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| Fig. 1: Comparative upfront costs of purchasing a conventional vehicle vs. a standard electric vehicle depending on the price of lithium ion batteries. [1-7] |
Battery electric vehicles (BEVs) are seen as the future of the automobile industry due to their potential to free the United States from foreign oil, their more efficient engines, and the possibility of reducing greenhouse gas emissions. However, their high costs associated with the lithium-ion batteries are currently prohibiting many middle-class consumers from making the switch. The purpose of this paper is to investigate the energy usage and emissions associated with BEVs, the economics behind electric vehicles, and what must be done for them to make a significant impact on the vehicle fleet.
The average car in the United States drives approximately 15,000 miles per year with a fuel efficiency of 22.6 miles per gallon. [1] While using averages skew the precise number slightly, we can arrive at a ballpark estimation that each car uses an average of 663 gallons of gas a year. Using this estimation and a conversion factor of 130 MJ per gallon of gasoline, we can approximate that an average vehicle burns 86.3 GJ of gasoline every year.
For the sake of comparison, we must define some sort of electric vehicle to compare to the average combustion engine vehicle. With the recent news that Automobile Magazine plans to name the Tesla Model S as the Car of the Year, it seems appropriate that we choose this wonderfully engineered, albeit rather expensive car to represent the future of the electric vehicle fleet. [2] In order to calculate the amount of energy needed to run the Model S for an entire year, we must arrive at an accurate miles per kilowatt-hour (kWh) efficiency for the battery. While theoretical literature and Tesla both claim to travel 4 miles per kWh, recent testing by the EPA reported an average driving range of 265 miles for the 85 kWh premium version. [3] To be on the safe side, lets assume the car uses a kWh for every 3.11 miles, which would amount to 4,823 kWh of electricity being consumed by the car in a given year. Taking into account that only 86% of the energy supplied by the wall turns into usable electricity for the battery, the car would actually consume 5608 kWh of energy per year. [4] Using the conversion factor of 3.6 MJ per kWh, the Model S would use 20.2 GJ per year, or essentially four times less energy than the conventional vehicle.
While the energy used by the electric vehicle itself is four times lower than its gasoline-powered counterpart, we must take into account how much raw material is needed to create this energy. From the oil standpoint, the well-to-take efficiency of gasoline is somewhere between 80% and 82% depending upon the source you trust. [4] A simple conversion reveals that a conventional car uses 106.5 GJ of gasoline every year.
Electricity on the other hand, suffers from a much less efficient process while converting raw coal and natural gas into power for the grid. On average, only 44.2% of the raw energy in coal is converted into useful electric energy, while natural gas is only slightly better at 52.5%. [4] Assuming an electricity mixture with 50% conversion efficiency, 40.4 GJ of coal and natural gas is needed to support an electric vehicle for an entire year.
Using these new, more accurate numbers, conventional vehicles have a well-to-wheels efficiency that is still 2.63 times worse than the Model S. Even after we take into account that coal produces more greenhouse gases per GJ than gasoline (~30%), the substantial decrease in raw energy needed to run a BEV would result in a significantly less emissions from the vehicle.
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| Fig. 2: Comparative 8 year costs of upfront costs plus fuel costs for a conventional vehicle vs. a standard electric vehicle depending on the price of batteries. [1-7] |
The three main components of cost for a vehicle are the initial purchase price, the price for fuel, and the maintenance costs. Assuming maintenance to be the same for both vehicles, lets first look at the upfront costs of the two types of vehicles. In 2009, the electric motor and other internal controls were estimated to cost $2,600 more than conventional gasoline components. [5] While $2,600 is nothing to scoff at, it pales in comparison to the additional cost due to the lithium ion battery inside electric cars. A recent McKinsey & Co. study found that current batteries cost between $500 and $600 per kWh. [6] Taking an average of $550 means the battery in the baseline Tesla Model S (40 kWh) costs $22,000, a number that nearly doubles the price of electric vehicles in comparison to conventional gasoline-run cars.
As we turn to the fuel cost of the cars, we find that the average price of gasoline spiked at a national average of $3.79 on October 6, 2012. [7] Extrapolating this price to the entire year, the average car can expect to pay $2,513 a year for gasoline. Similarly, the current cost of electricity in the United States is $0.12/kWh which would extrapolate to a yearly fuel cost of $673 to drive an electric vehicle. Over the 8 year guaranteed lifetime of a battery, assuming these prices are good enough indictors of the future, driving an electric car would save the consumer $14,720 in fuel costs.
Looking at the two graphs to the left which were formulated using the numbers calculated above, it is clear that the initial costs for electric vehicles will remain significantly higher for years to come. However, it can also be seen that the vehicles have the potential to be cheaper alternatives over the lifetime of the car as lithium ion battery technology is developed further. The same McKinsey study that predicted current batteries cost ~$550 per kWh predicted that the price of batteries should fall below $250 by the year 2020. [6] Fortunately, the price at which electric vehicles become cheaper over the 8-year battery lifetime is $260, and that is without taking into account the unavoidable rise of gas prices over the next decade.
These numbers suggest that there could be a time in the next decade where it becomes economically advantageous to purchase a battery electric vehicle in lieu of the conventional combustion engine car. The numbers become even more advantageous when you consider the United States currently offers a $7,500 subsidy for any electric vehicle purchase.
In conclusion, this scenario paints a very optimistic picture for the short-term and long-term growth of electric vehicles both economically and emissions-wise. However, there are still momentous obstacles to overcome in the coming years both with adding enough electric capacity to power the vehicles, and to get over the "range anxiety" associated with electric vehicles. While it is outside the scope of this paper, there has been promising research done that suggests the capacity problem may be partially mitigated by regulated charging schedules and vehicle-to-grid capabilities which would allow power plants more flexibility when electric cars are plugged into the grid. [8] As far as range anxiety is concerned, the 40KWh battery in the Tesla Model S would support at least a 123 mile range which would encompass at least 95% of all one way car trips. [9]
While it is not a given that electric vehicles will take over in the next decade, there is considerable evidence suggesting that they will be a major player in the future of the vehicle market.
© Lucas Prokopiak, the author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 Through 2011 - Executive Summary," U.S. Environmental Protection Agency, EPA-420-S-12-001a, March 2012.
[2] P. Valdes-Dapena, Automobile Magazine Names Tesla Model S 'Car of the Year'," CNN Money, 1 Nov 12.
[3] B. Kong, "Topline 300-Mile Tesla Model S Projected to Earn 265-Mile EPA Range," Motor Trend, 14 May 12.
[4] S. Campanari, G. Manzolini and F. G de la Iglesia, "Energy Analysis of Electric Vehicles Using Batteries or Fuel Cells Through Well-to-Wheel Driving Cycle Simulations," J. Power Sources 186, 464 (2009).
[5] M. Werber, M. Fischer and P. V. Schwartz, "Batteries: Lower Cost Than Gasoline?" Energy Policy 37, 2465 (2009).
[6] R. Hensley, J. Newman and M. Rogers, "Battery Technology Charges Ahead," McKinsey Quarterly, July 2012.
[7] G. Flaccus, "Calif. Gas Prices Spike at $5 Per Gallon," USA Today, 6 Oct 12.
[8] K. Clement-Nyns, E. Haesen and J. Driesen, "The Impact of Vehicle-to-Grid on the Distribution Grid," Electric Power Systems Research 81, 185 (2011).
[9] R. Van Haaren, "Assessment of Electric Car Range Requirements and Usage Patterns based on Driving Behavior Recorded in the National Household Travel Survey of 2009," Solar Journey USA, December 2011.