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Range anxiety? Today's electric cars can cover vast majority of daily U.S. driving needs
Posted on 5 September 2016 by Guest Author
By Jessika E. Trancik, Associate Professor in Energy Studies, Massachusetts Institute of Technology
This article was originally published on The Conversation. Read the original article.
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 percent 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 and 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.
General Motors is developing the all-electric 2017 Chevrolet Bolt, which is designed to have a driving range of about 200 miles. General Motors
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 five percent of 58-mile trips could not be covered on one charge, and five percent 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 percent 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 percent, even with today’s fossil fuel-based supply mix. In total, the trips taken by those cars represent roughly 60 percent 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 percent to 93 percent.
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 percent daily adoption potential estimate would rise to 98 percent, and the gasoline substitution potential would rise from 61 percent to 88 percent. 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.
The expansion of car-sharing services makes it easier to get a car for a long-distance trip. davereid/flickr, CC BY-NC
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.
Associated with the range of electric vehicles is the more important need for electricity generation to be better than natural gas burning and plug-in infrastructure to be built as a public utility (not expecting a popularity and profitability motivated system to rapidly develop the required result).
Electric cars do make sense as long as the electricity generation to power the vehicle produces less CO2 than the burning of natural gas to generate electricity.
An eia presentation indicates Natural Gas generation produces about 0.55 kg of CO2 per kWh but the total amount of CO2 would be higher due to electrical delivery losses and CO2 or equivalent, like fugitive methane emissions, generated in the production and delivery of the natural gas.
I chose to buy a hybrid because I live in Alberta. In Alberta in 2015 more than 50% of the electricity generation was coal fired (Alberta Government Report for 2015)
Electric vehicle efficiency ranges from 20 to 25 kWh/100 km. If the generation was from natural gas, that would be a minimum of 11 to 14 kg CO2/100 km (higher when other CO2 impacts are added). Alberta's average would be poorer than that. At 50% coal (0.95 kg CO2 / kWh) and 50% natural gas the result would be a minimum of approximately 0.75 kg of CO2 / kWh. That means a minimum of 15 to 19 kg of CO2 / 100 km (actual amount higher due to distribution losses and other considerations).
Burning gasoline generates 2.3 kg CO2 per litre. With a 40% bump of emissions for extraction, refining and transportation of the fuel (what seems to be a reasonable value based on many different values provided by many different sources) there would be 3.3 kg of CO2 per litre. And my hybrid is running 4.7 l/100 km combined city and highway use (in the city I am getting close to 4.2 l/100 km). So my hybrid use generates a total of 15.5 kg CO2/ 100km (only 14 kg/100 km in the city).
Another important consideration I had to make was that Alberta currently lacks decent electric vehicle plug-in locations for long distance travel (or for in city travel). And in Alberta most day-trips to destinations near the city of Calgary or Edmonton would be a round-trip that is well beyond 100 miles total distance (many local day-trips would be longer than 200 miles round-trip).
So the focus needs to be on vastly improving the elctricity generation in many regions. And vastly improving the infrastruction for plugging in when travelling outside of cities in many regions. That will take leadership that many regions are unlikely to have a clear majority vote to support. That may require external motivation on those regions to "Do Better than their population would prefer to do".
Electric cars might not emit CO2 when driven, and electricity from renewable sources can be used to recharge them, but how much CO2 is emitted in their manufacture? I have read elsewhere that there are significant emissions involved in the manufacture of an electric car.
Digby.
Most cars are considered to have an embodied energy content equal to severla years of driving. Electric cars would be no different. Whether electric cars particularly have a higher content, dunno.
The point hopefully is that as we transition to zero-carbon technologies, the production processes behind car (and everything else) manufacturing also become low/zero carbon.
A car that only works for you 87% of the time is not going to work for a lot of people. It certainly wouldn't work for my family. We use a pretty common strategy (I think) of one small, fuel-efficient vehicle and one larger vehicle with poor mileage. Can an electric replace either? No! It can't replace the Prius because range is critical for this vehicle as most of the miles come from road trips far beyond an electric's range. And it can't replace the truck because the entire purpose of the truck is to haul stuff.
The problem I see with electrics is that they leave a gap in a two-card household. If your other car is small and fuel efficient, you have no ability to haul. If your other car is heavy duty, you have no vehicle that can cheaply take you long distances. Additionally, if you are in a one-car household, an electric would leave you with both of these gaps rather than just one, as a non-electric would.
The 'power plant CO2' and 'manufacturing CO2' issues are both red herrings. Certainly we should continue to improve CO2 emissions in both areas, but even if we didn't neither would be a valid argument against electric vehicles.
As Glenn noted, manufacture of all cars involves CO2 emissions. The primary difference being that electric cars replace the internal combustion engine with a larger rechargeable battery pack. The primary source of CO2 emissions from car manufacture is due to the use of steel (commonly made by heating iron oxide and carbon, with CO2 as a byproduct)... and the internal combustion engine is a huge block of steel. Nothing in the electric vehicle battery pack comes close to requiring similar emissions. However, since many of the materials used in rechargeable batteries are currently mined in China, using coal power, the net emissions come out about the same (unless of course you get your steel from China too).
On power plants OPOF's rough estimate calcs above showed coal and natural gas powered EVs in roughly the same range as ICEs. More detailed studies are not far different... 100% coal powered EVs are towards the high end of ICE emissions, but for most of the world EVs get their power from sources that put them on par with the most fuel efficient ICEs and in places with high renewable energy generation there is just no comparison... EV emissions can be as much as two orders of magnitude less than ICEs.
However, the biggest reason that these comparisons are bunk is that they ignore the function of the EV battery. The more EVs are sold the more large rechargeable batteries there are connected to the electricity grid... and the more short term fluctuations in power (such as might be seen by wind and solar power) cease to matter. In short, EVs make wind and solar power more economically viable. Thus pushing the power industry towards cleaner power sources. An effect which completely dwarfs their manufacturing and operational emissions... even if those weren't already on par or better than ICE emissions.
CBDunkerson: How about some references and data? Sorry, but claims that EVs running on electicity generated predominantly from coal are comparable to ICE vehicles sounds like spin from a vested interest.
Where I live, almost all of our electricity comes from coal powered generators. In this case a hybrid vehicle makes more sense than an electric.
One Planet is correct that the generation mix where you live is important. While his example of Alberta generates more than 50% from Coal, Ontario generates most of its electricity from nuclear (~60%) and hydro-elecrtic (~24%), with a few natural gas peaking plants (~10%), which are intended to reduce occasional peak-use coal-generated imports from the US midwest. Solar and wind combined are bit players (~6%).
Digby's CO2 emissions of manufacturing (and recycling) are a red herring already dealt with.
Ogemaniac's example of two-car families is a large part of the problem in the first place, while the occasional need for greater range and/or cargo capacity is what car sharing and rental companies are designed to solve.
The fact is we're stuck with the infrastructure we have until we build it's replacement. If you are waiting for perfect you will be waiting forever.
What is missing is the affordable electric car. http://mtkass.blogspot.co.uk/2009/05/inexpensive-electric-car.html
As we transition to renewa le energy in our grids, less and less of the "EMBODIED ENERGY" of an electric car is from fossil fuel