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Interesting article, thanks for posting! A few things to add. Your article actually says that cars use 7x as much embodied energy as devices, (7 to 1), but the

Interesting article, thanks for posting! A few things to add. Your article actually says that cars use 7x as much embodied energy as devices, (7 to 1), but then corrects both for lifetime (10 and 2 years), thus you get 0.5 vs 0.7 for devices vs cars respectively, not 1 vs 0.7. The article then concludes cars use 40% more embedded energy than all devices on the planet, not 30% less. Then, we're talking about phones here, the article about devices, including 60 million laptops which the article assumes use 18x the embodied energy of a phone. i.e., next to the 1.9 billion phones, the article essentially adds in 1.08 billion phone-equivalent laptops, which carry a worse energy/mass ratio, but aren't adjusted for a much better lifetime than 2 years average. Same for smartphones, btw. The article leaves out embodied energy of cars and just assumes a car to perform without any repairs or maintenance for 10 years, like a phone does for 2 years. It also doesn't really explicitly mention the context which is that it's a comparison is between more than 2 billion devices servicing an approximately similar amount of humans, vs 72 million vehicles. The article does mention that a phone's energy use in 2 years would add, at most, 8% to its embodied energy, for an indexed figure of 1.08. A car uses 5x as much of its embodied energy, for a total figure of 6x. Again, this is without figuring in maintenance. In short, for a real impact figure you'd multiply the 0.72 by 6, and you end up with energy to 72m cars using more than 8x as much energy than 2 billion smartphones and more than a billion phone-equivalent laptop/tablet devices, at minimum.

dredmorbius 9y ago
The book and article differ on the 30% / 40% point, and Smil is IMO not entirely clear here (or I'm up too late reading this). The general upshot is that silicon is very energy-intensive stuff -- to manufacture, and to operate. Several authors (including Smil) have noted that the highest energy use densities, in terms of watts per unit-mass of equipment, are seen in information systems. There's a reason for all those massive cooling systems at datacentres. (And yes, I've just shifted the discussion from embodied energy to operating energy, in the interest of the general point of energy consumption of information systems, not trying to confuse the two points, though that has been done several times already in various parts of this thread, including your own response above.) That density still doesn't necessarily imply greater total energy use, though it starts getting you that way. As for transport vs. information: a further point to consider is that there are constraints on moving people around in a physical environment, imposed by mass, air, rolling resistance, and braking (or regen) losses. We're relatively close -- definitely within an order of magnitude, and possibly a power or so of two, to those limits. For information, the theoretical efficiencies are high (Feynman did work on this IIRC), but our technology is nowhere near that bound, and we seem quite good at throwing additional tasks and requirements on our computing systems as efficiency improves. (This is also true of transport -- both are subject to the Jevons paradox.) This also gets us to a sort of Amdahl's Law problem: as the operational energy of computers falls, the embodied energy costs seem to increase and become a larger portion of the overall expense. Since the operating cost == marginal cost, this also means that market dynamics alone, which function based on marginal costs, are exceedingly unlikely to discourage this trend. It's another zero-marginal-cost dynamic (see Jeremy Rifkin's recent book). Smil has a great deal of expertise and experience here, his writing is usually pretty clear, and I'm inclined to credit his claims. Though I may need to evaluate this particular one more closely. Though at some time when my neurons are not in isolation cells....

dredmorbius 9y ago

The book and article differ on the 30% / 40% point, and Smil is IMO not entirely clear here (or I'm up too late reading this). The general upshot is that silicon is very energy-intensive stuff -- to manufacture, and to operate. Several authors (including Smil) have noted that the highest energy use densities, in terms of watts per unit-mass of equipment, are seen in information systems. There's a reason for all those massive cooling systems at datacentres. (And yes, I've just shifted the discussion from embodied energy to operating energy, in the interest of the general point of energy consumption of information systems, not trying to confuse the two points, though that has been done several times already in various parts of this thread, including your own response above.) That density still doesn't necessarily imply greater total energy use, though it starts getting you that way. As for transport vs. information: a further point to consider is that there are constraints on moving people around in a physical environment, imposed by mass, air, rolling resistance, and braking (or regen) losses. We're relatively close -- definitely within an order of magnitude, and possibly a power or so of two, to those limits. For information, the theoretical efficiencies are high (Feynman did work on this IIRC), but our technology is nowhere near that bound, and we seem quite good at throwing additional tasks and requirements on our computing systems as efficiency improves. (This is also true of transport -- both are subject to the Jevons paradox.) This also gets us to a sort of Amdahl's Law problem: as the operational energy of computers falls, the embodied energy costs seem to increase and become a larger portion of the overall expense. Since the operating cost == marginal cost, this also means that market dynamics alone, which function based on marginal costs, are exceedingly unlikely to discourage this trend. It's another zero-marginal-cost dynamic (see Jeremy Rifkin's recent book). Smil has a great deal of expertise and experience here, his writing is usually pretty clear, and I'm inclined to credit his claims. Though I may need to evaluate this particular one more closely. Though at some time when my neurons are not in isolation cells....