Posted on November 10th, 2007 2 comments
I previously wrote about using ethanol as an aviation fuel. After noticing that the national average for aviation fuel is now around $4.60/gallon, and E85 is available for $2.19/gallon, it seems fitting to revisit the subject. As oil heads toward $100/barrel, pushing regular gasoline over $3/gallon again it would seem that E85 is poised see some renewed interest at the fuel pumps around the country.
In order to take advantage of E85’s lower pricing in comparison to gasoline, it requires that you have a ‘flex-fuel’ vehicle that is approved for use with E85…or does it? I began to ponder the question of whether you can safely run E85 in a vehicle that is not specifically designed for it. I decided to do some research and experimentation on the subject. There is a lot of misinformation floating around about ethanol, much of it by people who don’t have the slightest understanding of fuel chemistry. It’s sometimes so often repeated that you have to wonder if there is some sort of conspiracy against ethanol. I have a little more experience than the average man off the street about gasoline and ethanol. I worked in HP’s Chemical Analysis group for 7 years (now part of Agilent Technologies) where one of the instruments I helped to design and support measured oxygenate content in gasoline. So I am constantly amazed at how people with no technical background in the subject will confidently repeat common myths about ethanol. I covered a few of those in the aviation fuel article so I won’t repeat them here.
I was interested to know if anyone had developed a kit to convert a conventional car into an E85 flex fuel vehicle. I found that there are several conversion products on the market that splice into a car’s fuel injection system that allow any fuel-injected vehicle to use E85 fuel. Just about all cars manufactured in the past 15 years use fuel injection systems instead of carburetors to adjust the air-to-fuel ratio to the engine. The advantage of fuel injection is that it can be computer-controlled to vary the air-to-fuel ratio based on a number of factors such as throttle position, engine speed, manifold pressure, engine temperature, and oxygen content of the car’s exhaust. The ability to monitor all of these parameters and adjust the mixture accordingly has helped significantly with advances in fuel economy and emissions reductions. The computer is able to adjust the fuel amount by pulsing the fuel injection valves to allow just the right amount of fuel to enter the intake manifold. The air-to-fuel ratio is thus determined by how many milliseconds the injector valve is opened each cycle. By monitoring the oxygen content in the exhaust, it’s possible to tell whether the fuel injectors are providing too much fuel (too rich a mixture) or too little fuel (too lean a mixture) and that information can be used to help close this control loop. Although I haven’t been able to find any technical descriptions on the theory of operation of these conversion devices, the only thing that one can assume that they do is to stretch the pulse generated by the car’s computer to compensate for the air-to-fuel ratio difference required by E85 to extend it beyond what the car’s computer had included in the lookup table for the air-to-fuel ratio settings. It needs to do this because the air-to-fuel ratio for ethanol is about 30% lower than it is for gasoline. So the effect of adding one of these devices to your car is to shift the lookup table to favor E85 fuel in the event that the standard lookup table cannot reach the lower air-to-fuel ratio required to keep the mixture rich enough when running ethanol.
I would estimate that the cost of the electrical components to implement a simple scheme like this would be well under $50, and so you would think a conversion kit would sell for somewhere around $150 or less, but they are charging as much as $500 to $750, which is more that I wanted spend to run some E85 experiments. So I won’t be discussing the efficacy of E85 conversion kits. Instead, I will concentrate on blending ethanol with gasoline at the pump.
Ethanol has about 28% less thermal energy (measured in BTUs) than gasoline. However, the process to convert the BTUs into mechanical energy on cars is rather inefficient, usually less than 30%. Thus it doesn’t automatically follow that your fuel economy will be reduced by exactly 28% when you run E85 in place of gasoline if you can improve the conversion efficiency. In fact, E85 may deliver similar fuel mileage if your car’s computer can advance the timing of the ignition and convert more of the BTUs into usable mechanical energy. This is possible due to ethanol’s superior octane rating, which is a measure of resistance to engine knocking, also known as ‘pinging’ or detonation.
E85 has a 105 octane rating, which exceeds the octane rating of even the most expensive premium gasoline by a wide margin. For example, in Colorado we have 3 commonly available grades of fuel: 85 octane, 87 octane, and 91 octane. These are lower than what you’d find at sea level because at Colorado’s higher altitudes, the risk of detonation is lower and thus you can safely use lower octane fuels
Gasoline’s price goes up with increased octane rating because of its higher ‘grade’ and to cover the expense of the blending agents required to enhance the octane rating. I’ve noticed that the price goes up approximately 7% per grade here in Colorado. I’ve often wanted to use 85-octane gasoline since that’s the lowest price for fuel advertised on the gas station signs, but I know how destructive detonation can be to an engine, so I always use at least 87 grade on my Dodge Durango. On the few occasions I tried 85 octane, I could hear the tell tale signs of knocking when climbing hills. The knocking goes away in a few seconds since the computer is able to monitor a ‘knock sensor’ on the engine and retard the ignition timing accordingly but I still don’t like to hear that sound so I stick with 87 or higher octane.
I noticed that there is a rather extensive Wikipedia article dedicated to using E85 in standard engines. Although there are a number of warnings about all the things that could happen when running E85 in a vehicle not specifically designed to run on E85, most of them don’t apply to vehicles manufactured after 1990. For example, much of the rubber seal material in automotive fuel systems was changed after ethanol became a common blending agent. Ethanol is typically mixed at the rate of 10% ethanol to 90% gasoline to help reduce emissions, and most cars can run fine on a mixture with as much as 20% ethanol. I became curious to see what would happen if I tried running on 30% ethanol, so lately I’ve been filling my tank w
ith 2/3 of the less expensive 85 octane gasoline mixed with 1/3 of E85. This gives me something close to a 30% ethanol ratio (E30) with an expected octane rating of around 91 and a BTU content that would be 90% that of gasoline. Since I’m saving 7% per gallon on the gasoline, and 30% per gallon on the E85, my fuel bill effectively is reduced by about 15%.
I have a fuel computer in my Durango that gives me instantaneous and average MPG and I’ve noticed about a 10% drop in MPG on my E30 blend, so it’s still about 5% cheaper to do this than to fill up with regular gas.
I’m not blending my own E30 for the savings, but rather to satisfy a curiosity about using ethanol. I suppose if one is of a mindset to reduce our nation’s dependence on fossil fuels, blending in E85 at the pump could have an immediate impact of reducing our demand for gasoline by about 30%, or 40 billion gallons per year while increasing the demand for ethanol by a similar amount. The ethanol industry doesn’t produce enough to satisfy this level of demand yet, but if more people started blending E85 with regular gasoline at the pump it may help to drive demand for E85 to help to increase its availability. One of the common shortcomings of E85 is the fact that it’s only available in a relatively small number of locations. For example, in my own town of about 77,000 people, we have only two stations that carry it.
What I’d really like to do is reprogram my car’s computer, often referred to as the ECU (engine control unit) or PCM (powertrain control module), to accommodate E85. However, the information to do something like this isn’t readily available. If you’re an automotive engineer with Daimler-Chrysler and know how to reprogram the ECUs to be E85 compatible, please contact me ;-).
My nephew is currently in the process of installing an open source-based ECU called a MicroSquirt II in his 1981 DeLorean and I have become his technical support hotline, giving him tips on proper soldering techniques and electronic debugging issues with the device. The more I read about it, the more I like the idea of a completely user accessible and reprogrammable ECU. That would make it easy to experiment with various ethanol ratios and once it’s debugged, the data could easily be made available to anyone with a similar vehicle who wants it.
The EPA is concerned about aftermarket products in this category, of course, because the ECU is largely responsible for keeping the tailpipe emissions compliant with clean air regulations. But I see that as a relatively easy problem to solve because using oxygenated fuels such as alcohol and reducing tailpipe emissions tend to be mutually compatible goals. The EPA has issued laws against altering the ECU in a way that makes the vehicle non-compliant with clean air standards. This was a problem when people were converting cars to run on propane and natural gas back during the first energy crunch but today I think those laws are mainly aimed at companies selling ‘performance chips’ which tend to sacrifice fuel economy and tailpipe emissions for more power.
It will be interesting to see what happens with E85 because the stock market seems to be predicting a glut of ethanol in the near future, but with the recent increase in gas prices it may take care of any potential ethanol over supplies, especially if the idea of using it in standard vehicles becomes popular.
Posted on August 15th, 2007 22 comments
A few months ago I bought an engine for the Cozy that is a 200 HP version of the Lycoming IO-360. This engine produces about 20 HP more the standard 180 HP O-360 engine. In order to get to 200 HP, it has higher compression ratio and that requires the use of 100 octane fuel. Today, 100 octane fuel is available at most U.S. airports, but I worried about its continued availability in the future. Aviation fuel, or 100LL as it’s called, uses tetraethyl lead to increase the octane rating of fuel. Adding lead to auto fuel to enhance its octane used to be quite common but fell out of favor when it was found to distribute the lead, now recognized as a poison, into the atmosphere. Just about all countries in the world have discontinued the use of lead as an octane enhancer for auto fuel.
I began to wonder what I might use for fuel in the future should leaded aviation fuel be outlawed, and my attention turned toward alcohol, ethyl alcohol, to be specific. It’s also called ethanol or grain alcohol and is used as an octane enhancer. It also makes gasoline burn more cleanly. Ethanol is the form of alcohol that you find in alcoholic drinks. Because of this, it is subject to liquor taxes. The only way to avoid paying liquor taxes is to add poison to it. If fuel was drinkable and available for a few dollars per gallon, it’s assumed that no one would bother buying beer, wine, or spirits. With that logic, it’s hard to understand why anyone would buy an 18-year-old bottle of scotch for $75 when Everclear can be had for $10. 🙂 This poisoning is called ‘denaturing’ and as long as it makes the alcohol undrinkable, just about anything can be used.
It’s not unusual for auto fuel in the U.S. to contain 10% alcohol since most cars can run on fuel with this concentration of alcohol. It’s beginning to become available at 85% concentrations, called E85, but that requires that the fuel system is compatible with that level of alcohol concentration. Only a small number of vehicles manufactured over the past 10 years or so claim compatibilty with E85 and you can look up whether yours is compatible by searching for “E85 compatibility” on the Internet. Each year, more vehicles are introduced that will run on E85 or regular gasoline and these are referred to as ‘flexible-fuel’ vehicles. There’s even an effort underway to make an aviation grade ethanol called AGE-85 that is not without controversy.
Back in the 1980s and 1990s when aviation fuel cost about twice as much per gallon as auto fuel, several efforts to qualify auto fuel in aircraft were conducted. They were targeted at older aircraft with low compression engines which were able to run on an aviation fuel called 80LL whose octane rating was close to regular unleaded auto gas. Quite a few aircraft were eligible to burn auto fuel, provided they purchased a placard called an ‘STC’ for about $200. Some airports actually began carrying it as a less expensive alternative to 100LL after 80LL went out of production. However, the tests to get approval for the STC were conducted before alcohol became a common additive to auto fuel. After it became commonplace to use alcohol as an additive, it was found that some aircraft had problems with it attacking the rubber seal materials in the fuel system. The entities that granted the STC, namely Peterson Aviation and the EAA, do not allow the use of auto fuel that contains alcohol. The octane enhancer of choice back in the 1980’s was MTBE, methyl teriary butyl ether, and it had no issues with fuel system compatibility. But it has subsequently fallen out of favor because it has environmental and health concerns. It has largely been replaced by ethanol. Adding ethanol has now become so common with auto fuel, and the difference in price between auto fuel and avgas is not as significant as it was in the 1980s so the popularity of using auto fuel in aircraft is beginning to wane.
The IO-360 engine I mentioned earlier would not be a candidate for an auto fuel STC anyway because the octane rating of auto fuel available in the U.S. runs about 85-91 octane which is much too low and would damage an aircraft engine designed to run on 100 octane fuel. To get a fuel that had an octane rating around 100 would require using some additive. Otherwise, engine knock, also known as auto-ignition, would create multiple flame fronts that collide in the engine’s cylinders, increasing pressures and temperatures that over stress and damage the engine.
It would appear that a solution to my concern would be to make the plane compatible with ethanol because it has an octane rating of 105. I recall seeing a group of experimental aircraft showing up at Oshkosh for many years now that all run on ethanol. They are known as the Vanguard Squadron and are shown in the image above. I tracked down one of their members, Dick Pearson, and he generously allowed me to pick his brain regarding his experience of using ethanol in an airplane. Dick has nearly 14 years of experience of using ethanol in 2 separate experimental aircraft that he flies as well as that of the other 4 aircraft in the Vanguard Squadron. He is quite a proponent of the fuel. He told me that there is a lot of controversy and misinformation floating around regarding ethanol. For example, there is a persistent belief that the energy that it takes to grow corn and convert it into ethanol exceeds the energy content of the resulting ethanol, giving it a negative energy balance. This is not true. The reason that this misconception persists is because natural gas is often used in the conversion process to provide heat for making alcohol from corn. But there’s a good reason for using natural gas for heat. The value of natural gas per BTU is much lower than it is for ethanol per BTU. It’s about a third the cost per BTU as ethanol. So even though one could use a portion of the ethanol to provide heat in the process that makes it, it’s not as economical as using natural gas for heat. It’s this business of using a fuel other than ethanol to help make ethanol that leads people to believe that it has a negative energy balance. It actually has a positive energy balance widely accepted to be around 1.34, or getting a third more energy out of the process than is put into it. That takes into consideration the energy required to fertilize, plant, irrigate, spray, harvest, transport, and convert the corn into alcohol.
Energy balance is only part of the equation, since when you talk about energy you must consider more factors that the energy balance or cost/BTU. It’s also important to consider factors such as energy density, convenience, and fuel compatibility. This is particularly true when it comes to transportation fuels since there is high value to having a fuel that is compatible the existing engines. If energy balance and cost/BTU were the only measures of concern, we might see coal-fueled vehicles since its cost per BTU is about 10% of what we pay for gasoline.
In Brazil where they make alcohol from sugar cane, they are able to burn the waste parts of the sugar cane called bagasse to generate the heat needed for the process. As a result, they get 10 times more energy from the sugar cane than is required to grow and convert the sugar cane to ethanol. This is similar to the energy balance expected with cellulosic alcohol.
A number of companies are working on deriving ethanol from cellulosic plants instead of corn kernels. These materials include waste products such as wood chips, corn and wheat stalks, and other organic waste materials that have limited use today. In most cases, you have to pay someone to dispose of them. The processes that convert cellulose to alcohol are currently not mature enough to be cost competitive with making ethanol from higher-value materials like corn. However, there are a number of companies working to improve the processes and if they become competitive, it could reduce the cost of ethanol to be lower than gasoline in a direct fuel mileage comparison, and when that occurs, it has the potential to change everything.
Some cellulose-to-alcohol processes are based on enzymes that can unlock the sugars in cellulose and convert it into alcohol using conventional fermentation. There is an ethanol plant in Canada already doing this as well as a few more under construction. There is a also a non-fermentation process developed by Range Fuels of Broomfield, Colorado that can convert cellulosic materials to alcohol. Range Fuels is building a cellulose-to-ethanol plant in Georgia that will be capable of producing 100 million gallons of ethanol a year from wood chips. I think this will substantially change the perception that ethanol is nothing but a farm subsidy, which is the view a lot of people have about it today. Can you imagine a lawn service where they reduce the fee if you let them take away the lawn clippings, leaves, and other yard waste? I think that would be a huge step in the direction of energy independence because recovering energy from local waste materials would reduce an energy supply chain that currently extends around the globe to a short loop within your own neighborhood. It would also reduce CO2 emissions because plants generally release their carbon back into the atmosphere in a relatively short time, and so instead of digging up carbon that has been buried for millions of years, we’d be able to use carbon that was essentially on its way back into the atmosphere anyway. [UPDATE 2014-02-26] Range Fuels burned through $234M in capital, about a third of it from taxpayers, before shutting down operations in 2011.
There are a lot of competing and complementary renewable energy technologies under development including wind, solar, and biomass. I don’t think that there will be a single winner in the race to replace our convenient yet exhaustible fossil fuels. I feel a lot more optimistic about it after doing my own investigation of alternatives like ethanol instead of listening to pundits arguing for or against it, because it doesn’t take long for people to get emotional about their point of view when it comes to renewable energy. I guess that’s because mixing politics with science can be such a volatile combination. Now if only that volatility could be converted into usable energy our future would be secure!