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Another cut at US electric vehicle range requirements and usage patterns; fully-charged LEAF could handle 83-95% of all driving days
12 January 2012
|Cumulative distribution curve for daily driven distance by cars that were used on the Travel Day (representing 61% of all cars owned by the participating households). Data source: NHTS 2009. Click to enlarge.|
In an effort to calculate what percentage of daily trips in the US could be covered with a fully charged electric vehicle, two Columbia doctoral candidates recently conducted a statistical analysis using the National Household Travel Survey of 2009 on distances driven by the US population. They projected the results on typical range bins seen in the portfolio of electric cars that are available as of 2011.
The second part of their study, Assessment of Electric Cars’ Range Requirements and Usage Patterns based on Driving Behavior recorded in the National Household Travel Survey of 2009, covers car usage patterns on an hourly basis for weekdays and weekends, which are in turn used to assess when cars are connected to the grid and available for charging.
|Solar Journey USA project|
|This study was conducted as part of the Solar Journey USA project, an initiative to educate Americans about electric vehicles, solar energy and the synergy of Sustainable Driving that arises from the two.|
|In the summer of 2012, Rob van Haaren and Garrett Fitzgerald plan to make a cross-country trip powered strictly by solar energy, generated by a towed PV array. Each day, they will recharge the batteries in their electric car for the next leg of the trip, while giving presentations and workshops about the technologies.|
The National Household Travel Survey (NHTS) includes data from 150,147 households gathered between March 2008 and May 2009 on four levels: household, person, vehicle and travel day. The dataset was downloaded from the NHTS website and imported into SPSS 18 for analysis.
Among the top-level findings of the study are:
61% of all participating cars, SUVs, vans and pickup trucks were used on the Travel Day and they drove an average of 40 miles per day.
For individual trips (i.e., one-way), 95% are below 30 miles and 99% are below 70 miles. When driven distance is aggregated over the whole day, ~95% are below 120 miles and 99% are 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. Assuming the electric car is charged overnight only, a Nissan LEAF with a 62-138 mile range would be able to satisfy 83-95% of all travel days, depending on driving conditions as described before. A 2011 Tesla Roadster would be able to satisfy >98.5% of travel days, assuming a minimum range of 0.85 times the EPA-labeled range.
Vehicles owned by households in districts constrained by area—such as Hawaii and District of Columbia—were driven shorter distances than others (~24 miles per day, compared to a national average of 39.5 miles per day). 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 (up to 49 miles per day).
Perhaps the most important conclusion is that the majority of US 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?”—Rob van Haaren
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