Friends:
Forgive me if this point has already been made:
When designing PV feeders, one typically looks at the Impp of an array for
current specifications. Impp is rarely achieved, however -- only a
handful of days per year and for only a short period of time per
day. This is particularly true for a fixed array.
I took the hour-by-hour data from the PV watts tool, subtracted out the
zero values (night time) and averaged the remaining values. The result was
about 50%.
Therefore, a 2% VD at Impp is actually a 1% VD on average. This gives a
bit more headroom in any PV feeder design.
William Miller
At 04:25 AM 4/9/2010, you wrote:
IMHO it seems like we're all really on the same page here...... trying to make
the the most out of the the resources we have available to work with......sun
hours, pv, copper, labor, dollars, etc. Job specifics come into play.
There are
definitely times when a detailed cost/ benefit analysis is called for. Many
other times, let's not miss the forest for the trees, an increase in wire size
to avoid waste of other aforementioned resources, is low hanging fruit. As a
percentage of the overall system cost, the decision is a no -brainer.
Dick Ratico
Solarwind Electic
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