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September 18, 2000
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Energy: Facts and Fiction
With a potential oil crisis, increasingly frequent power shortages, global warming etc., there is no doubt that "alternative" energy sources will make more headlines soon enough. There will be new scams - the first signs are already there (energy from zinc, Xogen, ... just in the last few days). The stakes are high, and it pays off to know the facts. On this board we know more about energy than most people. But one can always learn more.
So I've prepared a brief tutorial on energy: What forms of energy are there, how is energy converted from one form to another, what does energy conservation really mean, what about nuclear energy, what about mass? I'll also mention some energy scams. Mostly familiar stuff, but perhaps something new as well. There are few opinions here - this is mostly physics. Don't get scared now - I'm not going to lecture on QED or anything like that. I'll just go over some basic facts about energy at a level which is easily accessible to the canonical "educated layman". The only equation in this post is E=mc^2, and I'm sure you've seen that.
The concept of energy is important for two very fundamental reasons. The first reason is the law of energy conservation: The total energy of an isolated system is conserved. (An isolated system is one that does not interact with it's environment, for all practical purposes). This is an absolute law of physics which applies to all processes at all times. Because it's a conservation law, it applies regardless of dynamics, i.e. regardless of what the forces are or what the details of interaction may be. When applying this law, you need to keep in mind that mass is a form of energy. Conservation of energy follows from translational invariance in time, which states that laws of physics don't change as time goes by. We cannot cheat on this law. It puts constraints on absolutely everything we try to do. It's the ultimate law.
The second reason is that energy represents a capacity to do work. This of course is why energy is not just useful but absolutely necessary. It keeps the wheels rolling, the heart pumping, and the house warm. And the neat thing about energy is that, in most cases, you can store it until you need it. In some cases nature even stores it automatically for you: during the day some of the energy received from the sun gets stored as kinetic energy of air molecules, and that keeps us warm when the sun goes down. It's a neat arrangement.
For the purposes of this tutorial there are three forms of energy in nature: kinetic energy, potential energy, and mass. Kinetic energy is energy of motion (bullets, trains, X-rays). Potential energy is stored energy that a system has by virtue of it's position, or by virtue of the positions of it's parts (water behind a dam, compressed spring, excited states of atoms). Mass is equivalent with energy through Einstein's famous equation E=mc^2. Other forms of energy you've heard about, such as heat, chemical energy, electrical energy, nuclear energy, etc. are just different manifestations of these 3 forms. For example, heat is nothing but kinetic energy of atoms and molecules. Chemical energy is potential energy of electrons in atoms, potential energy of atoms in molecules, etc. Energy carried by an EM field is kinetic energy of photons (even though you can also think of it as field energy of the classical EM field). What the press refers to as "nuclear energy" is ultimately mass converted into kinetic energy of fission fragments, neutrons, photons, etc.
In principle any form of energy can be converted to any other form, provided that total energy is conserved in the process. Potential energy of water behind a dam is first turned into kinetic energy of falling water, then into rotational kinetic energy of turbines, then (with the help of Maxwell's 3rd equation) into electrical energy (= kinetic energy of electrons + field energy of EM field), then into heat and light in your lightbulb. The entire electrical power industry is basically just energy conservation, Maxwell's 3rd equation, and a bunch of copper!
Most of the time we want energy in the form of heat or electrical power. And most of the time it takes several steps to get there, as the above example indicates. Multi-step processes through various intermediate forms are inefficient because there are losses at every step. Higher efficiencies are obtained with direct energy-conversion devices, such as batteries and fuel cells. These devices convert chemical energy directly (more-or-less) into electrical power. The most efficient energy-conversion process in nature is electron-positron annihilation into two gamma rays: it converts mass into pure EM energy with 100% efficiency.
Speaking of mass: it's a form of energy that you can pretty much ignore in everyday situations because mass is conserved in low-energy processes. The energy is "tied up", and you don't even notice that it's there. On the other hand, some of us high-energy physicists deal with mass-energy conversion every day. In Fermilab experiments that my colleagues and I have been doing for 10 years, we routinely collide protons and antiprotons at energies such that the total mass after the collision is typically 1-2 orders-of-magnitude higher than before the collision. This does not violate conservation of anything, it merely means that some of the kinetic energy of the initial proton/antiproton was converted directly into mass of particles created in the collision. The most spectacular "events" are those where heavy quark-antiquark pairs are made - that's how we discovered the top quark, the heaviest particle in the universe, back in 1995:
Nuclear binding energy is a form of potential energy that deserves special attention. The fact is that when two light nuclei combine into a heavier nucleus (e.g. inside the sun), the mass of the resulting nucleus is less than the sum of the masses of the two light nuclei. We say that the heavy nucleus is "more tightly bound" than the light nuclei, and the mass difference is called the nuclear binding energy. This is the energy that's released in nuclear fusion - it's what makes the sun (and the hydrogen bomb) tick. Now, iron is the most tightly bound nucleus of all. This means that there is another way of extracting useful energy from nuclei: you can take very heavy nuclei (much heavier than iron) and split them into lighter ones - this is nuclear fission and that's how nuclear reactors work. The kinetic energy of fission products is first used to boil water, and the resulting steam drives turbines which then generate electrical power. Some countries (e.g. France, Finland) get most of their electrical power from fission.
The reason for emphasizing nuclear binding energy is that, in the end, it is the only form of energy which is available in unlimited supply, forever. A small atomic bomb can do a few things as we all know, yet the mass that is actually converted into energy in the explosion is a fraction of an ounce (0.7% of at least 0.45kg of uranium). That's right, the amount of chemical energy available in fossil fuels, or solar energy hitting the earth, or geothermal energy, or whatever - these are nothing relative to the amount of nuclear binding energy that's available out there. The ultimate reason is that atomic/molecular binding energies are of order eV (electron volt) whereas nuclear binding energies are of order MeV. That's a factor of 10^6 right there, and it will never change. Some people don't like nuclear power for various reasons, but let's just wait a few thousand years and opinions may be different. There's a tremendous amount of energy tied up in mass, and my guess is that some day that'll come in real handy. For the time being, though, controlled fusion is just not practical - the technical challenges are formidable.
The earth receives essentially all of it's energy from the sun. The rate is given by the so-called solar constant, which is the power per unit area (perpendicular to sun's rays) hitting the earth's surface. Numerically it's about 1.4 kW/m^2. So if the roof of a small house (100 m^2) is covered with solar cells (average efficiency 10%), and the sun shines at 45 deg angle 30% of the time, you'll get 3 kW out of it, which is plenty to power the house. But it's not a huge amount, and you can't increase it a whole lot (besides, it doesn't work in Seattle!). On the other hand, solar power has some major advantages: it's free, it'll last for a long time, and it's non-polluting. Overall, it's thumbs up for solar energy.
And what about fuel cells? I honestly don't know. Ballard is among my largest holdings, so I certainly view it as a good investment, but I have my doubts about the "hydrogen economy" as the wave of the future. It's true that hydrogen is the most common element in the universe, but so what? It's true that burning of hydrogen is clean, but extracting lots of hydrogen to burn is not. There's the whole infrastructure question, and so on. I just don't know.
OK, it's time to move on to scams. I have addressed the question of spotting scams in general in a post almost a year ago, on Rat's board:
Let's now look at some things that can't happen because they violate energy conservation. A few days ago someone here mentioned a claim that some outfit is extracting energy from zinc. Just hook up a couple of wires to a zinc plate, and BINGO! - the wheels start spinning. This is absurd. You cannot extract energy from the ground state of any atom, because there is no lower energy state for the atom to go to! The whole thing violates energy conservation. It's irrelevant whether there is or isn't elemental zinc on earth. The point is that there must be a process involving at least two elements which can interact/combine so that some form of binding energy is released. So much for that - it's thumbs down for zinc.
Then there's Blacklight Power, and the man behind the magic, Dr. Mills. His "Grand Unified Theory of Classical Quantum Mechanics" (an oxymoron, incidentally) predicts that the ground state of the hydrogen atom is not the ground state! This allows him to extract an arbitrary amount of energy from a single hydrogen atom (using a proprietary catalyst, of course). Pretty impressive stuff for a medical doctor with no scientific publications, wouldn't you say? Impressive enough so that he has managed to get millions of dollars from rich people who don't have a clue. Oh well, I suppose in the end people get what they deserve.
Cold fusion - we haven't heard much about that recently. The fiasco of Pons and Fleischmann ten years ago didn't exactly violate energy conservation, but it was a splendid example of what happens when people ignore, or are ignorant of, basic facts of physics. Time Magazine asked "Cold fusion or confusion?" on their front page - well, at least we got that question answered. Univ. of Utah fired Pons and Fleischmann, and the last I heard they were living in Monaco. (Wait a minute! - Monaco ... perhaps they are not as stupid as I thought they were ;-)).
Magnetic charges. I'm kind of expecting that one of these days some company announces they can make magnetic monopoles, by cutting bar magnets in half or whatever. Now that would be something, because the magnetic field of a monopole, unlike the fields of real magnets, could actually do work and speed up charged particles. There would be zillions of applications, lots of money to be made. Unfortunately, Maxwell's 2nd equation get's in the way - no monopoles. Darn it; it was such a clever idea!
Let me close on a serious note. Laws of physics, such as energy conservation, are a harsh opponent - they don't care about our opinions. Magnetic monopoles may be a cool idea, but they do not exist. Cold fusion would be great, but it does not take place because the electrostatic repulsion between two protons is too strong for that. And the ground state of the hydrogen atom will remain just that, regardless of what crackpots and scam artists say on the internet.
May the Energy be with you,
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