Richard, I know this is a bit late, but I just arrived back home after
a couple of months on the boat (and I'm away again for another month).

A 50" by 20" solar panel (rated at 80 watts, for example), will
generate about 20 amp-hours per day if the panel is not adjusted to
face the sun as the sun (or the boat) moves. If you optimize the
panel's alignment, perhaps twice that - 40 amp-hours. The panel will
provide about 5 amps in full sun when properly aligned, less when the
sun's angle to the panel and the light intensity change.

If you connect panels in series, the voltages add, as another poster
pointed out. If you connect them in parallel, the current's add up.
(E.g 5 amps per panel gives 10 amps for two)

However, most panels are affected by shadows falling on the individual
cells; this reduces the output of the panel. Putting two panels in
series, where one is slightly shadowed and the other is in full
sunlight will affect the output of BOTH. You are better off connecting
them in parallel to avoid this.

Just as a note on my system: I have a cold-plate system (EZ-Kold)
that uses a Danfoss BD35 compressor. I have a 4.5 cubic foot box, with
roughly R20 insulation. About 1/4 of this is a freezer section, with
an insulated partition and spillover of cold air from freezer to
fridge section.

In Lake Ontario (43 degrees north) in the spring and fall, when air
temp is moderate (75 degrees or so), I use about 50 amp-hours per day
- the compressor runs about 50% of the time - on for about 3 hours,
off for about 3 hours.

I would need three "randomly oriented" panels to keep the batteries up
if solar were my only charging method.

(Richard Kollmann) wrote:

David:
You are right holding plates store energy the same as batteries, but
they do not have the problems with maintenance and regular replacement
that batteries do. A full time cruiser or live aboard with twelve
volt refrigeration can wear out cheap batteries in less than three
years. Over the years when I was building holding plates I sold
hundreds of them with dual coils. Many of those plates were designed
as hybrid refrigeration 12 volt and engine driven. With the hybrid
system energy could be stored in both the batteries and in the holding
plates. When there were several no sun days the engine alternator and
engine driven compressor could replenish the stored energy. There is
a very small market for 12 volt solar powered refrigerators without
batteries. The hardware is available; motor controllers, soft start
variable speed and variable voltage compressors so why not use it. I
have many design upgrades in the 12 Volt Refrigeration Manual but they
all require battery support this one will not require batteries.

Richard Kollmann
http://www.kollmann-marine.com


Larry Bradley VE3CRX
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