Page 130 - Applied Photovoltaics

when the concrete is moist. High temperatures and localised heat sources should also
be protected against.
The Australian requirements are detailed by Standards Australia (1997). Adequate
venting must be provided, to minimise any potential for explosions, whenever liquid
electrolyte batteries are used. In large, open sheds, a wall extending 500 mm above
the batteries may be used to separate them from potential spark sources and particular
methods are recommended for other situations (Standards Australia, 2002).
Enclosures must also be safeguarded against access by unauthorised people,
particularly children. Safety signage is required, including one with the words
“WARNING: SPARK HAZARD” (Standards Australia, 1999–2000a). For small
systems, truck or marine battery boxes are an inexpensive option and will even
withstand direct sunlight.

6.8.9 Housing of electronics
It is essential that all electronic equipment, including regulators, controllers and
inverters, be well protected from the environment to ensure good reliability and long
life. All printed circuit boards must be covered by a conformal coating, to protect
against dust.

Provision also needs to be made for adequate ventilation, to keep circuitry
temperatures to acceptable levels. This in turn can lead to problems with dust, and
dust filters should therefore be considered on the ventilation air inlets. Electronic
equipment should not be mounted directly above batteries for three reasons: acidic
fumes may damage the equipment, the equipment may cause sparks, and tools may
drop onto the batteries during maintenance, causing short circuits and sparking.

6.8.10 Module mounting
The type of module mounting used for a PV array will impact on the power output,
the capital cost and the maintenance requirements. Support structures can vary widely
but should be configured to comply with local standards for structures, with wind
loading being the most critical design criterion (Standards Australia, 2002). This and
other mechanical engineering and materials science issues for PV systems are
discussed in detail by Messenger and Ventre (2000). Elementary mechanical
engineering books give methods for calculating wind loadings on such structures.
Significant advancements in recent years in the aerodynamics of solar and electric
cars and other transportation vehicles suggest there is considerable scope for
innovation in the design of mounting structures for solar arrays to minimise wind
loadings. In particular, for large arrays, attention to the aerodynamic design of
structures at the perimeter of the array may facilitate the use of appropriately
designed low cost and low weight structures in central regions of the array.

Ground mounting, such as in Fig. 6.7, is the most common at present, either fixed at
an angle appropriate to the site, or on a tracker. Most PV panel manufacturers offer
suitable ground mounting hardware for their panels, particularly of the fixed tilt type.
Some residential systems use roof mounting, in which case a gap of at least 7 cm
should be provided beneath the modules for air flow, while some small lighting
systems and telephone transmitters have their solar panels mounted on poles.

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