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As oil prices recede from all-time dollar highs and some of the hot air gets let out of energy policy debates, it’s a good time to remember that here’s a key concept missing from almost every popular discussion of the subject: energy density. Specialist economists get it, but almost nobody else does. It is important to understanding why most forms of “alternative energy” are mirages, and what a sane energy policy would actually look like.
The background to this is that the few technologies we have for storing electricity (batteries, pump-fed ponds above hydroelectric turbines) are lossy and don’t scale well. Worse, power transmission is significantly lossy as well. These mean several things, all of them bad.
Absence of a decent storage technology means we can’t really time-shift electricity demand. When more electricity is needed (for example, to run air conditioning during the day in the American Southwest) more power plants have to be running and feeding power to the grid in real time. There’s no way to run plants at night and store the generated power for daytime use.
Transmission losses mean our ability to space-shift demand is limited, too, though not as severely. Electricity-intensive industries (the classic example is aluminum smelting) need their own dedicated power plants nearby.
The combination of these problems means that household energy conservation is mainly a way for wealthy Westerners to feel virtuous rather than an actual attack on energy costs. Household conservation slightly decreases the maximum capacity needed locally where the conservation is being practiced, but has little impact further away, where demand has to be supplied by different plants. Industrial efficiency gains are far less visible; but, because the scale of industrial energy use is so much larger, they matter a lot more.
The combination of these problems also means we cannot, practically speaking, aggregate lots of very small flows of electricity into one big one. It’s not just total volume of energy production that matters, but the energy density available to high-volume consumers at a given place at and at a given time. This may sound like a dry technical point, but it has huge and nasty implications.
One is that the most touted forms of so-called “alternative energy” and are largely (though not entirely) useless. Solar and wind power are both time-variable and low-density. Lacking good ways to time-shift and aggregate electricity, this means you can’t count on them to run factories and hospitals and computer server farms. The best you can hope for is that they can partially address low-density usage, running climate control and appliances for homes and some purpose-designed office buildings.
Those costs are not denominated just in money; low-density energy sources are more labor-intensive to operate and that causes more illness and death. Compare annual deaths from coal mining to annual deaths in the petroleum industry to the annual deaths associated with nuclear power; the trend is dramatic and favors higher-density sources, even if you ignore chemical air pollution entirely.
Nothing on offer from advocates of low-density “alternative energy” even comes close to coal as an industrial baseload source. let alone oil or nuclear. Ethanol and hydrogen look like it, until you consider life-cycle costs; basically, making either costs a lot more than mining coal, both in money and in input energy.
Another key point is that, for transportation, oil is basically the only thing we have that will do. For fixed-location power plants, the energy yield per gram of fuel matters a lot and the weight of the plant machinery only a very little. On the other hand, for automobiles and ships and airplanes, power-to-weight ratio matters a lot. Nuclear and coal basically cannot make that cut, cost-insensitive military applications of nuclear notwithstanding.
For fixed-location power plants, however, nuclear is the clear winner. Coal and oil have lower density and serious pollution costs. They are also much less safe. Yes, I said less safe; the historical evidence is extremely clear on this.
There are some kinds of non-polluting fixed-location plants that might become available in the future: notably tidal generators and atmosphere towers. They will probably be good replacements for nuclear down the road, but they’re not an answer to the transportation problem. Oil is non-renewable; the price is rising and eventually (though not in the near term and not as rapidly as predicted by peak-oil-collapse hysterics) it will run out.
And no, electric cars aren’t the answer either; the power to run them has to come from somewhere. The best case is that people will charge them off the grid at night. This will require power plants to be burning just as much additional fuel as if the cars themselves were doing it, perhaps more given transmission losses. What electric cars can do, at best, is give us fuel flexibility, replacing direct oil-burning with nuclear plants and coal. But that’s not going to net out to lower pollution and lower costs unless we build a lot of nuclear plants very quickly. Thanks to decades of scare-mongering and NIMBYism, this probably isn’t possible in the U.S.
The pressing question, then, remains: What’s going to replace oil?
Let’s draw up a specification for the ideal replacement. We’d like a fuel with the energy density of oil, or better. We’d like the only per-unit cost to be sunlight, because that’s the only thing that’s 100% renewable and (unlike tidal, hydropower, and geothermal) available everywhere. Ideally, we’d like the stuff to not require a huge, expensive conversion job on our energy infrastructure.
Happily, I think this spec can be filled. There are demonstration plants making synthetic oil from algae at a per-unit cost not far above that of oil, and plenty of venture capital looking to fund more. As this technology scales up, algal-synfuel costs will drop below that of oil. At that point, the free market will have solved the problem.
It’s largely forgotten now, but we’ve actually been through a similar transition before. In the mid-19th century whale oil was heavily used for lighting and as an industrial feedstock. Prices rose as whales were hunted to near-extinction; fortunately, the stuff proved to be replaceable by petroleum. Yes, that’s right; big oil saved the whales. A century and a half later, pond scum looks likely to save civilization.
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