On Sun, 3 May 2009 17:18:44 -0700 (PDT), JimConlin
wrote:

On May 3, 6:17*pm, "Capt. JG" wrote:
"Mark Borgerson" wrote in message

g...



In article lutions,
says...
"Lew Hodgett" wrote in message
.. .
"JimConlin" wrote:

I'm thinking of a solar panel on my house top which is curved. About
50 watts will be enough.

When it comes to sizing solar panels, it is CYA time.

A reasonable assumption is about 50% output based on location of panel,
clouds, etc, and 50% output/24 hours since it averages 12 hours
daylight
per day over a year.

Thus:

(NamePlate Output)*(50%)*(50%)= 25% NamePlate Output

Factor in an additional 20% derate for what I call the
"StupidityFactor",
thus:

(25% NamePlate Output)*(100%-20 StupidityFactor) = 20%.

IOW, to practice CYA for solar panel requirements, calculate needs
based
on 20% of NamePlate Output.

Lew

We have a system on the house that's rated at 3.4 kwh. The meter
typically
shows 2.90 to 3.2 during the peak hours. I've got 26 panels.

House panels are generally tilted to match the average sun elevation
and are sited to avoid shadows. *Boats have masts (even if not
their own) and seldom have the panel tilted properly outside
the tropics. *I would expect higher average efficiency for
a household panel.

If you leave the boat unattended for a while you may have to
clean up salt spray and seagull poop when you get back.

Mark Borgerson

I would also. I don't think a curved panel on a roof would help that much,
which was what was asked.

--
"j" ganz

Sorry for my ambiguous language. I'll be more precise.
I have a 29' sailboat whose cabin (house) top is curved. The cabin
top is the ONLY possible place to put a solar panel. For good reason,
a flat panel there won't do, so the panel needs to conform to the
curvature of the cabin top. Shading of the location is minimal and
the cabin top is close to horizontal.
The boat's power requirement is small. I have satisfied myself that a
30-50 watt panel will be sufficient.

I want suggestions of supplier(s) for 30-50 watt flexible solar
panels.

Jim


I think that you will be surprised at how little electricity viv-a-vis
the panel rating you actually get out of the beast.

I have three old panels, mounted on a "roll bar" which is an extension
of the aft pulpit so shading is not a problem. The three panels are
barely able to keep a DC fridge working.

From watching my charge meter there is little current flow until at
least 09:00 and it starts to taper off about 16:00 so perhaps (God
willing) the panels put out rated power from about 10:00 'till 15:00
or about 5 hours a day. and this is on a day where there is no cloud
cover. A bit of overcast and things slow down even more.

This is not to say that solar panels aren't worth having, they are.
I'm only trying to point out that they do not produce their rated
power with any consistency.



Cheers,

Bruce in Bangkok
(bruceinbangkokatgmaildotcom)