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APPLICATION
2. Surge-current capability: by supplying, when
necessary, currents higher than the PV array can
deliver, especially to start motors or other inductive
equipment.
3. Voltage control: thereby preventing large
voltage fluctuations that may damage the load.
Charge Controller and Array
Regardless of the battery type chosen for a
Issue I 2010
particular system, a charge controller remains an
essential component. The primary function of a
charge controller is to prevent the battery bank
from being overcharged when there is abundant
solar insolation available. Overcharging a battery
can lead to electrolyte imbalances and depletion.
In cases of severe overcharging, batteries can be
-pv-management.com completely destroyed along with any
instrumentation in the vicinity.
.solar
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There is a wide range of charge controllers
available, and the design requirements of the
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system dictate which charge controller should be
utilized. The maximum charge rate is the first
parameter to consider along with the system
voltage. The amp rating of the charge controller
should be oversized by a minimum of 25% for
enhanced reliability. Greater functionality will be
required for more complex systems and those that
are deployed year-round.
On a clear day at solar noon, about 1,000 watts
per square meter will fall on a surface placed
perpendicular to the sun. If that surface is a PV
Number of different purpose, but other energy storage mediums do panel working at 10% efficiency, the solar energy
battery configurations exist. Fossil fuels and combustion generators can will be converted into 100 watts of electrical power.
resulting in 12 volts be used to provide on-demand power. The PV array functions to securely mount the
individual PV panels and maximize the conversion
Dynamic flywheels have been successfully utilized efficiency as much as possible by maintaining the
in several larger systems to kinetically store orientation perpendicular to the sun.
energy. For now, batteries provide the most cost-
effective solution for energy storage for small- to There are two basic types of arrays for mounting
medium-sized autonomous power systems. PV panels: fixed and tracking. Tracking arrays can
move in one or two planes and can employ active
A battery stores electrical energy in the form of (motor drive) or passive mechanisms for following
chemical energy. For a PV-battery system to the course of the sun. In high latitudes, dual-axis
function effectively, the electrochemical processes trackers can increase the output of an array by up
must work in both directions—in other words, the to 60% in summer applications, yet they are rarely
system must be rechargeable. To this end, employed for mission-critical applications such as
batteries perform three main functions in a stand- autonomous instrument platforms. The reason is
alone PV system: reliability. To date, no automated tracking system
has proven to be robust enough to withstand polar
1. Autonomy: by meeting the load requirements at weather conditions. Until such tracking
all times, including at night, during overcast mechanisms are more reliable, the power budget
periods, or during the winter when PV input is low is better spent on obtaining more PV modules on a
or absent. fixed array.
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