Yes, it is true that a bit of shade on the panel drops the output  
dramaticly, but in some situations, full sun is available for a  
limited amount of time due to trees, canyon walls, etc. and a higher  
output panel can help make up for the diminished exposure time.

On Apr 8, 2009, at 1:22 PM, Rocket J Squirrel wrote:

> On 4/8/2009 11:53 AM Keith Ovregaard wrote:
>
>> Some volks like the simple approach and permanently mount the panel  
>> to
>> the roof. Using a larger higher output panel will help compensate for
>> off-angle alignment to the sun and shady campsites.
>
> True that off-angle output doesn't drop panel output super fast like  
> shade does. But one could put a thousand watt panel up there and the  
> shade from a few branches would drop the output to 5W or less. BTDT.
>
> Hook an ammeter in series with the panel and shade a portion of the  
> panel with your hand. The output will go down faster than Lehman  
> Brothers.
>
> "Orientation of the modules to the sun is critical to the successful  
> operation of a PV system. Ideally, the modules will be at a 90�  
> angle to the sun's rays at all times. In practice, this is not  
> always practical. Tracking mounts are available which will  
> automatically reposition the modules continuously throughout the  
> day, although they are quite expensive, and installed only on large  
> arrays. Most systems are installed on a fixed-azimuth mount, which  
> is adjustable seasonally for elevation. This means that the modules  
> are pointed due south (Northern Hemisphere) or north (Southern  
> Hemisphere), and the angle to the horizon adjusted several times a  
> year as needed to keep the modules best aligned with the sun's rays.  
> The result is slightly lower output power during the morning and  
> evening, but results also in a much lower installed price. Even  
> small areas of shade on a module will decrease the output  
> dramatically, so location is an important consideration during  
> installation."
>
> http://www.mrsharkey.com/busbarn/electrics/chapt1.htm
>
> -- 
> Mike "Rocket J Squirrel" Elliott
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> Bend, OR
> KG6RCR
>
>