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To meet the the electrical need of a home or
an industrial setting, PV Modules are assembled together to form a
PV Array that meets the total energy requirement.
A PVC system design begins with determining
the total energy requirement for a facility to be powered. Next the number
of solar panel units required and other components of the PVC (description
below) are determined. A basic PVC system comprises of the following:
-
Solar panels – collects visible light from Sun and
converts it to electricity (direct current
(DC));
-
Batteries
(rechargeable) – Store solar energy up to
provide electricity for sun-down periods (nights and cloudy days).
They must be able to discharge and
recharge. Rechargeable batteries are a little
more expensive than the disposable batteries.
Without batteries a PVC system can only provide electricity when it is
sunny.
-
Charge
Controller -
feeds
electricity from the solar panel to the batteries
in a manner that prevents the solar panel from overcharging the batteries.
-
Power Inverter –
converts the low-voltage direct currents
(DC) from the battery to high-voltage alternating current (AC) required by
most household appliances.
Solar panels generate low voltage Direct Current (DC) electricity. Some appliances (e.g. incandescent lights) may be
powered directly by the energy from the panels as these appliances are DC
compliant. However, most electrical
appliances require Alternating Current (AC) electricity and usually at high
voltages (110V in North America and 230V in most of Europe and developing
world (e.g. Africa)) to function. Inverters are
used to convert the low voltage DC to AC at required voltages.
In summary, the solar cells collect direct
sunlight, converts sunlight into low-voltage DC. Where energy storage in a battery for future use is
required, the DC is stored directly in batteries. A charge controller is
installed between the Solar panels and the batteries to ensure he
batteries are not overcharged. A Power Inverter is
used to convert the DC from battery to AC to power the AC appliances.
PVC System
Other PVC system components that may be
required are: wires and cables (for connection of the components) and
meters and monitors (for monitoring the voltage and reading the currents
of the system.
PV system is a preferred approach for
electricity supply because of its modular features, its
ability to generate electricity at the actual point of use, its low
maintenance requirements and its non-polluting technologies. It is
an attractive option for electricity supply in developing countries where
there is abundant sunlight and large rural population
without the proper infrastructure to develop an electrical grid. In
such countries, PV system can be used to provide electricity to homes,
rural clinics and government/corporate offices.
PV systems are also useful in remote and
isolated locations in developed Worlds (e.g. northern Canadian territories
- Nunavut, Yukon and NWT, arctic Greenland and Iceland and various World
Islands).
PV systems are not
suitable for water heating or other heat related appliances. A solar
heater can heat water more quickly and efficiently than an electric water
heater powered by PV panels. Solar heaters convert up to 60 per cent of
the sun's energy into heat whereas PV cells are
far less efficient and convert only 12 to 15 per cent of the sun's
energy into electricity.
The Size of
a PV system
To size a PV system, follow
these process:
1. Determine the amount
of electricity required:
-
Determine the number of devices to be
supported,
-
Multiply the power (in watts or KW) on
each device by the number of hours in a day the device will be used to
obtain the electrical energy required in KWh,
-
Add all the KWhs together to get the
current total energy requirement for the PV system;
-
Allow for expansions to your system.
Depending on your resources, you may want to consider a factor of safety
of 1.3 (i.e. 30% above your current requirement) or 1.5 (i.e. 50% above
your current requirement).
2. Size your
PV Module and your battery capacities:
Keep in mind that a PV cell of say 100mm by
100mm cell produces about 1 to 2 watts of electricity. The battery should
be sufficient to store electricity for use during sun-down hours (nights
and cloudy days).
The
Cost of PV system
Sample costs (source:
Solar Energy Society of Canada Inc.):
A
portable PV unit with a 50-watt solar panel, low-power inverter and
battery, are about $700 and can operate three high-efficiency lights, a
small TV and a water pump.
A more
powerful PV system that produces 600 watts and operates several lights, a
TV, stereo, microwave oven and water pump - but not at the same time -
costs about $8,000.
New
production techniques and applications combined with lowering prices for
photovoltaic should increase the acceptance of this environmentally
friendly technology.
What to do do with excess electricity
If you generate more electricity than you
require to power your home, you can store the excess electricity in
batteries or sell the excess electricity to the utility provider in your
area under a feed-in-tariff scheme. To do the later, your home solar power
electricity has to be connected to the regional or national grid in your
area. You will need to find about the possibility of tying your grid to
the regional/national grid in your area. Tying a solar (or other energy
type) power to a national/regional grid is governed by some
laws/regulations of the country in which you are. You will need to contact
the responsible authority. obtain the permit to do grid tie and collect
the specialized equipment that links your power source to the national
grid. The equipment has to be installed by certified individuals. When you
are under using power, the unused electricity is sent to the grid and used
to provide power for other people, and you get a refund or credit from the
regional /. national supply of electricity and vice versa.
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