Civil Engineering Reference
In-Depth Information
1. The mathematical model of the system must be determined based on energetic
balances, where the main energy accumulations existent within the system are
considered, as follows:
(a)
the accumulation of electrical energy in a battery, through which the
power transfers are achieved;
(b)
the accumulation of thermal energy in a heat accumulation tank, through
which the thermal power transfer from the sources to the thermal con-
sumers is also achieved.
2. The principle applied in the process control consists in using the voltage of the
electrical energy accumulator and the temperature of the heat accumulation
tank, as values sensitive to the misbalance between the produced power and the
consumed one. In the case of both accumulations, if the power produced is less
than the consumed one, then the electrical/thermal potential decreases and vice
versa. The control system must maintain at constant (nominal) values the
capacities through which the electrical/thermal potential (voltage and temper-
ature) are evaluated, by adjusting the produced power. Thus, the equilibrium
between production and consumption is achieved.
3. The dynamic components of the system
'
s global model are generated by:
(a)
the energetic mass-balance equations, at the level of the two accumulators
mentioned before,
(b)
the models of the control subsystems, and
(c)
the simpli
ed models of the dynamics of those energy sources which have
their own control system (such as the Stirling engine or the pellet boiler).
4. For some sources, such as the solar thermal collector or photovoltaic system, as
well as for the thermal and electrical consumers, steady-state models can be
used.
5. As models of the solar collector and photovoltaic system, the diurnal power
graphs are adopted representing the powers delivered by these sources when
they are located in the residence site. The graphs are built based on the sta-
tistical data regarding the site.
6. The diurnal power graphs (built on the basis of some plausible hypothesis
regarding the consumption requirements over a 24 h interval at a residential
level) are used as models of the electrical load components and of some of the
thermal load components (such as the power consumed for heating the
domestic water).
7. The electrical load has two components: the load used at the residential level
and the load generated by the own consumption of mCCHP system equipments
(such as pumps, ventilators etc.).
8. Designing the mCCHP system and analyzing its dynamic performances must
be carried out in two distinct operating regimes: in winter regime, when the
thermal energy is mainly used for heating the residence, and in summer regime,
when the dominant thermal load is the air conditioning system. The thermal
load in both operating regimes is designed in steady-state regime, but also for
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