It seems to be -0.5%/degC:
http://rredc.nrel.gov/solar/calculators/PVWATTS/moreabout.html
-------- Original Message --------
Subject: [RE-wrenches] PVWatts Module Temperature Coefficient (was
Enphase derate)
From: Joel Davidson <joel.david...@sbcglobal.net>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Date: 2010/4/18 12:23
Wrenches,
PVWatts does not accurately predicate Unisolar and Sunpower module
performance because it uses a generic single crystal silicon solar
module power temperature coefficient (I think -0.4% per degree C). Does
someone have the technical paper that specifies PVWatts module
temperature coefficient? Thank you.
Joel Davidson
----- Original Message -----
*From:* Kirk Herander, VSE <mailto:k...@vtsolar.com>
*To:* 'RE-wrenches' <mailto:re-wrenches@lists.re-wrenches.org>
*Sent:* Sunday, April 18, 2010 4:32 AM
*Subject:* [RE-wrenches] Enphase derate (was Tilt biased....)
Enphase has a tech note pdf for download that recommends and
rationalizes a PV watts derate of .819 instead of the standard .77
(which IMO is a little conservative to begin with).
http://www.enphaseenergy.com/downloads/EnphaseAppNote_PVWatts.pdf
Kirk Herander
Vermont Solar Engineering
802.863.1202 fax 802.863.7908
VT RE Incentive Program Partner
NYSERDA Incentive-eligible Partner
NABCEP^TM Certified Installer
*From:* re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of
*Allan Sindelar
*Sent:* Sunday, April 18, 2010 3:18 AM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Tilt biased....
Holt,
Feedback re the low tilt angle: Go for it, you're good.
Re wind loading: check out UniRac's Code Compliant Installation
Manual, http://www.unirac.com/pdf/ii227.pdf, especially pages 3-9.
Less wind loading is one of the main reasons for going with a lower
tilt angle. Another is closer module row spacing (at 3X height RoT)
without inter-row shading.
No experience with Enphase.
Allan
*Allan** Sindelar*
_alla...@positiveenergysolar.com_ <mailto:al...@positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
EE98J Journeyman Electrician
*Positive Energy, Inc.*
3201 Calle Marie
Santa Fe, New Mexico 87507
*505 424-1112*
_www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
_hol...@sbcglobal.net_ <mailto:hol...@sbcglobal.net> wrote:
Searching for opinions.....is this "over design"?
Designing small system (2.35kW). Customer uses gas for heating.
Typical A/C unit. I was thinking of biasing the tilt to summer
production for greater offset of summer demand (lat 31.6, proposing
18). No net metering in this part of the world. PVwatts shows a drop
of 2% /yr. in production , 5% higher production for A/C months.
Feedback?
Also, this array will go on a carport. I understand that windloading
is actually greater for an open structure than one with walls
(another reason for lower tilt) - is there any one that can direct
me to data on finding out how much more?
Lastly, what is a good avg. target derate factor for Enphase
inverters (real world)?
Holt E. Kelly
Holtek Fireplace & Solar Products
500 Jewell Dr.
Waco TX. 76712
254-751-9111
_www.holteksolar.com_ <http://www.holteksolar.com>
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