This study collected electric demand, energy consumption, and activity data from March 2013 to February 2018 from 50 electric vehicle charging stations owned and operated by the Alameda County General Services Agency. Researchers analyzed each charging session to determine: (1) arrival and departure times; (2) duration of plug-in and charging; (3) total number of charging sessions; and (4) charging load flexibility. The analysis also covered the power pattern of the entire facility during this period and evaluated and quantified the effect of smart charging control systems on utility bills.
Based on this analysis, the researchers developed a set of smart charging frameworks to manage charging demand for fleet and non-fleet electric vehicles that use Alameda County’s publicly available charging stations. For public electric vehicles, implementing these frameworks reduced the peak electricity demand during the peak time of 8 a.m. to 11 a.m. from 24.2 kilowatts (kW) to 10.0 kW. The aggregated charging power of all the public charging stations decreased by 12.0 kW, which was 26.7 percent of the original uncontrolled peak demand. For fleet electric vehicles, the smart charging frameworks reduced peak demand during the on- and mid-peak periods by 10.7 kW and 13.3 kW respectively in a week during the summer. For direct current fast charging vehicles, the maximum power reduction was 20 kW, which was nearly half of the direct current fast charging power in the normal mode. The median value of the power reductions was 4.3 kW, which is equal to the kW shed from one active charging session. Researchers also quantified the potential for the aggregated fleet of electric vehicles to participate in multiple demand response products in the California retail and wholesale electricity markets.
