Page 122 - Solar Power in Building Design The Engineer's Complete Design Resource

92 SOLAR POWER SYSTEM DESIGN CONSIDERATIONS

Maintenance

In general, solar power system maintenance is minimal, and PV modules often only
require a rinse and mopping with mild detergent once or twice a year. They should
be visually inspected for cracks, glass damage, and wire or cable damage. A periodic
check of the array voltage by a voltmeter may reveal malfunctioning solar modules.

TROUBLESHOOTING
All photovoltaic modules become active and produce electricity when illuminated in
the presence of natural solar or high ambient lighting. Solar power equipment should
be treated with the same caution and care as regular electric power service. Unlicensed
electricians or inexperienced maintenance personnel should not be allowed to work
with solar power systems.
In order to determine the functional integrity of a PV module, the output of one
module must be compared with that of another under the same field operating condi-
tions. One of the best methods to check module output functionality is to compare the
voltage of one module to that of another. A difference of greater than 20 percent or
more will indicate a malfunctioning module. Note that the output of a PV module is
a function of sunlight and prevailing temperature conditions, and as such, electrical
output can fluctuate from one extreme to another.
When electric current and voltage output values of a solar power module are meas-
ured, short-circuit current (Isc) and open-circuit voltage (Voc) values must be com-
pared with the manufacturer’s product specifications.
To obtain the Isc value a multimeter ampere meter must be placed between the
positive and negative output leads shorting the module circuit. To obtain the Voc read-
ing a multimeter voltmeter should simply be placed across the positive and negative
leads of the PV module.
For larger current-carrying cables and wires, current measurements must be car-
ried out with a clamping meter. Since current clamping meters do not require circuit
opening or line disconnection, different points of the solar arrays can be measured at
the same time. An excessive differential reading will be an indication of a malfunc-
tioning array.
Note that problems resulting from module malfunction or failure seldom occur
when a PV system is put into operation; rather most malfunctions result from
improper connections or loose or corroded terminals. In the event of a damaged
connector or wiring, a trained or certified technician should be called upon to per-
form the repairs. PV modules, which are usually guaranteed for an extended peri-
od of time, that are malfunctioning should be sent back to the manufacturer or
installer for replacement. Caution: Do not to disconnect dc feed cables from the
inverters unless the entire solar module is deactivated or covered with a canvas or
a nontransparent material.
The following safety warning signs must be permanently secured to solar power
system components.