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Hybrid Future: Electric vs. Electrified Powertrains

– Welcome everyone to Wednesday Nite @ the Lab. I’m Tom Zinnen. I work at the UW-Madison Biotechnology Center. I also work for UW Extension and Cooperative Extension. And on behalf of those folks and our other co-organizers, PBS Wisconsin, the Wisconsin Alumni Association, and the UW-Madison Science Alliance, thanks again for coming to Wednesday Nite @ the Lab. We do this every Wednesday night, by Zoom, 50 times a year. Tonight, it’s my pleasure to introduce to you Andrea Strzelec. She was born in Milwaukee and went to high school in Waukesha, then she came to UW-Madison to study biochemistry. She stayed for a master’s and PhD in engineering. And now she’s the director of the online Masters in Engineering program in Engine Systems.

Tonight, she’s gonna talk with us about internal combustion engines, electric motors, and hybrids of those two, and ways we can use those to help drive our cars. Please join me in welcoming Andrea Strzelec to Wednesday Nite @ the Lab.

– Thanks, Tom. I really appreciate the opportunity to be here tonight, and to talk about the difference between electric and electrified powertrains, especially when it comes to things like their impact on energy and the environment. I wanna start with an outline for this talk. I wanna start by giving you my objective: why am I here? And that’s to explain the need and how to properly compare apples to apples when we’re talking about energy systems and vehicle powertrains. I’ll start with an introduction to who I am and why am I here. And I want to tell you upfront that I may be an engine doctor, but I believe in climate change. I believe CO2 is a problem. And I’ve, in fact, dedicated my career to working on cleaning up engines to help our environment.

I’ll give you some background into how we use energy in transportation and a few engine basics, and then talk about how to evaluate an energy system. And that means a thermodynamic system. Thermodynamics is the study of energy, its transfers, and transformations. So we have to apply thermodynamic principles when we consider systems of energy. And then I’ll provide some information. I want to challenge some incomplete claims that you’ve probably seen in the news media or on the internet when it comes to talking about internal combustion engines or battery systems. I want to show you the options and the progress that we’ve made in both batteries and the engine field. And I want to leave you with the charge about what I think we should do, and that’s continuous improvement in all areas. I think we should make sure that we aren’t choosing winners based on political pressures. I think we should be choosing winners based on the energy science.

So I have to start with a couple acknowledgements. I have used material from Dr. Kelly Senecal, who is from Convergent Science here in Madison. He is my inspiration for this talk and also a Badger. He started the defense, if you will, of the internal combustion engine with his TEDx Madison talk, and started the Hug Your Engine movement. Professor David Foster, my PhD advisor at the Wisconsin Engine Research Center, and also a Badger. I used material also from Professor Dennis Assanis, who spent his career running the Auto Lab at the University of Michigan before becoming the president of the University of Delaware, and Dr. Graham Conway from Southwest Research, and Dr. Todd Fansler from the Engine Research Center here. I’m really honored to have this opportunity to add my voice to theirs, and thank you to Wednesday Nite @ the Lab and PBS Wisconsin for this opportunity.

So what is my objective in talking to you today? Well, in this talk, I really wanna trash some false ideas. I wanna tell you that electric vehicles are not zero emissions. In fact, nothing is. Zero is not a real thing when it comes to emissions in terms of any energy situation. Even renewables like solar or wind have emissions associated with them, and I’ll tell you where. I also wanna tell you that engine technology has not been stagnant. This is not Rudy’s diesel from 1892. We have been working on engines and continuously improving them since their inception. And I want to try to convince you that a green future does not rely on a single technology. To quote Kelly, the future is eclectic.

I also want to show you that dirty is actually in the details. We’re gonna talk about thermodynamics and how to draw proper thermodynamic boundaries. We’ll see that engines are continuously getting cleaner, and we’ll talk about some novel combustion strategies and aftertreatment catalysts as ways to make engines even cleaner yet. I think this cartoon shows a really great example of the point I’m trying to make here. The guy on the top is driving a diesel vehicle, and his thought bubble says, “I feel so dirty,” because he has emissions right there in the vehicle at the tailpipe. Whereas the guy on the bottom shows that he feels so clean, but you see that his electric vehicle is actually using energy derived from the power plant and that the emissions exist, but are just not at the tailpipe. So this is also true for fuel cell vehicles. Fuel cells burn hydrogen and produce only water as their product, but hydrogen has to be produced somewhere. And it takes a lot of electricity to produce that hydrogen. So fuel cell vehicles and electric vehicles may not have emissions at the tailpipe, but they absolutely have emissions associated with them.

So why am I in particular talking about this? Well, I am quite literally an engine hugger. I am the program director of the Master of Engineering and Engine Systems program here at Wisconsin. And my education is in this area. I like to tell people that I’m a triple threat Badger. I graduated from the Engine Research Center at University of Wisconsin, and I did my PhD work in collaboration between the ERC and Oak Ridge National Lab, sponsored by DOE. So thanks for the PhD, DOE. And then my work experience has continued in this area. I worked at two national labs, Oak Ridge and Pacific Northwest before becoming a professor of mechanical engineering. And then in 2019, I got the dream call for a Badger, and I was offered the opportunity to come back to Wisconsin and run this Engine Systems master’s program. And I came home to Wisconsin to do that.

So something about me. Anyone whose taken one of my classes can tell you I’m passionate about thermodynamics. Like I said before, thermodynamics is the study of energy, its transfers, and transformations, but the real key thing to solving a thermodynamic problem is setting the boundary for analysis. And we’re gonna talk about that. I also think it’s really important that we don’t demonize or ban any technology. There’s nothing that’s all good or all bad. There’s no silver bullet when it comes to clean transportation issues. And I do believe in engineers. I believe that CO2 emissions are a real problem that needs to be addressed. However, I believe that the fastest way to reduce CO2 is by improving all technologies, and that includes the internal combustion engine.

I think it’s part of our clean transportation future. So let’s give a little bit of background. Transportation accounts for 34% of all energy used in the United States. So you can see in my pie chart there that transportation is that green block, 34%. Now, fuel economy is not just good for your wallet. Fuel economy is also related to CO2 emissions. Hydrocarbon fuels contain carbon and hydrogen, and when they’re burned, the products of combustion are water and CO2. Therefore, fuel economy, fuel use, right, is synonymous with CO2 emissions. So when we talk about improving fuel economy in a vehicle, we’re also talking about reducing CO2 emissions on a relative basis. Transportation energy still predominantly comes from fossil fuels.

You can see my magnifying glass there shows that 91% of the energy that goes into the transportation sector comes from fossil fuels, mostly petroleum products. Those are those hydrocarbons that we just mentioned. And if you look at the history of engines, the one thing I want to point out is actually, the very first engines were not run on fossil fuels. They were run on steam, right? So the first on-vehicle engine was a steam engine in 1789. We didn’t see internal combustion engines start showing up until the early 1800s. And then, since then, there has been continuous improvement of internal combustion engines. New types of engines developed, new combustion strategies, new fuels, new ways of delivering the fuel, and fuel injection systems. So this is. . .

Engines are not stagnant. One thing I think people misunderstand when they talk about electric vehicles, they tend to give it a very sunny outlook and say, “Well, batteries are getting better all the time, and electricity is getting more renewable,” but that’s true of engines as well. They’re continuously improving, and I’ll show you some examples of that in a little bit. And fuels are also becoming renewable in the transportation sector with internal combustion engines as well. So I think it’s really important to realize engines are not a static technology. They are continually developing. So what’s the purpose of an internal combustion engine? Well, what we’re trying to do is produce useful work, you know, the motive power for your vehicle, by using readily available, stable combustible fuels. These can be liquid or gas. Engines have high power density, which is a really important feature for functionality and speed. They are efficient, and generally relatively low cost in comparison.

And in some cases, their efficiency can exceed 50%, which may not sound great to you, but later, when we talk about energy and how it changes and transforms, you’ll understand that you’re never going to approach 100% efficiency in a real process. There are things that we lose energy to, like friction or heat. And so 50% efficiency is actually really pretty great when we’re looking at engines. Engines come in two main types that we’ll talk about. Spark ignition engines, those are your gasoline engines. Fuels for those are things like gasoline or alcohols like ethanol or methanol. And those could be two-stroke, four-stroke, or rotary. Then the other main class is compression ignition engines. These are your diesel engines that are in two-stroke and four-stroke varieties. When we look at fuels, the fuel is predominantly diesel, but diesel engines are really robust.

And so you can run hydrogen directly in a diesel engine, or natural gas. Lots of fuel options there. So how does a reciprocating engine produce power? Well, combustion of the fuel releases the energy stored in the chemical bonds of the fuel in a closed volume. The oxygen portion of the air provides the oxidizer, and that heat released increases the temperature and pressure of that trapped gas in that closed volume. You might remember ideal gas law, right? Which relates pressure and temperature and volume. That increased gas pressure is used to push the movable piston. Pressure is a force acting over an area. And so it’s acting over the area of the surface of the top of the piston and it pushes it down. The combustion, therefore, has to be coordinated with the piston motion. And you’re gonna see that in just a minute when we talk about the four-stroke cycle, and we’ll talk about the difference of how we coordinate that combustion with spark ignition with a spark, or in diesel in the compression ignition.

I’ll tell you what that means. The physical limits of the engine have to be maintained. You can’t exceed them. So that means you can’t overly stress the engine, or run the temperature up too high. So it does put some limits on the combustion process. Overall, the combustion process is a thermodynamic process that’s repeated, and very quickly, by the way, over and over again. That closed volume is continuously recharged with new air and new fuel. That’s why it’s not a thermodynamic cycle. It’s a mechanical cycle, but a thermodynamic process. It does not meet the definition of a thermodynamic cycle because the air and fuel change as we go through each round.

Engine control systems attempt to optimize all of these processes. The engine control unit or ECU is the car’s computer, right, that we think about that’s helping run everything and keep the timings correct. Let’s talk about the four strokes of an internal combustion engine. The intake stroke begins with the intake valve open process. The intake valve opens, and that’s what allows the air to come through. And the piston sweeps from top dead center down to bottom dead center, pulling the air into the cylinder and filling that volume. Then the intake valve closes, and the piston moves from bottom dead center back up to top dead center, compressing that trapped air in the volume. In the power stroke, that’s where we’re initiating combustion and letting that temperature and pressure rise happen, where the pressure then will begin to push down on the piston, and that starts the generation of work, the shaft work in the rotating shaft engine. Finally, after the combustion gases have all been burnt up and the piston is at bottom dead center ’cause the force of the gas has pushed it down, then we begin the exhaust stroke. So the exhaust valve opens, and the piston sweeps from bottom dead center to top dead center to push those spent combustion gases out and to empty everything out so that the process can begin again.

When we talk about gasoline spark-ignited combustion, what happens in a gasoline engine is that intake charge is actually a homogeneous mixture of fuel and air. So gasoline engines can either be carbureted, that’s pretty old technology. If you have a car past about 1990, it’s probably fuel injected, or we do what’s called port fuel injecting. We inject the fuel into the intake port so that as the air mixture is drawn into the cylinder, the fuel and air can mix, giving us a well-mixed, homogeneous, hopefully, mixture. That mixture is what we compress, and then we light off that mixture with a spark, and that is what gets burned. So the load control in a spark ignition engine is controlled by throttling the intake. Combustion is initiated by a high-energy electrical charge across the spark gap. And you see in the image that the flame front that is around the spark plug, you see the flame front burning out on the edge of that kind of sun shape there. And you see the burned products close behind the flame front, and then you see the flame front is gonna propagate through those unburnt reactions that have that nice kind of yellow color throughout. In comparison, a diesel engine is compression-ignited combustion.

So only air is drawn into the cylinder and compressed. And we control the load in the diesel engine by the quantity of fuel that’s injected. The fuel is injected into high-pressure air, and that initiates combustion in a process called auto ignition. So because the air’s already at high temperature and pressure from that combustion process, and the different chemical properties of the diesel fuel, as soon as that diesel spray hits that high temperature and pressure air, combustion begins. So in diesel, whereas we had a very homogeneous mixture before in gasoline, diesel is a heterogeneous mixture within the cylinder. That means that we have a wide range of mixture concentrations over which the chemical reactions are occurring. This is why emissions are a much more significant issue for diesel engines is because of that heterogeneity of the mixture. However, we can clean up those emissions with exhaust aftertreatment catalysts. And this is something I know a lot about because I literally wrote the book on it. Oh, it’s right there.

So when we’re talking about engines, fuel economy standards are. . . We talked about that, right? Fuel economy is related to CO2 emissions, but when we’re looking at how we impact CO2 emissions from the transportation industry, these fuel economy standards alone are not enough. The problem is that the targeted vehicle fuel economy standards for 2020, so last year, were insufficient for CO2 level stabilization across the globe. And that’s because in general, we see that there is a continuous increase in the number of vehicle miles traveled. That we are seeing more and more CO2 emissions coming on from developing nations. And that there is a slow rate of penetration of new and improved technologies into the vehicle fleet. People aren’t buying new cars every year. And so these new technologies that are cleaner are taking a longer time to have impact.

I wanna talk just a minute about CAFE, the Corporate Average Fuel Economy standard. If you’ve ever wondered why the PT Cruiser is considered a light duty truck, it’s actually because of CAFE. CAFE says that for a particular vehicle class, a manufacturer has to hit an average fuel economy. So when you take the PT Cruiser and make sure that it meets specifications to be classified as a light duty truck, its relatively higher fuel economy averages in to that class and helps out the CAFE numbers for light duty trucks by averaging in that higher number with maybe the lower numbers from some of the other vehicles. So CAFE is a metric, and it’s a standard that we can look at, but it alone is not going to do it for us. So I want to take a minute and start asking the question, well, when did engines become the villain anyway? We all loved our engines and our cars up until quite recently when the demonization began. And unfortunately, I can tell you really when that happened. You can kinda pinpoint it to Dieselgate. And if that sounds familiar but you don’t completely remember, I can explain a little bit. Dieselgate was a scandal that involved 11 million vehicles from model years 2009 to 2015, specifically, Volkswagen vehicles that were intentionally programmed to only meet emissions when they were being tested.

So really, key point on this is those vehicles, because of exhaust aftertreatment, could be clean. They absolutely could meet the emissions standards, but Volkswagen was choosing not to meet the emissions standards and prioritizing fuel economy for the driver over clean air. The Dieselgate situation resulted in some really big fines, and even jail time for some VW executives. And it also kicked off the, you know. . . media end of the internal combustion engine. So you can see the cover of The Economist that shows the engine as roadkill. And then it also really started the beginning of what I’m going to call the EV hype. And you’ll see why I call it hype as we continue on.

It’s not that I don’t believe in electrification. I do, and you’ll see that, but the idea that EVs are the answer and engines are evil is wrong. There’s no such thing as a completely evil technology or completely good one. So note here, too, another thing that happened, and this is really notable because the headquarters of BMW was specifically designed to look like a four cylinder engine, and they used lights to make it look like batteries, and had that saying, “The future is electric. ” And I think that’s what inspired Kelly to say, “No, no, no, the future is eclectic. ” And hopefully, by the end of this talk, you’ll think so too. So now let’s talk about some science, my favorite science, thermodynamics. We have to start with defining systems, boundaries, and surroundings. A system is whatever we want to study. Could be a engine, could be a car, could be a can of Coke, doesn’t matter.

It’s whatever we’re interested in studying. And it’s the first thing that we need to do in defining our energy analysis is define that system. The surroundings is everything else, everything outside that system, and the boundary is what distinguishes the system from its surroundings. So are we comparing apples to apples if we only consider tailpipe emissions of a Tesla and a Ford Edge? I chose that ’cause that’s what I drive. So let’s focus on just CO2. To do a proper comparison, you can’t cherry-pick the thermodynamic system. One vehicle in my picture is considering the source energy, and the other isn’t. You know, when we look at CO2, we all live in the same system, and that’s planet Earth. And as it continues to fill up with CO2, it’s a problem for all of us. So that is the system that we all have to care about.

And so playing games with choosing the incorrect system for the vehicle comparison hurts us all. Okay, so for the Tesla, which by the way, doesn’t even have a tailpipe, it doesn’t have any CO2 emissions, and the Ford Edge does have it at the tailpipe. And therefore, people tend to think, “Well, the Tesla is clean, and the internal combustion engine car is dirty. ” However, you have to make a fair comparison. You have to compare the system of study to the system of study. So we have to consider the source energy for both cars. Electricity isn’t naturally occurring. Although it seems magic when it comes out of the outlet when you’re trying to charge your phone, you had to make it somewhere, and making it is what creates CO2. In Wisconsin, a lot of that electricity comes from coal-fired power plants. So I’ve updated my Tesla picture to include its source energy.

And now there’s a coal power plant inside the system boundary. Now we have a fair comparison, and CO2 emissions associated with both systems. So the Tesla is not so clean and the internal combustion engine car is not so dirty when we compare them apples to apples. In the United States, more than 70% of our energy still comes from fossil fuels. Now, across the world, it’s a little bit different. For example, if you live in Norway, almost 98% of their electricity comes from renewables. So there, the Tesla is quite clean. Same thing in Iceland, where 100% of their electricity is coming from renewables, but across the world, that’s not true. Those are more the exceptions than the rule. And you can see by the chart there from WIRED magazine how it breaks down.

So the answer about which of them is cleaner is not such an easy question, right? It depends on where is the energy coming from. With the internal combustion engine, that energy is always coming from the fuel and, therefore, there’s associated CO2 emissions. And from the Tesla, whether or not there are CO2 emissions depends on how clean your energy source is. So I want to introduce another concept to you. And that’s the idea of vehicle analysis versus life-cycle analysis. In vehicle analysis, which is sometimes also called wells-to-wheels analysis, we only consider the emissions that are produced during the usage of the vehicle, but that’s not the full story. Life-cycle analysis, which is also called cradle-to-grave analysis, also considers the emissions that are produced by extracting or fabricating the materials that make up the vehicle. Transporting those materials to the factory, assembling it, as well as that usage phase. So when we talk about wells-to-wheels emissions, we’re just talking about the primary fuel production process. We’re talking about the fuel reforming, the fuel distribution to the fuel station, then where you put it into the vehicle and use it in the vehicle.

But I would also argue that we need to consider the materials production, the vehicle manufacturer, and the vehicle transport portion of this as well. And another thing to remember is that each time we transfer energy, it comes at a cost. So before, when I told you actually 50% efficiency is really pretty darn good, it’s because of the fact that every time we transfer energy, it’s going to cost us some of it. Real processes have losses associated with them. Things like friction, or electrical resistance as the energy transfers from the power plant to the magical outlet in your wall. Every time we handle energy, we lose some of it. For an engine, we put that energy directly into the system in the form of fuel, where it is directly converted via combustion to power. We do lose some of that energy in the combustion process, and we lose some of it to things like friction within the engine. For a battery electric vehicle, to put energy into the system takes more steps. First, we need to turn the fuel, which is still often done via combustion, especially in Wisconsin, we saw the coal-fired power plant, into electricity at some sort of power plant.

Then we need to transfer that electricity via the power lines to our magical wall outlet. Then we need to transfer and chemically store the energy in the battery. And then we withdraw the energy from the battery to power the electric drive motor. So remember, every one of those transfers that we’re doing there, every one of those steps is reducing the amount of energy that we have to work with. So now, if we compare the efficiencies on just the tank-to-wheels basis, you see that people often say, “Well, from the electrical power outlet to the vehicle,” so I’m talking about my right box here on the right. “We see 80% efficiency for a battery electric vehicle. ” And we see only about 30%. And actually this data might be a little bit old. So it might be a little bit higher, maybe 32, 35% if we consider the efficiency from the fuel tank to the power of the vehicle. However, when we add that well-to-wheels basis, and we consider the transfers that I just talked through on the last slide, you see that the process to turn the fuel into electricity is less efficient than refining products into fuel, which is more efficient.

The combination of those two efficiencies, remember, efficiencies are multiplicative. So the combination of those two efficiencies means that overall, the process from raw fuel to vehicle energy is actually more similar than you think. So again, cherry-picking your boundary for your system can create different numbers, right? You have to look at the overall thing, you have to treat the things equally. You have to consider the energy generation in your process in order to make a fair comparison between the technologies. Oh, also related, fun fact, as we’re in a lovely Wisconsin winter, this is DOE fact of the week number 1164. So this is from a couple of weeks back. And it shows you that fuel economy is directly impacted by cold weather. And it also shows you the comparison between vehicle types. So you see the largest bar on the left is the fuel economy of a gasoline vehicle at 77 degrees Fahrenheit. So Wisconsin summer, doing city driving.

So that’s set at 100%. And you see that same gasoline vehicle, when we get to colder temperatures, actually is 15% less efficient in comparison. When you look at a hybrid vehicle, it’s now on average somewhere around 30% to 34% less efficient, and then the battery electric vehicle is nearly 40% less efficient. So batteries are highly impacted by ambient conditions. And so this is another thing that people tend to forget about is the impact of climate on these things. Maybe if you’re having a nice, warm Texas winter, it’s not as big of a problem, but fuel economy is directly impacted by ambient temperature. And in the winter, battery electric vehicles are impacted more than internal combustion engines. Again, in the beginning of what’s going to become a theme here, notice that the hybrid is in the middle of two extremes, and that’s going to be a recurring theme. You’re going to see why I think hybrids are the future. So this is still not the whole picture because we haven’t considered the manufacturing.

So we need to do the full cradle-to-grave analysis. Cradle-to-grave includes the manufacturing sources of CO2. And, unfortunately, battery production means that you’re starting with a lot more CO2 in the battery electric vehicle total at the start. I’m gonna use the BMW 320d as the comparison vehicle. The 320d has a diesel engine, and it creates about 109 grams per kilometer of CO2 when driving. So that’s the number standard I’m going to use when I talk about how many miles we can drive, or how many miles driving equivalent the CO2 production is. The CO2 for producing that diesel engine is the equivalent of driving that pretty vehicle 950 miles. Now let’s take a look at the Nissan Leaf. The Nissan Leaf is a small, subcompact vehicle. It has 150-mile range and a 40 kilowatt hour battery.

It creates 4,800 kilograms of CO2 to produce that battery. And that means that’s the equivalent of driving that 320d 26,600 miles before we’ve ever driven that Leaf one mile. The Tesla, which has a bigger battery, also has a bigger driving range. So the Tesla has about a 325-mile driving range, depending upon the battery. And it comes in a 100-kilowatt hour battery. So that battery, because it’s larger, also generates more CO2 in its production. So there’s about 12,000 kilograms of CO2 for producing that battery. That’s the equivalent of driving the 320d 70,000 miles before we’ve even driven the Tesla one. So notice here that when we make the column of all the CO2 associated with these vehicles, before we’ve driven each vehicle even one mile, we have numbers in their columns. And here’s a great plot from Graham Conway at Southwest Research, where he shows you CO2 produced over the life of the vehicle.

So what we just talked about on the previous slide explains why those don’t start at zero at the origin of the plot. You see that the conventional engine starts at the lowest because we saw the engine has the lowest amount of CO2 associated with its production. The electric vehicle with the smaller range is above that. And then the electric vehicle with the larger range is above that. And so you see that when we add the in-use, even though the slope of the curve, the slope of the line there is steeper for the conventional engine, it takes driving it around, somewhere around 90,000 miles before we’ve caught up to the smaller electric vehicle in terms of CO2 production. And it takes more than 180,000 miles before we’ll catch up to the battery electric vehicle just based on how much it took to generate the battery. Okay, but now you’re probably thinking, “But engines are old technology, and batteries are the future. ” Well, actually, electric vehicle sales peaked in terms of the percent of total vehicle sales in 1912. And then they were nearly extinct by the early 1920s for many of the same issues that we face with them today. Battery energy storage capacity, the so-called range anxiety.

Limited charging stations, infrastructure, right? You can see a gas station every so often. We don’t have that kind of charging structure for batteries yet. And competition with the internal combustion engine, which can carry a stable fuel onboard. If you say, “But wait a minute, “batteries are always getting better, “and we’re moving towards renewables for electricity. ” Well, engines have been improving too. There’s a number of technologies, variable valve actuation, aggressive exhaust gas recirculation, high-pressure direct fuel injection, catalysts like my beloved particulate filter, and Lean NOx aftertreatment like selective catalytic reduction, as well as cylinder pressure sensing and feedback control that have been continuous improvement for both fuel economy and emissions from engines. So batteries are getting better, but so are engines. And these improvements are getting results. There’s programs like the U. S.

DOE SuperTruck Program. We’re actually in SuperTruck II. And there’s a plot there showing from Daimler that shows how fuel economy in semi-trucks, those big class 8 vehicles that carry all our freight, and especially our Amazon packages around. SuperTruck’s been able to demonstrate that they can nearly double the fuel economy of a semi-truck by making improvements such as the ones I showed on the last slide. There’s also things like the DOE Co-Optima Program, where we’re co-optimizing engines and fuels to work together to reduce emissions. And these things are having results. The little gas pump icon there shows how fuel economy has been increasing since the ’70s. We’re getting continuously better. We’re continuing to innovate. This is not Rudy’s diesel, right? We are continuing to innovate and get better.

So batteries are getting better, but so are engines. And by the way, just like we talk about energy getting greener through renewables like nuclear or wind power or solar power, there are things like biofuels, which are renewable too. Sustainable biofuels enable the carbon recycling loop. Biofuels are things that are derived from biomass. Plant matters like trees or grasses or agricultural waste or algae. And we have a range of options for biofuels, things like biodiesel, bioethanol, bioreformates. Things like companies like Virent right here in Madison are working on. Biomethanol, bioethers, there’s lots of opportunities. And also Big Oil, as we like to think of them, is already greening up their refineries. This is a slide from Chevron that shows that they can use existing refinery infrastructure to make renewable fuels.

That’s pretty impressive. Also, there’s this really neat thing called e-fuels. These are really pretty new, but they’re exciting because you use solar voltaic generation, which is a cheap source of electricity, and you capture CO2 and create fuel molecules from it. So these are net zero carbon fuels because you’re taking carbon out of the air to make the fuel, which will then be released again. And again, we have that carbon recycle loop. So what should we do if we want to go green? Well, the answer, in my opinion, is hybridize. There are many levels of electrification. So there’s a difference between electric versus electrification. An electrified car isn’t electric, but an electric car is electrified. So a battery electric vehicle is 100% electric.

However, there’s a wide range of things that are electrified. If a car has an exhaust, it’s not electric. So I told you the Tesla doesn’t even have an exhaust, right? When you talk about a vehicle being electrified, it means using electric power beyond the just basic accessories, but it’s inclusive of vehicles using varying levels of that power. We could be talking about micro hybrids; that’s start/stop technology, regenerative braking. There’s mild hybrids, where then you start to get some torque assistance from the electric drive motor. And then we have full hybrids, where you start seeing electric driving and battery charging from the internal combustion engine. Plug-in hybrids, which get the battery charging from the grid power, but still have an internal combustion engine. And then an extended range vehicle, where you only use the internal combustion engine to charge the battery or run the electric generator, and the engine never directly drives the vehicle. But all of those options can include an internal combustion engine. And that’s the point, engines aren’t all bad.

Hybrids, which have some of both, are actually a great solution. So if we define battery electric vehicles, battery electric vehicles are powered by an electric motor. The battery stores the electrical energy that we’ve gotten from the wall power, and that powers the motor. The battery is charged by plugging into some sort of outside electric power source, and there’s no tailpipe emissions. The driving range on these can be up to 400 miles per charge. And it really depends due to model, trip, drive cycle, or environmental conditions like winter. Hybrid electric vehicles, on the other hand, use an electric motor in combination with an internal combustion engine. There are several configurations that exist, and each has different capabilities. Basic types of hybrids include mild hybrids, which means the internal combustion engine never shuts off to keep the battery pack charge, and there’s no independent EV mode. In strong hybrids, you can also run on electric-only power for significant periods of time.

And then plug-in hybrids have further increased battery capacity with less reliance on the internal combustion engine. Going through these briefly, plug-in hybrid vehicles employ the plug-in feature to increase the electric-only range further than a hybrid vehicle. So the plug-in hybrids are using grid energy, which may be coming from whatever kind of power plant is in your locality to propel the vehicle, and they lose battery charge during driving. Hybridization, overall, increases fuel efficiency. It allows you to downsize the internal combustion engine because you make up for that extra power from the batteries. You run the internal combustion engine at its optimal settings, and you can use things like regenerative braking to recycle previously lost energy that you would have been losing due to brake friction, you can send back to the battery. And also allows you to shut off the engine at idle, which means you’re not generating those emissions if you’re not getting motive force. Again, we’ve talked about, there are several levels of electrification, and both series in parallel arrangements. Both have their advantages and disadvantages. In general, I’ll say that a series hybrid is more efficient.

It’s just a little less powerful than a parallel hybrid. If you want to see what a hybrid powertrain looks like in series, it means that the fuel converter, the internal combustion engine is used to generate electricity, which then in turn charges the battery, or powers the electric motor. In a parallel configuration, the hybrid electric vehicle can drive the wheels from either the engine or through the battery through the electric motor. There are several variations on the parallel that exist, and they are named by where they’re located. So pre-transmission, post-transmission, or parallel through the road. Gotta love engineering nomenclature. We name it what it is. There’s also something called a power split where you can be propelled by either the engine or the battery, or both. So kind of more similar to a parallel. But now this enables us to make a fair comparison of hybrids against the electric vehicles or combustion engine vehicles that we saw before.

So now let’s go back to those plots and look at how CO2 production over the life of the vehicle compares for the fully battery electric, or the fully internal combustion engine, compare that to the hybrid. So the engine line is in blue, and the fully electric vehicle is in white at the top. And the hybrid vehicle is the green curve there. So you see that the hybrid starts just a little bit higher than the internal combustion engine. That’s because it uses a smaller battery and a smaller engine. So its initial CO2 for manufacturing is pretty darn close to the IC engine to start out. So they produce slightly more emissions in the manufacturing stage than just a conventional internal combustion engine, but much less than the full battery electric vehicle because they’re smaller batteries. When you start looking at using then the hybrid, you see that the slope of the hybrid line is less steep than the conventional engine, and a little bit steeper than the fully electric engine, but since it’s starting from that much lower CO2 starting point, you see that even after 180,000 miles of driving, it’s still the lowest of all three. And then if you really extend it out and you look at the CO2 produced over the life of the vehicle, you see that it takes a really, really long time in terms of mileage driven before the hybrid catches up to the battery electric, simply because of that differential in the starting point for manufacture. So making and using a hybrid in the United States produces less CO2 emissions than either a conventional internal combustion engine powered car, or a fully battery electric vehicle.

Hybrids are the winner here. Hybrids are electrified, meaning they have both the electric and the internal combustion engine. It means that you will not see the internal combustion engine disappear overnight. They have economic and society benefits. They have high power and energy density. They have low specific cost. They’re robust and versatile. They’re well-matched to the available fuels that we have. And there’s a strong infrastructure for those fuels, as you know if you’ve stopped at a gas station. They meet performance, fuel economy, and emissions requirements to date, and they are continuously improving.

With hybrids, there is a future for engines. So “Reports of my death have been greatly exaggerated,” says the internal combustion engine, in a slight misquoting of Mark Twain. So wrapping up, the future of transportation should be diversity. It’s an eclectic mix of things like the spark ignition engine, the compression ignition engine with gasoline and diesel, or advanced technologies in spark ignited engines, like gasoline direct injection or hybrid powertrains, or advanced compression ignition, like we see in the Supertruck program, or fuel cells, or running hydrogen directly in an engine, or electrifying the powertrains, or alternative fuels. All of these things together can come into play and create a cleaner transportation future. There are many technology enablers out there for efficient powertrains. Energy storage solutions like batteries or hydraulic accumulators, clean combustion technologies, hybrid propulsion options, fuel cells, alternative fuels. There are more than one way to get us to cleaner or hybrid propulsion. When we consider vehicle technology and fueling strategies, when we have the conventional vehicle with an internal combustion engine propelled by petroleum, it generates CO2. However, as we hybridize, even still using petroleum, we start to reduce that CO2.

And we can go further by using electricity coming from renewable sources on the electrical grid. All of these things continually decrease the amount of CO2 that we’re putting out because we’re enabling efficiency. And if we replace that petroleum fuel with some biofuels, we have even less CO2 that we’re generating. So what I hope you understand after this presentation is there’s no silver bullet solution. It’s all about the power of “and. ” Dramatic reduction in fuel consumption and net vehicle emissions of greenhouse and other toxic gases through the synergy of efficient energy conversion and next-generation biofuels and vehicle electrification and lightweighting of structures need to be guided by a holistic life cycle design and optimization framework. We have to choose our system boundary correctly and address all parts of it, not just pick and choose winners in this. Hopefully, you see that the future is eclectic because it requires all these different strategies. So what did we learn? Hopefully, that there’s no such thing as a zero-emissions vehicle. That’s my number one pet peeve.

You have to draw the system boundary to consider the energy source. And when we do that, even battery electric vehicles have CO2 associated with them. They are not zero emissions. And then also, manufacturing generates emissions far more so for batteries than engines. So when we include life cycle analysis, the comparisons are not so straightforward, choosing one over the other. I hope you see that both batteries and engines are old tech, and both of them have been continuously improving, even if they have been around for a long time. And I hope you see that we shouldn’t pick the winner in advance. We should choose targets, whether that’s efficiency or emissions, and let engineers go to it. Thermodynamics is not political. We need to improve all technologies in order to achieve our goals.

And by the way, we’ve seen that hybrids are better than either extreme. They have higher efficiency, lower emissions without the range anxiety of battery electric vehicles. They’re the best near-term solution, and the fastest way to go green. So I have to thank a few people and make some acknowledgements. I stand on the shoulders of giants in the field who have led the defense of the internal combustion engine. Kelly Senecal, Gautam Kalghatgi, Professor Rolf Reitz, Professor Dennis Assanis. And I only got to this point where I could talk to you today with the guidance of my PhD advising team, Professor Dave Foster and Chris Rutland of the ERC and Dr. Stuart Daw and Tod Toops of Oak Ridge National Laboratory. And my PhD work was funded by DOE. So thanks, Gurpreet and Ken.

I’m really honored to have this opportunity to add my voice to the conversation about energy efficiency and emissions. So I thank you very much, Wednesday Nite @ the Lab and PBS Wisconsin for this opportunity. So the fastest and greenest solution, hybrids. The future is eclectic.