Wednesday, September 07, 2005

Energy Density

As anyone who has stepped out of the house in the past few days knows, gas prices have jumped to unheard of levels. I distinctly remember paying 75 cents a gallon when I was in high school and just starting to pay for gas myself. I remember how everyone started getting excited (and outraged) as gas prices started creeping towards a dollar a gallon. A lot of gas pumps in rural Tennessee, where I grew up, were still the old analog kind (with numbers on rotors instead of digital displays). These older pumps literally couldn't charge a dollar a gallon -- there was no way to represent the price on the pump. A lot of gas stations had to delay going above a dollar while they upgraded their pumps. All this was during the worst of the energy crisis, when people in California were only being allowed to buy gas on alternate days. Prices were high, but energy was scarce -- supply and demand.

Gas prices are more than three times that "shocking" level now.

Yes, we lost some refineries. Yes, our supply lines have been reduced. But last year in Phoenix the main gas line broke completely -- there was almost no gas coming into the Valley at all -- and gas prices still barely reached $2/gallon. Here's the kicker, though: once the pipeline was fixed, gas prices didn't come down. Gas station owners realized that people will pay that much for gas, so why should they charge less? Yes, the price of oil has gone up, but it hadn't at that point in time. The thing that really annoys me about the current situation is that the gas we are paying $3.50/gallon for now is the exact gas we were paying $2/gallon for two weeks ago. The cost to the gas station owners is going to go up, true. But it hasn't yet. A significant portion of the increase is just due to panic (and profiteering).

And yet, I have a friend who hopes that gas prices continue to rise, perhaps doubling or tripling again. Say what? Here's his reasoning: the only way Americans are ever going to seriously commit to developing alternative fuel sources is if it is cheaper than our existing sources. Right now, alternative fuels are expensive, so his answer is to raise gas prices to where they are even more expensive. Once we have the infrastructure for these alternative fuel systems in place, the cost will come back down -- but we will no longer be dependent on foreign oil. Let's face facts: We did not invade Iraq to get control of their oil supply, in spite of what you may have heard. But one of the considerations prior to the invasion was that having a "friendly" Middle Eastern country with a huge supply of oil that also owed us a huge favor would be a major strategic gain. We wouldn't control the oil, but we would have a friend that we could be sure wouldn't deny it to us. When the president said he was protecting our interests, he wasn't just talking about terrorism (even if I disagree that Iraqi oil is in our best interest).

The question becomes, what kind of alternative fuel? It all comes down to energy density. Energy density is the amount of energy contained in a substance per unit volume. The highest possible energy density is antimatter, which releases energy when it is annihilated by normal matter. The amount of energy released is huge, as Einstein's E=mc^2 will show you. There's a reason science fiction authors like antimatter for fuel! Unfortunately, antimatter is not likely to ever be used for vehicles -- even if we could safely store it, the tiniest accident could wipe out an entire city. The risk factor is just too high. The next highest energy density comes from nuclear power. Now, in spite of what many people think, we don't use the energy released in nuclear fission directly. We use the the energy to heat water which then drives steam turbines to produce electricity, just like coal-burning plants. Unfortunately, fission reactors are a bit too bulky and complicated to try to put in the hands of your average 16 year old, so that's not likely to happen. We could use nuclear power to charge batteries for use in electric cars, however. Unfortunately, the energy density in batteries is pretty low, too. You can't drive very far or very fast on a battery. That's why electric cars have never really caught on.

The next highest energy density is probably hydrogen fuel. Here again, hydrogen is a bit too unstable to burn directly to produce power (remember the Hindenberg?). Hydrogen fuels cells are another matter entirely. A fuel cell combines hydrogen and oxygen to produce electricity. So hydrogen fuel cell cars are still electric cars, with all the benefits that go with them (quiet, pollution-free, etc.). The only waste product from a fuel cell is water. In fact, that water can be purified for drinking, used to cool the engine, recycled to be separated back into hydrogen and oxygen, or simply dumped out the back as steam. We just said that electric cars never caught on, though, right? Why are fuel cell cars any better? It all comes back to energy density. A battery doesn't have a very high energy density, but the fuel cell doesn't need a battery -- it stores its energy in the hydrogen itself, which has a very high energy density indeed. The oxygen needed for the reaction is free -- just pull it from the air.

Just how high is the energy density of a hydrogen fuel cell? The scheme I've seen most used would dissolve the hydrogen into small "chips" a little larger than a couple of dominos. That chip would be the equivalent of a full tank of gas. In fact, you could safely carry a couple of extra chips in your jacket pocket as backup. The fuel cell would cause the hydrogen to slowly bubble out of the chip, be combined with the oxygen in the air, and release electricity on a more or less continuous basis. "Gas stations" would become places to buy more chips.

We can do this now, although we still have some efficiency issues to work out. The biggest problem is that we have no distribution or production network for the hydrogen chips. The raw material is easy to find -- we just need water. We don't have to worry about running out of water because the waste product of the fuel cell is -- water! It's really an elegant solution, the problems with it are cultural, logistical, political (oil companies have a lot of power in Washington), and economic (it's still more expensive to make the chips than to buy gas, because they are currently non-mass-produced items). Personally, I think the way around all of this is devise a home version of the hydrogen production machine. Fill it with distilled water, plug in the machine, and make your chips at home. The chips themselves can be reused. The only distribution network you need is for the distilled water.

What I've been doing here is taking a near-future technology and project its consequences on society. This is the basis of most good science fiction. Now that we know how a "hydrogen economy" would work, we can use this in our stories. For the characters in our stories, hydrogen fuel cells would be nothing special. But when we need to describe how they refuel or how long they can go without refueling, we as writers need to understand how the technology works in order to see the impact on our characters' lives.

Now if we could just these prototype hydrogen cars advanced to the next stage so we can live a bit of science fiction int he real world!

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