At least two aspects should be cons

At least two aspects should be considered to model an EV
aggregator. First, since the principal utility of vehicles lies in
their availability to provide transportation to its owners, the
EVs may not always be plugged into the grid. Second, the energy
stored in the EVs plugged into the aggregator and available
for the EV service provision is variable and depends on the
distance travelled during the day. These aspects should be
properly represented in the aggregator model. Moreover, since
the power the EV aggregator can provide for unidirectional
service depends on factors such as type of batteries, size,
number and type of vehicles, EV state (driving pattern),
charge/discharge rate of the battery [9], the definition of these
is also necessary for the modeling. All these factors are affected
by uncertainty (e.g., the EV state, which depends on the
driving pattern) or by variability (e.g., the type of vehicle,
which could be “non plug-in”, or “plug-in charge-only”, or
“plug-in charge/discharge”)