My top ten lessons learned

jcgee88
jcgee88 Solar Expert Posts: 154 ✭✭
I started to think about doing a PV array in February 2010,
and had one installed and operational by June 2010. That
means I went from PV "Neophyte" to "Graduate" in a span of
four months. Here are some things I learned. These are
not listed in order or importance; I have sort of sorted
them by functional area.

Planning

1. Choosing which PV module to go with is tricky.
Besides there being a lot of vendors out there,
each claiming that they are the best, the
contractor may have a preference that is based
on comfort level or even "deal of the day" from
his distributor. SunPower has a unique efficiency
advantage (actually, it's a size advantage),
which draws you to them. I ultimately went
with my contractor's recommendation, Sharp,
because: I wanted black on black for asthetic
purposes; Sharp is a well established industry
leader (i.e., it's a safe choice); the cost and
capacity were in the desired range; and the
contractor could get delivery of these sooner.
I gave up on the SunPower when I realized that
it would have given me only 1, maybe 2 extra
panels' capacity...with the remaining panels
all burdened with SunPower's higher price.

2. I was lucky that I had upgraded my circuit breaker
box a couple years ago. The default "builder grade"
box was maxed out. It took about a month to
schedule that upgrade, cost about $1000, and
required a separately scheduled utility company
inspection. If I had not done this upgrade earlier,
it would have inpacted the schedule and the
financials.

3. I am grateful that my contractor educated me
about the difference between micro-inverters
and central/string inverters. I went with Enphase
micro-inverters for a different reason than why
they were originally proposed, but beyond their
bringing me additional efficiency, the Enphase
management software has opened my eyes to
subtle layout issues that snip you here and there
for harvest.

4. The contractor was very good about involving
me with the placement of the PV modules. He
explained the various choices, used tools like
PV-Watts and Pathfinder images to maximize
harvest and to minimize shading effects/need to
trim trees. I'd call this sort of effort "first order
site planning." It's possible to leave this all up
to the contractor, but I wouldn't feel comfortable
doing it that way...I'd want to know the rationale
behind critical design decisions. I sense that it
was my involvement at this level which also
helped properly set expectations as to how much
output I was going to get from my investment
(so far I've been at or higher than my goals).

5. The first order planning gets you to, say, 90% of
optimal. Because I didn't have any real life
operational data, what I missed out on was the
"second order" planning that seeks to avoid the
2-10% losses attributable to the idiosyncrasies
of the site. AFTER I saw these things from my
Enphase management software, I started to
ask myself, "could we tweak this tilt angle or
move the arrays 5 inches over to the left more or...?"
This is when I then learned it was too late to
consider those factors. Tweaks are not economically
viable then because it costs too much to bring
the contractor back out to do remounting, and
because, strictly speaking, any changes have to
be re-done for wind load analysis. If I were to
do this process again, I would ask my contractor
to do a talk on fine tuning with me that is separate
from the first order site planning.

6. Everyone notes how important shading is, but
until you see the actual effect, you don't really
appreciate it. I see a flue cap on my roof barely
shading one PV panel. A thimbleful of shadow is
costing me 100 watts for 90 minutes. This would
cost me at the string level ten times that if I
didn't have micro-inverters.


Installation

7. Obviously, there is a need to run wiring from the
roof top panels to the area near the power meter/
breaker box. What's not obvious is that you might
have to run this wiring in conduit along a wall on the
outside of your house! I think exterior conduit is ugly,
yet it's what installers come prepared to install.
I advise to instead find an existing chase or find a
wall you can make into a chase. The former is
preferable if it doesn't make the wire run too long or
convoluted. The latter is preferable if you want the
shortest possible wire run. When I did propose a
chase I had used previously for another purpose, he
agreed to use this chase, but he had to then leave
the site to go buy the flexible conduit to run down
that chase, thereby extending the install time.

8. Try to accident proof some of the working areas.
My attic has a very narrow walkway down the
center, and while I am used to that, others of
course are not. Naturally, one of the workers
made a mis-step and stepped through my ceiling.
They have repaired that, but I should have just
added a couple of boards to the walkway on my
own.


Post-Installation

9. A string does not turn on uniformly instantaneously.
For me, the western-most panels light up first and
the light up time can be 20-30 minutes. In other
words, I can have 110 watts on my western-most
panel for 20 minutes, while the eastern-most is
still sitting at 20 watts. This behavior is something
to think about when choosing the inverter technology.


General

10. Picking the right contractor is the single most
important factor to being successful and feeling
good about the results. I wanted a partner I could
work with, not a supplier. You have to look at this
like it's a marriage - you are going to have ups and
downs, and you are going to have to live with the
results for 25 years. I gave him the opportunity
to make a fair profit and use me as a reference, and
in return, I expected - and got - good service before,
during, and after the installation. [My contractor
is StraighUp Solar of St Louis, MO.]

--

Hope other prospective solar graduates find the above useful!

John

Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: My top ten lessons learned

    Very nice! I'm glad you are up and running, and that your experience will be valuable to others!

    Tony

    PS Bill/Niel, this might make a pretty good sticky, especially if it doesn't get too convoluted.

    T