Modelling embedded technologies in energy service networks - Modelling Distributed Energy Resources in Energy Service Networks - page 59

The operating ratio of the compressor at node k is denoted as:
p k 2 − R com p k 1 =

·

0 (4.19)

k

Equation (4.19) specifies the compressor ratio, thus limiting the capacity of
increasing the pressure level; this variable is analogous to the tap magnitude variable
in electrical networks.
After these modelling equations are introduced into the TCOPF framework,
wherever compressors are located, it will help to identify their level of influence
in regulating pressure levels. For example in a study with a high presence of CHP
units it can be interesting to evaluate the role compressor stations have in guaran-
teeing adequate gas supply. An efficient coordination between natural gas-fuelled
distributed sources and compressor controllers must be carefully engineered for the
benefit of this particular infrastructure.

4.3 Modelling CHP technologies

4.3.1 Fundamentals of combined heat and power units
Nowadays the conventional manner to satisfy electrical and thermal power demands is
to purchase electricity from the local grid and obtain heat by burning fuel in a boiler.
Yet, a considerable saving in fuel consumption can usually be achieved if a CHP
scheme is applied. Cogeneration or combined heat and power refers to 'the process
where there is a simultaneous provision of usable heat and electrical power at high
efficiencies and near the consumption point [76].' This increase in energy generation
efficiency can result in a reduction of greenhouse gas emissions when compared to
conventional methods of generating electricity and heat separately.
For electrical and natural gas DNOs, some possible consequences they might
face for having cogeneration units embedded in their infrastructures include [186]:

Increasing protection schemes and security of supply;

●

Altering natural gas and electricity delivery costs;

●

Reducing electrical delivery losses;

●

Increasing natural gas delivery losses;

●

Applying closer monitoring of operating variables ( e.g. voltage and pressure).

●

Cogeneration systems can cover a broad range of capacities, applications, fuels
and technologies. In its simplest form, it employs a combustion engine to drive an
alternator and the resulting electricity can be used either entirely or partially on-site.
The heat produced during electricity generation is recovered, usually in a heat-recovery
boiler and can be used to raise steam for a number of purposes, such as water and
space heating.
Today, several conversion technologies can transform the chemical energy stored
within a fuel and offer cogeneration services. Cogenerator types include recipro-
cating engines, gas and micro-turbines, Stirling engines and fuel cells. Figure 4.7
outlines the conversion steps of the main CHP technologies either currently available