Thinking About EV Efficiency

Bardeen Quad, UIUC, with the Mechanical Engineering Laboratory and Engineering Hall visible in the distance.

When I came back to school and met with an advisor last summer before registering for my fall semester classes, I was gobsmacked to find that the university required me to take RHET 105, a 100-level freshman composition course. A perfect storm of stupidity happened to flail together: the Transfer Credit Office did not accept the freshman writing course I took in my first undergraduate degree program to satisfy this requirement (for whatever reason); SAT and ACT scores could not be submitted after admission to satisfy this requirement (my scores are more than twenty years old, but easily exceed the minimum for composition credit); none of my masters or doctoral coursework apparently satisfied this requirement, nor the fact that I have the master’s degree and have taught at 3 universities including this one. So, here I am—a victim of mindless university bureaucracy, stuck in a course that is, at best, a waste of my time.
 
The only redeeming quality here is the fact that I get to spend more time writing than I have the past few years—although far less of that writing has been for personal projects like this blog. Our final assignment of the semester, however, offered a chance for some overlap: we were told to take a position essay we had written earlier in the semester and adapt it to a new audience in a new medium. So, here it is. You're welcome, audience, whoever you may be.
 
Position Essay
 
In my position essay, I chose to argue about a topic that interests me but is still accessible to a non-technical audience (i.e. my peers in this class and the instructor). I wrote a middling paper, with this thesis:
 
“While manufacturers must address the complete lifecycle emissions of electric cars and implement strategies to reduce the required energy inputs in the construction and eventual disposal of these cars, equally as pressing is the need to reduce on-road energy consumption and emissions of both carbon dioxide and particulate matter by optimizing the aerodynamic profile of EVs and working to reduce their mass—both critical factors in on-road efficiency.”
 
It isn’t great, but it is arguable. Ruminating on possible topics for this essay, I found myself thinking about the EV market
the cars that are available to purchase today and those that are coming soon (especially big SUVs and pickup trucks). The problem with a lot of them, if not all, is twofold: they have high aerodynamic drag and are quite heavy. These problems are related, since they share a cause: EVs today are huge. Gone are the days when work trucks were quite compact (as I pointed out in this post, my Hilux is shorter than my Prius despite having a very useful six-foot bed—longer than most full-size trucks today—and is only a few hundred pounds heavier than the “small” car).

And yes, I use it to haul stuff.

As I began researching the emissions characteristics of EVs, I came across some surprising papers which suggested these enormous EVs aren’t as “green” as they might appear.
 
EV Emissions
 
Specifically, two types of emissions from EVs may be higher than people think. First, EVs are widely characterized as “zero emissions,” meaning “zero CO2 emissions”; however, they are not. Significant emissions of carbon dioxide may be associated with the manufacture of EVs, and their on-road emissions depend on the source of the electricity that provides the power to recharge their batteries (side note: I really hate when car magazines and websites refer to charging as “sucking down electrons.” Electrons are negative charge carriers; for a battery to hold a positive charge, electrons have been removed, not added). Second, non-CO2 emissions—specifically, 2.5-micron (PM2.5) and 10-micron (PM10) particulate matter—may be higher in EVs than traditional combustion-powered cars, even accounting for the particles that come out of their exhaust pipes. This is all down to the weight of EVs: higher mass means more tire and brake wear, and when tires and brake pads are worn, they shed microscopic particulate matter.
 
How do we address these? Well, to reduce CO2 emissions we have to “green” the supply chain and manufacturing process, choose materials carefully, decarbonize the electricity grid, and reduce aerodynamic drag and mass—basically, make the car as energy efficient as possible across its entire lifecycle. To reduce particulate matter emissions, we have to reduce mass. The commonality between these two is, as you may notice, mass.
 
Argument
 
Focusing on just one half of my original position paper thesis, I think it is imperative that we reduce the mass of electric vehicles—for many reasons. First, this is necessary to reduce particulate matter emissions, improve brake and tire wear (which also extends the lifespan of these consumables, reducing waste), and reduce carbon dioxide emissions as much as possible. Second, a less massive vehicle requires less material to build, and less material means less energy required to process it, less energy to move it around over the vehicle’s life, and less energy to smash it up and recycle it when the vehicle is no longer usable. Third, a lighter EV means its battery can be downsized for the same range, which lowers weight again; as I put it in my original paper,
 
“My feeling is that the best approach in future is to reduce the dimensions of EVs and move toward smaller cars, a technique that by its nature reduces mass, while introducing limited use of lighter and more expensive materials to keep costs down. However, barriers to this that must be overcome include issues of range limitation due to smaller battery size and the perception of consumers, who increasingly prefer larger and larger SUVs and trucks. Consumer preference can be addressed through marketing, although this will take some time, and reduced range from smaller and less massive batteries is mitigated through reducing aerodynamic drag and the lower overall vehicle mass—a virtuous cycle.”
 
And fourth, lighter cars are more fun to drive. Yes, this is subjective—but I did own a Dodge Ram SRT-10 (5200 lb) and Honda Civic (2700 lb) back-to-back, and one of those was definitely more fun to bomb around mountain roads in the Cascades.

One of these was way more entertaining to drive, and it wasn’t the one with a Viper engine.

Will we see lightweight EVs in the future? I’m not hopeful; the market seems to prefer gigantic, heavy SUVs and trucks, and even small EVs like the Chevrolet Bolt and Hyundai Kona EV weigh upwards of 500 lb more than ICEVs of the same or similar dimensions. Look at something larger like a Rivian R1S (6800 lb) or Ford F-150 Lightning (6000 lb in its lightest trim) and the difference between the electric and comparable conventional vehicles is even greater.
 
The market will never support the EV I want: a small car with no “infotainment” or electronic gizmos (manual door locks and windows, please), as light as possible, with as small a battery as possible for a moderate but acceptable range with low-drag aerodynamics. Perhaps three people would buy that car.
 
I can still dream, though.

Comments

Popular Posts

How Spoilers Work

Optimizing Aerodynamics of a Truck: Part 5

A Practical Guide to Aerodynamic Modification