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Green Collar Careers - Solar PV
System Specification
Sizing the system is always a balance between what the customer can
afford to spend vrs what they can afford. In most cases the
system is financed through a home equity loan with tax credits and any
utility incentives to pay the loan down. From the example given
in Section 503 the homeowner
borrowed $35,000 and will repay $30,540 from credits and incentives by
the end of the first year, along with the accrued principal payments
on their line of credit. 4000 watts DC is the most common size
chosen for a residential solar PV system. Most wholesalers price
the 4000 watt DC systems the lowest because of that reason. In
some cases it will cost less to buy two 4000 watt systems then it will
for a 6000 watt system. From the site survey you should have
identified the location and effective daylight the system will
receive.
You will need to sketch up and design the mounting rack system.
If you need some help learning about modular rack systems try this
tutorial:
T Slots Learning the System. The rack mounting system will
require a Bill of Materials. Also during the site survey you will
know if the system is Grid Tied or Off Grid. For Grid Tied systems
you'll need to contact the utility for a list of approved inverters,
circuit breaker requirements, and surge protection requirements. For
Off Grid systems you'll need to identify all the powered equipment
load requirements:
- Continuous appliances such as refrigerators and well pumps
- Lighting requirements
- Comfort devices such as fans or any HVAC appliances
- Entertainment
- Cooking
- Cleaning
From these devices you'll need to identify the expected demand and
time of day usage. What you'll find is that you'll never have
enough battery power to run the expected loads at night, nor will you
have the solar PV capability to produce enough power to keep the
batteries charged. Generally a 4000 watt DC system should
provide 2 people with ample power as long as the power is not used for
an HVAC system or to heat water. Add roughly 1000 watts DC for
every additional person. Off Grid systems sometimes have to
endure cloudy days suggesting more battery reserve would be
recommended. Each application will have a totally different set
of requirements (and owners) so keep the #1 rule about Solar Energy in
mind:
There is no perfect solution.
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