Re: [A/S] Solar Panel Suggestions

["Jim Dunmyer" <jdunmyer@xxxxxxxxxxx>]

Bob,
 The flexible panels are usually far less efficient than the rigid ones.
Look at the output vs. size to see what I mean.

The other point is that solar cells degrade in output very rapidly as their
temperature rises. That's why you always see them mounted on brackets that
give a 2" or so space between the back of the panel(s) and the roof.
Remember that due to the cell's dark color, they get very hot in direct
sunlight, and that heat must be allowed to dissapate.

It apparently bears repeating: picking solar panels is the LAST of 3 steps
in spec'ing and installing a solar system:

First, add up your usage for a typical day/night, the numbers should be in
Amp-Hours
Second, decide how much battery storage you need. Most folks want to be able
to operate through at least 3 sunless days. Batteries are rated in A-H, so
simple math with your usage numbers tells you "how much".
THIRD, you now know how much solar capacity is needed. You must replace at
least 110% of your daily usage due to inefficencies, plus a bit of extra is
needed to recharge the batteries after those 3 sunless days.

Once you know your solar requirements, you can choose size and type of
panels. Mounting flexible panels directly to the skin of your trailer will
work, but you can now use the manufacturer's specs to determine how much you
need to oversize your system to make up for the loss of output due to heat.

Conserving power is the first step in this exercise. As you'll see when you
start running the numbers, providing just a bit more power gets very
expensive, so it behooves you to cut back where you can. Even very small
loads add up quickly. In our trailer, the bulb that tells us that the water
pump is on uses about 2 1/2 AH per day. That's enough to operate a reading
light for over an hour! If we didn't have a bit of excess in our charging
system, I'd probably replace that bulb with an LED, cutting the usage by
about 80%.

One person made the excellent suggestion to install a larger-than-necessary
charge controller so you don't have to replace it if/when you add panels.
I'll give you a few more:

An eMeter or equivilant is an excellent investment. Not being able to
monitor your electrical system is like driving your tow vehicle without any
dashboard guages, even a speedometer.

Plan for additional panels, but try to use as physically large ones as will
fit. You don't want to cover your roof with 50-watt panels and find out that
it isn't enough. Better to start off with 75-watt panels if they'll fit.

Even a single panel of 50+ watts can make a significant difference in how
long you can boondock w/o running out of power. Start with one (see above!),
then add more later if/when you see the need.

Educate yourself! There's been a number of URLs posted here in the past
couple of days, and most of them have tutorials on solar power. Read 'em all
if you can and it'll start making sense. I've heard of nearly NO one who
regretted adding a solar system, but I have heard of folks who were
disappointed initially because of a lack of understanding. One bus owner
found that he had something like 100AH/day of phantom loads! He ended up
covering the roof of his unit with panels and never did achieve total energy
independance. (point of reference: we use <20AH/day and Sherry gets by with
even less!)

                                                                    <<Jim>>