Author Topic: Panel positioning?  (Read 3279 times)

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juiced

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Panel positioning?
« on: November 16, 2004, 09:23:53 AM »
Should panels lie long facing the south sun (more hours of low input?), or stand tall all day?( Short, higher input?)


  Ideally, you have enough panels not to worry; but for starters....


 Also i know that there is a longitude caculation for angle; but i am curious if anyone knows of a chart to figure out effectiveness in variable situations, ie 90* , 0*, 60* etc...

« Last Edit: November 16, 2004, 09:23:53 AM by (unknown) »

jimovonz

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Re: Panel positioning?
« Reply #1 on: November 16, 2004, 12:25:37 PM »
Check out this post for lots of information (including panel positioning/orientation) specific to your area:


http://www.fieldlines.com/story/2004/10/6/164945/703


Generally your panels should face as close as practical to due south (north in southern hemisphere) and should be more vertical in winter/more horizontal in summer. How much depends on your latitude. The orientation figures you get from the above link assume a flat surface that absorbs energy equally from any incident angle. Glass covered cells reflect much of the energy at low incident angles so I would mount my panels 5-10 degrees more vertical than is indicated from the data on this site.

You can also get an idea of your total daily output at different times of the year for different panel inclinations from the data on this site. The daily energy figures in kWh are per sq meter. So measure your panels and assume a panel efficiency of 10-15%.

« Last Edit: November 16, 2004, 12:25:37 PM by jimovonz »

Tyler883

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Re: Panel positioning?
« Reply #2 on: November 16, 2004, 01:38:00 PM »
I've never tried this, but here's an idea:


If you've got a multimeter that will show you the output voltage of your solar cells while still showing you differences in voltages in the tenth or thousandth of a volt...You might try optimizing your inclination for maximum voltage on your volt meter.


I like this idea better than using a chart, because if you stick to real world results you aren't leaving yourself vulnerable to  unexpected error that the charts haven't calculated for.


cheers


Tyler

« Last Edit: November 16, 2004, 01:38:00 PM by Tyler883 »

wpowokal

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Re: Panel positioning?
« Reply #3 on: November 16, 2004, 04:26:27 PM »
Homepower published an artical on tracking sola panels in their last issue, this may help. Go to their site, register and read on line.

http://www.homepower.com

regards Allan
« Last Edit: November 16, 2004, 04:26:27 PM by wpowokal »
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ghurd

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Re: Panel positioning?
« Reply #4 on: November 16, 2004, 05:44:12 PM »
Lie long. Stand tall. ?

Are you asking short side up or long side up? The panel doesn't care.

The Junction box might, the instructions should say.

I mount them long side up. Makes for less material in the brackets. Maybe a little less leverage for the blowing wind.

I get asked that every week, like if its tipped the electric will pour out easier.


Mount them South facing, at about 10' steeper than your latitude.  This will give a little less in summer, but a little more in winter when you need a little more.


For adjustable brackets. Spring and fall at your latatude X, winter X+10, summer X-10. I read adustable brackets, done everyday, will only increase the output for the year about 15%. I never figured it was worth adjustable brackets, and just throw another $100 at the panel, so it won't need adjusted 4 times a year(idiot-proof).


I'm not big on trackers until you have a BIG PV system. Expensive and breakable. I mean, if you are putting up 200w and a tracker, its cheaper and easier and more output to put up 300w fixed.


What you want is the biggest shadow from the PV.  The bigger the shadow, the more sun it is catching. Close is good.

Hold you hand flat under a desk lamp, 12" up from the desk. Tip your hand both ways 15'. Not much change in the shadow. Now hold it verticial and tip it both ways 15'. Big change in the shadow. Thats degrees, not feet.


If it snows up there (lol), mount them where you can get the snow off with a broom.

A quarter inch of snow will shut them down. If they are on the roof of a 3 story house, nobody wants to go up in the snow to brush them off.


G-

« Last Edit: November 16, 2004, 05:44:12 PM by ghurd »
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jimovonz

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Re: Panel positioning?
« Reply #5 on: November 16, 2004, 11:45:41 PM »
While what you propose is fine, it would only give you the optimal orientation for a specific time on a specific day. Ideally you want to optimize your total daily output and maybe adjust a couple of times a year to better accomodate the low/high winter/summer sun
« Last Edit: November 16, 2004, 11:45:41 PM by jimovonz »

Ungrounded Lightning Rod

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Re: Panel positioning?
« Reply #6 on: November 17, 2004, 08:48:23 AM »
While what you propose is fine, it would only give you the optimal orientation for a specific time on a specific day. Ideally you want to optimize your total daily output and maybe adjust a couple of times a year to better accomodate the low/high winter/summer sun


So (assuming you don't have morning or evening shadows) do it at local noon on a day in early November or early February, so it's near-optimum during the coldest (and probably most demanding) season.


"Local noon" is when the sun is highest.  About standard time noon if you're near the middle of your zone, half an hour earlier if you're near the east edge, half past if you're near the far edge.  (And check a world map to see where your zone SHOULD be.  Some of the zone edges are skewed for politics.  For instance:  The eastern zone extends across Michigan so Detroit shares a timezone with New York to ease communication between the auto and financial industries and so the whole lower peninsula shares a zone.  That makes the western edge nearly an hour off.)


Measuring the short-circuit current (or current into a resistive load, or voltage across a resistive load) would be more effective than measuring the voltage of the panel while it's in circuit, though the latter may suffice if your charge controller doesn't screw up your meter.  If you panel isn't connected directly to batteries you should be able to put a heavy load on it and pull the voltage down to where the rest of the system isn't affecting the measurements.

« Last Edit: November 17, 2004, 08:48:23 AM by Ungrounded Lightning Rod »

Ungrounded Lightning Rod

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Re: Panel positioning?
« Reply #7 on: November 17, 2004, 08:52:06 AM »
Oh, yes.


The downside to adjusting it for maximum output is that it's hard to get it pointed right, since the curve of output versus angle is flat at the maximum.  So it takes a lot of motion to affect the reading.  Better would be to put a carpenter's square on the front surface and adjust the panel so its shadow just disappears.

« Last Edit: November 17, 2004, 08:52:06 AM by Ungrounded Lightning Rod »

ghurd

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Re: Panel positioning?
« Reply #8 on: November 17, 2004, 09:22:01 AM »
Measuring the angle is easier with a round thing, 2 flat sides, graduated in degrees. Like a compass, but the needle points up to the degee marks.

Usually orange. They have them at all the different 'everythings a buck' stores around here.

Much eaiser than a roofers square and level.
« Last Edit: November 17, 2004, 09:22:01 AM by ghurd »
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