Lowest DAYTIME temp records [RE-wrenches]

[Jay Peltz, Peltz Power]

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HI Travis,

This is correct most of the time.

But then there is dawn and sunrise, not the same thing.

Also the sun doesn't have to be directly on the panels for them to be  
at their highest voltage.

I have seen my panels at their full voltage well before the sun  
actually hits them.

thanks,

jay

peltz power

On Feb 2, 2006, at 6:59 PM, Travis Creswell, Ozark Solar wrote:

> I watch my local weather closely and commonly see the lowest daily  
> (24 hrs)
> temp about an hour after sunrise.
>
> Travis Creswell
> Ozark Energy Services
>
>
>
> -----Original Message-----
> From: Jeff Clearwater [mailto:clrwater at earthlink.net]
> Sent: Thursday, February 02, 2006 8:42 PM
> To: RE-wrenches at topica.com
> Subject: Re: Lowest DAYTIME temp records [RE-wrenches]
>
> 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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