Environmental Engineering Reference
In-Depth Information
The maximum nodal electric and thermal power capacity provided by CHP
units, as well as the energy required to charge and discharge the fleet of PHEV
units, are predetermined and dependent on the degree of penetration at each
node;
●
Although the owners of DER technologies are not able to completely con-
trol the operation of their devices, they do have the freedom to establish the
moments at which the PHEV battery or thermal stores must be fully charged
(
e.g.
7 a.m.).
●
5.2
TCOPF objective functions
Although there are a number of reasonable objective functions that can be formu-
lated to optimise the operation of energy utilities, this work mainly focuses on
assessing the techno-economical impacts embedded technologies can have on the
optimal operation of energy service networks when applying different operating
strategies.
5.2.1 Plug and forget
If it is assumed that, as generally occurs with new technologies, no proper monitor-
ing efforts are done on PHEV and CHP devices, let alone any load control strategies;
the DNOs will just concentrate on supervising that the technical conditions of its
assets are met. This implies DNOs will not bother using their control devices unless it
is absolutely necessary. Based on these premises, this operating strategy (
i.e.
business
as usual) is labelled the 'plug-and-forget' formulation. Accordingly, the conditions
for this problem consist in minimising the use of control mechanisms, while always
supplying the demand in each node and guaranteeing all operational boundaries are
met. Hence, in natural gas networks the objective is to minimise the compressor gas
consumption, while for electrical networks the tap magnitude being as close as possi-
ble to a fixed value is the goal. The approach taken sums the behaviour of these control
devices, both stated as scalar-valued functions. Henceforth, the operating patterns of
DER units solely follow the instructions set by their users, which in modelling terms
refers to the nodal weight factors of the technologies.
5.2.2 Fuel cost
Fuel cost minimisation, popularly referred to as economic dispatch, is probably the
most common optimisation target regarding the operation of energy systems. The
classical approach consists of dispatching thermal units based on their costs which
are modelled as quadratic functions of the generated power. Therefore, within the
framework of the TCOPF tool, the aim of the objective function consists of the eco-
nomic dispatch of the grid supply points and DER units that can contribute with power
generation, such that the total fuel cost is minimised while satisfying operational
feasibility constraints. In this work, the fuel costs to deliver the energy requested
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