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By JESSIKA TRANCIK
Electrifying transportation is one of the most promising ways to significantly cut greenhouse gas emissions from vehicles, but so-called range anxiety — concern about being stranded with an uncharged car battery — remains a barrier to electric vehicle adoption. Is range anxiety justified given current cars and charging infrastructure?
It’s a question my research group and I addressed in a paper published in Nature Energy, by taking a close look at this problem with a new model.
Specifically, we asked: When looking down on the geographic area of the U.S. from a bird’s-eye view, how many personal vehicles on the road daily could be replaced with a low-cost battery electric vehicle (EV), even if daytime charging isn’t available? Our analysis is, to our knowledge, the most expansive yet detailed study to date of how current and future-improved electric vehicle technology measures up to people’s energy-consuming behavior.
We found nearly 90% of vehicles on the road could be replaced by a low-cost electric vehicle available on the market today. What’s more, this number is remarkably similar across very different cities, from New York to Houston to Los Angeles. That is, there is a high potential for electrification of cars in both dense and more sprawling cities in the United States.
To realize this potential, however, the needs of prospective electric vehicle drivers have to be met on all days, even high-energy ones, such as days that require long-distance travel.
Two key innovations can enable this. The first is to predict the days on which drivers are likely to exceed the car’s range, which our model is designed to do. And the second is institutional or business-model innovation to provide alternative long-range vehicles on those high-energy days. For example, conventional cars, and eventually low-carbon, long-range alternatives, might show up at a user’s door at the click of a button. This need may last for some time even as battery technology improves and charging infrastructure expands.
Vehicle range is not a single number
An electric vehicle’s range is typically thought of in terms of a fixed number, but the number of miles covered on a single charge changes with factors including driving speed, driving style, and outdoor temperature. To understand the range of a car, we need to look beyond the car itself to how people are behaving.
Over the last four years in my research group, we’ve built a model (called “TripEnergy”) of the second-by-second driving behavior of people across the United States, how they are likely to use heating and cooling systems in their cars, and how various electric and conventional vehicles would consume energy if driven in this way.
This approach gives us a probabilistic view of electric vehicle range. For example, for the Nissan Leaf, we find that 74 miles is the median range — based on driving patterns, half of the cars on the road in the U.S. would be able to travel this far, and half would not. (A Ford Focus electric performs similarly.) There is a distribution in this range, which demonstrates how widely actual performance can vary. We estimate, for instance, that 5% of 58-mile trips could not be covered on one charge, and 5% of 90-mile trips could.
Evaluating electric vehicle technology against driving behavior
With the TripEnergy model in hand, we asked how many cars on the road could be replaced with a low-cost electric vehicle available today. We considered a case where drivers can charge only once daily: for example, at home overnight. This allowed us to study a situation where only limited changes are needed to existing public charging infrastructure and cars can use power plants that would otherwise sit idle overnight.
We found that, given how people are driving across the U.S., 87% of cars on an average day could be replaced with a current-generation, low-cost electric vehicle, with only once-daily charging. This is based on the driving behavior of millions of people across the U.S. across diverse cities and socioeconomic classes.
Switching from conventional to electric vehicles for those cars would cut emissions by an estimated 30%, even with today’s fossil fuel-based supply mix. In total, the trips taken by those cars represent roughly 60% of gasoline consumption in the U.S.
This large daily adoption potential is remarkably similar across both dense and more sprawling U.S. cities, ranging from 84% to 93%.
While it’s true that people behave differently across cities — in how they use public transport, whether they own a car, and how often they drive the cars they own — when they do drive, we found that a similar number of cars in different cities fall within the range provided by a low-cost electric vehicle.
Returns on technology improvement
What if batteries improve, and allow for longer driving range for the same cost as current-generation lithium ion batteries?
The federal research agency ARPA-E has set a target for batteries to store roughly two times more energy by weight than today’s batteries in electric vehicles. If that technical target is reached, we estimate that the 87% daily adoption potential estimate would rise to 98%, and the gasoline substitution potential would rise from 61% to 88%. The 2017 Chevy Bolt and 2018 Tesla Model 3 are expected to achieve roughly similar increases in potentials at an increased cost compared to today’s Nissan Leaf, though these costs are still close to the average cost of new cars. The Tesla Model S travels even further but costs significantly more.
Even with substantial battery improvements, however, other types of powertrain technologies will be needed to cover those days with the highest energy consumption. This need may persist for some time, even with expanded charging infrastructure, due to a small number of very high-energy days.
The upshot on range constraints
For people to overcome range anxiety and feel comfortable buying an electric vehicle, they need to know their needs will be met on all days, including high-energy days. Predicting when this will occur — and in advance when buying a vehicle on how many days this will occur — is something that our model is well-suited for.
Our model can, with limited input on travel distance, time and location, predict the probability of exceeding the car’s range, and point to days where drivers need to turn to other, longer-range cars, for example, within households, or even within communities and through commercial car-sharing programs. The results also shed light on the quantity of long-range cars that would be needed at the population level, a gap to be filled by private sector innovation as well as national and local policy.
Reasonable financing to help distribute the upfront costs over the car’s lifetime and increasing the opportunities for charging, even if only once daily, would also encourage EV adoption.
In all, our analysis shows that current electric vehicles can meet most daily driving needs in the U.S. Improved access to shared, long-range transport, alongside further-advanced batteries and cars and decarbonized electricity, provides a pathway to reaching a largely decarbonized personal vehicle fleet.
Jessika E. Trancik is an associate professor in energy studies at the Massachusetts Institute of Technology. This column was originally published at The Conversation.
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15 Comments
Cold weather
Does anyone have any first hand experience with electric cars actual performance in colder climates during the winter? I know my lithium ion power tools really take a dive in performance when it gets below 30 F.
Re: cold weather for EVs
I've had a LEAF for 3.5 years in Chicago. The LEAF is significantly impacted by weather, largely due to the fact that the pack designed without active thermal management. In my experience, range decreases under 50*F pretty linearly to about 20*F and then plateaus at about 40% reduction.
On nice days longest I've gone on one charge is 92 miles (and still had 10% capacity left). In the winter I'd say that is down to to about 50 on the highway. That said I drive all around the suburbs for customer meetings and it has met my needs (by using our spotty public charging network) on all but 2 out of 1300 days with it (used the wife's ICE car instead). I'm at 36,000 EV miles or so.
Next gen EVs wont have this problem as notably due to actual thermal management of the packs. Just a guesstimate but cold impact is probably reduced to a 10-20% range decrease.
Kye, the NY Times reporter
Kye, the NY Times reporter that got into the tussle with Tesla reported that the Model S lost 2/3 of it's charge one bitterly cold night parked at a hotel.
I take issue with the first sentence of this article. Both the new generation Prius and upcoming Hyundai Ioniq hybrids have carbon emissions under 200gm/mi. This is about the same or lower CO2 emissions of electric cars powered by coal (80% of grid power).
http://www.scientificamerican.com/article/electric-cars-are-not-necessarily-clean/
Hybrids have 600 to 700 miles range, can be refueled in under 5 minutes with existing infrastructure, and are much less expensive to buy than battery electrics.
I have 60k Tesla miles under
I have 60k Tesla miles under my belt and I can say that the answer is no, range anxiety is not justified for a few reasons:
1) charging infrastructure has vastly improved over the the past few years.
2) 99% of daily driving is short range that is within the capabilities of most pure EV and easily within range for hybrids
3) EV's start their day with a full tank thanks to home charging. However, it seems like every time I get in my wife's gas car, there is only 20 miles of range left and I start to get range anxiety driving in a gas car.
As an example, I drove down to Philly on Saturday to the PHIUS conference and I left with a full charge of 255 miles of rated range. It was 188 miles roundtrip and I returned home with 52 miles of range left. Weather averaged 70 degrees, most of the highway driving averaged 73mph, AC was on, radio on. This was a no brainer trip and outside of 99% of my daily driving of 40-ish miles per day. When I first got my car, the closest Supercharger was in Newark, Delaware, 104 miles away. However, 3 years later, there are now 4 Superchargers on my trip to Philly, including 1 just 20 miles from home. I even stopped at a rest area on my way home that had a Tesla Supercharger, but I did not bother plugging in. I did not need the charge to get home and I am not one who will inconvenience themselves for free charging (free firewood is a different story).
To Kye's question regarding cold and range. Yes range is affected by cold, although nothing like what the NY Times reporter claims. Had the weather for my trip to Philly been rainy, mid-30's with a headwind, then for planning purposes I would subtract a good 30% from my rated range. I still would not have had range anxiety though because of the Superchargers along the route and the ability to conserve range by driving slower, say 65 mph instead of 73. In this cold scenario, the question for me would have been could I make it home without charging or would I need to plug in for 10 minutes while at the rest area.
Btw, there was quite a line at the rest area for cars getting gas. Easily a 10 minute wait to fill up. So safe to say it was more convenient driving an electric car than a gas car on this trip.
And at the end of the day, the same person who runs out of gas is the same person who is going to run out of charge. You can't go 40 miles with 30 miles of range in the battery, but some people just don't get it.
Range Anxiety
I had a Leaf EV for three years and now have had a BMW i3 for over a year. Like Dan H, I am in Chicago and the cold weather has a tremendous impact on range. There is a very good article on it with charts http://www.fleetcarma.com/nissan-leaf-chevrolet-volt-cold-weather-range-loss-electric-vehicle/
I have had similar issues with winter range in the Leaf, at about 50 miles of actual driving distance. Going further than that begins to potentially deep discharge the battery and cause damage. I ALWAYS had to watch the range and do math in my head to be sure I could go where I needed to. There was a joke that the range meter should be called a 'guess-o-meter' - it never seemed to be very accurate and would fluctuate quite a bit while driving.
With the BMW i3, however, I have not had that anxiety at all. The car does have a range extender, for which I use about 2 gallons a year for local driving. It is an excellent security blanket. But even without that, the i3 manages its range much better. It is designed to drive all the way down to zero without damaging the battery system.
All of that being said, having 200+ miles of range completely puts that issue to bed. The fast version of charging stations will allow for very fast charging, so the range and recharge issues are converging. I have a Tesla Model 3 on order (likely for 2019 delivery!) and can't wait! Everyone I know that has had an electric car will never go back to ICE cars. The experience is so much better - smoother and faster acceleration, lower driving costs, lower ownership cost, quieter driving - expecially with the longer ranges coming.
Is ‘Range Anxiety’ Really Justified?
In a word "no".
Jay S, you have been mislead
"the NY Times reporter that got into the tussle with Tesla" lied. And his lies were well proven. Now that vehicle emissions are the largest source of greenhouse gases (they have just passed the power grid), " Electrifying transportation is one of the most promising ways to significantly cut greenhouse gas emissions from vehicles,"
I power my electric car with my solar panels and if I need to buy electricity, it comes from wind power. There is a LOT of mis-information being spread around by the Koch brothers and others like them trying to keep their jobs in the fossil fuels industry. Electric cars ARE the future and the future is here today.
"Low Cost"
I do not consider the $30K plus for a Bolt or Tesla S to be "low cost" at least as far as up-front costs. The point of comparison for me is the comparable (in size and general level of quality and amenities) Honda Fit, which lists at the top end at $21K but entry level at $17.5K.
I have not seen lifecycle cost analysis for the Leaf or Tesla, so I would be interested in a pointer to that, to help me evaluate whether I should be looking at a pure electric,car, a Fit, or a hybrid like the Prius.
I am speaking as a non-building professional consumer.
Geary. You need to consider
Geary. You need to consider your transportation needs. A used Leaf might be fine if you only have to drive a few miles per trip and have secure access to a charging station. That said, it's hard to beat a Honda for overall economy.
RE:Is ‘Range Anxiety’ Really Justified?
Unfortunately - nearly all the articles I've seen that suggest range anxiety does not exist - are written with the urban city users in mind. And many of the comments thus far are from individuals that live in or near large cities. For the urban use case... range anxiety is likely to be far less and diminishing. But as you move away from the urban/suburban cores -- range anxiety - returns.
For a better answer you need to ask...
For northern climates - would you be willing to drive the electric to grandmothers house for Christmas 200 miles away... That's Chicago to let's say someplace by the Wisconsin Dells. Or from Perhaps St. Paul toward Fargo ND, or from Denver Colorado toward Gillette Wy. If the answer is yes - with planning and a little thought... then range anxiety is still there... you're spending time planning stops to make the trip. The equivalent with a hybrid or gas automobile is we gas up before and then anywhere along the route if needed... you don't generally think about it because the fuel stations are ubiquitous.
Now do the same for west coast say SF Bay area and say you're going to go up to Crescent City and into the redwoods and the national parks... make a trip over to Lassen. That would require an immense planning activity with a Leaf... because the public charging infrastructure isn't very obvious or common... worse yet from Crescent City to Lassen - roads are torn up... possible charging stations are inaccessible. Once you get past Redding on the road to Lassen National Park... the charging stations are virtually NILL. It's less than 200 mile trip to Lassen and back.. but there are not public charging stations in the common visitor areas... you'd be calling a tow truck.
If you pre-plan your stops before starting a trip so you can charge... or if you need to pay attention to the car for instructions on how to find charging stations... you're still worried about range. And range anxiety still exists...
Range anxiety can be solved... if charging stations are pushed onto the oasis and rest areas across the country, if public destinations like parks, and if the gas stations offer charging points... and the charging stations can't be designed to work with only certain brand vehicles.
Re: Is Range Anxiety Really Justified
Dennis, another thought would be not to buy a car of the '100 year storm', i.e. the 5% of the time you need it, but get the car you use 95% of the time, and rent an ICE car for the long trips. If this is the inconvenience that is required to deal with climate change, it doesn't seem that bad to me. I had this arrangement with the Nissan dealer, where they offered an ICE car for a week a year if I wanted it. I took them up on that for a vacation from Chicago to Montreal.
Dennis,Check out the link to
Dennis,
Check out the link to the Tesla map. North Dakota and Nebraska are tough states to drive through with a Tesla, but you can travel through basically every other state and never run out of charge using just the Super Charger network.
https://www.tesla.com/findus#/bounds/49.000692,-96.55449090000002,45.935072,-104.05003999999997,d?search=store,service,supercharger,destination%20charger&name=North%20Dakota,%20USA
Like Nathan said, it really depends on whether you are trying to use an EV as your daily driver or your family vacation car. I could handle 99% of my daily driving with a Leaf or an i3.
Even when you get outside of the Urban areas and into the sticks, there are plenty of charging resources available. For example, I took a builder class up in Waitsfield, VT last March. I drove from my home in NJ to the Tesla Super Charger in Albany, NY. I grabbed lunch while the car charged. There were no Super Chargers anywhere near Waitsfield and my motel did not have any accessible 110 outlets, but there was a Level II charger in town at the local gas station - how ironic. But I found it more convenient just to plug into the 110 at the school where I was taking the class. At the end of the week, I had to head to Boston for the night and then onto Providence, RI for the JLC show. I left the school with 80 miles of range, 70 miles to the next Super Charger in Lebanon, NH and it was 30 degrees. That usually is not a problem and I was doing fine until I got to the the top of the mountain I needed to go over to get to Lebanon and saw a sign that said "unpaved road next 7 miles." Oh Sh*t. If I turned back I would have had to go back to town, charge at the Level II in town for a few hours, then head north for 20 miles to avoid unpaved roads before heading south to Lebanon. That is not my style, so I kept going. Thankfully, I did not get stuck, despite the ice and snow, and I made it to Lebanon with 12 miles to spare. The hotel I stayed at in Boston has its own charger, so I left the next morning with a full charge, and then after the JLC show, I stopped at the Milford, CT Super Charger and grabbed a late lunch before heading home.
So moral of the story is charging resources are available but not all roads are paved.
Response to Jonathan Lawrence
Jonathan,
Ah yes, the well-known Vermont problem... Gravel roads and ice.
I'm curious to see how self-driving cars will handle the Vermont problem.
Martin,
I was not expecting
Martin,
I was not expecting to find those conditions. I grew up in farm country and spent most of my teenage years working on a dairy farm. I have plenty of experience driving in mud with trucks and AWD tractors, but not in a RWD sedan. I later found a YouTube video of someone driving down that same road with same conditions as me. I really thought I was going to bottom out in the ruts.
https://www.youtube.com/watch?v=RTSphVHsCKE
Btw the view of Sugarbush at the top was spectacular.
Response to Jonathan Lawrence
Jonathan,
Everything in the YouTube video looks like smooth driving to me. I guess you don't know about real mud season conditions.
.
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