IEEE Power & Energy Magazine - July/August 2021 - 18

Charging flexibility reaches a peak in the evening, which
is advantageous because it aligns with the times when
smart charging may become necessary.
Trial participants had a wide range of vehicles, with battery
capacities from 4.4 to 100 kWh. The trial cohort was
split between two providers of smart charging: CrowdCharge
and GreenFlux, with 328 and 345 participants, respectively.
Figure 2 shows the composition of the two cohorts by battery
capacity.
The impact of battery capacity on various metrics (the
charging frequency, estimated state of charge at plug in, flexibility,
attitude toward smart charging, and so on) were analyzed
within the final report. The demographics of the trial
participants (see Figure 3) were strongly influenced by the
demographics of those in a position to buy or lease an EV at
the time of the trial.
Table 1 summarizes the four trial stages. CrowdCharge
and GreenFlux developed different apps that were used in
trials 2 and 3:
✔ CrowdCharge: The participants could enter journey
plans into the app in the form of a schedule (journey
distance and departure time). They were also asked to
enter the vehicle's state of charge into the app when they
plugged in. The CrowdCharge system prioritized the
charging sessions with earlier departure times or higher
energy requirements. In trial 3, the system utilized the
schedules to attempt to use the cheapest energy possible.
For example, if a driver had entered a journey plan that
showed that the vehicle was not needed again until the
next morning, its charging would take place overnight,
when the lowest price applied. If no instructions were
given, the vehicle would charge up regardless of the tariff
(including during the peak period).
✔ GreenFlux: From trial 2 onward, a high-priority button
was available in the app when a charge session was active.
The GreenFlux system allocated current to all of the
charging events where high priority had been requested
first. The remaining current was then allocated to all
the other charging sessions. Due to the amount of current
available and the relatively low usage of the highpriority
feature, it effectively functioned as an opt-out
system. The app functionality was extended in trial 3 to
offer the participants three charging preferences, which
set the times at which their home charger would operate,
for example, pausing the charging in the period between
4:30 p.m. and 10 p.m., when the price was high. Once
the user had selected a charging preference, it applied to
all the charging sessions using their smart charger.
During the trial, 150,105 charging events were recorded
with meter values equivalent to 1.2 million h. These data reveal
a great deal about the charging behavior of the participants:
how often they charge, how much energy
is taken, how much flexibility is available,
and so forth. The volume of data and diversity
of the participants in terms of vehicle
type and battery size allow this behavior to
be disaggregated by these characteristics.
Customer research was also a key
element of Electric Nation and enabled
the project to understand the participants'
responses to the demand management
they experienced, the use of the
apps, and charging incentives. The participants
completed surveys before they
experienced smart charging, at the end of
each trial they took part in, and at the end
of the project in December 2018. Also, a
small number of participants engaged in
focus group discussions.
figure 1. Western Power Distribution's license areas (green shading, southwest
of England, South Wales, and the East and West Midlands) and Electric
Nation participants (red dots).
18
ieee power & energy magazine
Overview of Domestic
Charging Behavior
An understanding of charging behavior
is crucial in determining both the need
july/august 2021
IEEE Power & Energy Magazine - July/August 2021

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