Environmental Engineering Reference
In-Depth Information
hr
total
nβ
P
phev
Gk
,
β
V
2
G
store
k
,
β
W
store
V
2
Gk
,
β
=
·
·
(4.53)
hr
total
nβ
M
phev
Gk
,
β
V
2
R
store
k
,
β
=
·
(4.54)
Similar to variable
W
phev
k
, weight factors
W
store
G
2
V
and
W
store
V
2
G
are dispatch factors
that can take either values of 0 or 1, serving the purpose of enabling the time inter-
vals in which it is possible to charge or discharge the storage systems. Although it
must be noted that no weight factor exists for transport purposes since drivers will not
be constrained from using their vehicles at any moment. Expressions (4.52)-(4.54)
when combined are related to (4.51), thus allowing us to determine the variation
occurring in the SOC of the units for each time interval.
The utility factor (UF) measures the amount of energy employed for travelling
purposes when compared to the total energy capacity available; for node
k
it can be
expressed as:
nβ
V
2
R
store
k
,
β
EVSOC
store
k
,
max
UF
phev
=
(4.55)
β
=
1
where
EVSOC
store
k
,
max
represents the maximum storage capacity in node
k
.
The value the UF variable establishes is relevant since it quantifies how much
energy is consumed by the vehicles. If this data is analysed and forecasting tools
developed then it can start allowing utilities and other stakeholders to estimate the
amount of energy PHEVs will require, while also influencing the V2G capacity
dispatchable for ancillary services.
As a consequence, the UF indicator can help begin describing the allocated
proportion of a fully charged battery for V2G services is the ancillary-to-transport
ratio (
ATR
), defined for a group of batteries being assessed as:
nβ
V
2
G
store
k
,
β
EVSOC
store
k
,
max
ATR
phev
=
1
−
UF
phev
=
(4.56)
β
=
1
Naturally, the electrical power available to discharge from the storage units is
closely related to the efficiency of the battery system. So, for all the electrical power
stored in a battery, the power available to discharge will rely on the power electronics
and electrical motor characteristics. Since the batteries have the purpose of meeting
daily travelling energy requirements, it can be assumed that the discharging capa-
bility for a fleet of vehicles will be closely related to the energy they charge during
the day; this concept is related to the storage balance equation (4.49) and can be
defined as:
nβ
V
2
G
store
k
,
β
η
V
2
G
nβ
V
2
R
store
k
,
β
η
V
2
R
G
2
V
store
k
,
β
η
G
2
V
·
=
+
(4.57)
β
=
1
β
=
1
This concludes the formulation of the PHEV energy storage framework for the
TCOPF modelling tool. From this methodology it is clear that the presence of PHEV
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