[RE-wrenches] PVWatts Module Temperature Coefficient (was Enphase derate)
Dave Click
daveclick at fsec.ucf.edu
Mon Apr 19 07:01:32 PDT 2010
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.davidson at sbcglobal.net>
To: RE-wrenches <re-wrenches at 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:kirk at vtsolar.com>
> *To:* 'RE-wrenches' <mailto:re-wrenches at 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-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at 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*
> _Allan__ at positiveenergysolar.com_ <mailto:Allan at 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/>
>
>
>
> _holtek at sbcglobal.net_ <mailto:holtek at 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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