This paper summarizes early usage of EV Project residential EVSE in households with Nissan LEAFs, based on data collected during Q4 2011 from 2,704 EVSE. A method of data aggregation was developed to summarize EVSE usage by the means of two metrics: charging availability and charging demand. Charging availability was plotted relative to time of day and day of the week to show the range of percentage of EVSE connected to a vehicle over time. Charging demand was plotted to show the range of charging demand of the EVSE on the electric gird over time. In general, residential EVSE charging availability is low during the day, steadily increases in the evening, and remains high at night. Charging availability, which is a function of when individuals connect their vehicles to their EVSE, is consistent across EV Project regions. Day-to-day variation in charging availability and charging demand on weekdays is high during Q4 2011, because user behavior on the weekdays surrounding Thanksgiving and Christmas varies from the other weekdays in the quarter. On the weekdays surrounding the holidays, charging availability was low at night and high during the day, similar to weekend charging availability. To ignore the effect of the holidays and compare common weekday and weekend user behavior, the charging availability IQR was used. The IQR is highest on weekends between 20:00 and 06:00, indicating that this is the period of greatest variation in user "plugging-in" behavior from day to day, excluding days close to or on holidays. When EVSE in all regions are examined in aggregate, demand peaks on weekdays and weekend days during the 00:00 hour. Weekday demand is lowest between 06:00 and 12:00, during which time it is nearly 0 kW per EVSE. In order to identify regional differences in charging demand, EVSE usage in two individual EV Project regions was examined. In Nashville, where EV Project participants do not have time-of-use electricity rates, demand increases each evening as charging availability increases, starting at about 16:00. Demand peaks in the 20:00 hour on weekdays. In San Francisco, the majority of EV Project participants have the option of choosing a special time-of-use rate plan from their electric utility. In this region, demand spikes at 00:00, which is the beginning of the off-peak electricity rate period. Demand peaks at 01:00. In both regions, demand on weekdays and weekend days drops to nearly 0 kW per EVSE between 05:00 and 06:00, even though charging availability does not begin to fall off until 06:00 or later. This suggests that the Nissan LEAFs being charged have sufficient time to fully charge during the night. Note that this is a function of how much the vehicles are driven prior to charging. This topic will be addressed in future works. In San Francisco, financial incentive provided by time-of-use rates appears to successfully shift charging demand to off-peak hours. This may benefit the electric utility by preventing an increase in peak system demand. However, a large number of users in this region schedule charging to begin immediately at midnight, which is the beginning of the off-peak period. This low diversity in charging start time creates an unintended demand spike at the beginning of the off-peak period. This may pose a different set of problems to the electric utility.
A first look at the impact of electric vehicle charging on the electric grid in the EV project
EVS, Electric Vehicle Symposium, 26 ; 736-747
2012
12 Seiten, 25 Bilder, 1 Tabelle, 6 Quellen
Aufsatz (Konferenz)
Englisch
Impact of Electric Vehicle Charging on Grid Energy Buffering
SAE Technical Papers | 2022
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