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Page added on April 7, 2016
Timetables of power
For more than three decades, Vaclav Smil has been developing the concepts presented in his 2015 book Power Density: A Key to Understanding Energy Sources and Uses.
The concept is (perhaps deceptively) simple: power density, in Smil’s formulation, is “the quotient of power and land area”. To facilitate comparisons between widely disparate energy technologies, Smil states power density using common units: watts per square meter.
Smil makes clear his belief that it’s important that citizens be numerate as well as literate, and Power Density is heavily salted with numbers. But what is being counted?
Perhaps the greatest advantage of power density is its universal applicability: the rate can be used to evaluate and compare all energy fluxes in nature and in any society. – Vaclav Smil, Power Density, pg 21
A major theme in Smil’s writing is that current renewable energy resources and technologies cannot quickly replace the energy systems that fuel industrial society. He presents convincing evidence that for current world energy demand to be supplied by renewable energies alone, the land area of the energy system would need to increase drastically.
Study of Smil’s figures will be time well spent for students of many energy sources. Whether it’s concentrated solar reflectors, cellulosic ethanol, wood-fueled generators, fracked light oil, natural gas or wind farms, Smil takes a careful look at power densities, and then estimates how much land would be taken up if each of these respective energy sources were to supply a significant fraction of current energy demand.
This consideration of land use goes some way to addressing a vacuum in mainstream contemporary economics. In the opening pages of Power Density, Smil notes that economists used to talk about land, labour and capital as three key factors in production, but in the last century, land dropped out of the theory.
The measurement of power per unit of land is one way to account for use of land in an economic system. As we will discuss later, those units of land may prove difficult to adequately quantify. But first we’ll look at another simple but troublesome issue.
Does the clock tick in seconds or in centuries?
It may not be immediately obvious to English majors or philosophers (I plead guilty), but Smil’s statement of power density – watts per square meter – includes a unit of time. That’s because a watt is itself a rate, defined as a joule per second. So power density equals joules per second per square meter.
There’s nothing sacrosanct about the second as the unit of choice. Power densities could also be calculated if power were stated in joules per millisecond or per megasecond, and with only slightly more difficult mathematical gymnastics, per century or per millenium. That is of course stretching a point, but Smil’s discussion of power density would take on a different flavor if we thought in longer time frames.
Consider the example with which Smil opens the book. In the early stages of the industrial age, English iron smelting was accomplished with the heat from charcoal, which in turn was made from coppiced beech and oak trees. As pig iron production grew, large areas of land were required solely for charcoal production. This changed in the blink of an eye, in historical terms, with the development of coal mining and the process of coking, which converted coal to nearly 100% pure carbon with energy equivalent to good charcoal.
As a result, the charcoal from thousands of hectares of hardwood forest could be replaced by coal from a mine site of only a few hectares. Or in Smil’s favored terms,
The overall power density of mid-eighteenth-century English coke production was thus roughly 500 W/m2, approximately 7,000 times higher than the power density of charcoal production. (Power Density, pg 4)
Smil notes rightly that this shift had enormous consequences for the English countryside, English economy and English society. Yet my immediate reaction to this passage was to cry foul – there is a sleight of hand going on.
While the charcoal production figures are based on the amount of wood that a hectare might produce on average each year, in perpetuity, the coal from the mine will dwindle and then run out in a century or two. If we averaged the power densities of the woodlot and mine over several centuries or millennia, the comparison look much different.
And that’s a problem throughout Power Density. Smil often grapples with the best way to average power densities over time, but never establishes a rule that works well for all energy sources.
The Toronto Power Generating Station was built in 1906, just upstream from Horseshoe Falls in Niagara Falls, Ontario. It was mothballed in 1974. Photographed in February, 2014.
In discussing photovoltaic generation, he notes that solar radiation varies greatly by hour and month. It would make no sense to calculate the power output of a solar panel solely by the results at noon in mid-summer, just as it would make no sense to run the calculation solely at twilight in mid-winter. It is reasonable to average the power density over a whole year’s time, and that’s what Smil does.
When considering the power density of ethanol from sugar cane, it would be crazy to run the calculation based solely on the month of harvest, so again, the figures Smil uses are annual average outputs. Likewise, wood grown for biomass fuel can be harvested approximately every 20 years, so Smil divides the energy output during a harvest year by 20 to arrive at the power density of this energy source.
Using the year as the averaging unit makes obvious sense for many renewable energy sources, but this method breaks down just as obviously when considering non-renewable sources.
How do you calculate the average annual power density for a coal mine which produces high amounts of power for a hundred years or so, and then produces no power for the rest of time? Or the power density of a fracked gas well whose output will continue only a few decades at most?
The obvious rejoinder to this line of questioning is that when the energy output of a coal mine, for example, ceases, the land use also ceases, and at that point the power density of the coal mine is neither high nor low nor zero; it simply cannot be part of a calculation. As we’ll discuss later in this series, however, there are many cases where reclamations are far from certain, and so a “claim” on the land goes on.
Smil is aware of the transitory nature of fossil fuel sources, of course, and he cites helpful and eye-opening figures for the declining power densities of major oil fields, gas fields and coal mines over the past century. Yet in Power Density, most of the figures presented for non-renewable energy facilities apply for that (relatively brief) period when these facilities are in full production, but they are routinely compared with power densities of renewable energy facilities which could continue indefinitely.
So is it really true that power density is a measure “which can be used to evaluate and compare all energy fluxes in nature and in any society”? Only with some critical qualifications.
In summary, we return to Smil’s oft-emphasized theme, that current renewable resource technologies are no match for the energy demands of our present civilization. He argues convincingly that the power density of consumption on a busy expressway will not be matched to the power density of production of ethanol from corn: it would take a ridiculous and unsustainable area of corn fields to fuel all that high-energy transport. Widening the discussion, he establishes no less convincingly, to my mind, that solar power, wind power, and biofuels are not going to fuel our current high-energy way of life.
Yet if we extend our averaging units to just a century or two, we could calculate just as convincingly that the power densities of non-renewable fuel sources will also fail to support our high-energy society. And since we’re already a century into this game, we might be running out of time.
17 Comments on "Timetables of power"
PracticalMaina on Thu, 7th Apr 2016 12:51 pm
One of the last articles on this site was pushing indoor led growing as the answer to food insecurities, now we have one saying that there is no way away from fossil fuels because we need huge power densities. Power needs per capita are something that should decrease over time because of increases in efficiency. Leds vs incandescents, cell phones vs old pcs, heat pumps are much more efficient now. Pumping and heating water along with refrigeration are still energy hogs, but there are ways around this. For example use the waste heat from the refrigerator to pre heat water.
Comparing charcoal or corn ethanol to a solar panel is stupid. The conversion process in either of these of solar to final product would be way below 1% efficiency, compared to solar hot water efficiency of 90% on a good day. Think of what temps can be achieved with concentrating solar thermal. You can get a small Fresnel lens to smelt metal
PracticalMaina on Thu, 7th Apr 2016 12:54 pm
We are absolutely running out of time, but saying that surface area for power production is gonna be a constraint is stupid. The least of our problems, there is enough roof top area to power a majority of our needs.
Outcast_Searcher on Thu, 7th Apr 2016 1:08 pm
OTOH, the power densities of wind and solar are gradually increasing, as the technologies become more efficient.
Also, once a modern large wind farm or solar installation is there, it is there producing power for DECADES, with little additional input (some maintenance) needed. Unlike fossil fuels of course, as the article pointed out.
So no, we’re not going to replace all the fossil fuel energy in the short term with wind and solar. No one numerate is saying that.
However, gradually, if an eye toward efficiency (i.e. consider the dramatic improvements in light bulbs over the last couple decades), coupled with a long term build out of improving green energy tech should get us a LONG way in, say, four decades or so.
Now, if we add to this an intelligent, safely managed nuclear base with technologies like thorium reactors and have the backups and planning in place to handle the obvious emnergencies with spent fuel, floods, quakes, etc. — then in total we’re really getting somewhere.
No one numerate thinks it will be easy, cheap, or quick. That doesn’t make it impossible, even if it is daunting.
The big problem is that by the time we don’t need to burn much fossil fuel, AGW will be wreaking havoc. Star-Trek like technology will be needed to fix it. Unless humanity makes some good choices in the mean time instead of running BAU at full tilt (and expanding the population and the scope and severity of the basic problem), then all green tech will do is buy as a little time.
So my biggest concern is running out of time — not facing an impossible situation due to low energy density.
eugene on Thu, 7th Apr 2016 1:43 pm
I don’t think we might be running out of time. We have run out of time.
PracticalMaina on Thu, 7th Apr 2016 2:20 pm
I wonder what the man who designed that power station, Nikola Tesla would think of our current situation. For a passive man he probably would have turned one of his machines against JP Morgan or Edison if he saw the current state of affairs.
OutcastSearcher, with the improvements we are seeing in PV tech ect. why not spent billions more on improving pv tech and implementation vs spending the money and engineering on nuclear. The more than decade it takes to build a reactor could be better spent on a massive renewables build out. If we had a large nuclear build out we would have a decade of having to come up with stop gap measures to keep BAU going until the reactors came on, by that time we may have super high efficient pv and the whole shebang was a waste.
Plantagenet on Thu, 7th Apr 2016 2:26 pm
If the earth’s population was smaller we wouldn’t need so much power. In nature (and humans are part of nature) these kinds of problems tend to be self-correcting over time.
Cheers!
PracticalMaina on Thu, 7th Apr 2016 2:44 pm
Planty you must crank threw the power up there in the cold dark. If you were more modest, then the same thing would happen, and if ifs and butts were candy and nuts we would all have a merry Xmas.
Apneaman on Thu, 7th Apr 2016 2:50 pm
Practical, it’s a whole new world and a whole new Alaska – Planty be cranking up the A/C any day now.
The temperature just hit 71 degrees. In Alaska. In March.
“Alaska has had plenty of uncharacteristic weather in recent months, but Thursday took it to a new extreme.
The temperature measured at Klawock Airport in Southeast Alaska hit 71 degrees, which University of Alaska Fairbanks climate researcher Brian Brettschneider said is a record high for the state for the month of March, in any year on record.
Before 2016, Alaska temperatures in March hadn’t hit the 70-degree mark for any years on record.
Brettschneider said the previous March record-high temperature in Alaska was 69 degrees, recorded in Ketchikan on March 28, 1915.”
https://www.adn.com/article/20160331/temperature-just-hit-71-degrees-alaska-march
GregT on Thu, 7th Apr 2016 3:54 pm
“The least of our problems, there is enough roof top area to power a majority of our needs.”
There is enough energy from the Sun to power our needs, without any form of planetary destructing human industrialism. Our wants, however, are an entirely different story.
HARM on Thu, 7th Apr 2016 4:48 pm
It’s 86 F and sunny in Portland right now, and breaking temperature records almost every day this week. But again, AGW is “Lies from the pit of Hell” (Congressman Paul Braun, GA (R)).
Anonymous on Thu, 7th Apr 2016 5:42 pm
Ah, efficiency. Everyone’s favorite trope.Mine too, I prefer ‘efficient’ devices over wasteful ones sure. But, there is still a problem. Many of these ‘efficient’ devices, take a lot more power(to manufacture), often require more exotic materials, and require more complex production chains than the old ‘inefficient’ ones they are meant to replace. IoW, in a great many cases, the embodied energy in new, more ‘efficient’ devices can be many times higher than the ‘old’ version. End result? The amount of resources and energy used by society continues to rise regardless. Efficiency gains never outpace resource utilization or population growth in this age.
A good example would the current fixation with the the full-sized 0-100kph in 8 sec, 500km range electric car, that pseudo-liberal faux ‘greens’ are convinced will save suburbia and casual driving for all time. The argument often deployed by their advocates is that EVs are very ‘efficient'(less wasteful) than oil-burners. And its true, but only in a very narrow sense. But even a cursory investigation shows over its entire lifecycle, the kind of EV everyone seems to want, consumes just as many resources as their oil burning counterparts.
Nor does the notion that more efficient light-bulbs, or similar, will pave the way to the star-trek future, or green eco-villages hold much water. So far none of the current crop of ‘efficient’ devices have managed to stop or reverse, total energy usage from going up. At best, they may have very slightly slowed the rate of increase in very certain instances. Where I live, they still talk about building new mega-dams or NG plants to provide more ‘power’. If we are so damned efficient these days, why the constant push to build new power generating facilities?
Clearly the message the writer is attempting to convey, is that renewables will not lead to a powered up, larger, green eco-topia version of current civilization, no matter what the tech or energy input we use to try to replace oil, or nukes with. At least it sounds like he has made a serious effort to quantify this argument, rather than simply say, renewables or corn-from fuel bad.
makati1 on Thu, 7th Apr 2016 8:03 pm
Techie dreams and collapse deniers.
And the “over population” bullshit thrown in for good measure. No mention that <14% of the world's population uses 45%+ of the world's energy.
Davy on Thu, 7th Apr 2016 8:09 pm
“Over population bullshit issues”. Someone has been in the big city too long and has gotten normalized to a really bad situation. I mean come on 20Mil plus people in greater Manila metro within a country the size of Arizona with 1/3 the population of the entire US population. Hum, cognitive dissonant anyone.
Apneaman on Fri, 8th Apr 2016 2:45 pm
A Country Breaking Down
“It would be helpful if there were another word for “infrastructure”: it’s such an earnest and passive word for the blood vessels of this country, the crucial conveyors and connections that get us from here to there (or not) and the ports that facilitate our trade (or don’t), as well as the carriers of information, in particular broadband (if one is connected to it), and other unreliable structures. The word “crisis” is also overused, applied to the unimportant as well as the crucial. But this country has an infrastructure crisis.
The near-total failure of our political institutions to invest for the future, eschewing what doesn’t yield the quick payoff, political and physical, has left us with hopelessly clogged traffic, at risk of being on a bridge that collapses, or on a train that flies off defective rails, or with rusted pipes carrying our drinking water. Broadband is our new interstate highway system, but not everyone has access to it—a division largely based on class. Depending on the measurement used, the United States ranks from fourteenth to thirtieth among all nations in its investments in infrastructure. The wealthiest nation on earth is nowhere near the top.”
http://www.nybooks.com/articles/2016/02/25/infrastructure-country-breaking-down/
Jerry McManus on Sat, 9th Apr 2016 11:48 am
Sorry, but Smil is a shill. Where do I start?
First, anyone with even a rudimentary understanding of the subject can see at a glance that all of his heroic struggles with this so-called “power density” are just a rehashing of the “ecological footprint” calculation that has already been around for decades.
It’s the same calculation which usually leads to the conclusion that we need 4 or 5 Earth’s worth of resources every year for everyone to enjoy an affluent western lifestyle.
Second, if you want a brilliant analysis of different energy sources, including the energy embedded in all resources, and you want it expressed in terms of units that are common to all of those resources, then look no further than the work of the late ecologist H. T. Odum.
Odum’s concept of eMergy, or embedded energy, is as universally applicable to both energy and society as any of the other laws of thermodynamics are.
Clearly Smil needs to do his homework, until then don’t waste your time, people much smarter than him had this stuff figured out a long ago.
onlooker on Sat, 9th Apr 2016 12:02 pm
The problem as I see it is no longer about energy. It is about the generosity or lack thereof of the Earth. We simply have overshot the carrying capacity for much of the areas we live. Energy cannot magically create water or food. The acute limiting factor is now shaping up to be what it has been for most of our history namely food and water. Of course climate change is and will be just aggravating all these limitations.
Davy on Sat, 9th Apr 2016 12:28 pm
The problem I see is we are systematically behind the 8ball. Nothing can overcome this momentum of decay and decline. From our individual standpoint this may play out over serval years. The effects may be a slow boil punctuated by notable events. There is no longer real growth and or aggregate growth. This situation is like PO we are going to know this decline situation in the review mirror after a major event results. This macro process will have another event occur soon that will be a transition marker. The 08 crisis was the bumpy plateau marker. We are now in the post 08 marker period and this time it will be the bumpy descent. We are surely going to see a business cycle recession only this time because of debt and deflation there will not be a recovery. There will likely be a stabilization but never a recovery to status quo growth. This will ensure demand and supply drop in a lockstep. Globalism has a minimum operating level for proper economic health. We are very close to breaching this. This breach will especially be true with oil. When oil supply capacity drops so will industrial capacity. With this economic drop all other activities and resources will follow this momentum down. The important point to remember is this is a process with events so time frame is deceiving. This could bounce around for a few years in a status quo pseudo normal.