Structural Design of the mCCHP-RES System - Design for Micro-Combined Cooling, Heating and Power Systems - page 133

1.2 System Conceptual Scheme

The mCCHP system (Fig. 1 ) has as input the so-called residence energetic envi-
ronment, which has two sets of characteristics. The first set refers to the structure

and potential of the residence energy sources that are available at the place where
the residence is located. These could be the electrical and heat grid

— which are

secondary energy sources which

are primary energy sources (in particular renewable or nonrenewable they can be).
The second set refers to the potential energy exchange, which may occur naturally
between the residence and their environment.
As output, the system has the residence functional needs, which leads in a set of
residential functions (lighting, air conditioning, space heating, or food preparing,
for example) of that residents in using it to obtain residency-desired comfort. These
functions can be considered as characteristics of the residents living environment.
The mCCHP system is de

— or the sun, wood, thermal water, gas grid, etc., —

ned as energetic interface between the environment
in which the residence is located and the environment in which the occupants of
residence are living. In short, it uses the residence environment to create the living
environment. Above, the system is viewed as unitary item. If we look at it as a
structured element, three groups of components can be distinguished, as follows.
Firstly, the satisfaction of the residence functional needs requires energy in
various forms such as mechanical energy for lift, light energy for lighting, thermal
energy for DHW, cold for air conditioning, and so on. Under this forms, the energy
is obtained from the domestic equipments, which in terms of energy are consumers.
They provide various forms of energy, consuming energy in only two forms,
namely power and heat. The amount of energy that the consumers utilize them
during a time period (for instance 1 month) is called consumption.
Secondly, to power the group of consumers, the system should incorporate
another group of structural elements, called suppliers, which (a) by utilizing the
energy resources from the environment generates energy, and/or (b) by connecting
system to the energy grids exchanges energy (taking or giving up energy). The
amount of useful energy transmitted by suppliers, be it generators (prime movers)
or grids, during a period of time (for instance 1 month) in one way or another (i.e.,
to or from power and heat storages) is called load. It should notice that the suppliers
offer energy in only two forms, namely power and heat.
Thirdly, in every moment, the consumption and load should be equal. Because,
practically, this does not happen naturally, the consumption and load are continu-
ally monitored, and when their imbalance exceeds certain limits the control sub-
system intervenes to mitigate them. Due to the delayed reaction of the system
components, cult (or even impossible) when the

imbalances are minor (i.e., duration and/or magnitude of imbalances is small). This
is why, to mitigate minor imbalances, the system must incorporate two additional
structural elements, namely the power and heat storages. The higher the capacity of
these storages is, the longer can be the duration of imbalance between consumption
and load, and the greater may be the magnitude of imbalance (i.e., the minor

the mitigation becomes dif