Theory/How far do we drive?/8. Conclusions

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The electric car adds a new feature to the list of car specifications: ‘Driving Range’. The fear of getting stranded on the side of the road with an empty battery (Range Anxiety) presents a roadblock for future buyers, and several surveys have shown that the large majority of people want a driving range far beyond what most electric cars are capable of, but also far beyond the average distance they drive. People demand freedom and comfort, so that they can go wherever they want, whenever they want.

The cause of this is the relatively low energy density and high price of EV batteries, which limit car manufacturers to build affordable electric cars with a high range. Until battery prices come down, range anxiety remains a major hurdle for buyers.

Range anxiety is especially problematic because the range of an electric car is greatly affected by driving velocity, aggressive driving, as well as the use of climate control. Actual range may be ±40% of the displayed range by the manufacturer (Nissan, 2011). The use of different drive cycles allows for the derivation of multiple energy consumption figures and range estimates, but these are not communicated to the public; instead, a single number is used. The inclusion of a ‘±x miles’ metric in the EV driving range specifications and more education on this topic are strongly recommended in the implementation process of Electric Vehicles.

Plug-in Hybrid Electric Vehicles (PHEV) do not have this problem, as they allow the driver to get more acquainted with the concept of electric driving, while having the comfort of ‘unlimited range’.

This study attempted to give more insights into the distance people (or: vehicles) drive, using the National Household Travel Survey of 2009. From this resourceful dataset, it was found that 61% of all participating cars, SUVs, vans and pickup trucks were used on the Travel Day. For individual trips, 95% is below 30 miles and 99% is below 70 miles. When driven distance is aggregated over the whole day, it is found that ~95% is below 120 miles and 99% is below 250 miles. Car commuting distances were found to average 12.6 miles nationally, with 95% below 40 miles and 99% shorter than 60 miles.

Great variation was found over all States. Vehicles owned by households in districts constraint by area like Hawaii and District of Columbia were found to be driven shorter distances than others. On the other hand, States with primarily rural areas and a large fraction of the population living in single dwellings or small towns (typically in the Midwest) averaged higher driven distances.

Perhaps the most important conclusion is that the majority of U.S. households have the luxury to simply pick their gasoline car in case they plan on a long trip. 64% of households that own one or more cars have the luxury of owning a gasoline car besides their future EV (assuming the EV replaces a gasoline car). Think of it as owning both a two-seater and a sedan: would you choose the two-seater if you’re picking up three friends to go watch the football game? We’ve seen that 39% of all cars are not even used on the Travel Day. This gives rise to a new research question: ‘From all cars owned by members of a household, how many vehicles drive beyond a distance of x miles on the Travel Day?’

Car usage patterns were also derived from the NHTS dataset. The percentage of cars parked during the day was found to differ between weekdays and weekends, with a minimum of 93% (5pm) and 94% (11am-12pm), respectively. The results presented in this paper can be useful to grid operators in assessing additional load from EVs connected to their system. Together with the distribution of driven distances, charging patterns can be derived and applied to models of future load scenarios in electric grid systems. Population density maps can be used to derive the locations of this additional demand in the grid. All data is made available for download from the website. Also, requests for State-specific data or other inquiries can be sent to rv2216@columbia.edu.

 

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According to Nissan, their LEAF has a range of 100 miles, but different scenarios yield a range of 62-138 miles (Paragraph  4.1).

 

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