PV north facing in US [RE-wrenches]

[matthew tritt]

Bill,

Egad. Does the CEC recognize a North-facing system as viable for the
rebates? I just declined a job precisely because of a bank of trees right
behind the house (South). If the production is 25% less than South the
payback should take 25% longer, yes?

Since the break-even point is already at 10 yrs + (with rebates) for a
system that actually is where it's supposed to be, I can see this as a major
deterrent for buyers who care about the "bottom line". Will other wrenches
find this kind of installation so amusing that they assume it was done by
someone fro Home Depot? ;-)

Matt T
----- Original Message ----- 
From: "Bill Brooks" <billb at endecon.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, July 22, 2003 3:41 PM
Subject: RE: PV north facing in US [RE-wrenches]


Bill and Joel,

My SPAM filter caught this because it said north facing PV in the US (not
really). However, Joel asks a good question and there is very good answer.

Case in point. A homeowner has a south-facing house with a 4:12 roof pitch
(18 degrees). The detailed version of Clean-Power Estimator works for a
North facing array. In Vacaville (Northern California) the north roof face
will produce 75% of the south face on an annual basis. Now consider a short
and fat tree on the south side that provides lovely shade to the house and
south roof, but leaves the north roof unshaded. The Pathfinder shows that
the tree limits performance by 40% on an annual basis.

Question: Which location will produce more energy?
Answer: North face (and we're not in New Zealand!)

Of course system performance could be improved by going flat or tilted on
tilt legs to the south, but the owner may think that is ugly (and they would
be right).

As long as you and the customer know the impact of the decision, go for it.

Bill.


-----Original Message-----
From: Bill Roush [mailto:solarguide at everestkc.net]
Sent: Tuesday, July 22, 2003 1:50 PM
To: RE-wrenches at topica.com
Subject: RE: PV north facing in US [RE-wrenches]


Why North facing? I will never speak ill of a client, they are so rare
in these parts, so my lips are sealed.

Best,
Bill Roush
Solar Electric Systems/KC, Inc.




-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net]
Sent: Monday, July 21, 2003 9:17 PM
To: RE-wrenches at topica.com
Subject: Re: PV north facing in US [RE-wrenches]

Bill,
You can input north-facing azimuths in PVWATTS
http://rredc.nrel.gov/solar/codes_algs/PVWATTS/version1/text_only.html
I've heard about north-facing arrays in Hawaii because the islands are
so
close to the equator and I saw a grid-connected 25 kW array in India
that is
manually tilted north and south depending on the season. But PV on a
north-facing roof in the U.S.? Why?
Best,
Joel Davidson

Bill Roush wrote:

> I am not finding the references I see periodically to de-rating for a
> north facing roof in the US. Any links for me?
>
> Best,
> Bill Roush
>
>
>
>
>

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