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In the interconnected
case, PV system produces energy from the panels
during the sunny days and provides this energy to
the house, but If more energy is needed then it is
currently being produced, grid supplies the
difference. In case PV system produces more then
needed, surplus is then fed back into the grid,
often for a benefit to the home owner. In
battery-based systems, there is no backup of the
grid and all energy that is produced is used or
stored in the batteries for later use.
Solar Photovoltaic
Systems consist of few key components: solar
photovoltaic panels, inverter, battery chargers and
batteries (if off-grid installation), PV combiner
boxes, DC array disconnect, wiring, and panel
mounting racks.
PV Panel
 The
most important component of the PV system is the
solar photovoltaic panel. Electricity is generated
when sun rays hit the silicon wafers in the solar
panels. Sun's energy knocks out "free" electrons
from the silicon atoms which then generates the flow
of electrical current. This simple principle of
using sun's rays and harvesting of "free" electrons
from the silicon actually generates the electrical
energy that you can use for your house needs.
Installing a
photovoltaic system in your home is not too
complicated but it should be left to a professional.
The panels are usually placed on your south facing
roof or in some other un-shaded area that gets
maximum exposure to the sun (no trees, other
buildings, etc). In a typical installation, a
certain number of panels is connected in a series on
your roof into what is called an array in order to
give you a cumulative power capacity that matches
your home needs. Each panel has its own nominal
power rating and operating voltage, so for example
connecting five 200 W, 48 VDC panels in series gives
you 2000 W of total power capacity producing 240 VDC.
A couple of series can be connected in parallel to
form a larger solar panel array in order to give you
even more rated power. In that case connecting
another five panel series will give you 4000 W of
total rated power but at the same Voltage output of
240VDC. More details on wiring procedures of typical
solar panel installations can be found in sources
like Home Power magazine.
There is an ever
growing list of PV manufacturers, both foreign
(Germany, China...) and domestic that are offering a
large variety of panels ranging in power from 100 W
to 300 W. The efficiencies of solar panels are still
somewhat low, ranging from 11-20%. Some of the
manufacturers to check out are BP Solar, Evergreen,
Kyocera, Mittsubishi, Sanyo, Schuco, Sharp, SunPower...
Inverter
Next important
element of the PV system is the inverter. Solar
panels produce DC power but your house needs AC
power. Also voltages are different (48 VDC vs. 240
VAC). This device "inverts" the VDC power output
that comes from the solar panel array into the 240
VAC output that you household appliances consume.
Grid connected inverters also synchronize and make
grid quality electricity so it can be freely
exchanged with the grid. Battery-based inverters
often include battery chargers that can take
electricity either from the panels or grid to charge
the batteries when needed.
Inverters have their
own voltage ratings. They should be chosen to match
the range of voltage that your panel array will
produce during the day. For example, an inverter can
have 600 VDC maximum input voltage, with an
operating range between 90-580 VDC with a 240 VDC
output. That rating should be carefully matched with
you array ratings so you get maximum energy produced
from your system in any given day. Most prominent
manufacturers of inverters are Fronius, Sunny Boy,
Xantrex, OutBack, Magnum. |
