Environmental Engineering Reference
In-Depth Information
The electrical power generated whenever cogeneration units are dispatched is a
slight variation of (4.20), and can be detailed as:
η
el
W
chp
k
Dk
P
chp
Gk
G
chp
=
·
(4.26)
where
η
el
represents the CHP electric power conversion efficiency.
Similarly, the thermal power obtained from conventional boilers in node
k
is
defined as:
T
boiler
Gk
G
boiler
Dk
=
η
b
·
(4.27)
where
η
b
represents the boiler conversion efficiency.
In this formulation it is key to establish the terms that help to state what por-
tion of the thermal power produced through CHPs flows into the thermal stores and
what amount is consumed instantaneously. The values for these variables are deter-
mined by the TCOPF optimal solver according to the specified objective function (see
Chapter 5).
Possible cogeneration thermal flow outputs within node
k
are represented by
symbol
T
(
i.e.
after being processed by CHPs); these are expressed as:
η
th
W
chp
Dk
+
W
store
k
Dk
=
T
chp
Gk
G
chp
T
store
·
·
(4.28)
k
where
T
store
Dk
represents the thermal power injection that is stored.
Subsequently, the total thermal load required by the end-users can be satisfied in
node
k
by coordinating all possible thermal flow sources, stated as:
T
total
Dk
+
W
store
k
Gk
T
chp
Gk
T
boiler
Gk
T
store
=
+
·
(4.29)
where
T
store
Gk
is the thermal power injection that is discharged from the storage system.
Equation (4.29) guarantees that the total thermal power obtained from burning
the natural gas at predefined efficiencies, through either the boiler or cogeneration
units plus the thermal storage discharge, will entirely satisfy the load demand in
node
k
at each time interval.
4.3.3 Thermal energy storage management equations
Nowadays, three types of TES systems are commonly applied for either domestic or
commercial purposes; these technologies include:
Sensible TES;
●
Latent TES;
●
Thermo-chemical TES.
●
The storage system employed for a particular application depends on many
factors such as operating conditions, investment costs and storage period required
(
i.e.
daily or seasonal) [87]. However, for this particular research, sensible TES is
used due to its proven features for domestic and commercial applications.
For an individual system, the capacity to store energy by a sensible TES unit
is directly proportional to the temperature difference between the input and output
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