Lowest DAYTIME temp records [RE-wrenches]

Jeff Clearwater clrwater at earthlink.net
Thu Feb 2 18:42:27 PST 2006


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Hi Joel,

But the fact is that the coldest recorded temperature COULD BE in the 
sunlight at sunrise.  In fact in the North snow country or at 
altitude that is often the case - having lived in New England half my 
life, we often see the coldest temps an hour before sunrise and then 
it might go up just a few degrees.

Yes it would be good to have records of coldest daylight temps.  But 
then two things would happen I think - first they would mostly likely 
be very close to the same as coldest temp,   and secondly,  I would 
tend to design for coldest temps anyway - with changes in climate 
happening - I would tend to be safe and use that coldest temp to be 
safe - it only takes once to blow the top off your caps.

So I agree with Bill.

peace,

Jeff Clearwater
Village Power Design



>Should PV systems be designed using nighttime temperatures when it 
>is obvious that voltage is not present in the dark? Should climate 
>data from a weather station be used because it is available even if 
>the system location has a different microclimate? Does this seem 
>reasonable? SMA's string sizing tool has the right idea. They ask 
>you to select the coldest record low ambient temperature when 
>sunlight will be on the array.
>
>
>www.weather.com only lists record high and low temperatures. NEC 690.7(A)
>specifies the lowest expected ambient temperature which implies sunlight on
>the array to cause voltage. Except in rare situations record low
>temperature occurs at night or before sunrise when no voltage is present.
>
>Does anyone know a source for the lowest expected ambient temperature when
>sunlight will be on the solar array?
>
>Joel Davidson


-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com

877-SOLARVillage
FAX: 413-825-0372
72 Baker Rd
Shutesbury, MA 01072
425 Nimrod St,
Nevada City, CA 95959
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~

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