Electric Vehicles, Part 3

I asked on Instagram about what questions you have on electric vehicles. Here are my answers

“Is an EV I buy now going to be as good as one I buy in 10 years?”

I assume this question is mostly aimed at the battery. Electric vehicles are in some ways much simpler than conventional cars because they are a battery and a drive-train. They usually have less maintenance costs, but the upfront cost of the battery is what makes them so (prohibitively) expensive [1].

Near future (within the decade): Lithium ion batteries are likely to dominate the market for at least the rest of the decade; the costs of a lithium ion battery have already come down significantly [1]. Really there are several metrics that get optimized in the design of an EV battery: they could make cheaper batteries, but at the reduction in lifespan, range on a single charge, or weather resilience. Likewise, they could make a car that goes further and has a longer battery life, but it would cost more or weigh more. Assuming drivers require a good range (300 miles), a good lifetime (10-15 years), and good weather resilience (among other reliability and safety standards), how much could the cost still come down?

Sakti 2015 [2] shows that the costs come primarily from materials and the material costs come primarily from electrode active materials. Labor is less than 5% of the costs overall, so batteries reach economies of scale really quickly and have already benefited from learning curves as the manufacturing processes developed. EV batteries need to reach 100-125 $/kWh to be cost competitive with gas cars [1] [3]; getting at least close to this goal is potentially realistic (depending on how you count the costs), but the current technology can’t get significantly cheaper than that.

Image Source: Sakti 2015 [2], Breakdown of the cost of a battery inside a plug-in hybrid electric vehicle.

Other battery technologies show potential for a major battery breakthrough that launches us into a more energy-dense era for batteries; however, a breakthrough like this will almost definitely not impact the car industry within the decade. After that, who knows? I’m sure there is a yet-undiscovered technology that will really change the game. I just don’t think lithium ion batteries will get there through marginal improvements in production, efficiency, or chemistry. I think that there will eventually be strides in battery technology, but I don’t think it will impact the car market any time soon in terms of dramatic price reductions or range expansions.

“How do people without access to a garage charge their car? This seems like an equity issue…” (Question from my Grandma!)

Great question. I think this is a huge issue that hopefully state and federal governments will tackle, because if you require people to have zero emission vehicles, you also need to provide a way to charge them. Right now most people I’ve talked to express range anxiety about long road trips, but I think the more pressing issue is the lack of charging right outside their apartment! I couldn’t get an EV right now because I rely on street parking and have no close access. Traut et al 2013 really highlights this by showing that only about 47% of car owners also own their parking spot (as opposed to renting) and only 22% of vehicle owners have their parking spot within reach of an outlet [4]. 

“Possibilities on what to do with the battery?” (I assume this question means second-life)

This is a really interesting question too!

You can re-use, directly recycle materials, or basically melt down the components (either by heat or chemically) to extract raw materials to make new batteries.

Re-using a battery would be taking the EV battery and using it for a different application, like storing energy from your solar panels. Batteries don’t just go from good to bad, they slowly lose range. A battery could provide half its original range and not be sufficient to meet driving needs, but work very well for a different application (Harper et. al [5]). 

Even if batteries get a second or third use, eventually it will hit its end of life.

Harper 2019 explains that EV battery recycling can basically be split into two larger groups that I’m calling direct recycling and metals reclamation. In direct recycling, the components are taken apart and the cathode is re-used (and probably replenished). This method in some ways is most energy efficient, but the problem is that electric vehicle batteries aren’t standardized in their shapes or chemistries, which makes this option not very viable right now. It also has limited returns as the battery gets really old and degraded. If the battery is just melted down and separated into its raw metals through chemistry or high heat, the battery doesn’t need to be taken apart to the same degree; this method can use a lot of energy and labor. Currently the raw materials are cheap enough that recycling isn’t worth the cost to do it compared to just extracting more [5].

It would be nice if battery shapes and chemistries were a little more standardized for the purpose of recycling. I also think as more electric vehicles hit the road, more will eventually hit end of life and recycling will become more necessary.

“How does the cost of charging compare?”

EV’s are a lot cheaper to charge. Electricity is cheaper than gasoline and also less sensitive to global factors like oil cartels, pandemics, and recessions. The difference varies, but my back-of-the-envelope math puts it at about a third of the cost if electricity is 10 cents/kWh and gasoline is about 2.90 $/gallon. Will you make up the cost difference over the life of the car by saving on gas? I think it depends on a lot of factors and isn’t super predictable. For example, the pandemic caused me to stay at home all day and also caused the price of gasoline to drop. I spent way less on gasoline than I would have anticipated in a projection.

Additional cost point, EVs are much simpler than combustion cars; they’re basically a battery and a drive train. The reason they are expensive is the battery. Combustion engine cars can have costly maintenance fixes over its lifetime surrounding the engine, etc. Some of those costs are avoided with an electric vehicle too. Batteries can’t be fixed as easily as combustion engines. If there is a serious problem with the battery and it’s out of warranty, a new battery is a substantial portion of the cost of the car.

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References:

[1] Ciez, R.E., Whitacre, J.F., 2017. Comparison between cylindrical and prismatic lithium-ion cell costs using a process based cost model. J. Power Sources. https://doi.org/10.1016/j.jpowsour.2016.11.054

[2] Sakti, A., Michalek, J.J., Fuchs, E.R.H., Whitacre, J.F., 2015. A techno-economic analysis and optimization of Li-ion batteries for light-duty passenger vehicle electrification. J. Power Sources 273. https://doi.org/10.1016/j.jpowsour.2014.09.078

[3] Schmuch, R., Wagner, R., Hörpel, G., Placke, T., Winter, M., 2018. Performance and cost of materials for lithium-based rechargeable automotive batteries. Nat. Energy. https://doi.org/10.1038/s41560-018-0107-2

[4] Traut, E.J., Cherng, T.W.C., Hendrickson, C., Michalek, J.J., 2013. US residential charging potential for electric vehicles. Transp. Res. Part D Transp. Environ. 25. https://doi.org/10.1016/j.trd.2013.10.001

[5] Harper, G., Sommerville, R., Kendrick, E., Driscoll, L., Slater, P., Stolkin, R., Walton, A., Christensen, P., Heidrich, O., Lambert, S., Abbott, A., Ryder, K., Gaines, L., Anderson, P., 2019. Recycling lithium-ion batteries from electric vehicles. Nature. https://doi.org/10.1038/s41586-019-1682-5

Electric Vehicles, Part 2

I asked on Instagram about what questions you have on electric vehicles. Here are my answers

“How do you do a road trip?”

I’m going to answer this in four parts:

Time to charge: EVs take longer to charge than combustion engine cars take to fill up, even fast-chargers take about 30 minutes minimum. Ranges on EVs are really improving, so if you’re not going super far it’s probably a non-issue, but if you are travelling cross-country it just means doing a little bit of planning, like taking a lunch break while the car charges or stopping for the night. The potential complication with this involves queuing, especially if EV adoption outpaces charging stations getting built. Right now charging stations are outpacing EV adoption, but it would suck to be in the middle of a pass-through state, ready to take your lunch break, and the two chargers available are already in-use.

Types of chargers: There are different types of chargers: type-1 (slow) this is basically a typical outlet, type-2 (still slow) this is the type that your laundry machine uses. Home chargers are type 1 or type 2 (Hardman 2018 [1]). There are also fast-chargers that use DC current; but, there are different types of plugs for fast-chargers, basically Tesla and everybody else. There are converters between the fast-charger plugs, but I would love to see the federal government officially require one universal fast-charger plug. Regardless, charger options are expanding rapidly enough that range-anxiety is a non-issue (in my opinion).

Table Source: Hardman 2018 [1], Types of chargers for electric vehicles.

Range-anxiety: Tesla has a great network of public fast chargers across the country (Tesla [2]). Below in pink is what the map looks like for non-tesla public chargers (Bloomberg 2020 [3]). You can still go almost anywhere without issue.

Image Source: Tesla [2], Map of Tesla DC Fast Chargers

Image Source: Bloomberg 2020 [3] non-Tesla public fast chargers available along main highways.

The bigger issue: local access. Range anxiety is fairly unfounded with the pace of highway charging station expansion. If you live in an apartment and park your car on the street, public charging access can be a problem. In fact Traut et al. 2013 found that only 22% of US vehicles have a parking spot close enough to an outlet to charge [4]. From the IEA 2020 [5] we know that the US has a lot of private chargers, but we’re lacking in terms of residential public chargers for sure (we’re also lacking in highway fast chargers compared to China).

Image Source: IEA 2020 [5] Global EV outlook

“I’d love to learn more about vehicle-to-grid (V2G)?”

Vehicle to Grid! So electric vehicles take electricity and store it in a battery so that they can drive, but there’s no real reason that the energy stored in the battery can’t be turned back into electricity! We all do this on a micro-scale when we charge our phones in the car. If EVs are used like batteries rather than like cars than they can be thought of as transmission lines through time and space. You can imagine a scenario where people would charge in a place or time when electricity is cheap and then wait or drive elsewhere and off-load where and when it’s expensive to make money! This could also help flatten the demand curve that we talked about above. So, is it worth it? Is it realistic??

Peterson 2010 found that for plug-in hybrid electric vehicles, even if drivers had perfect information, meaning they knew exactly where and when electricity is cheap or expensive, they’d only make $142-249 dollars through the whole year [6]. $200 bucks over a year does not seem worth the effort. If I had perfect information about when prices of things are low and high, I can think of better ways to make my fortune than vehicle-to-grid. However! This is all assuming normal circumstances. Even if vehicle-to-grid is never ‘worth it’ economically, it could have value. For example, if your power goes out and you NEED to have the lights on in your home. In the winter storm that devastated Texas in February 2021, having people drive full EV batteries into some of the communities and offload electricity to areas that needed it could have been really valuable. Though this assumes they would be able to off-load some electricity and still have enough to drive back to where the power is not down.

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References:

[1] Hardman, S., Jenn, A., Tal, G., Axsen, J., Beard, G., Daina, N., Figenbaum, E., Jakobsson, N., Jochem, P., Kinnear, N., Pötz, P., Pontes, J., Refa, N., Sprei, F., Turrentine, T., Witkamp, B., 2018. A review of consumer preferences of and interactions with electric vehicle charging infrastructure. Transp. Res. Part D Transp. Environ. https://doi.org/10.1016/j.trd.2018.04.002

[2] Tesla Super Chargers, https://www.tesla.com/superchargers

[3] Bloomberg, “Electric Car Chargers Will Determine America’s Green Future” 2020. https://www.bloomberg.com/news/features/2020-06-01/electric-car-chargers-will-determine-america-s-green-future

[4] Traut, E.J., Cherng, T.W.C., Hendrickson, C., Michalek, J.J., 2013. US residential charging potential for electric vehicles. Transp. Res. Part D Transp. Environ. 25. https://doi.org/10.1016/j.trd.2013.10.001

[5] International Energy Agency, 2020. “Global EV Outlook 2020.” https://doi.org/10.1787/d394399e-en

[6]  Peterson, S.B., Whitacre, J.F., Apt, J., 2010. “The economics of using plug-in hybrid electric vehicle battery packs for grid storage.” J. Power Sources. https://doi.org/10.1016/j.jpowsour.2009.09.070

Electric Vehicles, Part 1

I asked on Instagram about what questions you have on electric vehicles. Here are my answers!

“Doesn’t owning an electric car cause greater damage than a gas car because of the energy generation?”

This is actually a surprisingly complex question to answer.

Electric vehicles (EVs) get their energy from electricity, which is regional. Combustion engine vehicles get their energy from gas which has a similar impact regardless of where you live in the US. In a region with a majority of the electricity coming from coal, an electric vehicle is probably worse than a fuel efficient car (in terms of carbon emissions), especially when comparing an electric vehicle to a hybrid (Yuksel 2016 [1]).  The image below from Yuksel 2016 has hybrids in the columns and battery electric vehicles in the rows. What it shows is that in 2013, the Toyota Prius hybrid was less carbon emitting than the Chevrolet Volt; whereas the plug-in Prius was less emitting than the Mazda hybrid. For the Prius hybrid vs. Prius plug-in electric vehicle, it depended where you lived. In 2010 an electric vehicle was better than a gasoline combusting car in California, but worse in North Dakota [1].

Image source: Yuksel 2016 [1], Comparison of carbon emissions between battery electric vehicles and hybrids. It’s important to note that this is a comparison with hybrids, not your gas guzzling SUV or even your grandma’s old car.

Differences across the map are a reflection of California having a cleaner grid (more renewables, less coal) than places in the upper Midwest. The grid has gotten much ‘cleaner’ in the past decade (Holland 2020 [2]) primarily because of coal getting decommissioned and natural gas plants (and wind & solar) getting built. Today, in most places around the country, the grid is clean enough that a plug-in electric vehicle is less emitting than a combustion engine vehicle (although good hybrids can be just as clean as electric vehicles in some places!)

Image Source: Holland 2020 [2], Emissions from electricity has really come down in the US in the last decade. This makes having an EV less-emitting today than it was in 2010.

Marginal vs. Average electricity consumption:

Let’s say that there is 100 MW of electricity demand in your area. Adding an electric vehicle to your house’s electricity demand increases the demand to say, 100.1 MW in your area in the evening. This extra marginal demand isn’t enough to build a whole new power plant, instead it is just enough to make the local utility add their ‘peaker plants’ to the grid, the power plants that are small, inefficient, and only go on when they have a tiny bit of extra demand. Graff Ziffin 2014  argues that these dirty coal plants should be what count towards your EV emissions, because it is the plant that actually gets turned on to meet your EV’s demand [3]. The case is always true that the last bit of power used comes from the most expensive electricity than the first bit of power. Renewables cost almost nothing to operate, so once they’re built they are going to always be ‘on’, but demand changes throughout the day, so it’s the coal and natural gas plants that go on in the evening and late at night to meet the last bit of electricity demand (the margin).

Image Source: PJM Learn [4] “How PJM Schedules Generation to Meet Demand”

My personal push-back to the ‘marginal emissions’ argument is that electric vehicles are getting adopted at non-marginal numbers; instead of causing a marginal increase (increasing the red in the curve above), they could cause their region to need new electricity generation (raising the whole curve, so increasing the green and blue), especially as people charge more evenly throughout the day, like at work or while they grocery shop. When new power plants get built they tend to be cleaner than the one’s getting shut down, so new EVs can drive new generation expansion (pun intended, sorry).

Last thought on the ‘greenness’ of EVs: combustion engine cars will always have high emissions. EV’s have emissions reflective of the grid, so an EV’s emissions in three years may be less than its emissions today if the grid gets cleaner. The transportation sector is the largest source of greenhouse gases in the US, so we just won’t make our climate goals by continuing to drive gasoline cars. We need the grid to ‘clean up’ for EVs to be truly low emission, but there’s no scenario where a gasoline car can be low emission.

Ask me a question about electric vehicles!

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References:

[1] Yuksel, T., Tamayao, M.A.M., Hendrickson, C., Azevedo, I.M.L., Michalek, J.J., 2016. Effect of regional grid mix, driving patterns and climate on the comparative carbon footprint of gasoline and plug-in electric vehicles in the United States. Environ. Res. Lett. 11. https://doi.org/10.1088/1748-9326/11/4/044007

[2] Holland, S.P., Mansur, E.T., Muller, N.Z., Yates, A.J., 2020. Decompositions and Policy Consequences of an Extraordinary Decline in Air Pollution from Electricity Generation. Am. Econ. J. Econ. Policy. https://doi.org/10.1257/pol.20190390

[3] Graff Zivin, J.S., Kotchen, M.J., Mansur, E.T., 2014. Spatial and temporal heterogeneity of marginal emissions: Implications for electric cars and other electricity-shifting policies. J. Econ. Behav. Organ. https://doi.org/10.1016/j.jebo.2014.03.010

[4] PJM, “How PJM schedules generation to meet demand”, https://learn.pjm.com/three-priorities/keeping-the-lights-on/how-pjm-schedules-generation-to-meet-demand

NSF GRFP Fellowship

I am fortunate enough to have received an NSF GRFP fellowship in 2021!

I applied before graduate school and did not win, but applied again in my first year of a PhD at Carnegie Mellon and won! (you can apply once in undergrad/before graduate school and once as a first or second year graduate student in a PhD program)

I found Mallory Ladd and Alex Lang had great advice and essay examples, but I also worried that they had some success/survivorship bias by primarily featuring essays from people who won the award. Below I’m going to list what changed between my essays from the year that I didn’t win and the year that I did.

Research Statement:

1. Talking to my advisors gave me a much better plan for what I actually wanted to research, so my research statement had a clearer vision. Before graduate school I had a vague sense of what I wanted to research, but hadn’t dived deep enough to write about the little details; my lack of a tangible plan probably came through in my statement the first year. If you’re not yet in graduate school, spend at least ten hours doing a literature review: really know your field and the gaps in research.

2. I opened with an overarching sentence on the whole topic, basically a short abstract. This told the reader right away the full concept. I then started with an anecdote, explaining why my topic has a broader impact.

3. I had a timeline. Although not mandatory, making a year by year timeline helped succinctly demonstrate my research plan. It also helped me figure out where the gaps in my plan were by actually writing down what I would be doing!

4. I had a graph of preliminary results. I hadn’t started researching the topic full-time, but I added a preliminary result from a few hours of work on the topic to anchor the research statement in an image and prove the viability of my proposal. The reviewers have to sift through so many essays, an image can really stand out for them!

5. I bolded my most important sentences to anchor the reviewers to their key take-aways.

6. I ended it with broader impact to tie it all together.

Personal Statement:

1. I wrote my research statement first, so I could be sure to connect my personal statement long-term goals back to the overall research goals of my project.

2. I bolded every sentence that was a key take-away from my personal statement (about 5 in total). This seems like overkill, but the reviewers don’t have a lot of time to read and re-read essays, so having key sentences for them to review can help!

3. I made it very clear that my past experiences set me up to complete the project and completing the project will help me towards my long-term goals.

Overall Application:

1. I chose the correct topic field in the application. This sounds trivial, but my topic is somewhat inter-disciplinary and depending on which field I chose as my primary really impacted the perspective it was read from. I made sure to choose the primary field that give reviewers most able understand my research statement.

2. I had strong recommendations. I told my recommenders early, reminded them often, and also provided them with my research statement to better speak to what I was writing about. This helped.

3. My work and research experiences were stronger than my undergraduate GPA. Neither of these changed between the year I applied before grad school and my first year in graduate school. Instead, my personal statement on what I learned from these experiences was better written.

4. I did not have any publications at the time I submitted, but I had made an effort to attend talks and conferences, work in the field, and volunteer in STEM education. There are ways to standout as a committed researcher besides having a long publication list. I was worried that my lack of publications as a first year graduate student would preclude me from serious consideration, but it didn’t seem to impact it.

The last thing to remember is that whether you win or lose, there’s always a bit of luck involved. Everyone gets different reviewers; you may get reviewers excited about your topic, or you may not. You should make your application as competitive as possible, but if you don’t get it do not take it as a reflection of your worth or capabilities. I got rejected from one fellowship the day before I won the NSF GRFP with a review score of 5 Excellents & 1 Very Good. So a rejection today, doesn’t mean you won’t succeed tomorrow (literally in my case!)

Winning vs. Losing Essays and reviews

Year I won: Personal Statement - Research Statement - Reviews

Year I lost: Personal Statement - Research Statement - (E/E, VG/VG, G/F)
E = Excellent, VG = Very Good, G = Good, F = Fair

Want to share your winning or losing essays on my site? Email me a copy!

Email me essays or questions about NSF

Email me essays or questions about NSF

Charting a Career in Sustainability….

In High School and even throughout college, I knew I wanted to dedicate my life and career to sustainability. However, I didn’t know what a career in sustainability looked like or what to major in to get my dream job! Many jobs within sustainability didn’t even exist 5-10 years ago so it can be hard for counselors and career centers to keep pace with emerging jobs in sustainability. I focused on STEM majors for this flow-chart, but there are jobs in sustainability for all sorts of majors.

This is definitely not comprehensive, but it’s a start! I made this from my own experience and from watching my friends’ career paths. I consulted friends across most of these majors/fields to better understand a typical career trajectory for their area of specialization within sustainability.

For more resources, the Department of Energy has a careers page that’s a little more detailed by energy source.