This post powered by ethanol.
The peak oil doom-merchants love to say "ethanol is a net energy
loser! It takes more than a gallon of gas or diesel to produce a gallon of ethanol! We're
doomed!"
Yesterday, I found out that this is just FUD. In hindsight, I am amazed that I was gullible enough to believe them without investigating further, but it just goes to show... Don't believe everything you read on the internet.
Here are two excellent rebuttals to the "ethanol is an energy loser" meme:
And here's my summary of what's wrong with the doom argument:
The claim that ethanol is a net energy loser seems to be based on a recent study by David Pimmental. I won't go into the full laundry list of what's wrong with his study (see the first link above) but suffice it to say: He assumes 1979 ethanol refining technology. He commits various fallacies regarding how much energy it takes to fertilize and harvest the corn. He mistakenly assumes that all of the corn harvested is used to make ethanol - in reality the byproducts of the conversion process include plant protein and corn oil, both of which we have ample use for (human and animal food).
And that's not even going into the small matter of fact that corn is
not the only ethanol feedstock, nor is it even remotely the best! Ethanol can also be produced from plant cellulose, which means that native prairie grasses can be used to make ethanol. These plants once covered substantial portions of the great plains, and so they obviously don't need pesticides, fertilization, or irrigation, if polycultured, are perrenials, so they don't require the energy investment of replanting every year. The biggest benefit, of course, is that these sorts of feedstock produce far more yield per acre than corn, rendering all the ultra-pessimistic land-use estimates of the doomers null and void.
Doomers like to say that peak oil isn't about technology, it's about energy, and the foolish optimists conflate the two when saying that technology will save us. But they then completely ignore technology, which will ultimately make fools of them. The efficiency of ethanol-producing techniques has substantial room to grow, and is nowhere near running into any of the laws of physics that the doomers love to quote.
Just think about the energy involved: I've read plants are about 2% efficient at converting sunlight into chemical energy. Sounds pretty crappy. Let's assume that ethanol production from plants is 1% efficient. Also pretty crappy. The total efficiency then is 0.02%. Sounds shitty, huh? But, the average solar irradiation per square meter at north american latitudes, over a full 24 hour period, is maybe 200 watts. (I got this assuming 1000 watts for 5 hours and 0 watts for 19 hours). So, the average power production of an ethanol agriculture utilizing 55 million acres is about 9 gigawatts. That's a hell of a lot of power. Of course I just pulled that model out of my ass, but I find it completely impossible to believe that it's going to be a net energy loser.
If you don't believe my analysis, look at brazil: The unsubsidized price of ethanol in brazil is much cheaper than gasoline. (source: http://www.khoslaventures.com/presentations/Biofuels.Apr2006.ppt) If they have to burn two gallons of gas to make a gallon of ethanol, how the hell can ethanol be cheaper than gas?
People like Jim Kunstler rebut these arguments by swearing, and saying "people are letting themselves be deluded into thinking we can run all our cars on ethanol forever". This is just suppressed american puritanism at its best. Cars are evil, and the evil will be purged.
RIP Stanislaw Lem
Lem dies:
http://salon.com/wire/ap/archive.html?wire=D8GK0EQ04.htmlIf you have never read Stanislaw Lem, you must. Though much of his work was done during and about the cold war, it completely lacks the quaintness that makes so much early science fiction so very difficult to read. Perhaps this is because, unlike Clark and Asimov, he wrote from behind the Iron Curtain, giving his words an authority sorely lacking in the works of corn-fed American authors of earlier eras. His allegories on the nature of conciousness, global military conflicts, and the vast gulf between the everday and the alien are vitally important to today's world. As a bonus, his less serious work is among the funniest I've read. He is somewhere between Vonnegut and Swift in hierarchy of satirists.
If you can read only one Lem book, read Fiasco. If you can read more than one, read:
The Futurological Congress
The Cyberiad
Solaris
For a more exhaustive review and catalogue of his works, see
http://world.std.com/~mmcirvin/vitrifax.html.
bicycle wheels part 1
Today I started building up the rear wheel for the maruishi in the garage. I have it all laced up, and have just started tensioning it. Before I explain what all that means, let's talk about how a wheel works. I'm not talking about rolling. You already know that a wheel rolls. But a wheel does something else. It supports a heck of a lot of weight in proportion to its own weight.
My wheel - hub, axle, rim, and spokes (no tire or innertube on it), weighs just a hair over a kilogram. When it's finished (if I build it right), it should be able to support around 200 kilograms of radial force - force applied to the axle and pointing straight down. How is this possible?
A lot of people think that bicycle wheels support the weight of the rider because the hub hangs by the spokes from the top of the rim. In other words, they think that when you sit on your bike, the tension in the spokes at the top of the wheels increases (which is to say, the spokes at the top of wheel stretch), and that force is then transmitted around the circumference of the rim to the ground. Well, that's not the way it works.
How does it really work? In fact, the hub "stands" on the bottom spokes! That is, the bottom spokes get shorter which transmits the force of the rider directly through to the ground. A bicycle wheel actually works just like an olde-fashioned wagon wheel with wooden spokes. Don't buy the explanation? You can verify it for yourself. The easy way to verify it is by having someone straddle their bike and hold onto the handle bars. Then, pluck one of the bottom spokes with your fingernail. It will make a sound of a certain pitch, just like a guitar string would. Now, have your friend press down on the handle bars as hard as possible. Pluck the same spoke. The pitch will have gotten lower. You can use this same method to find out if the tension of any of the other spokes changes. You'll find that a few spokes at the bottom of the wheel change, but the ones at the top and the sides stay the same. If you don't believe that, ask yourself the following
question: If you had an un-laced rim (i.e. no spokes in it), would you expect to be able to sit on top of the rim without bending it? I wouldn't! Well, the rim would have to be that strong if it were to support your weight from the top.
Maybe you still have some doubts. How is it that the spokes can support weight pressing down on top of them? If you take a spoke by itself, and try to stand on it, it will bend immediately. The answer is pre-tension. (which is different than 'pretension', something I'm exhibiting by trying to add something new to the internet on the subject of the bicycle wheel). When you finish building a wheel, there's a lot of tension in the spokes - that is, each spoke is pulling outward on the hub, and inward on the rim. Then, when you put weight on the wheel, the tension of the spokes at the bottom of the wheel decreases slightly.
In other words, with no weight on the wheel, the spokes at all points of the wheel might be pulling the rim in towards the hub with 20 Newtons of force. When you put weight on the wheel, the spokes at the bottom of the hub decrease in tension, while the spokes at the top retain the same tension. So then you have, say, 10 Newtons at the bottom wheels and 20 at the top. This means that the hub is being pulled up towards the top of the rim harder than it is being pulled down towards the bottom of the rim, and so the rim can support as much weight as it takes to restore balance to the forces acting on the rim.
That's hard to conceptualize. People who have taken (and understood) a physics class have it beaten in to them to look at things this way, but most people find this counter-intuitive.
Here's another way to understand it. Suppose you and your friend are playing tug of war. You have a rope with a red flag in the middle of it, and you are pulling on the rope exactly as hard as your friend is. This means that the red flag in the middle of the rope doesn't move at all. Now, your other friend Manfred comes up behind you and starts to to push on your back. You're still pulling just as hard on the rope, but suddenly you start to move forward, and so does the red flag. But if
Manfred's sister, Uma, comes along and grabs the flag and starts pulling it back toward you with the right amount of force, then the flag will stop moving again. At this point, the tension betweeen the flag and your friend is the same as it was before, while the tension between you and the flag has decreased (because Manfred is pushing on your back). Well, substitute Manfred for the ground, and Uma for the weight of the rider - a bicycle wheel works the same way.
There are a lot of other forces that a bicycle wheel can support besides radial force. For instance, when you pedal, the spokes transmit the twisting force (the torque) on the hub to the rim, which makes the wheel turn, which makes you go. I'll write about how that works next time.
Lastly, if you want to build your own wheel, see
http://sheldonbrown.com/wheelbuild.html
Wow! A really, really good column by Cary Tennis:
http://salon.com/mwt/col/tenn/2006/02/28/bigoted_speech/
This is a humbling point if you believe it is true about yourself. I can personally remember times in my life when I was conciously bigoted in one way or another. Can you?
In other news - yes, I really am going to start on the bicycle wheel soon. Lately I've just been gathering up all the parts needed.
