Environmental Engineering Reference
In-Depth Information
600
120
Heat
Power
500
100
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80
300
60
200
40
100
20
0
24
0
0
4
8
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Ti
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Figure 4.13
Aggregate thermal and electricity demands from 50 dwellings in the
UK on a weekday in January [192]
as a negative load in the electrical network, while simultaneously being a positive
load in the gas network. As a consequence, these power fluctuations modify the net
electric and thermal power demands seen by DNOs from their grid supply points.
In order to portray this type of behaviour, both infrastructures need to include several
terms into each nodal balance equation wherever these units are under considera-
tion. Therefore, this section details the set of nodal terms required to describe the
presence of cogeneration units with thermal storage capabilities in energy service
networks.
It is necessary to stress that with respect to TES systems, the equations detailed
here build upon sensible thermal storage theory, a proven and mature field that
focuses on satisfying short-period thermal demands, as depicted by systems such
as the one in Figure 4.12 (
i.e.
daily hot water and space heating demand), and
thus suitable for the granular simulation requirements of the TCOPF modelling
framework [87].
From the perspective of natural gas networks, all load nodes must transform the
fluid supplied into thermal power to satisfy the required demands of the end-users.
For this, it is assumed that for any node the incoming gas stream can be processed
by either a conventional boiler or a cogeneration unit. In case the boiler processes
the natural gas, it will immediately contribute to satisfy the thermal load. However,
in contrast the micro-CHP needs to decide if its thermal power production will be
stored or used at that instant of time. Naturally, the efficiency and capacity with
which the CHP burns the gas will rely on both the features of the unit and efficiency
equations (4.20)-(4.23) described in the previous subsection, while the proportion
of the technology employed within a node depends on the degree of cogeneration
and thermal storage penetration. The penetration level is defined as the percentage of
dwellings with generators connected, as expressed by term (4.24). Needless to say,
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