mantle many miles below. In terms of sheer quantity of thermal energy, it looks really good, but away from hot spots, it’s very diffuse – and as a result, you can show pretty easily by way of Carnot’s law that the energy you’d get from pumping the heat to the surface and using it to drive a heat engine will be less than the energy you need to run the pumps. On the other hand, if all you want is diffuse heat, you’re looking in the right place – and in fact hooking up a heat pump to a hole in the ground and using it for domestic heating and cooling has proven to be a very efficient technology in recent years.
The same thing is true for OTEC, another of those ideas whose time is always supposedly about to come and never quite arrives. The acronym stands for Oceanic Thermal Energy Conversion, and it does with the thermal difference between deep and surface water what a geothermal power plant does with the thermal difference between hot rocks half a mile down and the cold surface of the planet. You can, in fact, run a heat engine on OTEC power, but it takes about 2/3 of the power you generate to run the pumps. That means you’ve got a net energy of 0.33 or so, even before factoring in the energy cost of the OTEC plant; in economic terms, what it means is that you run on government grants or you go broke. On the other hand, there’s at least one resort in the Pacific that uses OTEC for the far simpler task of air conditioning. Again, if all you need to do is move diffuse heat around, a diffuse energy source is more than adequate; if you need to do something more complex you may well have problems.
Let’s take a closer look at why that happens. The core concept to grasp here is that for reasons hardwired into the laws of thermodynamics, converting energy from one form or another, in most cases, is highly inefficient. That’s what an engine does; it takes in thermal energy – that is, heat – and puts out mechanical energy – in most cases, a shaft spinning around very fast, which you hook up to something else like a drive train, a propeller, or a generator. Of all the energy released by burning gasoline in an average automobile engine, which is one form of heat engine, around 25% goes into turning the crankshaft; the rest is lost as diffuse heat. If you’re smart and careful, you can get a heat engine to reach efficiencies above 50%; a modern combined-cycle power plant working at top efficiency can hit 60%, but that’s about as good as the physics of the process will let you get.
Most other ways of turning one form of energy into another are no more efficient, and many of them are much less efficient than heat engines. (That’s why heat engines are used so extensively in modern technology; inefficient as they are, they’re better than most of the alternatives.) The reason nobody worries much about these efficiencies is that we’re used to fossil fuels, and fossil fuels contain so much potential heat in so concentrated a form that the inefficiencies aren’t a problem. 75% of the potential energy in the gas you pour into your car gets turned into waste heat and dumped via the radiator, but you don’t have to care; there’s still more than enough to keep you zooming down the road.
With alternative energy sources, though, you have to care. That’s why the difference between diffuse and concentrated energies matters so crucially; not only specific technologies, but whole classes of technologies on which the modern industrial world depends, embody such massive inefficiencies that diffuse energy sources won’t do the job. Lose 75% of the energy in a gallon of gasoline to waste heat, and you can shrug and pour another gallon in the tank; lose 75% of the energy coming out of a solar collector, and you may well have passed the point at which the solar collector no longer does enough work to be worth the energy and money cost to build and maintain it. The one kind of energy into which you can transform other kinds of energy at high efficiencies — sometimes approaching 100% – is relatively diffuse heat. This is why using sunlight to heat water, air, food, or what have you to temperatures in the low three digits on the Fahrenheit scale is among the most useful things you can do with it, and why, when you’re starting out with diffuse heat, the most useful thing you can do with it is generally to use the energy in that form.
What this means, ultimately, is that the difference between an industrial civilization and what I’ve called an ecotechnic civilization isn’t simply a matter of plugging some other energy source in place of petroleum or other fossil fuels. It’s not even a matter of downscaling existing technologies to fit within a sparser energy budget. It’s a matter of reconceiving our entire approach to technology, starting with the paired recognitions that the very modest supply of concentrated energy sources we can expect to have after the end of the fossil fuel age will have to be reserved for those tasks that still need to be done and can’t be done any other way, and that anything that can be done with a diffuse energy source needs to be done with a diffuse energy source if it’s going to be done at all.
A society running on diffuse energy resources, in other words, is not going to make use of anything like the same kinds of technology as a society running on concentrated energy resources, and attempts to run most existing technologies off diffuse renewable sources are much more likely to be distractions than useful options. In the transition between today’s technology dominated by concentrated energy and tomorrow’s technology dominated by diffuse heat, in turn, some of the most basic assumptions of contemporary economic thought – and of contemporary life, for that matter – are due to be thrown out the window. We’ll discuss one of those next week.
What do you think? Leave a comment below.
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