USS Clueless - Obscure energy sources
     
     
 

Stardate 20020925.2305

(Captain's log): Several people have written to me about something called biodiesel. It represents a process whereby things like waste cooking oil and excess animal fat from slaughterhouses can be converted into a fuel which can be burned in existing diesel engines. It evidently works now.

It doesn't help. The problem here is scale. There isn't a sufficiently large source from which to make this stuff so that it could actually produce a total quantity of energy per year large enough to even begin to offset our petroleum use.

It's actually a rather indirect form of solar energy. What's going on is that the two primary sources, animal fat and vegetable oil, both come out of agriculture. But unlike direct burning of biomass, as I described in the last article on this subject, it only represents a very small proportion of the total solar energy per acre which was captured by the original plants. (In that regard, animal fat is far worse. The animal consumes only part of the plant matter, and only converts a small part of that into fat.)

As a form of recycling it's probably a good way to get rid of that kind of stuff. (Certainly better then burying it or dumping it in a river to be carried out to sea.) But as a source of energy, it barely generates a blip on the scale.

There are a heck of a lot of ideas like this one. The problem with all of them isn't that they can't be made to work, it's that the amount of power (energy per time) they can provide us is several orders of magnitude too small to make any real difference if our goal is to significantly reduce our consumption of petroleum. What you find is that most of them can generate really substantial amounts of power in short bursts, but the average power generation is tiny on the scale we're discussing.

Small sources of energy are easy. Big sources of energy aren't, and the small sources of energy can't be scaled, and there aren't enough of them so that even when added up they would be enough to matter. One person asked if I had researched new sources of energy; I don't need to, because the physical reality is that there aren't all that many natural sources of energy which are large enough to make any difference, and the process of utilizing all of the large ones is reasonably straightforward, or else it's damned near impossible. There are probably all sorts of weird and obscure new energy technologies out there. Each may have its place; each might be able to solve some kind of problem. But not this problem.

For instance, we use solar cells now. The highway between here and Las Vegas is lined with emergency telephones, and each of them has a solar cell which trickle charges a storage battery to power the phone. But they're being used because they don't have to be wired to the power grid, not because the amount of energy they generate is very large.

You've got to think big. I've run into this before. Most non-engineers (and even a lot of engineers) don't actually have an intuitive understanding of large numbers. (That's why people play the lottery.) For most people, any number above about a thousand is the same size. I am, perhaps, exaggerating but only a bit; people know that a billion is larger than a million but don't really understand how much larger. Maybe the reason I have some idea of the kinds of scales is that as an engineer I'm used to dealing with really vastly different time scales. I'm used to dealing with things in nanoseconds, and over the years I've come to internalize just how small a nanosecond truly is. It can be demonstrated with factoids, but that's not the same. But let's give it a try:

KHz: A millisecond is to a second as a second is to 16 minutes and 40 seconds.
MHz: A microsecond is to a second as a second is to 11 days, 13 hours.
GHz: A nanosecond is to a second as a second is to 31 years and 8 months.

My new workstation's processors are running 2.4 GHz. One clock cycle to one second is as one second to 76 years. And when you're talking about energy use at the level of big industrialized nations, the range in the scale is even bigger. By the standards of power engineers, we're wimps.

When you're talking about energy for the kinds of stuff I was designing, 100 watts is pretty large. (When you're working with batteries, a hundred milliwatts is pretty large.) But when you're talking about power sources for major nations, you've got to think REALLY big. And there aren't a lot of actual sources of energy, real or speculative, which are at that kind of scale.

My dad was an electrical engineer and he worked on power generation. (He spent most of his career on the hydro projects on the Columbia river.) He lived in an entirely different world than I did, a world where units like kilofarads and kilohenries were actually useful. That's the kind of numbers you see when you're describing long distance transmission lines. In my world, a microfarad is huge. In his world, a farad was tiny. (If you don't know what that means, just let it pass.)

You've got to start thinking really, really big.

Anything which, when fully deployed, generates less than ten gigawatts average (1010 joules per second) is useless for our purposes in terms of actually making a meaningful contribution to the total amount of energy we consume. For scale purposes:

Hoover Dam = 1.5 gigawatts.
Grand Coulee Dam = 6.

Captured by MemoWeb from http://denbeste.nu/cd_log_entries/2002/09/Obscureenergysources.shtml on 9/16/2004