[VAC] Re: Solar panel mounting ideas

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

David,
 Pictures of how I did it on our Avion are at
http://www.oldengine.org/members/jdunmyer/avion/index.htm.

In my opinion, tiltable bracketry is a waste of time and effort.
Although getting the panels pointed at a right angle to the sun will
result in significantly more output, it would be too much bother for me
to climb a ladder to reposition them. I've seen schemes that allow
tilting in one direction only, but that means that you have to park your
rig in a certain position to take advantage of the tilt direction.

Real World Experience: My panels are rated at 75 watts/each; I started
with one that I would set on the ground (see
http://www.oldengine.org/members/jdunmyer/airstream/) and did some
measurements with a DVM. The single panel would provide 4 amps in bright
sunlight when pointed directly at the sun. Cleaning it would usually
result in a measurable increase in output. With the panels mounted as
shown (you can see the overall view at
http://www.oldengine.org/members/jdunmyer/avion/sep01_05.jpg), I'll see
as much as 6 amps total, with 4-5 amps being pretty common near mid-day.
These panels are about 21" X 48" and are mounted about 2" off the roof
to allow cooling.

The Avion has a sorta flat roof profile compared to the older A/S
trailers, so this might not work out quite as well for you. In my case,
I'd sort of like to have a couple more 75-watt panels mounted behind the
A/C, straddling the roof vent like in front. Only thing is, I've not
found that I need more power than I have and don't know what I'd do with
it if I had it. Of course, that's for OUR lifestyle and may not apply
for you.

I was perusing http://www.ajlsolarelectric.com yesterday and downloaded
their design sheets. They have some figures on efficiency loss due to
panels' not being aimed directly at the sun, that information might help
you in your decision. Personally, I'd mount them a couple of inches off
the roof for ventilation and add some capacity to make up for the
mis-aiming; that's how most RV'ers do it. Installing 4, 75-watt panels
should give you 60 AH+ per [sunny] day when mounted in this fashion.
Based on my experience, I'd guess that 2, 100-watt panels mounted flat
on the roof would give you 8-9 amps max, or about 50 AH/day.

Something you might want to consider is one of those SolarBoost 2000
controllers, if you don't already have a suitable charge control. They
capture/convert the "headroom" of your panels and give you significantly
more output than is usual. If you're unfamiliar with that outfit, the
ajlsolarelectric site has information and explanations on the operation.

                                           <<Jim>>