I did a quick simulation using PV Watts for a small system in Western Mass.
Here’s what I found:
Azimuth Roof Pitch kWH/year % of optimum
180 40 2593
100%
0 40 1291
49%
0 10 1996
79%
75 40 1829
70%
Looks like roof pitch makes a pretty big difference in our area.
Thanks,
Will
Will White
Director of Construction – East Coast
RGS Energy
64 Main St. |Montpelier, VT 05602
tel 802.223.7804 | mobile 802.234.3167 | fax 802.223.8980
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From: RE-wrenches [mailto:[email protected]] On Behalf
Of Chris Mason
Sent: Tuesday, July 28, 2015 1:50 PM
To: RE-wrenches <[email protected]>
Subject: Re: [RE-wrenches] Using the North Facing Roof
In the Caribbean, low tilt roofs that face North can work very well, we (16
degrees) are below the Tropic of Cancer (23 degrees) and the sun is in the
North for much of the year.
On Tue, Jul 28, 2015 at 12:24 PM,
<[email protected]<mailto:[email protected]>> wrote:
Jarmo,
The sun’s geometry is not nearly that simple. To understand the impact of
north-facing arrays, you have to perform a simulation. PV:WATTS does this just
fine and it is easy to show that a 18-degreed North-facing tilt produces 75% of
a perfect 30-degree south-facing array. Far more than your assumption of 50%.
To compare 15-degrees South to 15-degrees North, the numbers are slightly
better at 77%. We are going to see a lot of north-facing arrays once people
understand that low tilt angles are very forgiving on North slopes. Steep
slopes are a totally different story and you have to run the numbers….
Bill.
From: RE-wrenches
[mailto:[email protected]<mailto:[email protected]>]
On Behalf Of
[email protected]<mailto:[email protected]>
Sent: Tuesday, July 28, 2015 8:04 AM
To: RE-wrenches
<[email protected]<mailto:[email protected]>>
Subject: Re: [RE-wrenches] Using the North Facing Roof
I did a slide on the effect of North facing modules. For even a fairly
aggressive rotation North as shown, the effect is "only" a 50% reduction.
The questions of whether or not to do it, are,
- is the mounting structure simpler, lower cost
- security against wind
- can I put a larger array on the roof (typically yes, if you make back to
back pyramid shaped structures)
- overall, what is the cost versus benefit
[cid:[email protected]]
JARMO
_____________________________________________________________________________________
Jarmo Venalainen | Schneider Electric | Xantrex Brand | CANADA |
Sales Application Engineer
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Email:
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Way, Burnaby, BC V5G4M1
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From:
"Peter Parrish"
<[email protected]<mailto:[email protected]>>
To:
"'RE-wrenches'"
<[email protected]<mailto:[email protected]>>,
Date:
07/28/2015 12:22 AM
Subject:
[RE-wrenches] Using the North Facing Roof
Sent by:
"RE-wrenches"
<[email protected]<mailto:[email protected]>>
________________________________
I recently read a short piece that caught me up short, and I quote:
“The fast dropping cost of solar, while a huge boon to the adoption of solar
PV, has counter-intuitively altered design parameters. No longer is the
north-facing roof considered unusable because limited application in less-than
optimal orientations can still show a positive net benefit. Arrays are thus
designed now with elements or sub-arrays in these locations, increasing overall
kW installation while reducing the energy production per capacity installed.
This might have been anticipated based on sheer economic analysis from a users
perspective, but so long has solar been expensive that these less optimal
orientations were never seriously considered.”
I doubt that the individual who wrote this piece came to these conclusions
him/herself. Does anyone know of a recent article that argued this perspective?
Is this an emerging design practice? If so, I’d like to know more about it.
- Peter
Peter T. Parrish, Ph.D.
President, SolarGnosis
1107 Fair Oaks Ave., Suite 351
South Pasadena, CA 91030
(323) 839-6108<tel:%28323%29%20839-6108>
[email protected]<mailto:[email protected]>
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Chris Mason
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