Environmental Engineering Reference
In-Depth Information
Figure 5.9
Principle of a photovoltaic island system.
soon as the battery reaches a certain charge level again, the charge regulator auto-
matically switches the power consumer back on. Once the battery is fully charged,
the charge regulator separates the photovoltaic module and prevents the battery from
overloading.
The costs can be kept low if the power consumers are economical users. Battery
voltage higher than 12 volts is recommended if power consumers have high require-
ments, as otherwise the losses in the lines will be too high. Island systems work on
a direct voltage basis, so, if possible, only direct voltage power consumers should
be utilized. Special refrigerators, lamps and even entertainment electronics are being
offered with 12 or 24 direct voltage supply. If alternating voltage power consumers
are operated, an island inverter fi rst has to convert the direct voltage of the battery
to alternating voltage.
Normal low voltages are usually relatively safe, at least as far as contact with the
voltage is concerned. As batteries are pure bundles of power, improper handling
can cause short circuits, fi re or even explosions. Battery rooms should always have
good ventilation as hydrogen gas can build up in them. Lead batteries contain diluted
acid. As time goes by, water evaporates from the battery and the battery has to be
refi lled regularly. With maintenance-free batteries the water is bound in a gel and
cannot escape.
A large array of photovoltaic modules can end up costing the same as a mid-range
car, and even individual photovoltaic modules are quite expensive, so thieves are
making life increasingly diffi cult for the operators of remote photovoltaic systems.
Solar modules installed on remote roads are particularly vulnerable to theft. As
island systems are usually installed in even more out-of-the-way places, the risk of
theft is especially high. This risk should be minimized in the installation. Optimally,
photovoltaic systems should not be visible from public roads. However, if this
cannot be avoided, systems should at least be assembled in places that are diffi cult
to access (Figure 5.10 ).
