PV grid-tie output (Was PV roofing material) [RE-wrenches]

[Allan Sindelar]

Travis,
1. We lack Santa Fe figures. Albuquerque is 6.4 average annual hours for a
fixed array at latitude, according to Sandia figures. We extrapolate 85% of
that for Santa Fe, but can't defend that figure. We are 1,200 feet higher
and against mountains that are closer in. Homes that are near the base of
the mountains, as this is, have more clouds.
2. A single large cottonwood on the eastern edge of the property provides
some winter shading, according to our Pathfinder analysis. The client knows
about this, but has not yet trimmed it as he said he would. This affects one
of the four subarrays.
3. Our peak solar seasons are spring and fall, because of high desert summer
monsoons. The period of recording excludes late summer and early fall, which
are peak insolation times. Also, we had about three weeks of about 70% of
normal insolation in June because of smoke from AZ and CO fires. I would
expect these to contribute slightly to the apparent discrepancy.
4. John Wiles says expect 65% overall system efficiency. Most installers
that I have heard use 70%, as do we.
Allan

----- Original Message -----
From: "Travis Creswell, Ozark Solar" <ozsolar at ipa.net>
> 8.54 kWh/day / 2.24 kW array = 3.81 average daily sun hours for an 1 full
> year of data. That's a pretty interesting number (I think).  How does that
> compare to Santa Fe's published annual average?  All I can find right now
is
> the map of the US that shows you in the 6 hr annual average. Assuming your
> annual average is 6 hours (and the site is in full sun all day long) that
> comes up to a net system efficiency of 63%.
>
> Comments?
>
> Travis Creswell
> Ozark Energy Services
> ----------
> >From: Allan Sindelar <allan at positiveenergysolar.com>
> >To: RE-wrenches at topica.com
> >Subject: Re: PV grid-tie output (Was PV roofing material) [RE-wrenches]
> >Date: Wed, Aug 21, 2002, 1:26 PM
> >
>
> >Here are some numbers to toss into the output stew:
> >Our first batteryless system used 32 BP70s on two GC-1000s on a roof in
> >Santa Fe. We installed a Hialeah kWhr meter on the AC output. Between
> >11/12/01 and 8/1/02, we fed back an average of 8.54 kWhr/day from 2,240
> >rated watts of PV. One of the four subarrays was on a section of roof
that
> >is partially shaded during winter months.
> >The GC-1000s have to date performed flawlessly, and the client is
satisfied.
> >Allan at Positive Energy
> >
> >> Does the system have a kWh meter on the output of the inverter? That is
> >> really necessary to quantify energy production.
> >> Bill.
> >
>
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