Select Solar PV Panels to Meet Your Need
What is a Solar PV Energy?
When I was in elementary school, the movie projector had a light
inside. I asked what was the light for? My teacher told me the light
shined through the film onto a special surface in a vacuum tube. The
surface turned the light into an electric signal that produced the
sound for the movie we were watching.
Solar PV panels
work much the same way. Sunlight is transformed into electric energy.
The amount of energy is determined by the intensity of the light. Sun
angle, shadows, clouds, haze, and temperature all affect the energy
transfer. Solar Panels are made up of solar cells in series to increase
voltage and in parallel to increase current.
When any one cell in a series group is not illuminated or faulty, then
the total current of the series is zero -- no current, no power from
When any one cell in parallel group is not illuminated or faulty, then
only the power from one cell is missing from the group.
Wiring the cells in a series-parallel matrix gives you reliability but
it sure makes it hard to find and replace a failed cell.
How much power would you like to generate from a Solar Panel array?
(a) Enough to charge your battery bank to last 5 day in a row without
kwh per month / days in month
x 5days = energy used
energy used /days in month/ sunshine hr per day
additional system capacity to recharge storage in a month
For July 1908 kwh /31 days x 5 days
= 307.74 kwh
307.74 kwh /31 days /6.5 hr/day = 1.53 kw system
Month avg 2359 kwh/(365 days/12 mo) x 5 days =387.8 kwh
387.8 kwh /(365 days/12mo) /4.5 hr /day = 2.83 kw system
For Dec 4136 kwh /31 days x 5 days
= 667.1 kwh
667.1 kwh / 31 days / 2.5 hr /day = 10.25 kw system
The above calculations
show the additional system capacity necessary just to recover in a
month from 5 strait days of cloud cover or grid
(b) Just to cover average monthly use?
kwh/mo /(usable sunshine hours/day x
days in month) = system size kw
For July 1908 kwh /(6.5 hr /day x 31
days) = 9.47 kw system
Average -- Net Metered Zero Average Grid Use
Year avg 28319 kwh /(4.5 hr/ day x 365
days) = 17.24 kw system
For Dec 4136 kwh / (2.5 hr
/day x 31 days) = 53.36 kw system
above calculations show the size of a system necessary to handle power
consumption for a current life style. You can easily see that your
electric utility using fossil fuels doesn't experience the extreme
constraints that a pure solar PV system would have trying to keep pace
with your current life style, sun cycles and the whims of weather
style would have to be modified to thrive within the capability of a
reasonable and economical stand alone solar PV system. Net metering is
a reasonable solution for keeping the initial cost of a solar PV system
manageable and still not need to drastically change your life style.
However, you would still be dependent on the utility grid.
need to do your own calculations because your location and life style is probably different
Space & Orientation
About 70 feet from my house is a barn with unshaded roof area facing
south that is 20 ft x 24 ft. If one were to choose Sun HS-195 (195 watt
Solar Panels) that are approximately 3 feet wide by 5 feet long and
produce about 190 real watts each. They each
weigh 40 lbs and are listed at $503ea. A 4 long
by 8 wide matrix will fit the roof nicely.
That would be 40 lb x 32 = 1280 added
weight to the roof.
$503 x 32 = $16,096
panels x 190 watts = 6080 watts or 6.08 kw
$503 per panel x 0.7 tax credit /190
watts = $1.85+ per watt from panels
I'm currently paying something like $0.09 /kwh. An installed panel
remain functional for about 25 years.
If you assume 25 years x 365.25 days x
4.5 hrs x 190 x 0.9 time loss
7026.5 kwh per panel lifetime
$503x 0.7 tax
credit / 7026.5 kwh = $0.0501 per kwh fixed
And It won't be affected by any fossil fuel tax, oil prices or
inflation. But it will take some up front money.