On Sun, 29 Sep 2013 17:24:05 +0100, wrote:

I'm after some adjustable stays for varying the slope (manually on an as
needed basis, on a boat) of some solar panels.

Tweaking them for summer / winter makes some difference but not as much as you
might think and as panels are now dirt cheap why not simply oversize them say
1.5x and keep them fixed and flat?

See

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php

and plug in a few variables

Fixed slope and azimuth for example in London, a 1kW panel produces 982 kWh per
annum
2 axis tracker 1260 kWh
Flat (0 deg) 832 kWh
Vertical (90 deg) 703 kWh

The database is reasonably accurate, certainly within +/- 10% and most of that
can be seen in the variations in Met Office reported regional sunshine figures.

http://www.metoffice.gov.uk/climate/uk/datasets/

On a standalone PV system in service for about 10 years now the output figures
have been logged and checked against the predictions and the met office sunshine
figures. The panels were originally adjustable for angle but have been fixed
now for at least five years, they were adjusted for maximum output around solar
noon on a sunny day sometime in iirc April, just because that was a day when I
had a spanner to hand So too steep for summer, too shallow for winter, output
is perfectly acceptable.

Since then a few Chinese produced panels bought off Ebay have been fitted
totally flat in another installation. Apart from problems with the extended
snow cover this past winter / spring they work just fine. Just size them
correctly for the midwinter load and irradiation


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