Solar Power in Building Design
Author:
Peter Gevorkian, Ph.D., P.E.,
ISBN: x
Publisher: x
Sample Page
Ground-Mount Photovoltaic Module Installation and Support Hardware
Ground-mount outdoor photovoltaic array installations can be configured in a
wide variety of ways. The most important factor when installing solar power
modules is the PV module orientation and panel incline. A ground-mount solar
power installation is shown in Figure 3.15.
In general, the maximum power from a PV module is obtained when the angle of
solar rays impinge directly perpendicular (at a 90-degree angle) to the
surface of the panels. Since solar ray angles vary seasonally throughout the
year, the optimum average tilt angle for obtaining the maximum output power
is approximately the local latitude minus 9 or 10 degrees (see Appendix B
for typical PV support platforms and hardware and Appendix A for tilt angle
installations for the following cities in California: Los Angeles, Daggett,
Santa Monica, Fresno, and San Diego).
In the northern hemisphere, PV modules are mounted in a north-south tilt
(high end north) and in the southern hemisphere, in a south-north tilt.
Appendix A also includes U.S. and world geographic location longitudes and
latitudes.
To attain the required angle, solar panels are generally secured on tilted
prefabricated or field-constructed frames that use rustproof railings, such
as galvanized Unistrut or commercially available aluminum or stainless-steel
angle channels, and fastening hardware, such as nuts, bolts, and washers.
Prefabricated solar power support systems are also available from UniRac and
several other manufacturers.
Figure 3.15 A typical ground mount solar power installation used in solar
farms. Courtesy of UniRac
When installing solar support pedestals, also known as stanchions, attention
must be paid to structural design requirements. Solar power stanchions and
pedestals must be designed by a qualified, registered professional engineer.
Solar support structures must take into consideration prevailing geographic
and atmospheric conditions, such as maximum wind gusts, flood conditions,
and soil erosion.
A typical ground-mount solar power installation includes agricultural
grounds; parks and outdoor recreational facilities; carports; sanitariums;
and large commercial solar power-generating facilities, also known as solar
farms (see Figure 3.15). Most solar farms are owned and operated by electric
energy-generating entities such as Edison. Prior to the installation of a
solar power system, structural and electrical plans must be reviewed by
local electrical service authorities, such as building and safety
departments. Solar power installation must be undertaken by a qualified
licensed electrical contractor with special expertise in solar power
installations.
A solar mounting support system profile, shown in Figure 3.16, consists of a
galvanized Unistrut railing frame that is field-assembled with standard
commercially available manufactured components used in the construction
industry. Basic frame components in general include a 2-in galvanized
Unistrut channel, 90-degree and T-type connectors, spring-type channel nuts
and bolts, and panel hold-down T-type or fender washers.
The main frame that supports the PV modules is welded or bolted to a
set of galvanized
rigid metal round pipes or square channels. The foundation support is built from
12- to 18-in-diameter reinforced concrete cast in a sauna tube. Then, the metal
support
structure is secured to the concrete footing by means of expansion bolts. The
depth of
the footing and dimensions of channel hardware and method of PV module frame
attachment are designed by a qualified structural engineer.