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Author Topic: Positioning Solar Trackers?  (Read 3777 times)
clockmanFR
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« on: January 23, 2012, 07:59:39 PM »

Any Ideas?

I am putting 2off 1.5Kw Solar Trackers up.

Dilemma, what distance appart for mounting to stop each shading each other, when start East and finish west?

 I have about 100 meters to mess with east to west, with 2m low hedges, (which could be modified). Max height of each tracker will be 5.5m and 3.5m wide. I will get about 160 degrees arc.

In practical terms for PV panels, Is the sunrise sun better that than the sunset sun.?

Or i could mount/install them on true south to north line at say 60m apart, but then in winter when the sun is low i will get shading problems again, hmm.
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JohnS
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« Reply #1 on: January 23, 2012, 08:18:01 PM »

What lattitude are you?
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2.1kWp solar PV  PHEV West London
clockmanFR
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« Reply #2 on: January 23, 2012, 08:44:49 PM »

johnS,
N48 52 03
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renewablejohn
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« Reply #3 on: January 23, 2012, 09:36:47 PM »

clockman

Buy one of these then you dont have that problem

http://www.zenithsolar.com/product.aspx?id=287
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clockmanFR
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« Reply #4 on: January 23, 2012, 09:42:49 PM »

Thanks, but,
1. Me buy, steady on. onpatrol
2. My boy's would play at frying the sheep and the farmer down the valley.  hysteria

OO7 "Haa Mr Bond" as i stroke white fluffy cat.
« Last Edit: January 23, 2012, 09:47:34 PM by clockmanFR » Logged

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JohnS
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« Reply #5 on: January 30, 2012, 02:18:05 PM »

Clockman

Sorry I missed your reply.

At the winter solstice, the sun's elevation at noon will be 90-23-49 = 18 degrees.

A tracker of height X will cast a shadow of Y where X/Y = tan(elevation)

A 5.5m high tracker will cast a shadow of 5.5 / tan(18 degree) = 19.5m

Thus you could have 4 trackers on a north south axis, each 20m apart.

You can find the sun's elevation at any time here  http://www.srrb.noaa.gov/highlights/sunrise/azel.html

John
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clockmanFR
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« Reply #6 on: January 31, 2012, 06:21:02 PM »

johnS,
many thanks for that. Its allways good to get a second opinion and serious maths was never my best subject.

I will install on a North South axis/line.

I will post some pics as they go in.

Again many thanks. 
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Rodney
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« Reply #7 on: February 12, 2012, 12:40:15 PM »

Any Ideas?

I am putting 2off 1.5Kw Solar Trackers up.

Dilemma, what distance appart for mounting to stop each shading each other, when start East and finish west?

 I have about 100 meters to mess with east to west, with 2m low hedges, (which could be modified). Max height of each tracker will be 5.5m and 3.5m wide. I will get about 160 degrees arc.

In practical terms for PV panels, Is the sunrise sun better that than the sunset sun.?

Or i could mount/install them on true south to north line at say 60m apart, but then in winter when the sun is low i will get shading problems again, hmm.

Recently read that putting a mirror flat on the ground in front of the panel increases the yield four fold, the mirror needs to be four times the size of the panel.
I have not tried this myself but reckon if the mirror was vertically above the mirror it would still work and require less cleaning. The theory is whatever the azimuth of the sun it gets reflected onto the mirror so ads to the direct sun collection.
Mirrors are expensive so cant see why a sheet of ply silver painted or covered with baco foil would not work but probably to a lesser efficiency.
Drawback I see are heat in the panel reducing the working life. If a method of cooling the panels could be achieved this would increase the panel life and also the heat collected could be used.
Have read that cooler panels are more efficient
Rod


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clockmanFR
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« Reply #8 on: February 13, 2012, 08:12:28 PM »

Hi Rodney,
With my trackers i will also have an adjustable declination, about 5 positions that i can adjust manually 6 times per year.   

Did think about the mirror thing, but the hassle involved and the frame required to stop the lot blowing away started to get out of hand. If a mirror i would use 2m by 1m stainless steel thin sheets with one side ready polished.

The thing with my particular design is the lack of any thing behind the panels that would trap the heat. ie, theres no roof just a few inches away.
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clockmanFR
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« Reply #9 on: February 29, 2012, 08:34:24 AM »

JohnS,

I did a quick scale drawing, now that i have the panels and i understand the finished layout and dimensions.

As you can see from the Pic, with the ground with a slight slope of 400mm, i could position the trackers on a true North South line, and they would be at 10 meters apart for the Noon Winter, when the sun is at its lowest.

Panels are 4m high by 2.8m wide and pivot for winter. summer angles at 3.2m above the ground.


* P2290094b.JPG (111.6 KB, 461x346 - viewed 327 times.)
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JohnS
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« Reply #10 on: February 29, 2012, 09:35:42 AM »

Clockman

The elevation of you panels is 60.75o per my reading of the diagram.  Per my calc above, it would have to be 72o to have the noon sun 'overhead'.

I accept 11.25o is not much difference and will have minimal effect.  Is your lower angle a design compromise?

John
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Tobi K
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« Reply #11 on: February 29, 2012, 10:31:47 AM »

How about you download a free, fully functional 30 day evaluation copy of PV-Syst from http://www.pvsyst.com/ and play with that to give you the answer? It's powerful but painful (don't say I didn't warn you!)

But the short answer is, tracking in the UK may not worth the bother. Did some experiments with tracking, and also with mirror reflectors, for my university course at CAT (you can see a time laps video at . Tracking gives a bit of an advantage in direct sunlight, but as soon as you're under clouds light is coming from all over and the best direction for your modules to face is just up in the sky, really.

PVGIS suggests that in a location where a fixed system gives you 920kWh/kW, tracking gives you 1170kWh/kW. That's 30% gain, but it assumes your tracking never has any flaws (i.e. gets stuck in the wrong position), and are you sure you can do it for less than what 30% more modules would cost?
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clockmanFR
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« Reply #12 on: February 29, 2012, 08:07:25 PM »

Hi JohnS,

At my latitude of nearly 49o  with the winter 11.75o added gives the lowest.

Sorry not been very clear on this post, i have 3 posts running at present on these Trackers perhaps i ought to bring them all together on to this Forum Topic.

I can alter the tracker angle by 23.5o to follow the sun all year, yes I know its not much, but its not much effort to design and make the simple adjuster system, its just a pivoting arm with 6 holes in it.

Tobi K, Yes i would normally agree with you, but for me the only costs are the 1700 for the 3Kw of PV panels, steel costs which are coming in at around 380 per tracker and about 3 tonne of ballast and concrete say 140.
The controll circuit does not hunt for the brightest spot, it goes to Noon position and awaits the Sun if there is any, evening falls and the tracker parks itself facing East, circuit and actuator arm are approx 150.
 
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