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| Solar Power Generation
Systems
INTRODUCTION
Power
cuts are becoming a common feature now days in many cities,
metros, villages and remote areas. In addition, the electricity
tariffs are increasing every year.
The solar power generation systems are electricity-generating
systems that make use of benevolent solar power to generate
electricity cleanly, quietly and without causing any damage
to the surrounding environment. Such systems are ideal for
locations where the mains electricity grid is inaccessible,
the electricity quality is bad or the access is prohibitively
expensive. The solar power generation system can also be used
in conjunction with the existing AC mains to enhance the energy
delivered at that particular location.
An array of solar modules charges a battery
bank through a charge controller. An inverter converts the
battery DC power to mains grade AC power. The backup time
of the system can be designed as per the customer’s
requirement. |
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solar power generation system works either in the stand-alone
or grid interactive mode. In the stand-alone mode, the battery
bank is charged only on solar power. In the grid interactive
mode, a mains charger supplements solar charging. Logic built
into the charger senses if solar energy is inadequate to charge
the batteries (low sunshine or batteries deep discharge) and
switches the batteries onto the mains charger.
In
case of malfunction in charge controller, inverter or batteries,
a manual change over is provided, by means of which the load
on the inverter can be transferred on AC mains.
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SCHEMATIC
OF A TYPICAL SOLAR POWER GENERATION SYSTEM
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PORTRAYAL
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1.
Solar Array
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Solar
Photovoltaic (SPV) Modules:
The solar array consists of SPV modules
generating the desired design power. The array is configured
as series and parallel, connected sub arrays. The system voltage
made available to charge the batteries depends on the number
of modules connected in series.
The
inter-connections between panels are connected in a junction
box that also contains the blocking diodes, to prevent reverse
flow of power from batteries to panel in the absence of sunlight.
+ve and -ve cables are drawn from the junction box to the
Power Conditioning Unit (PCU). The array is mounted on a specially
designed common support structure.
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Support
Structure:
The support frame is a rugged, corrosion resistant, MS structure
that needs to be anchored on to the floor or rooftop, facing
the south. The entire frame can be tilted according to the
latitude of the site. If correctly anchored, the support frame
with the array installed can sustain wind speeds of up to
160 kmph. For safely, the entire frame and the array are securely
earthed.
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2. Battery Bank
The
battery bank comprises of number of batteries connected in
series and parallel to give the desired designed voltages
and currents. The batteries are of tubular plate type with
low self-discharge and require low maintenance. The batteries
are mounted on a wooden stand or on a MS structure with insulators
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3.
Power Conditioning Unit (PCU)
The
PCU comprises of two parts:
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Charge
Controller:
The charging of the battery bank is controlled by means of
the charge controller. The charge controller ensures that
the batteries are not over charged or over discharged.
The
mains charger is provided to augment the solar charging. Logic
built into the charger detects if sunshine is low (eg. on
rainy days) or depth of battery discharge is below the specified
limit, and automatically switches the batteries over to the
AC mains charger. When the batteries are fully charged, the
output of battery charger / charge controller ‘floats’,
thereby preventing battery over charge.
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Inverter:
The inverter converts the DC supply from the battery to mains
grade of 230 V, 50 Hz AC supply. The capacity of the inverter
is decided on the load that is to be connected to the solar
system. The output of the inverter is pure sine wave with
power factor correction. Hence poor power factor loads such
as conventional 40 W fluorescent tubes can also be safely
operated on the inverter.
The
PCU is provided with DC and AC voltmeters and ammeters that
indicate parameters such as charging voltage, charging current,
battery voltage, solar array voltage, output voltage, load
current, etc.
LED
indicators on the well laid out front panel backed up by audio
alarm (for fault / trip conditions only) indicate normal operating
and fault conditions.
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