Freedom and liberty - the flag, the Bald Eagle, the almighty dollar, Elvis, free speech, the Wild West, monster trucks, a passion of American life and our ongoing love affair with the cars and trucks we drive.
The ability to move about freely is deeply woven into the fabric of the American lifestyle, and so it is natural that Americans commit a significant percentage of time, money, energy, and emotion into their vehicles. At the same time, our quality of life has become highly dependent upon transportation, as so many of the materials, products, and goods are delivered to us via a massive and highly intricate transportation system. The energy to fuel all of this activity is available whenever we need it - although this has not always been the case.
This lesson is about the many ways in which people and products endlessly move about, the energy/fuel that it takes, and the environmental consequences. Like Lesson 1 on Electricity, this lesson is designed as an opportunity to connect the topic to your own personal experiences and to see yourself as a component of a larger system. But like Lesson 1, "the times they are a-changin." Watch the following (:56) video below.
[Dr. Mathews is standing off of a highway with vehicles passing by periodically.] Dr. Mathews: Today's lecture is all about transportation. I am standing out here at 322 it is the Mt. Nittany Expressway. Lots of people (goods and services) come up and down this route. When you think about it, think about all the things that move around. We have to have gasoline, crude oil transported. We have to have frozen vegetables. We have to have exotic fruits moved around. Not to mention moving people. I have flown from Europe to America and back again many times. I have been to Australia, China, New Zealand, etc. I have even traveled via canoe, boat, train, and air. I have even ridden my bicycle every once in a while. All of these things require energy and each of these things will have its own impact on the environment around us. [A loud truck drives by] [Video fades out]
Success in this lesson will be based on:
We travel with ease and often at high velocity (providing you are not in the big cities). Ease of movement is another one of those things that we take for granted, but think just for a minute about how important it is to the quality of your life and how the American way of life has been transformed by the automobile. Wal-Mart for example, would not exist unless we had our own cars, and although the bulk of this lecture is about personal transportation, think also about all the goods and services that have to move around the expanse of the United States of America and beyond!
We have already discussed some transportation issues such as how we move coal around: train, barge, and truck mostly and some natural gas and oil pipelines, tankers, and trucks. As my colleagues in the Mining Program (in the Energy & Geo-Environmental Engineering Department) like to remind us: if it does not grow then it is mined! (We do extract oil and gas without mining.) The metals in this computer, silicon in the glass, hydrocarbons that are the bulk of the plastics, building materials were all once in the ground (unless you are in a log cabin!) All this material is transported around the country, sometimes across the oceans. Thus, if you did not get the hint: TRANSPORTATION IS IMPORTANT TO THE QUALITY OF OUR LIFE. Unfortunately, our transportation system is not very efficient (I am thinking mostly of personal transportation for that remark), and contributes to some of the environmental challenges.
For those of you who have not flown, it can be a lot of fun. For example, on the way to India I saw an entire Game of Thrones season. Other times it can be a nightmare, the screaming kids, cramped surroundings, and that is just the drive to the airport! The advantage of flying is speed. Transatlantic flights across the "pond" take about 6 hours flying time. Most passenger jets fly at around 300 to 500 mph. To do this they fly at high altitudes where the air is less dense (thinner would be the popular term but think about it, how can air be thinner?) The lower resistance allows the plane to fly faster. As the flight is more efficient at the higher altitudes (32,000 feet or so) the plane can travel further. As you might guess moving people around via the airplane is not very efficient on an energy basis alone.
Noise pollution comes in many forms, and varies depending on whose definition you go by. Almost everyone would agree that airplane takeoffs [1] (text version [2]) are a type of noise pollution.
Aircraft weight also influences the quantity of goods the plane can carry [3]. (text version [4])
When my grandfather was a small boy, an orange or a banana was considered a fantastic Christmas present (bad behavior meant he would get coal!) We don't have the weather to grow oranges in the U. K., so his Orange would have come from somewhere else in the British Commonwealth, probably the British Virgin Islands (named after Queen Victoria, not the chaste locals), or perhaps Spain. Either way, about the only way of getting the fruit to the UK was via boat (you can fly more expensive foods in such as Lobster, but fruit is heavy as it contains a lot of water!) The trip is long, and expensive which is why a fruit was considered a treat. Listen to this example of the value of salt [5].
Text Version: Value of Salt
Dr. Mathews: Did you ever hear the expression, worth his weight in salt? Salt used to be a very valuable commodity. In fact, if you were Portuguese, at times, that's how you would be paid. That would be your currency, salt. And in the slave trade, a slave could actually buy his own freedom if they had enough salt. A very valuable commodity. Think about it, it has to come from quite far away, even though the salt water is surrounding us, energy is expensive. And to boil off the water to leave salt, which is what they do in Saudi Arabia to create drinking water, all require a lot of energy. So instead you need to transport salt over large distances. The salt trade, think about Lawrence of Arabia, think about trekking in the desert, looking for an old sea where the water is evaporated, like salt lake. In the UK spitting salt is considered to be unlucky. In fact you need to take a little pinch and throw it over your left shoulder to break the bad luck. So transportation of this salt would have cost an immense amount of money. Wars are fought over it. The whole salt trade, the whole spice trade has affected the shape of nations. It has affected national trade. It has affected war. The passage of religion. It has had a very major impact on the country and world we now know.
Most boats will use diesel as a fuel. It has a number of advantages over gasoline, the most important of those being its higher energy content. The downside, however, is that Diesel has emission problems with particulate matter and NOx, and traditionally there have been few environmental controls to control emissions on the trucks and boats that use Diesel. This is now changing, along with the development of cleaner diesel fuels (lower sulphur and lower soot-forming precursors), so cleaner diesel vehicles are beginning to be produced. Diesel also has a much higher energy content in a gallon than gasoline (so less filling up!)
The Icelandic fishing fleet is converting to fuel cells for their fuel of choice. An environmentally driven choice of fuel. More on Fuel Cells in a bit.
Ahhhh......the romance of steam trains [9]...... (Text Version [10])
Steam trains have long evoked feelings of romance and adventure, and these opportunities were long powered by, of course, coal. Diesel later replaced coal, and now in many locations, trains run off of electric.
If you fly into Orlando, the monorail you see at left will take you from the terminal (a terrible name for the place you board an airplane) to the baggage claim. You can see small sized trains like this in other exotic locations such as Morgantown, West Virginia.
Most of us, are at some point, going to own a car. Odds are that in the US that will be the gasoline-powered vehicle (although diesel, hybrid, natural gas, and electric vehicles are now available and increasing in numbers). The basics of the vehicle are that liquid fuel has the stored chemical energy that is released during the combustion process to power the car. It is an old technology. The Model T Ford ("available in any color as long as it was black"- Henry Ford) in the US was available in 1908. Diesel engines predate gasoline engines. Interestingly the Model T Ford managed 12 mpg - some of the passenger vehicles (SUV's for example) on the road 100 years later, achieve only a marginal increase at 18 mpg. This is one of the major issues with energy use - efficiency, measured here by miles-per-gallon (mpg). The lower the mpg the more gasoline is needed to cover the ~14,000 miles the average American drives annually, and thus more air pollution. This used to be a major source of the balance of trade challenge but now the U.S. is producing much more domestic oil and natural gas so imports are declining.
So almost 8 out of every 10 people in the US own a vehicle. This is much higher ratio than the rest of the world where much lower ratios are common. Car ownership, however, is increasing dramatically as the industrialization of the developing world continues. Recall too, that the population of nearly all of these countries is increasing, so the potential for more people to be driving more miles in a greater number of vehicles will, of course, create more pollution - at least given the current technology. China is one such example: lots of new vehicles but lots of pollution! Current technology, as we will see later in this lesson and others, is evolving. Our air is getting cleaner in the US (EPA air quality [11]).
Think about riding a bike, or roller blades - when you crouch low to reduce your drag (making you more streamlined), you reduce your wind resistance, allowing you to coast further before having to pedal or push off. In modern cars, having your foot on the accelerator doesn't mean you're actually accelerating - you could just be maintaining your speed, and working against the energy losses of friction and drag, which requires more energy (gas) just to maintain the same speed. Having a streamlined car helps to increase the mpg this way, or, in the case of sports cars, achieve a faster velocity.
We have discussed kinetic energy. Recall Ke=1/2mv2, thus, the heavier the vehicle (greater mass) the more energy is required to move the vehicle. Saving weight in vehicles is one way to increase the mpg, by taking out the full sized spare and replacing it with the "doughnut" tire saves weight and increases the mpg. Changing body materials to lighter plastics, metals, or fiberglass is another method. Making engines lighter by replacing the steel motor with ceramic components are also being considered. Please watch the following (:33) video. Vehicle mass is even more important with electric vehicles as they currently have driving ranges that are lower than desirable. The Tesla for example does not carry a spare tire (it comes with a tire change service).
[Video opens with Dr. Mathews standing in front of a corvette stingray.] Dr. Mathews: You might recall that force equals mass times acceleration. So if you have a certain amount of force made by a certain engine, you want to have a faster acceleration. One thing you could do is reduce the mass. This is what happened in the Corvette. It is actually made out of fiberglass so it could accelerate faster. If you lower the mass of the vehicle it will also increase the miles per gallon. Not the case here though, we are after speed. [Dr. Mathews gets in the Corvette.] [Video ends]
Heat losses from the engine, air resistance, and rolling resistance between the tires and the road all contribute to our vehicles achieving only about a 28% efficiency. This means that only 28% of the total chemical energy supplied in the form of gasoline is actually being utilized, leaving 72% of gasoline's potential energy content to go essentially unused. This is one of many areas in the automobile industry where future improvements are expected.
With climate change concerns, there will be significant pressure for more stringent standards for automobiles (President Obama's statements [12]). We have made some significant improvements in this area after decades of inactivity. However, the Trump administration has slowed the rate of this and other transitions — are potentially rolling back the efficiency standards (standards are under review).
Appropriate tire pressures are usually written on a sticker on the inside of the passenger compartment. Remember that the rolling losses heat the tire up and the gas inside, so don't measure tire pressure on a hot day after a long drive. Also check tire pressures again when the seasons change, for example in the winter you may need to add more air to pressurize to the appropriate level.
How you drive also influences your mpg. Check out the fuel economy website [13] and this MotoWeek movie clip [13].
You can always watch Mythbusters and argue about windows up/down/ac influences or tailgate up/down for you truck owners.
In 2017 there were the first indications that gasoline vehicles may be replaced by hybrid, electric, or renewable fuels. France is proposing a ban on diesel and petrol sales by 2040, and Volvo is dropping gasoline-only engines (will still allow hybrids) in 2019. So, pressure on gasoline is mounting but it has many advantages: dense energy (high calorific value), availability, and can be efficient with the correct vehicle. I expect we will still be using it the decades to come but expect climate change concerns to increase the pressure.
When men get together to discuss their prized vehicles, you can be practically guaranteed that the conversation will include, or completely be dominated by, talk about horsepower [14]. Before the motor vehicle, the horse was the vehicle of choice, the power source for moving supplies and goods, and a primary source of power behind the United State's early agricultural and industrial prominence.
The horse essentially did work for its owner. The more powerful the horse the more work it could do. A standard horsepower was defined as the mass that a horse could move in a specified time period. Suffice to say that since horsepower represents a rate of doing work, more horses means more work could be done, or the same work could be done more quickly. Standard lawn mower or snow blower engines now weigh in around 5 horsepower, riding mowers might be closer to 15, a typical car is in the neighborhood of 100-150 HP, and for you race car types, there are typically several hundred (figurative) horses under those hoods.
Please watch the following (:15) video:
[Video opens with a close-up of a spark plug.] [The spark plug it fed electricity and a blue spark is seen.] [We hear the noise of a loud shock.] [This is repeated several times.] [Video ends]
The combustion of the gasoline occurs because of the appropriate mixing of a vapor of the gasoline with air and a spark provided by the spark plug (see left). The battery in the car provides the electricity to create the spark; it is also used to run the radio, lights, and to start the starter motor to start the gasoline motor. The motor needs to turn over so the piston rises in the cylinder, compressing the air and gasoline mixture, which is ignited by the spark. The timing of these events is very important, hence the need for a timing belt. The resulting combustion produces hot gases, which drives the piston down providing the energy to run your car. The starter motor has started the engine and now is no longer needed, until next time.
Thus, the basic four strokes (for a 4 stroke engine) are:
Engine Stroke | Description |
---|---|
Intake Stroke | Air and gasoline (sprayed in a fine mist to permit better mixing of the air and gasoline) enter the cylinder. |
Compressions | The piston head rises, compressing the air/fuel. |
Combustion | The spark ignites the combustion/detonation, which rapidly pushes the piston down (via a crankshaft connection; turns the vehicle's wheels). |
Exhaust | The products of combustion are vented out of the cylinder on the way to the catalytic converter and the tailpipe. |
Once again, I suggest that the curious amongst you take a trip to the "How Stuff Works" website to see a more detailed presentation of How Engines Work [15].
The lead acid battery that sits under the hood in nearly all our cars is heavy, and not inexpensive (especially if you leave your lights on regularly). Considering the size and weight of this battery, and its purpose to just start your car, you can imagine the size, weight, and expense of the one that would be needed to actually power your car? This is the major reason that electric cars running on stored electrical power did not make it off the golf course and onto the roads
Interestingly, living in England, the milk would be delivered to your doorstep, every day except Sunday, by a fleet of electric "milk floats" which started in the 1970's. As we will discuss later, many of the new approaches in vehicles and fuels will occur in those organizations with a large fleet of vehicles.
When the Model T Ford was filled up with gas, variations in the production and quality of the gasoline sometimes caused "knocking" in the engine. This violent shaking of the engine caused excessive wear on the engine and limited its power. The cause was the self-ignition of the gasoline and air mixture on the compression stroke (2nd stroke - remember?). In a diesel engine, this is actually desirable, as they don't have spark plugs, but in gasoline engines, it's not a good thing. The knocking is related to the shape, size, and type of molecules found in the gasoline, which is pretty complex stuff - when you account for the added cleaning compounds and environmental packages, your gasoline can include over 100 separate compounds! Please watch the following (1:15) video:
[Video opens with Dr. Mathews standing in front of a large machine.] Dr. Mathews: I am here at the energy institute research facility. To my left is an octane rating engine. When you go to buy gasoline from the garage you have a choice of several octanes. Most of you will be buying 87. Iso octane, the octane number, is based on a mixture of iso octane and heptane. When you are buying an 87 octane gasoline, what it means is it will have the same knocking behavior as 87 percent iso octane and 13 percent heptane. The way that is tested is in a device exactly the same as this. What we will do is take an 87 percent mixture of iso octane, a 13 percent of heptane, and blend them together, and see how they behave in certain conditions in this particular engine. Then we will compare it with a complex blended mixture of gasoline. Remember gasoline is going to contain at least a hundred different compounds. So you are not buying octane, your not buying iso octane, and you are not buying heptane. They might be there in small quantities but they are not a majority of the components. What we are looking at is knocking behavior. If we get that undesirable, spontaneous combustion when we compress the cylinders and the gasses and the fuel in the air, and it self ignites, that is called knocking. That is completely undesirable in a gasoline engine but it is exactly how a diesel engine works. [Video ends]
This knocking can be eliminated by changing the composition (or size, shape, and type) of the compounds. One of the early octane booster compounds added to gasoline was tetraethyl lead. This has been banned now to reduce lead vapors that end up depositing lead in the bloodstream, which resulted in reduced mental capacity, particularly in children.
A bit more about lead. [16]
Now we are required to make many changes to our gasoline recipe to meet environmental challenges (more on this in the next lecture).
We jump in our cars and we drive, without thought of the pollution that is being released from the tailpipe (and other locations). It is the same when we turn on a light. These pages will give you an overview of the issues related to pollution from motor vehicles.
Why is this an issue? Pollution if dilute enough is not going to have an impact. Unfortunately, anthropogenic activities are concentrated in the metropolitan areas and so the primary and secondary pollutants can become concentrated enough to cause severe health problems and even fatalities.
Unit 3 essentially covers environmental impact and mitigation strategies for pollution issues. There are 2 answers that are nearly always correct: conservation and efficiency (there are others that are correct too).
If we drive less we use less gasoline (I will never use the term gas to mean gasoline, petrol perhaps or if I feel a bit French 'Benzene", but that is a rare event ...feeling French.), we produce less emissions, and reduce our environmental impact. Unfortunately, the average number of miles we Americans drive (yes I am a citizen now) is increasing. We drive about 14,000 miles a year. If we can reduce that distance, we would be better off (reduce emissions). We tend to drive more after 9/11/01 too, and fly less. So how to conserve:
If we drive the same distance but do so with more efficient driving tactics, or with more efficient equipment, or we have more people in the car then the fuel used will be less and the pollution less. Miles per gallon (mpg) is a common measure of the efficiency of a motor vehicle. It is useful in comparing different models. If the car was 100% efficient (which it can't be - Third law of thermodynamics) we could achieve about 110 miles per gallon in a normal size (and normal mass) vehicle. Recall that diesel has more energy in a gallon than gasoline and that modern diesel cars can go 50 miles on a gallon! This means less greenhouse gas emissions and aids in reducing the growing dependence on foreign oil imports. See why fuel economy is important. [17]
Do you own a car? If not you are one of the few! About 8 in 10 Americans own a car. It is another example how energy use is entrenched in the American way of life. China might have 50 cars per 1,000 people. Much of the issue still remains that in many countries the automobile will be concentrated in the cities and there are very few in the countryside.
The American dream looks like this to much of the world: Even the lower wage-earners in our culture expects a big screen TV, a computer, their own home, and of course, at least one of the classic American symbols: a motor vehicle the size of a small yacht.
To prevent the masses from purchasing automobiles that are very energy inefficient there is a gas guzzler law. So if you purchase a vehicle with mpg below a certain value there is a special tax of $1,000 (which increases as the mpg decreases below the standard of 22.4 mpg) that you pay when you purchase the new vehicle. That is very much the American way: pollution is okay if you can afford it! Or if you were to look at the other side of the issue: the money is used to give tax breaks to those purchasing energy efficient vehicles then it does not seem so bad. An interesting issue? Finally, we are now in the process of raising the vehicle efficiency standards (CAFE standards) to tackle energy security and climate change.
In other nations, you are more likely to find higher occupancy in the vehicles. In Greece, for example, the occupancy is close to 5. Here is the US it is a tad over 1! By carpooling, the increase mass for the trip is small even as the cars are already very heavy. The new (2002) Corolla is 2,500 lbs so my 230 lb addition is about 10% increase in the mass. Lowering the weight of vehicles has already been discussed but weight savings (here) can significantly increase the mpg. In Washington DC and other locations, there are high occupancy vehicle lanes (LA has had then for almost 20 years-I know because I watched Chips). In DC a high occupancy vehicle contains 2 people! The situation is worse in Europe where the cities were built and designed (if there was a design) well before the automobile. For example in my hometown of Chester, the roads go through or over the Roman Wall that surrounds the city.
The European cars tend to be smaller for 3 reasons:
Take a look at the smart car, popular in Europe, there are even a few on campus and about town. How would you like to drive one of these babies [19](check out the movie!)?
It is similar with the Japanese/Asian cars that tend to be much smaller because they will be going to highly congested major cities with limited parking.
Have a look at these two pages from the Office of Energy Efficiency and Renewable Energy.
We have already discussed some of the methods for reducing the emissions from automobiles, and will revisit this topic in more detail in Unit 3 where we discuss pollution and pollution control. Another approach to reducing emissions is the changing the fuel, with the intent of yielding better performance, and reduced emissions.
What happened to all the lead: Text Version (click to reveal)
Dr. Mathews: I can recall in the late seventies, friends of my parents coming to visit us. And they are an American couple and they brought their own car from America. And they were doing the grand European tour. Which is fine because the rest of Europe drives on the wrong side of the road just like you Americans. And there was plenty of unleaded gasoline in Europe as well. But in England, and the whole UK, the issue was a navigation one, you had to travel about 300 miles before you would find another unleaded gasoline station. And so rather than plan a normal trip where you would plan on seeing all the major cities like London, Chester, York, Whales, and the Lake District, they had to do the same kind of trip but planning to hit all the unleaded gasoline stations on the way to fill up. This is in the late 1970s and unleaded gasoline hadn't really started yet in the UK and so it was a major problem. I see very similar issues now if I was to go buy a natural gas power vehicle or even an electric vehicle. I would have to plan my trips very carefully so I could stop at a place where I could recharge or fill up. It is an interesting comparison.
Lead (chemical symbol Pb, for Plumbum) was added to gasoline in the 1920's as an octane booster, and in some cases, to provide lubrication for the exhaust values. There are 2 problems with this approach (the addition of tetraethyl lead) - the first is that the gasoline fumes contained lead, which can enter the bloodstream. Indeed, studies have found that in city children, higher concentrations of Pb were discovered, where low levels of lead in the blood of small children can reduce brain development. (Perhaps this explains my reduced mental capacity? - Na I was a country boy, so it had to have been the cow that kicked me in the head!) The second issue is that while lead was in the exhaust gases, any attempt to use catalytic converters would be thwarted. The lead covers the catalyst, rendering it useless.
But not all the news is bad: the fix to this problem is relatively easy. Simply stop adding tetraethyl lead to gasoline, which is what the US did beginning in the 1970's, Some classic cars, however, did not fair well on unleaded gas, and so they could continue to use leaded gasoline. The former USSR, for instance, and other areas with less modern technology, continue to use leaded gas.
87, 91 or 93?
In America these are the common choices when we go to fill up. In Europe they often sell higher octane value gasoline.
These refer to the octane number of the fuel, and unless you own a high-performance car, 87 is just fine! Just what is Octane [23]
What is Octane Text Version (click to reveal)
[Video opens with Dr. Mathews standing in front of a large machine.] Dr. Mathews: I am here at the energy institute research facility. To my left is an octane rating engine. When you go to buy gasoline from the garage you have a choice of several octanes. Most of you will be buying 87. Iso octane, the octane number, is based on a mixture of iso octane and heptane. When you are buying an 87 octane gasoline, what it means is it will have the same knocking behavior as 87 percent iso octane and 13 percent heptane. The way that is tested is in a device exactly the same as this. What we will do is take an 87 percent mixture of iso octane, a 13 percent of heptane and blend them together, and see how they behave in certain conditions in this particular engine. Then we will compare it with a complex blended mixture of gasoline. Remember gasoline is going to contain hundreds of different compounds. So you are not buying octane, you're not buying iso octane, and you are not buying heptane. They might be there in small quantities but they are not a majority of the components. What we are looking at is knocking behavior. If we get that undesirable, spontaneous combustion when we compress the cylinders and the gasses and the fuel in the air, and it self-ignites, that is called knocking. That is completely undesirable in a gasoline engine but it is exactly how a diesel engine works. [Video ends]
We assign iso-octane an octane value of 100 and heptane an octane value of 0. When we mix the 2 liquid fuels, we can produce a fuel with knocking properties between 0 and 100. When you purchase an 87-octane gasoline it has the same knocking properties as a mixture of 87% octane and 13% heptane (octane number of zero). It does not imply that the composition of the gasoline is 87% "octane". Gasoline might well contain over 100 different compounds. The (R+M/2) you see on the gasoline pump indicates that the knocking is averaged between two engine conditions (one more stressful on the engine than the other).
The octane number relates to the knocking (premature ignition) of the fuel. When we compress the fuel the temperature of the fuel increases (opposite of our refrigerator) and it can self-ignite before the spark-plug fires. This is a desirable effect in diesel engines, as they do not have spark plugs (which is why radio astronomers drive diesel cars - no spark plugs to give off radio signals). This self-ignition property is known as knocking. It is related to the chemistry (don't panic) of the fuel.
The combustion of the gasoline occurs because of the appropriate mixing of a vapor of the gasoline with air and a spark provided by the spark plug (see left). The battery in the car provides the electricity to create the spark; it is also used to run the radio, lights, and to start the starter motor to start the gasoline motor. The motor needs to turn over so the piston rises in the cylinder, compressing the air and gasoline mixture, which is ignited by the spark. Timing of these events is very important, hence the need for a timing belt. The resulting combustion produces hot gases, which drives the piston down providing the energy to run your car. The starter motor has started the engine and now is no longer needed, until next time.
At left is a static 3-d model of an iso-octane molecule.
The octane that we know from filling our tanks is actually 2, 2, 4 trimethyl pentane (can you see five carbons in a line-that is the pentane part, tri means three (methyls) and methyl is one carbon with 3 hydrogen's, you should be able to find three of them, can you? The molecular formula is C8H18. Can you determine the molecular weight? (Hint: each carbon has 12 amu and H 1 amu (atomic mass units). This is an example of an alkane.
When we stopped adding tetraethyl lead we needed to have a replacement octane booster and MTBE was what we chose. Chemically it is methyl tertiary butyl ether.
Can you see the lone oxygen atom? Also notice the highly branched shape that is responsible for higher octane numbers than straight chain compounds. It is the property of the oxygen atom that has resulted in additional uses for MTBE in gasoline to reduce pollution. We'll cover this more in Unit 3, where the discussion shifts to pollution and environmental consequences, this is the condensed version.
This is a product of incomplete combustion (not enough oxygen and mixing). It is a lethal, odorless, and colorless gas. The hemoglobin in your blood usually carries oxygen to your cells and removes carbon dioxide. But it would rather "hang out" with carbon monoxide. So if there is enough CO in the air it bonds with hemoglobin and the oxygen does not get delivered to your cells and you die. This is why running engines in enclosed spaces, like garages, is a bad, or fatal, idea.
The oxygen in the MTBE permits better mixing of oxygen and fuel and so there is less CO produced. Normally, your catalytic converter can deal with CO to reduce the concentration (it does not remove all the CO from the exhaust gases) but it only does so when hot. In the winter the catalytic converter takes a while to warm up and so we add MTBE during the winter months. CO in the atmosphere at low levels causes headaches and reduced mental capacity. "Health threats are most serious for those who suffer from cardiovascular disease, particularly those with angina or peripheral vascular disease." Source: EPA
Smog is also a health issue in many major cities because that is where the cars are located (and electricity generation, etc). It is a summer issue for the US as smog formation (Smog is a secondary pollutant-meaning we do not release smog but it is formed from primary pollutants or pollutants that we do release) requires: warm temperatures, sunlight, hydrocarbons (such as unburned fuel), and NOx. The presence of MTBE in gasoline lowers the temperature of combustion, which lowers the formation of NOx. MTBE in the fuel provides better oxygen fuel mixing and so fewer hydrocarbon emissions. So the combination of less NOx, and less hydrocarbons = less ozone which is the main component of smog. Much more on "smog" issues in Lesson 09.
So MTBE is great, right? Not exactly - there is one problem.
The oxygen also makes MTBE soluble in water. It is a known carcinogenic at high levels but at very low levels (parts per billion) it imparts a foul taste and odor to drinking water.
The MTBE had been leaking into the groundwater for years in California.
Those underground tanks, which are used to hold gasoline, leak!
We are in the process of banning its use. This makes farmers very happy, because they have the replacement for the oxygenated fuel additives - ethanol (from corn).
So far, we have looked at efficiencies, conservation, changing the fuel, and now we have come to the treatment(s) of the products of combustion before they leave the tailpipe. Therefore, in a way we have covered abatement: before you get in the car, reduction strategies while driving, and now hot-gas cleanup while the engine is running. Recall that we have already discussed the issue with lead, now we need to discuss the catalytic converter.
We are required by law to have catalytic converters on our gasoline cars. We do not have them (yet) on diesel engines. They do "rob" the vehicle of a few horses (horsepower) and so were not particularly popular when first introduced but there are fines and penalties for those that disable their catalytic converter, so don't do it! The job of the catalytic converter is to lower the emissions of three gases: CO, NOx, and hydrocarbons (uncombusted fuel-coming out of the tailpipe, fuel escapes from other locations in the car too).
Step 1: CO → CO2 (Oxidation)
Step 2: NOx → N2 (Reduction)
Step 3: Hydrocarbons → CO2 and H2O (Oxidation)
Therefore, we have a system that can oxidize and reduce at the same time! It is a tall order, but we can do it because we use three catalysts and we operate the vehicle so the air to fuel ratio produces the correct oxygen concentrations in the flue gas. That is why we have an oxygen sensor in the car (anyone had it replaced?) We are required to have monitoring equipment so that we know the pollution control devices are working. In the more polluted parts of the country, the standard vehicle inspection also requires an emission inspection, where they monitor the emissions from the tailpipe.
The three catalysts that are used are Rhodium (Rh), Platinum (Pt), and Palladium (Pd). These are very expensive metals and so we use as little catalyst as possible. As only the surface of the catalyst is used to oxidize (or reduce) the gases, we spread it very thinly (just like marmite [24]) (text version [25]).
We are trying to achieve a high active surface area so the inside of the catalytic converter has a ceramic honeycomb-type series of channels. The actual surface is about a couple of American football fields. The catalysts are well dispersed throughout the channels.
In this diesel engine, you can see how the fuel injection process produces a fine spray that enhances the mixing of the liquid (now atomized into small droplets) and the oxygen from the air. Nitrogen from the air is also present and an unwanted side reaction is the formation of NOx. Some of the nitrogen will also be present in the fuel as well.
[Video opens with a close-up view of a diesel engine. The injector is spraying fuel.] Dr. Mathews: This is what the diesel injection process looks like. This is the top of the cylinder head. You can see the various sprays coming in the very fine atomization to enable the mixing with the air. And then if there was a cylinder in place, it would come up, compress the gases, and self-ignite the system. What you are seeing here is a number of injections of the mist. [Video ends]
In the energy diagrams above you can see that when compounds or elements react, the process is either endothermic (requires energy) or exothermic (produces energy). This is a result of the conservation of energy (First Law of thermodynamics) that we encountered in earlier lessons (remember? [26]). A common assumption is that the larger the energy gap, the quicker the reaction - but this is not the case. This delves into the realm of kinetics: the rates at which chemical reaction occurs. A reaction might be thermodynamically favorable, but the kinetics might be very slow (or very rapid). So often, the kinetics will control whether we observe a reaction or not. We have seen the equilibrium symbol already (insert equilibrium symbol) what this actually means is that the forward reaction is equal to the reverse reaction. So in the case of CO2 in the atmosphere being in equilibrium with the CO2 in the oceans, it does not mean there is no exchange taking place, that occurs all the time, it is just that as many molecules enter the atmosphere from the ocean as enter the ocean from the atmosphere.
Often there is a special excited state of the molecule or compound that needs to form before the reactions can occur. This requires that the molecule reaches an activation energy before it can complete the reaction. A catalyst works by offering an alternative route to achieving the excited state. So at the same temperature more of the gas molecules can achieve the excited energy state and so the reaction proceeds at a quicker pace. We could achieve the same results by increasing the temperature and the pressure but adding a catalyst is the lower-cost option. So, a catalyst is any material that changes the activation energy of a reaction. It can be used to slow reactions down, but mostly we use catalysts to speed reactions up.
Why does increasing the temperature increase the rate?
We use catalysts to help chemical reactions and transformations in the chemical industry and the petrochemical industry all the time. We also have very large devices that are similar to catalytic converters to power stations to reduce NOx emissions. So catalysts are very useful in controlling emissions. More in Unit III.
Examples of some of our initial "live snippets" efforts can be viewed by clicking below the following images.
In coal, the percentage of S is between 0 and a few percent (by weight). Thus, when we burn coal, there are lbs of Sulphur dioxide (SO2) released for every million Btu's of thermal energy. We will discuss crude oil in the next lesson and will discover that like coal, the quality (and hence the value), of the oil is influenced by the S content. But the S in gasoline, at 300 PPM, is very low already. We have to remove the S from the compounds in the oil ($$$) because S is a catalyst poison. Much like the CO and hemoglobin example, S will bond with the catalyst and that portion of the catalyst surface will no longer function. We are in the process of reducing S content even lower (as California has already done) so that new catalyst technologies can be employed.
S emissions also contribute to regional haze, and to acid deposition. More in Unit III.
CATA buses are a familiar sight in and around the University Park campus and State College area. The bulk of these buses are fueled by a Pennsylvania energy source that is not crude oil. They run on natural gas (methane: probably from shale gas). Pennsylvania has both crude oil and natural gas (and of course coal). One of the natural gas fields is North of State College 50 miles or so. It is a new technology for the automotive industry (although in WWII, buses and automobiles in the UK were converted to run on natural gas when the availability of petrol and diesel was limited due to rationing). But why read about these buses, when you can see and hear me playing with them instead. Please watch the following (3:14) video:
[Video opens with Dr. Mathews behind the wheel of a Cata Bus.] Dr. Mathews: We are all pretty familiar with these Cata Busses. And you probably mostly know too that they run on natural gas. And so why many of you are interested in seeing what the front looks like, we are going to go upstairs and show you what the top looks like. Before we do that, I want you to know that this is about a three-hundred thousand dollar piece of equipment. It is a more efficient means of transportation but only if you have more than one person in it, and with me driving that is not likely to happen. Ahhhhhh! [Camera follows Dr. Mathews to the top of the Cata Bus.] Dr. Mathews: The things I do for education. Oh, bloody hell. Well, if this were a diesel engine there would be a nice tank hidden away in the bottom of the bus. With this being natural gas, what they have done is added high-pressure methane tanks to the roof; that is why the roof is slightly elevated. This is where they store enough natural gas to run for about 400 miles. Natural gas comes from about 30, 40 miles north of here in one of our own Pennsylvania natural gas fields. It is more environmentally safe, running on emissions from these vehicles is not pollution free, but it is certainly better than diesel. It is a wonderful way of using new technology to have transportation that is even cleaner than what we currently use. [Camera view changes.] Dr. Mathews: Where did the bloody camera go? Oh, there you are. What we have here are the tanks holding the natural gas used to fuel the bus. These are composite material. They are very strong. They are designed to take impacts to prevent natural gas leak. Remember it can be flammable, or an explosive gas in the right mixture with the air. To make sure we don't have any leaks, there is actually a sensor in the cab... [The sensor flashes on the screen.] Dr. Mathews: ...and if there is one, it will be detected and the bus will be evacuated. There is a lot of fear when we go to a new fuel. We are used to traveling around with highly explosive and flammable gasoline, and somewhat less so diesel. But there is certainly a fear when you go to the gases. But these are compressed so they can hold much more gas and these cylinders here are enough to give a range of 400 or so miles. This is enough so the bus can drive around town and only get filled up but once at night. A splendid situation. [Camera view shows the back of the bus back at ground level.] Dr. Mathews: We have been inside, on top, in front, now we are going to be at the back. Let's take a look to see what is under the hood of this puppy. It is a relatively standard engine. You don't need to make many changes to make this run on natural gas, although this one was built from scratch. Running natural gas is a very nice fuel for the engine. It actually creates less wear for the engine. Do you know how you change your oil in your regular car? You put in this nice golden syrupy colored oil, and when it comes out it is jet black. That is particulates. This is not going to form that so the lifetime of this engine should be longer than the lifetime of a diesel engine. [Video ends with Dr. Mathews walking away from the bus.]
These buses are cleaner than the old diesel fleet that the buses replaced. They are not pollution free. The methane can be cleaned to remove S and other contaminants but the combustion process will still produce NOx and perhaps some CH4 emissions (methane is a greenhouse gas). The fuel switching approach is yet another method of reducing emissions (perhaps–it depends on the emission). But there are fuel choices other than diesel and gasoline. Methane is another example of an alternative fuel for vehicles.
Other alternative fuels, which we'll encounter in one form or another, might include hydrogen, methanol, electricity, biodiesel, and ethanol.
By now you should have a good grasp that traditional transportation causes pollution. There is also a supply issue with the source of the gasoline and diesel. We now produce nearly all of our own crude oil. But that is new. We had traditionally been reliant on foreign imports. This is why this unit contains the security lecture (Gulf War?) Now the main driving force is pollution control.
We can use alternative fuels to achieve reduced (or elimination) pollution and enhanced national security and balance of trade. They can be encouraged by using mandates such as renewable portfolio standards (x% of the diesel sold will be biodiesel for example) or by using feed-in tariffs (the fist X5 of biodiesel will get this high price). There are a variety of fuels to choose from:
Ethanol is a chemical compound we have already discussed as an oxygenate to reduce pollution from gasoline. But it can also be a fuel in its own right. You know ethanol as alcohol. The same compound is in beer and wine and is responsible for the intoxication effects.
The CH3CH2OH formula is important. If you drink enough methanol CH3OH, your retina will detach and you go blind (all because a CH2 is missing). The OH (that is the alcohol unit) also enables ethanol to be a liquid at the same conditions that ethane (CH3-CH3) is a gas. The liquid fuels are easier to handle and store than the gas version. Which is easier to carry: a gasoline container or a pressurized propane tank? You also need to know there is far more energy in the gasoline–if comparing similar volumes. This is one of the major problems with gaseous fuels - storage has to be in pressurized containers, which increases the mass. Why is mass important? And it increases the cost (thick steel is more expensive.)
Ethanol is a biomass fuel. This means that we can grow the energy without being required to import crude oil. There are many states where we can grow corn, and this would help employment in agriculture, particularly in the "corn belt" of the mid-West. It is also used for animal feed and its use as a fuel source means pork prices goes up. This is a problem for countries with large poor populations such as South America (there have been corn tortilla riots!) The greenhouse gas savings are also in question.
There are other ways of producing ethanol, it need not just be from corn. In warmer climates, sugarcane would be the appropriate choice. In Brazil, they grow sugarcane and use it to produce ethanol. The ethanol is used in an ethanol and gasoline mixture (97 % ethanol) to fuel their vehicles.
Why do Brazilians add gasoline to the mixture? [29]
There is only one good reason to add gasoline to perfectly good ethanol and that is to render it undrinkable. Pure ethanol is essentially drinkable. It's actually not very good for you. I've certainly handled restricted compounds in my career as a chemist and I have to follow the same rules and regulations, pretty much, for 96% ethanol as I did for 99.99% cocaine. That's in pure levels of course. But it is one of these things that you do not want the population literally drunk driving while their cars have been drinking as well. You can just imagine a situation where with one very long straw, drunk driving comes to a whole new level of incompetence. So essentially the 3% gasoline is simply to stop it from being one for you, one for me, one for you, one for me at the pump.
[Video opens with Dr. Mathews standing in front of a cornfield.] Dr. Mathews: The nice thing about biomass, of course, is that it recycles carbon dioxide back into the atmosphere. This is corn. Although most of it is used for animal feed, they are associated with a great deal with food. The other thing you could do with it is either take this corn and directly burn it or you could distill it into alcohol and use that alcohol as a transportation fuel. [Video ends.]
The use of a liquid fuel has major advantages because the infrastructure is in place already. We may have to change the hoses on the pumps or else some of the liquid fuels will dissolve them, but these issues are minor.
We have seen natural gas in CATA buses and in some of the OPP (Office of Physical Plant) trucks that park on the pavement (sidewalk) around campus. The average automobile can be converted to run on compressed natural gas (CNG) for about $2,000 so it is not cheap. There is less wear on the engine and less maintenance is needed. Most of our methane is domestic and there is the potential for making more via synthesis gas chemistry. Methane is a greenhouse gas, (more in Lesson 11 on that issue) and the cost of methane can vary with seasonal demand (as does gasoline). If methane was cheaper (for the same mileage) I think more of us would be using it as a fuel. All the alternatives are more expensive than gasoline. This is now popular with fleet vehicles.
Missing from this listing are electric vehicles and biodiesel. Propane is also a potential fuel that is being used in some fleet vehicles. More on this later.
As with previous coverage maps, this map is a summary of the lesson (mouseover the boxes). When finished take the L05 quiz. This is interactive so move your mouse over the topics.
Accessible Version (word document) [30]
After looking at this map, please take the L05 quiz.
Links
[1] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/747_Jet_Takeoff.aif
[2] https://courseware.e-education.psu.edu/courses/egee101/transcript/lesson_4_air_plane_take_off.html
[3] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/L04_aircraft_brakes.mp3
[4] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson05/Text_Airplane%20cargo.html
[5] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/L04_salt.mp3
[6] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/fruit_jpm.gif
[7] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/bear_beer_jpm.gif
[8] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/nuc_sub_NSF.gif
[9] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/Choo_Choo_Train.aif
[10] https://courseware.e-education.psu.edu/courses/egee101/transcript/lesson_3_steam_train.html
[11] https://www.epa.gov/air-trends#comparison
[12] https://obamawhitehouse.archives.gov/the-press-office/2012/08/28/obama-administration-finalizes-historic-545-mpg-fuel-efficiency-standard
[13] http://www.fueleconomy.gov/feg/drive.shtml
[14] http://www.howstuffworks.com/horsepower1.htm
[15] http://www.howstuffworks.com/engine.htm
[16] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/L04_lead.mp3
[17] http://www.fueleconomy.gov/feg/why.shtml
[18] http://www.fhwa.dot.gov/policyinformation/statistics/2009/in4.cfm
[19] http://www.smartusa.com/
[20] https://www.energy.gov/eere/electricvehicles/electric-vehicle-basics
[21] https://www.energy.gov/eere/electricvehicles/electric-vehicle-benefits
[22] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/search4unleaded.mp3
[23] http://youtu.be/zz9naP83ndU
[24] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/L04_marmite.mp3
[25] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson05/Just%20Like%20Marmite_Text.html
[26] https://www.e-education.psu.edu/egee101/node/762
[27] https://www.e-education.psu.edu/egee101/node/760
[28] https://www.e-education.psu.edu/egee101/node/761
[29] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson04/L04_ethanol_Brazil.mp3
[30] https://www.e-education.psu.edu/egee101/sites/www.e-education.psu.edu.egee101/files/Lesson05/Lesson%205%20Coverage%20Map.docx