Environmental Engineering Reference
In-Depth Information
5.4 Planning and Design
5.4.1 Planned on the Grid
The fi rst thing to do when planning a solar system is to check whether a system can
even be installed. From the standpoint of planning laws, solar systems are structural
items - even if they are simply screwed to the roof of a house. The authority respon-
sible for local building regulations determines whether approval is necessary, and,
if so, what type of approval. In most cases photovoltaic systems do not need
approval from the local authority unless they are erected in the middle of a green
fi eld. Complications arise when the sites for such systems are subject to architectural
conservation laws. A permit from the relevant authority is required if a solar system
is to be installed on top of or near a protected building. In addition to obtaining
planning permission, it is always a good idea to consult the building regulations
and the development plans of the local authority. These plans will include any
conditions that the local authority has stipulated for the construction of photovoltaic
systems.
If there are no legal obstacles, the planning phase can start. If a photovoltaic system
is to be installed on the roof of a house, it fi rst needs to be determined which parts
of the roof can be used for a solar-thermal system (see Chapter 6). As photovoltaic
systems are sensitive to shade, it is recommended that the part of the roof used to
generate solar power is shade-free. The installation should not be placed near chim-
neys, aerials and other roof structures.
Installable Photovoltaic Power
Once the type of solar module has been selected, an approximate calculation can
be made of the installable photovoltaic power based on remaining roof area A and
effi ciency
η
(compare Table 5.1 ):
=⋅ η 1
2
.
The installable power on a useable area of 28.6 m
2
with a module effi ciency of 14%
(0.14) is
PA
MPP
kW
m
P
MPP
2
.
=
28 6
.
m
⋅
0 14 1
.
⋅
kW
m
=
4
kW
p
2
The annual system yield can be calculated on the basis of this power output. What
fi rst needs to be determined is the supply of solar energy available. The map in
Figure 5.15 shows the yearly total for solar radiation in Europe based on averages
over many years. The radiation data for the USA can be found under http://www.
