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Green Collar Careers - Solar
Electric Site Survey
The same Solar Site Survey process used for solar heating will also
be used for the solar electric PV system with a few simple additions
for the PV equipment. If you looked the Site Survey Data
worksheet over carefully you may have wondered when we would get to
the solar electric portion. With the best wholesale cost per kWh
based on turkey kits the key will be to determine what size kit works
best. At the time of this page edit, complete Grid Tie quality
kits were selling for under $4 per DC Watt. The Site Survey Data
worksheet will need to be completed down to the Solar PV Requirements
section. We've taken the data from the example file for review
below:
|
Solar PV Requirements |
|
Total Annual kWh Requirement |
45000 |
|
DC Watt Output Rating of Kit |
8000 |
|
Quantity of Panels in Kit |
40 |
|
Rated DC Watts Per Panel |
205 |
|
Panel Width Inches |
35 |
|
Panel Height Inches |
65 |
|
Customer Price |
$36,200 |
|
Installed cost per DC Watt |
$4.53 |
|
Utility Incentive per DC Watt |
$2.46 |
|
State Tax Incentive Estimate |
$0 |
|
Utility Incentive Total |
$19,680 |
|
Federal Tax Credit |
$10,860 |
|
Projected Annual kWh Output |
11200 |
|
Percentage of Solar Electricity |
25% |
|
Projected Annual Electricity Savings |
$1,456 |
|
Square Footage of Panels |
632 |
|
Net System Cost to Owner |
$5,660 |
|
Return On Investment Years |
3.9 |
This example comes from a real job that was installed in June 2009.
It consisted of an 8000DC Watt ground mounted panel system and was
installed in Texas. The local utility was Oncor who is currently
paying out $2.46 per DC Watt to collect on the Carbon Credits the
system is capable of generating. Texas has no state taxes and
therefore no tax credits. The number of sunny days directly
determines the annual output. This 8000 Watt system is projected
to provide 11,200 kWh of electricity per year, and amounts to 25% of
the total used by this household. This homeowner uses a bit more
power then the average in part due to a small business operated out of
the home that has a few high power appliances in operation 8 hours a
day. On this particular home the roof angles just wouldn't result
with an attractive and easy to service system. You'll probably
find that in 2/3's of all the site surveys you perform. Solar PV
panels lend themselves to a creative eye. If the roof doesn't
meet the best fit consider awnings or even a stand-alone ground mount.
In this installation the panels were mounted adjacent to a pool that
provided a 55 foot long 12 foot tall privacy fence and is an
attractive feature of the landscape. Once you've identified the
equipment locations measure out all cable lengths. A list of
interconnections is listed the
Solar Site Survey
on the Solar PV Interconnect Worksheet. The key distances you'll
need to measure are:
|
Originating |
Terminating |
Length |
|
PV Panel |
Combiner Box |
|
|
Combiner Box |
DC Disconnect |
|
|
DC Disconnect |
Inverter |
|
|
Inverter |
AC Disconnect |
|
|
AC Disconnect |
Main AC Panel |
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CABLING WILL NOT RUN IN A STRAIGHT
LINE! Be sure when you measure cable route lengths
that every X, Y, and Z axis length is included in the total length!
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