Page 80 - Energize October 2022

TECHNICAL

Horizontal solar panel mounting

increases energy yield density

Solar PV panels are usually mounted in a tilted position to maximise the amount of energy
collected per panel. The tilt position is chosen to fully utilise the solar characteristics of a

particular site. A new requirement is emerging, which is to maximise the energy generated
in a given fixed area of solar PV, and this has led to the emergence of horizontal,
near horizontal and east/west mounting systems.

Mike Rycroft, Energize

he conventional approach taken with solar PV installations Two factors affect the angle of solar radiation reaching the panel
is to maximise the energy generated per solar panel. This surface: (Figure 1)
Tresults in the use of tilted mounting structures and solar • Azimuth, also known as bearing: this is the angle between
trackers. While this is an ideal approach where land usage is true north and the bearing or direction in which the sun is at
not restricted, it results in less than optimum land usage where any moment in degrees
space is limited. • Elevation: this is the height of the sun above the horizon in
Commercial and industrial (C&I) usage of solar PV is degrees
increasing, and this sector typically has restricted roof and
surrounding land availability and requires that maximum usage
of the available space is made. Agricultural use of solar PV is also
increasing, and this requires efficient use of land. This has led to
a new metric, the total energy developed in available space or
energy developed per square meter of available roof or ground
space, as opposed to the metric of energy per panel.
There are many instances where space is limited, such as
rooftops, commercial and industrial property (C&I), agricultural
land, etc., where it is better to install as many PV panels in a
given space as possible. Conventional tilted or tracked mounting
of panels requires spacing between rows of panels to avoid
shading, which reduces the aggregate PV energy which could be Figure 1: Azimuth, elevation and the solar dome.
collected.
Ground cover ratios, i.e., the ratio of the panel area to the For a vertically mounted panel the angle of incidence on the
total ground area occupied by an array, typically range from 40 panel at any time will depend on both the azimuth and the
to 50% for fixed-tilt plants, versus 25 to 40% for tracking plants. elevation at that time. The vertically mounted panel receives
But this value varies greatly by site, as it is based upon terrain, diffuse radiation from half of the sky dome.
tilt and other land features. In the C&I sector, this represents
a waste of space, given that the unused space cannot used for
other purposes.

Solar radiation parameters
The radiation received on an inclined surface is different from
that received on a horizontal surface for three reasons. Firstly,
the direct component is altered because of the change in
surface area projected on to the plane normal to the sun’s rays.
Secondly, an inclined surface will receive radiation reflected from
the surrounding ground cover. Thirdly, the diffuse component
changes as the fraction of the sky dome visible to the tilted
surface is reduced. 1 Figure 2: Vertically mounted panel

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