Environmental Engineering Reference
In-Depth Information
as long as the micro-CHPs are functioning they will also produce electrical power.
All micro-generators are assumed to be operating at a unity power factor or have their
power factor corrected to unit [96].
Based on the approach undertaken, the nodal capacities for boiler, cogeneration
and thermal storage devices are an aggregated quantity, which in turn are equivalent
to the sum of all individual units present in a particular node. Figure 4.14 shows
a schematic of the possible power injections and conversions involved in natural
gas node k with the final objective of satisfying the thermal power demand of this
specific node.
As seen from Figure 4.14, the thermal demand required by the end-users is
satisfied through a combination of flows from either conventional boilers or micro-
CHP devices with thermal store units. To successfully portray these power injections,
the modelling framework for thermal power conversion must establish basic princi-
ples and variables that will create coordinated interactions within the gas network
nodes. To simplify matters further, these nodal conversion equations are coherent
and easily adaptable to the basic gas load flow formulation explained in Chapter 3.
Taking Figure 4.14 as a reference, the set of nodal equations required to describe
the presence of cogeneration and thermal storage technologies in energy service
networks is developed using a control dispatch approach.
Thus, the total thermal power injections that supply the load required in gas node k
can be expressed as:
W chp
k
Dk
G grid
Dk
G chp
G boiler
Dk
=
+
·
(4.25)
The terms on the right-hand side of (4.25) represent the flows that will be con-
sumed either by the boilers or by the CHP units. Weight factor W chp takes binary
values ( i.e. 0 or 1 ) and serves the purpose of enabling the time intervals in which
it is possible to use the CHP technology. As it can be seen, the superscript of the
variables identify the elements that compose the total demand supplied from the
grid G grid
Dk
.
chp
P Gk
Electric
load
store
chp
G Dk
T DK
CHP
Storage
grid
G Dk
Gas
supply
store
T Gk
T G chp
Thermal
load
Σ
Boiler
total
boiler
boiler
G Dk
T Gk
T Dk
Figure 4.14
Representation of the possible power exchanges that a natural gas
node might have when embedded technologies are present
 
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