Structural Design of the mCCHP-RES System - Design for Micro-Combined Cooling, Heating and Power Systems - page 154

require no additional land use. While most of the free- eld installations tend to be

larger installations of centralized character, the building integrated PV/ST instal-
lations can be characterized as decentralized installations systems. They are ideally
positioned where are unshaded throughout the year and with an orientation towards
the South.
Unlike the free- eld installations, the building integrated PV/ST panels have

limitations regarding the use of the building surfaces (be they roofs or fa ades).

These are limits to the physical nature (caused by the fact that some areas of the
roof and the facade are shaded, i.e., the north facade of the building) and the
architectural nature (from the fact that the roof and facades have architectural
elements such as windows that do not allow the placement of the panels).
In order to assess the solar energy potential either of building or of panels as well
as to express the physical or architectural limitations, we de

ç

ne the utilization
factor, k, as the ratio between area of panels that convert solar energy (be it A PV ,
A ST ,orA panels = A PV + A ST ) and ground oor area (A GFA ). Notations k and A are

completed with indices, depending on the type of panels (PV panels or ST panels),
and their location [on the roof, (r), or fa ades, (f)], as shown in the Table 4 ).

The physical and architectural limitation is given by the methodology of the
International Energy Agency Photovoltaic Power Systems Programme and can be
synthesized with a simple rule of thumb: for every m 2 of building area ground
floor, there is on average 0.4 m 2 of rooftop area and 0.15 m 2 of fa ç ade area with
good solar potential. With the notations mentioned above,

ç

the limitations are

expressed as follows:

k r k f 0 : 4 0 : 15 ð 5 Þ

Both limits do not contain restrictions on (a) the type of panels placed (i.e. PV
panels or panels ST) considering that k = k PV + k ST , or (b) the type of surface on
which they are placed (i.e., roofs or facades), considering that k = k r + k f .
On the other hand, the solar suitability takes into account the relative amount of
irradiation for the surfaces depending on their orientation, inclination, and location
as well as the potential performance of the photovoltaic system integrated in the
building. A solar yield (Y) for building is understood as 80 % of the

maximum local annual solar input, separately de

“ good ”

ned for slope roofs and fa ç ades

and individually for each location.

Table 4 Utilization factor for buildings
Panels area Roof Fa ç ade Roof and fa ç ade

k r PV ¼ A r PV = A GFA PV panels,

A PV ¼ A ð r Þ
PV

k f PV ¼ A f PV = k PV ¼ k r PV þ k f PV A GFA

A ð f Þ
PV

þ

k r ST ¼ A r ST = A GFA ST panels,

A ST ¼ A ð r Þ
PV

k f ST ¼ A f ST = A GFA k ST ¼ k r ST þ k f ST

A ð f Þ
PV

þ

k r

¼ k r PV þ k r ST

PV and ST panels,
A pannels ¼ A PV þ A ST

k f

¼ k f PV þ k f ST

k ¼ k PV þ k ST or k ¼ k r þ k f