PV orientation [RE-wrenches]

[Bill Brooks]

Joe,

Really good question. I'm unaware of any good studies done on this issue
other than the initial work to validate the incidence angle modifiers for PV
FCHART and other similar programs. Basically it is a function of the sun
angle (which we know very accurately) and the incidence angle modifier of a
PV module. Many crystalline modules have similar IAMs with a few exceptions
on products that focus on the issue of off-angle irradiance. I have found
that a-Si products have very different IAMs so there are variations from
product to product.

The bottom line is that orientation is much less critical than shading. I
just did orientation analyses for California and New York and here are the
results:


These are orientation multipliers for the two states

For New York:

Direct./ oTilt	0o	15o	30o	45o	60o	90o
South			0.87	0.96	1.00	0.98	0.92	0.66
SE,SW			0.87	0.93	0.94	0.91	0.85	0.62
E,W			0.87	0.85	0.81	0.74	0.67	0.49


For California:

Direct./ oTilt	0o	15o	30o	45o	60o	90o
South			0.89	0.97	1.00	0.97	0.89	0.58
SSE,SSW		0.89	0.97	0.99	0.96	0.88	0.59
SE, SW		0.89	0.95	0.96	0.93	0.85	0.60
ESE,WSW		0.89	0.92	0.91	0.87	0.79	0.57
E, W			0.89	0.88	0.84	0.78	0.70	0.52



The punch line is that if you have 10-20% loss due to shading, it is almost
always better to reorient the array toward a part of the sky that is less
shaded (even if it is east or west). That being said, this orientation
information is for annual energy production and not for sizing related to
off-grid, winter-dominated load profiles.

Hope this helps.

Bill.

-----Original Message-----
From: Joe Schwartz, Home Power [mailto:joe.schwartz at homepower.com]
Sent: Thursday, August 22, 2002 8:18 AM
To: RE-wrenches at topica.com
Subject: SPAM: PV orientation [RE-wrenches]


Hey all,

I'm looking for real world data on PV orientation vs. KWH production.
 From what I've seen, much of the current orientation advice
(especially on-grid) is based on F-Chart simulations.

Have any of you collected KWH output data for systems with arrays in
multiple orientations at a particular site? And if you have, how
closely does the data correspond to simulation programs, i.e. F-Chart?

To keep it simple, I'd to limit the scope of this question to systems
with an array/inverter in any given orientation (not arrays with
different orientations feeding a single inverter). I'd also like to
ignore orientation considerations that may be based on economics,
like TOU metering. I'm just after KWH output data vs. orientation.

Thanks,

Joe
--

Joe Schwartz - CEO and Technical Editor
Home Power magazine
joe.schwartz at homepower.com
www.homepower.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email to: RE-wrenches-unsubscribe at topica.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================