November 10, 2008 –
It's been a while since I've posted anything of reasonable quality. I apologize for that, especially to the people that read and liked my stuff. Anyway, I've been quite busy with my graduate program as of late, and the stock market just isn't as interesting when the sectors you're investing in aren't doing too well. [more]
July 19, 2008 –
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Introduction
I thought I would talk about ethanol as transportation fuel in this post. I think overall this should be a good outlook for those of you that have considered investing in alternative fuels. My aim is not to provide a pitch for or against specific companies, but rather to educate you about a technology so that you, as an intelligent investor, can decide what to do with your money yourself.
As I’ve indicated elsewhere, I’m a Chemical Engineer, so I’ll try to stick mostly with what I know and am familiar with. When I branch off into company financials, I enter territory that I am not as familiar with, and other sources should be turned to for better and more accurate insight.
What is ethanol?
Ethanol is a hydrocarbon chain that looks like this: H3C-CH2-OH. If you’re chemistry is not up to par, it has two carbons bonded together, with an alcohol group (OH) attached to one of the carbons in the series. Let’s compare that to gasoline (assume octane): H3C-(CH2)6-CH3. It’s basically just 8 carbons bonded together with the hydrogens to complete the octet. Other than the chain length, the important difference to note is the OH group on the end of ethanol.
I had considered doing a full break down of the thermodynamics of combustion to compare the energy you can get with one molecule of octane versus one molecule of ethanol. Rather than showing the calculation and losing the remaining reader base that has not already vanished at the mention of chemistry, I’ll simplify it… a lot.
Each C-H bond and each C-C bond holds a certain amount of energy – when we combust these hydrocarbons, we lower the energy state of the species. Just looking at the molecules it’s easy to see that there is more energy available in a molecule of octane than ethanol (C-O bonds are not much higher in energy than C-C bonds).
This raises the question, “if ethanol has nowhere near the same amount of energy per molecule, why do I hear so much about it potentially replacing gasoline?” Well, you can pack about 3 times the number of molecules of ethanol into the same space as gasoline (it would be like making a 10 gallon tank 30 gallons… by magic). However, each molecule of ethanol has significantly less energy than gasoline. When you take that into account in our idealized and approximated situation, it’s found that the same sized 10 gallon tank filled with ethanol will only hold about 52% the energy that you would get from octane (if you take the experimentally observed energy densities of gasoline and ethanol that are not based on quick, fundamental calculations, you get about 57%) [1].
That’s not very sexy. However, these calculations are still based on the fundamental notion of fully reversible processes (that means nothing to the non-engineers) and processes that are not limited by thermodynamic efficiency. And this, dear reader, is where ethanol moves from the “worse than gasoline” range to being about the same as gasoline.
Compression is hawt
As we all know (at least most of us, I assume), the internal combustion engine (that which is found in your car) works by using a series of pistons. The fundamentals are based on compression and expansion. The more that you can compress the hydrocarbon fuel prior to ignition, the more energy you can harvest from the expansion – as such, fuels that can be compressed more will be overall more efficient. This is why diesel engines are more efficient than gasoline engines. In turn, ethanol can be compressed much more than gasoline, thus being more efficient. If we take the compression rating into account, it becomes possible to optimize engines to take advantage of this increase in compressibility, and reap the benefits [2].
It’s a very simple matter of tuning engines (they need to be mechanically altered) to support higher compression, and thus obtain the same mileage from ethanol as from gasoline. When I say “simple matter,” I really mean for car manufacturers. The “flex-fuel” vehicles in the US are made to run primarily on gasoline and thus are not optimized to take advantage of the added compression rating that ethanol allows for. Tragic, truly. Until cars are made to run on a specific ethanol fuel, as opposed to a flex fuel, the compression rating will not be taken advantage of (Several car companies are working on engines capable of altering the compression ratio on the fly. Even ford has a patent issued.). Until engines are reconfigured, cars will not get as good mileage on ethanol fuels when compared to gasoline. That is why your friends with E85 capable vehicles say, “I’ve tried ethanol fuel, and it’s crap.”
That pesky OH group
Now that we know that ethanol can in fact replace gasoline as far as being combusted in a vehicle, there are a few things that still need to be addressed. Most importantly is that pesky OH group.
As I already mentioned, gasoline does not have this OH group, and thus we have a significant difference between the two fuels. But of course the question you might be asking is, “So what does this OH group do, exactly?” Well, to be blunt, it facilitates hydrogen bonding (the few people that were reading up to this point just stopped reading.)
Hydrogen bonds and water go hand in hand, they’re practically married. It’s this sort of plentiful hydrogen bonding that makes water so unique. And because water likes hydrogen bonds, and ethanol has an OH group that says something like, “Hey, I can do hydrogen bonding,” ethanol and water are best of friends.
And again, some of you might be saying, “So what?” Well, water is one of the products of combustion, so facilitating combustion of water might be a bit difficult – it’d be like eating a Chipotle burrito when the burrito you want to eat is already contained within your stomach… only more difficult. When significant amounts of water get together with ethanol, combustion ceases to happen – it’s like having those two friends that are awesome when you spend time with them individually, but you start to hate life when they’re together.
Gasoline doesn’t have this problem – it’s not very friendly with water, and so combustion can continue to happen. Because water and gasoline do not get along, gasoline can be readily transported through pipeline infrastructure. However, concentrated ethanol cannot be transported through this infrastructure as water likes to gatecrash the party.
What’s more, separating water and ethanol is troublesome at best. Like, really insanely troublesome – this is why you can’t go to the liquor store and buy 200 proof alcohol. It’s not just because it would destroy your esophagus if you drank it straight.
What about gasoline-ethanol mixes?
Ahh, now we’ve arrived at some sort of plausible solution. We can use ethanol as an additive (we do because of the anti-knocking properties), it will mix nicely with the gasoline, and water will be kept at bay if the concentration of ethanol is not sufficiently high so as to attract water – none the less, there are problems with these mixes. Especially in the United States.
Rather than show you a ternary phase diagram of water, ethanol, and gasoline, I’ll just say this: water content in an ethanol-gasoline blend is an issue in the US because of temperature. In Brazil, the temperature happens to be just right to allow for reasonably high ethanol-gasoline blends without worrying too much about water. When you start worrying about water, the cost of removing it from ethanol climbs, dramatically, and thus its viability is lowered.
A study on the viability of ethanol in the US was conducted in the later part of 2007. Alexandre Szklo et al. at the University of Rio de Janeiro concluded that to make ethanol viable in the US, once the advantages of compression rating and the disadvantages of water affinity were taken into account, E30 fuel was necessary. Additionally, cars specifically optimized for the E30 compression rating would be necessary [3]. They also mentioned that in some regions of the US this blend would still be unsuitable – how many different ethanol-optimized cars would car manufacturers actually make? This pretty much means that variable compression rating vehicles will need to be cheap, and gasoline blends may need be optimized based on the region you are traveling in.
End of Part 4
Where does this leave us? It basically leaves us with the idea that ethanol is a reasonable fuel, as an additive, but will be unable to solely replace gasoline in the transportation market due to its affinity toward water. However, it has the potential to offset our gasoline usage by ~30% and significantly reduce environmentally detrimental combustion emissions (that is another advantage that merits some discussion and debate).
The production of ethanol is an entirely different beast, and I have already addressed production concerns in Part 3 of my Energy Outlook series. Given this discussion, I think it’s safe to say that ethanol may have some place as a fuel additive for cars to alleviate some of our dependence on gasoline, but is by no means a long-term solution or substitute for our current transportation fuel.
I hope that this posting provided some insight into ethanol, and why dismissing it simply as being “a bad technology” is not a fair assessment. Ethanol has its merits, and in many cases is being wrongly criticized. It’s not always the product that’s faulty, sometimes it’s the implementation.
As always, comments and further discussion are desired and appreciated. [more]
July 18, 2008 –
I had not actually heard of this presentation (despite being a Boulderite) until very recently. One of my friends, being a recent graduate with his PharmD, has now secured a high paying job working as a hospital pharmacist. As he now has more money than he knows what to do with, and mostly feels that the decline in American Society will hinder his ability to do luscious things in the future, he decided to rent out a movie theatre, purchase the film, and setup a catered event for his friends and friends' friends. [more]
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