Re: [A/S] RE: Flexible solar panels (was 66 Safari)

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Jim,
 The flexible panels are different in their physical construction/design
than the rigid type. Besides being flexible, their output drops off
somewhat less when a cloud passes than the rigid (crystalline) panels.

However, the peak output from an amorphous (flexible) panel is less for
a given physical size than from a crystalline panel.

Talking about panels before considering usage is putting the cart before
the horse: you must use one of those sizing worksheets such as that
available at http://www.rvsolarelectric.com to get an idea of your
needs/usage. If you can cut that usage by installing flourescent lights,
using a smaller TV set (mine draws only 1 amp, but it's just 5" in
size), you're way ahead of the game. Usage is measured in Amp Hours (AH,
or 1 amp for one hour).

After figuring out your usage, you can size your battery bank; you want
to use no more than 25% of your available (rated) capacity in a day if
you're to achieve maximum or even decent battery life. The typical A/S
trailer uses either one or 2 Group 27 "RV/Marine Deep Cycle" batteries,
rated at 105 AH/each. That means that if you have only one battery, you
should keep your usage below 25 AH/day. Use the worksheet to see if you
can do that.

Now that you have your usage and storage figured out, you can size your
solar charging system. It needs to be large enough in capacity to
replace the AH plus at least 10% for efficiency losses. As a point of
reference, a 75-watt panel (21" X 48" if it's the more-efficient
crystalline type) will provide about 30 AH/day, if it's nice and sunny.
If you want flexible panels for esthetic reasons, and want to mount them
right against the skin of your A/S, that's OK, but be aware that the
output will suffer dramatically, especially in hot weather. That's why
almost all applications use crystalline (rigid) panels, spaced a couple
of inches off the roof.

Now, all of these calculations are based on a full-time application; you
may not need this much if you're a weekend-only user. A small solar
panel can stretch your battery from "dead in 3 days" to "dead in 5
days", which might be enough.

Remember that all systems and users are different, what works for one
may or may not work for someone else. Sherry uses a couple of small
panels and gets by nicely. You'll note that she travels alone and her
usage is very frugal. Other folks, with lots of lights and perhaps an
inverter to run their microwave oven, will need 4 or 5 panels in the 50
-> 75 watt range. That's why it's so important to use those worksheets.

I remembered another very good educational source:
http://www.amplepower.com. Be prepared to spend at least a couple of
hours there if you're not very familiar with the technology, but you
WILL be much more familiar after that time.

Also, to Bob Kiger: Solar electricity in place of grid-provided never,
ever saves money. The ONLY exception to my knowlege is if you're a long
way from the grid: your cabin is up in the mountains or you're
boondocking with your trailer. If you have "factory" power available,
use it and be happy. Again, spend maybe a half-hour with one of those
worksheets, then another half-hour pricing a solar system, then compare
it to what it costs to buy the power. You'll see just how cheap grid
power really is.

                                   <<Jim>>