| Stand-alone Solar Power System Stand-alone systems are independent from the utility
grid,avoiding the possibility of losing power when the grid
goes down.Electricity from stand-alone systems are used on
site,such as an RV or cabin.Power that is generated can be
stored in batteries and used at night or on sunless days. A
generator may also be used for back-up.For PV
applications,the size of a stand-alone system is usually up
to 50kW.
The system diagram as follow
System includes:
1. PV Array: A number of PV panels connected in series
and/or in parallel giving a DC output out of the incident
irradiance. Orientation and tilt of these panels are
important design parameters, as well as shading from
surrounding obstructions.
2. PV controller:control battery bank charge and
discharge reasonable and safety.
3. Inverter: A power converter that "inverts" the DC
power from the panels into AC power.The characteristics of
the output signal should match the voltage,frequency and
power quality limits in the supply network.
4. Battery bank: can be a single battery or multiple
batteries connected together to create essentially one large
battery of the required voltage and amp-hour capacity.In
some ways the battery configuration and capacity are the
most important electrical power decision to make, and a wise
choice can help guarantee a steady supply of electrical
power as well as a system that is simple to operate and
maintain.
5. Loads: Stands for the network connected appliances in
the building that are fed from the inverter, or,
alternatively, from the grid.
Grid-connected PV system
In photovoltaic solar energy systems, light is converted
into electrical energy that is used immediately or stored.
In a grid connected photovoltaic system, the generated
direct current is transformed into an alternating current
that can be used in the house immediately. In case of
a??remainder of energy, it can be delivered into the grid.
 
Grid connected system avoid the need for electricity
storage in batteries by essentially using the utility as a
battery system. When your solar or wind system produces more
electricity than you need, the excess is sold back to the
utility.When your system doesn"t produce enough
electricity,you can draw power from the grid.All this is
done automatically through a net metering or net billing
program.In most cases,a special or second utility meter will
be added to keep track of how much electricity has been sold
to the utility.
Advantages of utility interconnection include having
access to standard AC power all of the time,not just when
your system produces electricity,and avoiding the cost of a
battery back-up system.A disadvantage is the utility
interconnection fee,which varies with each utility.The size
of a utility connected project depends on how much of your
electric consumption you want to displace and how much money
you are able to invest.
Grid Connected PV system design has the following
components:
1. PV Array or Generator: A number of PV panels connected in
series and/or in parallel giving a DC output out of the
incident irradiance. Orientation and tilt of these panels
are important design parameters, as well as shading from
surrounding obstructions.
2. Inverter: A power converter that inverts the DC
power from the panels into AC power. The characteristics of
the output signal should match the voltage, frequency and
power quality limits in the supply network.
3. Loads: Stands for the network connected appliances in
the building that are fed from the inverter, or,
alternatively, from the grid.
4. Meters: They account for the energy being drawn from
or fed into then local supply network.
5. Local Supply Network: A single or three-phase network
managed by a Public Electricity Supplier. The supply network
acts both as a sink for energy surplus in the building or as
a backup for low local generation periods.
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