Environmental Engineering Reference
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are stated as polynomial functions of the average power provided by each source
during a unit of time, implying the fact that the fuel cost functions are smooth
and quadratic in nature. Although also quadratic in nature, it is assumed the coef-
ficients for PHEV and CHP generation will be higher than those from the grid supply
point.
5.2.3 Energy loss
From an energy efficiency perspective in which losses are a necessary drawback for
active power transfer, it is conceivable for utilities to desire having the lowest amount
of energy losses as possible in order to enhance grid utilisation and meet incentives
from regulators. By reducing power losses, better voltage and pressure network pro-
files can be obtained, while simultaneously lowering advent contingencies. Along
these lines, the 'loss minimisation' operating strategy implies the TCOPF coordina-
tor dispatches both the control mechanisms and connected DER units in an effort to
reduce inefficiencies originated during the delivery of energy to consumers. There-
fore, in natural gas systems the objective function concentrates on reducing the
losses that are the product of the flow through a pipe multiplied by the pressure
drop between nodes. Meanwhile, the approach taken for the objective function in the
electrical counterpart reduces the losses that originate from the difference between
total generation and total load in the system.
5.2.4 Energy cost
Within an energy market context that regards as top priority the cost management
of PHEV and CHP resources, the proposed optimisation problem approaches the
day-ahead natural gas and electricity spot market prices to reduce total energy costs
incurred in the energy system. Hence, the TCOPF tool in its 'energy cost minimi-
sation' formulation allows the DER technologies to optimise their operation on a
purely economic basis as a function of time-dependent energy prices, dismissing
technical benefits as long as the infrastructures operate within boundaries. This fact
incentivises PHEVs to try and charge at moments during the day when electricity
is cheaper, regardless of the load conditions present in the system. Similarly, CHPs
would be keen to generate electricity if the price of the commodity merits such action,
even so if the thermal demand in the dwelling is not necessary. Therefore, the scalar-
valued objective functions for this optimisation algorithm consist of minimising the
energy spot market costs incurred from the different supply points in the service
networks.
5.2.5 Composite objectives
If a combination of two or more of the previous operating strategies becomes the
priority for stakeholders, the TCOPF formulation can implement a multi-objective
optimisation which can be stated as a weighted linear combination of individual
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