As some of you know, I bought one of these "45 Watt Solar Panel Kits"
last November (of 2007) and installed it on my deck, facing south.
The setup can be seen at
There you will also find graphs showing some representative daily
**Paragraphs that begin with "**" offer my conclusions.
It is now several days past June 22nd, so I now have seen the longest
days of the year. I won't be doing any more experimenting except maybe
to mount the panel out in the yard on a C-Band single axis tracking
mount just to see how soon after the sun comes up I can get "full" power.
**My simple calculations suggest that I am loosing about 37% of the
potential sun energy each day with the fixed collector.
For my location, It's even worse in the summer because some trees
interfere with the sun starting at about 5PM. This wasn't a problem in
the winter, because the sun never got that far in the west before it
**Maximum power from the panels: This kit can NOT generate anything
close to 45 watts. The best output I have ever seen is about 32 watts
and that was only for a few minutes. More typical Maximum output on
a sunny day here in western Wisconsin is about 26 watts.
I was "flamed" by a guy some months ago who thought that the way to
measure a panel's output was to short it, measure the current, then
open it and measure the voltage. He multiplied the two numbers together
to get the max. wattage. Maybe that's how they did it at HF. (This,
of course, is NOT correct. Google PV IV Curves if you want to learn
**So far, since about December of 2007, I have been very dissapointed in
the solar insolation at this place. December and January are almost
totally useless. Not because of the low winter sun, but because of the
clouds. Some of those days were so cloudy that the panels yielded less
than 10 watt hours all day.
**I am on my fourth controller from Harbor Freight now and this one is a
real good one. 2 of the other 3 developed minor but nagging problems
and one just quit. HF was very good about replacing them.
**I am VERY impressed with this controller. Somebody put a LOT of
thought into its design. It does a very good job of getting all it can
from the sun. Many people have beat me over the head about not getting
an MPPT controller, but this little device is almost as good!
To test the max output of the panels and to see what an MPPT
controller might do with this panel set, I added a 100 watt 35 ohm
rheostat to the test setup described on may webpage
(http://www.spaco.org/PV/PVSolar.htm ) so I could switch between the
controller and the rheostat. That way I could "tune" the load to
optimize the wattage whenever I wanted to.
**The only time I could manually get more power from the panels by
manually selecting a load was at maximum solar output and then I could
only gain 1 or maybe 2 watts.
**Summary: If you have an application where you are off-grid and you
require something in the range of 150 watt hours per day 9 months out of
the year,and you live where I do (western Wisconsin), then this setup is
for you. It would be a great vehicle battery maintainer.
Dear Pete and ALL
I'm glad you put in all the effort in documenting your system and
sharing your experience.
Can you put up more legible version of your diagrams, and perhaps the
For those interested in a very high quality instrumented PV
monitoring, please check
into http://jr-solar.stanford.edu/24Temp_and_Pyra.htm . The site was
designed by a
professor John Scofield at Oberlin College in Ohio. It is the best
site I know. Then
if someone knows about any other similar sites, please share it with
BTW I'm in a group of under-employed engineers in the Silicon Valley,
build an enterprise focused on PV performance monitoring and
diagnostics. For now
we rolled out a free public service website that offers a benchmark
output in KW
if a visitor can enter essential attributes about an installation. We
are doing this
because we see too many PV sites under-perform, and without their
operators' knowledge. Please check into www.solarperformance.org, or
www.pvperformance.com. Hope each of you can exercise it and give us
brutal critique, as we are trying to finalize this beta test and
initial development. Our goal is to evolve it into a truly useful
tool for all
PV owners and operators, to be able to checkup on their system on
Thanks ALL for your indulgence.