Optimising DERs in energy service networks: a case study - Modelling Distributed Energy Resources in Energy Service Networks - page 113

Case 3 : Represents the plug-and-forget scenario in which PHEVs charge in a
'delayed' manner (refer to subsection 4.4.1) while the CHPs operate under a
heat-led strategy;

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Case 4 : Represents the fuel cost minimisation strategy that aims to reduce the
costs of supplying power to customers; here PHEVs are free to charge whenever
it is convenient while CHPs operate under a heat-led strategy;

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Case 5 : Represents the energy loss minimisation scenario in the networks; here
DER technologies have no operating time constraints and operate whenever it is
convenient while respecting their constraints;

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Case 6 : Represents the energy cost minimisation strategy that recreates the con-
ditions for all assets in the energy system to operate according to spot market
prices; here DERs operate freely during the day as well;

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Case 7 : Represents the scenario in which both costs from spot market prices
and carbon emissions wish to be reduced ( i.e. composite objective minimisation),
thus linking the coordination of DERs with the real-time conditions of the grid.

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Overall, cases 2-4 have the intention to illustrate the impact a conventional
approach into the use of embedded technologies can have on the networks; in other
words these cases intend to show how the service networks and DER technologies
would perform if there is a lack of incentives to maximise holistic benefits. Mean-
while, cases 5-7 have a more ambitious approach than the previous scenarios since
they intend to maximise the efficiency of the whole energy system either technically
or financially.
To complement the operating conditions of DER technologies, it is important
to stress some key charging constraints concerning the storage facilities applied for
cases 2-7. For these scenarios, it is expected that the state of charge (SOC) of PHEV
units are at their maximum levels by 7 a.m., while thermal storage systems are fully
charged by 4 p.m. Furthermore, unlike CHP and PHEV power injections, which in
some time periods are not permitted, the thermal storage operation is not constrained
and is always functional throughout the day ( i.e. 48 time intervals). Figure 6.4 details
the natural gas and electricity day-ahead spot market prices employed to calculate
energy costs [93]. Finally, in case 7 the cost for emitting carbon due to electrical
generation is priced at £30 tCO 2 / MWh; this cost was taken from the peak oil prices
of summer 2008 [221].
Although the UK is committed to have by 2020 a 15% of its power generation
portfolio from renewable sources, currently its main sources ( i.e. natural gas and
coal) have a high carbon footprint that if not displaced soon will threaten its car-
bon mitigation targets [222]. Table 6.3 describes the carbon emission ratios for the
technologies present in the UK as well as their average share in the fuel mix [223].
Figure 6.5 illustrates the carbon emissions being generated in the UK on a typi-
cal winter weekday in 2010. On the other hand, natural gas combustion releases
approximately 184 kgCO 2 / MWh.
To complement the input data of the case studies, it is required to specify
some parameters that detail the characteristics of the energy system being analysed.
Accordingly, the techno-economical parameters for service networks and embedded