"You've got to recognize there are limits to how much corn can be used for ethanol. I mean, after all, we got to eat some."
My favorite car of all time is the Honda S2000. This vehicle is a wonderful piece of engineering that gets 26 MPG on the highway, has a 1.9L engine that can output 240 HP at 8300 RPM, and weighs in at 2855 pounds. But did you know that the engine weighs 326 pounds, the compression ratio (CR) is 11:1, the gas tank holds 13.2 gallons and weighs 80 pounds when full, and the peak torque is 153 foot-pounds? Why is this important? Because I was thinking to myself, "What would happen if I were to convert my high-performance Honda S2000 to an alternate fuel?". That type of data is exactly what one needs to know in order to answer this question. The fuels we are used to are all liquid and can be poured into thin-shelled containers like your gasoline tank. While the engines that run off of gasoline are complicated to build and are heavy, they are not unreasonably so. Let's hope that the alternative to gasoline is the same.
For the record, let me first state that there is no such thing as a 200 MPG carburetor, so don't get your hopes up. How do I know there is no such thing as a 200 MPG carburetor? Simple thermodynamics -- the maximum theoretical efficiency of any Otto-cycle engine is determined by its compression ratio only. Naturally, the actual efficiency will always be less than this. For the Honda S2000, the 11:1 compression translates into a maximum efficiency of 68%. If you compare the peak torque produced by the S2000 to the theoretical peak torque the engine could provide with the amount of fuel it consumes, you will find that the actual efficiency of the S2000 is 19.7%. While this sounds horrible, this is actually very typical for high-performance engines like the S2000. Even if the Honda S2000 had a perfect engine, the very most we could ever expect from it is 89.8 MPG (presuming that we changed nothing else but the engine). While 89.8 MPG sounds impressive, it still isn't 200 MPG and it isn't even remotely practical to build a perfect engine. That is also why it has never been done. The point is we need to restrict our choices to reality instead of fantasy and that is what this article is all about.
Gasoline is derived from crude oil in refineries. Refineries cook the oil and then pass the resulting vapor through cooling towers. Within these cooling towers are collection trays that are at fixed temperature ranges. Gasoline is obtained from one of those trays. In order to increase yields of gasoline, the crude oil is subjected to various modifications before being refined.
Crude oil is easy to mine (by pumping), easy to transport, and easy to process into gasoline. That is why gasoline is (or was) so cheap. It also explains why gasoline is not a simple chemical but a hodge podge of various hydrocarbons. Because of the numerous imperfections in raw gasoline, refinery stations will add other chemicals (detergents, anti-corrosion, coloring, reformers, etc) to improve the quality of the gasoline.
Crude oil is a natural resource, meaning that crude oil is something that exists naturally in the Earth. It also means that crude oil does not exist in infinite quantities. While no one can agree when crude oil production will peak or when it will expire, one thing is very certain: someday crude oil supplies will most definitely dry up. What will we do then?
Gasoline is a liquid hydrocarbon but there are lots of other liquid hydrocarbons besides gasoline. For reference purposes, gasoline is considered to be a mixture of only two liquid hydrocarbons: 2,2,4-trimethylpentane and n-heptane. I will only consider one of these two hydrocarbons during this discussion, 2,2,4-trimethylpentane, because of its higher octane rating.
Octane is not the resistance of fuel to detonation, since detonation is exactly what a 4-stroke engine needs during the power cycle to run. It would be better to say that octane is the resistance of fuel to premature detonation, but even this leads to misconceptions such as the myth that the higher the octane, the more slowly a fuel burns. 2,2,4-trimethylpentane (100 octane) has a flame speed that varies from 38 to 52 cm/sec, depending on fuel-to-air ratio, while n-heptane (zero octane) has a flame speed that varies from 47 to 58 cm/sec, under the same conditions. Most hydrocarbon fuels, regardless of octane, have similar flame speeds. The opposite of a slow burn is called knock, but anti-knock is not a requirement or even desireable in all engines, as evidenced by Diesel engines, which are designed to knock. What is not desireable under any condition, and is often confused with knock itself, is when knocking occurs before a piston has reached top-dead center and causes the engine to buck against itself. It is the bucking that is harmful, not the knock. Besides, flame speed obviously is a minor concern, seeing as Formula One race cars and high-performance motorcycles have engines that rev well over 12,000 rpm using high octane fuels, and wouldn't faster burning fuels be more desireable under those conditions? No, better stick to the more accurate definition for octane as the resistance of a fuel to autoignition.
Octane is what will determine the extreme upper limit on compression ratio of Otto cycle engines (like the S2000 has). This is called the "critical compression ratio" or CCR. Higher performance cars generally use higher compression ratios (or its equivalent in turbocharger/supercharger boost pressures) and therefore require higher octane fuels.
Let's consider what qualities we need to have in an alternate fuel, if we wish to make it comparable to gasoline:
Naturally, the Honda S2000 will be the baseline for all comparisons here, so we need to consider the effect of what switching to other fuels will have on MPG and power on our S2000. The following table displays the properties of certain alternate fuels that we want to consider:
Here we can see that five of the fuels would have problems with carburetor icing and eight of the fuels would have problems with vapor locking. Notice how very poorly hydrogen performs here in terms of MPG or range! This table also highlights the advantage of higher octane by leaving the stock S2000 CR alone (11:1) and boosting the intake to its maximum PSI it could withstand (ignoring MPG, which obviously would suffer).
NOTE: Do not confuse alcohol with gasohol -- which is a mixture of gasoline and alcohol.
The higher the hydrocarbon count of an alcohol, the better it will be on mileage, the less water it will absorb from the air, and the lower its octane rating will be. Because of this, no engine can run any of the alcohols without modification with the exception of butanol. While butanol is very similar in quality to regular pump gasoline, it is also the only alcohol that can be mixed or substituted for diesel fuel. The mediocre octane rating of butanol could easily be boosted with cheap and plentiful additives, such as t-butanol, and bring it up to the premium range. Butanol is also the cheapest of alcohols to produce ($0.84/gal at 2006 pricing, compared to gasoline which was $2.50/gal).
The easiest and cheapest (and still illegal for DIY) method for making ethanol is via old fashioned stills and corn mash. Ethanol can be distilled off of fermenting corn mash at a rate of 400 gallons per acre per year of corn. We are already facing a shortage of farmable land for agriculture, what would happen if all of a sudden there were huge demand for 138 billion gallons of ethanol a day, as there is for gasoline? This would require at least 345 million acres of land to produce. Last time I looked real estate was not cheap. This also assumes that we even have that much farmable land available. While the same situation exists for butanol, butanol holds an advantage here since yields for butanol are greater (500-600 gallons per acre or 230 million acres of land) and there are more stock ingredients that can be used to make butanol than can be used to make ethanol, i.e. -- high yielding butanol can be made from things other than corn or sugar beets, for example, cheap, low grade animal feed or natural gas.
Where does electricity come from? Some people seem to think that if we switch over to electricity, that the oil crisis will somehow magically disappear because we don't have an electricity crisis. But imagine if everyone switched to electricity tomorrow. Could the current electric grid handle it? What about all the electric power plants that still have to run off of crude oil?
The biggest challenge faced by electric vehicle manufacturers, is where to store the electricity. Current battery technology would enable me to store 10,000 A/hrs in a cube measuring 1.6 feet on each side. This would give me enough range to equal that of my stock S2000. The batteries would weigh 700 pounds, but that could be offset a little, seeing as a 200 hp motor would only weigh 100 pounds versus the S2000's 326 pound engine. It would cost me $40,800 for the batteries and $25,000 for the motor and controller. So if I wanted to convert my S2000 to electric, it would cost me at least $65,800 and it would be 400 pounds heavier. Remember that this is for an equivalent performing vehicle. If one was willing to give up some range, say for short distance driving like going to work (<100mi per day), you could cut that cost by 40%.
What about hybrids? Well you can see for yourself with this handy little calculator what the payback of a hybrid over a standard vehicle is...
The math here is simple. In the default example given, the hybrid will go 25 miles on $5.00 of gas. The difference between vehicles is 5MPG or 20%, which at $5.00/gal represents an extra $1.00 for the non-hybrid to travel that same 25 miles as the hybrid. The average American drives 12,000 miles per year, so we need to take the number of 25 mile increments that are in 12,000 miles, and multiply that by the $1.00 extra required for each of those 25 mile increments. The savings in gas of the hybrid over the non-hybrid is then $480 per year. While that sounds like a lot, remember that you also had to pay an extra $10,000 to save $480 a year so it would take $10,000/$480 = 21 years to make up for that additional $10,000 difference, even with gas at $5.00 a gallon. The numbers are even worse when you consider that for each multiple of ten years you need to add about $10,000 to the hybrid vehicle for the battery pack replacement. In other words, if your payback is not less than ten years, you will never ever realize a payback over the non-hybrid vehicle.
Chrysler announced in 2008 that they were planning to create three new hybrid vehicles. Unlike all the other hybrids, these use the gasoline or diesel engine to power a generator for long range, and use pure electric for anything under 40 miles. This allows the gasoline or diesel engine to operate at very high efficiencies (90% for diesel-electric locomotives for example) so we have a vehicle that is very cheap to run in the city, yet can go 600 miles on a tank of gas. The generator can even be used as a spare AC power source. Wow! Now there is something I would be willing to buy today, despite the fact that I dislike American cars because their quality is terrible and they are too noisey. It has annoyed me to no end that every hybrid that has come out so far has been a stupid design. Case in point: the Honda Accord hybrid. They took a high-powered 6-cylinder vehicle and attached a powerful electric motor to it. Now wait a minute! Why didn't they attach that powerful electric motor to a 4-cylinder engine so that power and performance would remain the same as the high-powered 6-cylinder engine, but instead of a modest increase in mileage, they would get a dramatic increase in mileage? Like I said, stupid. Lexus even did the same thing with their eight cylinder models! Once again, only the American companies had the right idea as you can see with the 2008 Ford Escape. The 4-speed Escape has a six cylinder engine and gets 22/28MPG. The hybrid version has a four cylinder engine with identical performance and yet gets 30/34MPG!
So I have to wonder then, did the Big Three know all along what consumers wanted but were holding back because they wanted to sell us something else not as good but better for profits and their skyhigh CEO salaries? Was their announcment bait for the "stimulus package" they shortly thereafter requested from the government due to a "poor economy". What's up with that? Chrysler landed a "stimulus package" for similar reasons back in the 70's and 80's too so is it my imagination or does everytime the economy goes sour the "Big Three" American automakers fall apart at the seams? The Big Three are supposed to be run by multimillion dollar execs who are supposed to know how to run multibillion dollar companies, keep them running, and have the foresight to plan ahead for tough times. Yet it seems like every twenty or thirty years, we have to bail them out because their companies are failing again. I say don't loan them the bailout money and let these bastards fall flat on their face -- they deserve it. Who is going to bail me out if I start a business and fail? Why should the Big Three be any different? The rationalization behind saving companies like this (other then saving face in front of the world) is that the unemployment rate would skyrocket. It makes more sense to me to let the Big Three American automakers go out of business and have 200,000 people out of work then to let all the mom-and-pop businesses go out of business and have 400,000 people out of work. It would be a different story if they didn't keep doing this over and over again, or it if they were actually making an effort to give consumers like me what we were looking for in a vehicle, but it isn't a different story, it is the same ol' story, but still, it was Chrysler that came out with the right idea, albeit for the wrong time and the wrong reasons.
Where does hydrogen come from? By electrolysis or the processing of natural gas. Electrolysis plants are not small and must use fresh water, meaning that precious drinking water would have to be diverted from homes to the hydrogen plants. Electrolysis is not only expensive, it requires lots of electricity to work -- now where is all the electricity going to come from again? Natural gas is not anymore plentiful than crude oil and would become even more scarce if everybody had to switch their cars over to hydrogen generated from natural gas.
Although gases can be compressed, you can no longer use a thin-shelled container or tank like you can with gasoline, you need something thick and heavy to withstand the high pressures (5000 psi) required -- like a propane tank. Hydrogen is inherently more dangerous than gasoline. This is not a myth but a common sense fact. Crack open a 13.2 gallon 5,000 psi propane-filled tank during an accident and you will have a very large explosion, so why would hydrogen be any different? And what an explosion it would be! Hydrogen compressed to 5,000 psi would require a 77 gallon tank that would weigh 265 pounds to give the same range as that 80 pound, 13.2 gallon tank filled with gasoline.
There are some alternatives to the thick-walled high-pressure tanks to hold hydrogen, but they amount to nothing more than metal "sponges" that soak up the hydrogen. While the tank no longer needs to be as thick as the highly pressurized tanks would, the metal "sponge" still reduces the ultimate amount of hydrogen it could have held by the amount of space the metal takes up -- not to mention the metal "sponge" is not very light. For example, a typical tank of this type would still weigh about 265 pounds but it would be as big as a 53 gallon gas tank in order to have the same range as an equivalent gasoline powered vehicle would have.
Liquid hydrogen is another alternative. The tank would be even smaller and lighter (37 gallons and 62 pounds), although still not as small as a gasoline tank would be for an equivalent range. The problem is, liquid hydrogen is very expensive to produce and once a tank is filled, it would not stay filled, but would meed to be slowly bled at a rate of 1.0% a day (a full tank would empty itself in three months), due to imperfect insulation materials allowing the tank to slowly heat up over time.
Let's say we have one of these big heavy tanks to hold our hydrogen...now what? Hydrogen could be used to directly fuel an internal combustion engine, but the problem is that hydrogen ignites too easily and runs much hotter than a gasoline engine, leading to excessive pre-ignition or backfiring. Direct injection would help here but would not be a perfect solution still. Hydrogen is also very corrosive to engines. Therefore hydrogen powered vehicles will be heavier, more expensive, and have less range than a gasoline-powered vehicle. Not to mention, they are still not pollution free, although they are much better than gasoline-powered vehicles in this regard.
What about hydrogen fuel cells to provide electricity for a motor? While fuel cells can truly be zero pollution, they are horribly expensive and have short lifetimes. Current fuel cell technology could enable me to store 10,000 A/hrs in a cube measuring 1.4 feet on each side. It would weigh 600 pounds but that could be offset a little, seeing as a 200 hp motor would only weigh 100 pounds versus the S2000's 326 pound engine. It would cost me $30,000 for the fuel cell and $25,000 for the motor and controller, not to mention, it would still require that large and heavy fuel tank to hold all that hydrogen. So if I wanted to convert my S2000 to a hydrogen fuel cell, it would cost me at least $55,000 and it might be as much as 559 pounds heavier.
In 2009, Honda has once again done a wonderful job coming up with something no one else could, by coming up with their hydrogen fuel cell power electric vehicle, the FCX Clarity. Using a fuel cell allows much greater efficiency than powering a piston engine directly (as I just explained) so it is no surprise that the Honda FCX Clarity gets 77 mpg in the city and 67 on the highway. What they fail to tell us is how much it costs to fill a tank or how many gallons of fuel it holds. Of course, even if hydrogen were cheap, this doesn't even remotely address the problem of how to go about creating a massive and highly expensive infrastructure to manufacture and provide shiny new hydrogen gas stations to replace all the current gas stations, but heck, it's the thought that counts, isn't it?
I had a co-worker who asked me why I didn't include biodiesel, especially do-it-yourself biodiesel, in my original report, so what I told him was, biodiesel is not just an alternate fuel, it is an alternate technology as well. Let me explain...
There are about 250,000,000 vehicles in the United States alone, and the vast majority of those are commercial passenger vehicles. The automotive industry has always prefered gasoline engines for passenger cars and diesel engines for trucks. Converting the vast majority of those 250,000,000 vehicles over to diesel just so we could run them on biodiesel would be terribly expensive, but why are gasoline vehicles more popular than diesel in the first place?
The difference between a gasoline engine and a diesel cycle engine is, a gasoline engine will take in a fuel/air mixture, compress it, and then ignite the fuel/air mixture to provide power. The diesel will take in air, compress it, and then inject fuel into that air to provide power. When air is rapidly compressed, it heats up, so that air in a diesel engine, in order for it to work, better be at a high enough compression ratio to ignite whatever fuel is injected into it. That is why the typical compression ratio of a diesel engine is around 20:1, whereas the typical compression ratio for a gasoline engine is around 10:1. Because of the different operating principles of a diesel as compared to a gasoline engine, the gasoline engine will be lighter, less expensive (think high temperature, high pressure fuel injectors for one thing), and more efficient, for a given compression ratio, than the diesel-cycle engine.
Diesel fuels are rated by their cetane number, instead of octane like gasoline is, and they are exact inverses of each other (so one hundred octane equals zero cetane and zero octane equals one hundred cetane). Because there are no cheap and readily obtainable high octane fuels for gasoline engines, unlike the high cetane fuels that are readily available for diesel engines, diesels can be run at much higher compression ratios. Now the higher the compression ratio, the more restricted the valve-to-piston clearances become for the piston when it is at top-dead-center. You don't want that piston to slam into the valve assembly (that would be bad), so there are two ways to provide more clearance in higher compression engines: increase the stroke of the engine, or lower the compression ratio but increase boost pressures to get an equivalent compression ratio. Unfortunately, the higher the boost pressure, the longer it takes for an engine to build up power so compression ratios cannot be lowered too much for a diesel (and you have to be able to start the engine in cold weather), but either way, the diesel will require a longer stroke than a corresponding gasoline engine. Where am I going with this? Because increasing the stroke of an engine lowers its RPM redline but raises its torque-to-horsepower ratio, so diesels, with their very high compression ratios (as compared to gasoline) tend to be built with lower RPM and higher torque than gasoline engines. This is a good thing since a reduced working RPM means a longer lifetime (read: more reliable engine) over that of higher RPM engines, since internal friction and stress increase exponentially at higher RPMs. The high torque-to-horsepower ratio means that diesels will be less affected by load and grade as compared to typically lower torque-to-horsepower ratio gasoline engines, but they will not perform well for 1/4 mile times. This a recipe for a hard working, low maintenance vehicle for the trucking industry niche market.
Now let's consider what qualities we need to have in an alternate diesel fuel, if we wish to make it comparable to Diesel #2:
Technically speaking, biodiesel is a fatty acid methyl ester, produced by the transesterification of animal/vegetable oil heated to 130°F, tritated with a methanol and sodium- or potassium-hydroxide solution, then skimming off the biodiesel (or draining off the glycerol soap byproduct), and "washing" the biodiesel with water. Vegetable oil can be directly used in diesel engines, but the viscosity of vegetable oils is about 2.5 times thicker than diesel fuel. Since this can cause extreme cold start problems for anyone who doesn't live in a very hot and dry climate, say like Phoenix, Arizona, clearly it is better to convert vegetable oil into biodiesel. Naturally, do-it-yourself biodiesel will not be a professional quality product. You can verify this for yourself simply by going to any do-it-yourself website, and see what the estimated cetane rating of their final product is. They not only don't know, they even believe that all do-it-yourself biodiesel provides exactly the same final product, which is scientifically and technologically ignorant. You can't tell me that if you use sunflower oil or rapeseed oil as a starting point, that you will wind up with exactly the same biodiesel, in terms of freezing point or cetane rating. These two parameters will affect cold start ability, engine performance, and pollution levels of the diesel.
I am not going to bother calculating power density (kj/gm) or specific power (typically providing only 90% of the power of Diesel #2), since all of these additional properties are overshadowed by the yield per acre: biodiesel is not easy to obtain in large quantities, forcing the issue of economics to override performance by a huge margin, and making performance comparisons irrelevent. The following table displays the final properties of certain oils that we want to consider in the production of do-it-yourself biodiesel:
As we can see, all of the biodiesel fuels have cold starting problems, even more so than standard Diesel #2. While additives can be used to lower their freezing point and viscosity, these additives can also be detrimental to the cetane rating and price. At least all of the biodiesel fuels have excellent cetane ratings. The cold starting problem is compounded at lower temperatures due to having to pump the higher viscosity biodiesel through the very fine tolerances of your typical fuel injector, so some people have tried to get around this whole cold starting mess by buying outdated vehicles, such as the Mercedes W123 series, where the fuel injectors are built more like an army tank then a fine watch. Of course, low viscosity or army tank fuel injectors won't prevent biodiesel (or diesel for that matter) from freezing up in weather that gasoline powered vehicles have no problem withstanding, so even some Mercedes W123 owners have had to resort to heating their gas tanks in a desperate attempt to solve this problem!.
Since commercial biodiesel is just as expensive as ordinary diesel, let's think about what a person has to go through for obtaining lower cost, do-it-yourself biodiesel. First, be prepared to give up every other weekend so you can waste gas while running around, looking for restaurants that will give their waste oil away for free. In the past restaurants had to pay for waste oil to be disposed of so they were more then willing to give it away, but more and more restaurant owners are starting to charge a fee for you to take it away from them, due to the increased competition for it. The most popular vehicle for biodiesel conversion is the diesel version of the Mercedes W123 series because they have "forgiving engines" with regards to the cold starting problems of biodiesel. The Mercedes W123 will go about 74.5 miles on 2.75 gallons of biodiesel, and a typical driver averages about 250 miles a week, so that equates to (250 / 74.5 = 3.36 * 2.75 =) 9.2 gallons a week or a 10 gallon vegetable oil tank. Since one gallon of vegetable oil will give one gallon of biodiesel (or less), that is a lot of messy, smelly, used grease to gather! My co-worker has a second vehicle he uses just for waste oil transportation so you will probably need to buy a second vehicle to transport the oil with too. Furthermore, just to set things straight here, there is no such thing as "taco grease", which is what my co-worker claims he is using, since what he is calling "taco grease" is a mixture of either olive oil, corn oil, or lard, depending on what oil the owner of the restaurant chooses to use that he collects the "taco grease" from. His starting point will always be a random mixture of these oils, which are the most commonly used oils in restaurants.
The most inexpensive ten gallon biodiesel reactor with all the "bells and whistles" will cost about $5,000 (actually, that is what my co-worker paid for his hobby built bioreactor, but I didn't have the heart to tell him that he could have bought a professionally made 40 gallon bioreactor from FuelMeister for only $2,995), a fully working Mercedes Benz W123 will cost about $4,000, a clunker Mercedes (to use as a workhorse for collecting taco grease on the weekends) will cost about $1000 (not including maintenance, insurance, and gas). My co-worker claims the cost of his biodiesel is mainly determined by the cost of the extremely toxic sodium methoxide, so his biodiesel costs $2.50 a gallon. Gas currently costs $4.10 a gallon so the payback time of an unmodified Mercedes to a biodeisel-powered Mercedes will be...
...eight-and-a-half years! This does not include service and upkeep of the reactor and second car. If you are an honest, law-abiding citizen (unlike some co-workers I know), you will also make sure that you register your biodiesel for an emissions waiver (biodiesel has much higher Nitric Oxide emissions) and your residence with the local Fire Department for using or storing highly toxic chemicals (such as methanol, sodium hydroxide, and sodium methoxide). That costs money too! So altogether, that makes for a hell of a lot of time, trouble, risk, and inconvenience to have to put up with, just so one can might be able to say their fuel prices are half what your's is. This is also assuming that (1) waste oil will always be free (they charge an arm and a leg for it in California), and (2) we could ever eat enough tacos (or fries or hamburgers or whatever) to power 250,000,000 diesel powered vehicles. There is research currently going on for making biodiesel from algae, but it is even more expensive to make biodiesel from algae then it is buy Diesel #2, despite the fact that algae is so easy to grow in large quantities. What this all means is that you would be better off buying $6,000 worth of diesel fuel and storing it away as investment to be sold later because your payoff would be much, much greater than do-it-yourself biodiesel.
The overall winner here is n-Butanol: no modifications would be required to the engine and stock performance is somewhat close to that of gasoline. Furthermore, n-butanol is cheaper ($0.84 per gallon at 2006 pricing), easier to manufacture then hydrogen or ethanol, and it is easily storable and transportable using current technology and methods. It would be a direct replacement for gasoline and diesel. The slightly lower octane rating could easily be offset by cheap additives, such as t-Butanol. The only problem is that the immediate (not future) benefits are not widely known. Maybe with the posting of this article, that will change...I could hope!
By the way, just for your information, a typical electric vehicle cost less than five cents a mile to operate, and that five cents also includes changing out the battery pack every two to ten years. If the cost of converting an electric vehicle were to come down 50% or more, the electric vehicle would be the way to go. Even with current battery technology, the range of an electric vehicle is not very good (anywhere from 100 to 200 miles per charge) and it takes a long time to recharge the batteries, so why not standardize on battery packs and have "gas" stations that exchange charged battery packs for used battery packs? You would pull up to the station, exchange the battery pack, and drive off. It would take five minutes and cost ($0.05 * 200mi =) 10$ for a "refuel". That is the equivalent of $2.10 a gallon of gasoline.