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Forum Index : Solar : Solar Tracking

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brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548
Posted: 09:19am 07 Mar 2011
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AH Ha,,, now you have bought up an important point I had to deal with .....

I requested that my 1Kw of panels (6) be mounted on my home made gal steel rotating frame .. Now this steel was off a Telecom microwave tower , so you can imagine how good that is ,and I told them that.

No, no deal , unless I got an engineers design and report ,mamy big dollars. Then they said they would only "consider" it , how about that . So I said bugger that ,whack them on the garage roof ,thanks ,,but there is a big tree covering that roof ... Thats my problem , just do it and give me the paperwork to sign ...

So,. now I'm removing them off the the garage shaded roof and installing them where,, ah,,u guessed on my tracker..

Bruce.
Bushboy
 
RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495
Posted: 11:06am 07 Mar 2011
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Jeez, Bruce, you're going to get me in trouble!

Some might put this down to a drunken rant - problem is, I'm not drunk!

Imagine you're some government from a banana republic, and all the "big boys" have invited you (probably out of pity). They're having this great big global-warming fest with lots of back-slapping and "out-doing the neighbours" routine over a few drinks.

So, el-presidente decides his dick is bigger than the next bloke and promises carbon reductions of something he can't pronounce, much less understand, and comes back to the banana-republic and says what a wonderful thing he's done on our behalf.

So now we're stuck. Like waking up the morning after the night before, you realize you've made a terrible cockup of the whole thing, but dare not back down. So we're lumbered with it. You can't cut emissions from all the industry players because there will be jobs losses, and economic downturns (I dare not say "recession"). You can't cut the coal industry, for the same reasons (that, and the unions have both hands firmly wrapped around your knackers). So how do do it?

Some bright spark has this idea about blowing the budget and splashing dollars right, left and centre. Use it like aftershave and splash it all around.

So out comes this great plan, how they can reduce emissions, keep industry and unions on-side and not piss off the population - they'll buy their way out of it!

So... they offer all these unsustainable incentives to people to buy and install solar panels, so they can meet the targets they promised.

There's a few flaws though.... the people who sell solar panels know that the people buying them are getting most of it paid for by the government. It's just like a great big insurance scam. So the leaches who sell them put the price UP - people don't care, the government is buying anyway.

And the the government decide to offset some of their cost by making it a requirement that these panels be installed - not by someone who knows what they're doing, but by someone *on the governments register*. So they charge stupid amounts of money - like $4,000 and upwards for a "course", where anyone who puts up the money "gets the certification"... it's a license to print money really.

So now you have to pay some fool who was selling used cars last week, but is installing solar systems this week, five times what it's *worth*, to install these panels in some half-arsed location that'll never work... and you'll pay them all this money because.... if you don't you can't claim your government incentive!

Meanwhile, those of us who genuinely could use panels to offset burning fuel to make power - but are off grid (not by choice, not that that's any consideration) - don't qualify because we're not grid-connected!!

I'll stop there before I say something some (lame, chickensh*t weenie) decides I've said something they can sue me for... and that's another quick income stream, nearly as lucrative as this whole solar scam was.

 
neil0mac
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Joined: 26/12/2009
Location: Australia
Posts: 210
Posted: 10:59am 07 Mar 2011
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  Joblow said  
... ... Would I have to have an accredited installer


Yes ... Find one (that you can consult with) before you go to the bother of getting the gear.

  Joblow said  ]
and would I still be able to claim the RECs?


Yes, if the above applies.
 
Joblow
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Joined: 05/01/2010
Location: Australia
Posts: 54
Posted: 11:33am 07 Mar 2011
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By george Ross, you certainly got my dander up there, but can I also add my beef about the incentives to convert your car to LPG, when the WA gov't matched the $1000.00 federal grant the price of converting your car went up about $750.00. The same rip off of our taxes went to Wobbly Garretts insulation scheme.
Now I'm so exited I need a stff Jameson and a bit of a lie down.
The man who never made a mistake never made anything
 
mid north Matt

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Joined: 06/01/2011
Location: Australia
Posts: 58
Posted: 01:01pm 07 Mar 2011
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most of the installations here in broken hill either face north east or north west but never true north even though some of them could have been twisted to face true north,other reason for me to cancel my 1.5kw system
Pt Wakefield Matt
 
Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904
Posted: 02:40pm 07 Mar 2011
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  neil0mac said   Using a set timer is a 'reasonable(?)' approximation. (Well it is better than a fixed array, at least.)

At latitude 30 deg. I find that the sun moves a 3 degree azimuth angle in two minutes at around midday, and a 3 degree move in 1/2 an hour in early morning and late afternoon which is quite a large variation. There is a reciprocal large variation in the tilt angles also. (I will be using 3 degree moves for my tracker very shortly.)

To see what I mean, download a calculator from http://pvcdrom.pveducation.org/SUNLIGHT/Animations/Sun_Calcu lator.swf, (the 'old' version'). It permits the entry of your GPS co-ordinates and time zone so that you get exact data to work with.



neilOmac, I have looked at the sun calculator and am aware of the sun's apparent movement.
However, having watched the Ampmeters connected to my solar panels on the tracker, I found that tracking at 15 degree intervals shows only a minute improvement in collected power at each panel adjustment. I set the timing so that the panels move at the hour but the sun is in alignment at the half hour. Presently only 90 degree of tracking is done due timer interval restrictions but I since have found another timer that will allow 120 degree of tracking. This will be used on the Mk II model presently under development.
Your suggested 3 degree tracking might add much complexity for little observed (not theoretical) gain. Good luck anyway, I hope it all works out.

With my tracker parked up on the shed roof it needs to run trouble free and the more the 'kiss' principle is followed the less potential problems. I try to steer clear of computer run tracking versions which require constant running & standby power, the power drain of which has to be taken off the potential tracking power gain.

What I would *like* to do is to have one fixed panel mounted at the latidude angle, one identical panel on a timed tracker and a similar one on a continuous tracker, all in the same location. Only after logging the output of each for a season would real figures emerge if the various tracking methods do justify their respective complexity.
Klaus
 
RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495
Posted: 09:48pm 07 Mar 2011
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  Tinker said  
However, having watched the Ampmeters connected to my solar panels on the tracker, I found that tracking at 15 degree intervals shows only a minute improvement in collected power at each panel adjustment.
[/quote]

Depends on your expectations I guess. 15 degrees off-axis is about 4% output loss. The losses rapidly increase after that though. 20 degrees 6%, 25 degrees 10%.


[quote]
I set the timing so that the panels move at the hour but the sun is in alignment at the half hour.
[/quote]

This one surprises me. Why is it that people think moving their panels every hour or two "wastes less power"? If you move the panels every hour, you probably need to run the actuator for 8-10 seconds. If you move them every 2 hours, you need to run for 20 seconds. Or 4-5 seconds every half hour.

You're doing *exactly* the same amount of work. Moving (x) mass (y) distance requires (z) watts. It doesn't matter if you do it every minute, 10 minutes or hour. It DOES have an impact on relay/contact wear (if your design uses them), but otherwise there is really very little to gain either way.


[quote]
Presently only 90 degree of tracking is done due timer interval restrictions but I since have found another timer that will allow 120 degree of tracking. This will be used on the Mk II model presently under development.
Your suggested 3 degree tracking might add much complexity for little observed (not theoretical) gain.[/quote]

Timers to do this need not be complicated. As you said, precise tracking for this sort of array isn't particularly critical. Perhaps you need a "gated timer"? One that free-runs for (say) 2 seconds, every 15 mins. (you can tweek this later). A second "sensor only". If it's bright (daylight), drive the panels west when the timer runs. If it's dark (night), drive the panels east. Couple of times a year, tweek the timer (either the interval, or duration, or both) to get a "reasonable" tracking rate. You could use two completely standard plugin timers cross-coupled to make an astable oscilator quite easily out of "over the counter" parts. Or one tiny little PIC could do it. One pot to set interval. LDR for "light" sense. Couple of lines of code.


[quote]
I try to steer clear of computer run tracking versions which require constant running & standby power,
[/quote]

I was lucky - the computer that controls it draws about 3 watts, and is already running (it's actually the touch-screen for the home-automation system), so there was zero "additional" power used.

[quote]
the power drain of which has to be taken off the potential tracking power gain.
[/quote]

I figure the actuators take about 9W each. To do a full 140 degree sweep (and return) on mine, thats 1620 watt-seconds per day. That would take less than 3 *seconds* of production of the panel to make up. Or to put it in terms more relevant - that 5% power loss you "can hardly see" - if you adjusted the panels so they were correctly aimed, you'd recover the ENTIRE DAYS ACTUATOR POWER in a mere 54 SECONDS simply by improving from being down 5% to being "on target".

[quote]
What I would *like* to do is to have one fixed panel mounted at the latidude angle, one identical panel on a timed tracker and a similar one on a continuous tracker, all in the same location. Only after logging the output of each for a season would real figures emerge if the various tracking methods do justify their respective complexity.


I have (as you would have seen in my last photo) a 12-panel seasonal-only adjusted array (ie, non-tracking but seasonally adjusted) and the power improvement - particularly early morning and late afternoon - is phenomenal. Eg, right now, I'm getting 1.8 amps (each half) from my fixed array, and 5.2 amps (each array) from the trackers (at 93V). That's nearly 300% more output from the tracking arrays. (it's only 8:40AM here at the moment)
Edited by RossW 2011-03-09
 
neil0mac
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Joined: 26/12/2009
Location: Australia
Posts: 210
Posted: 09:52pm 07 Mar 2011
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  Tinker said  
I found that tracking at 15 degree intervals shows only a minute improvement in collected power at each panel adjustment.

I have other reasons for the smaller increments.
  Quote   Your suggested 3 degree tracking might add much complexity for little observed (not theoretical) gain. Good luck anyway, I hope it all works out.

It does add scomplexity, but I think that the total package will be worth it. We'll see.
  Quote   With my tracker parked up on the shed roof it needs to run trouble free

Mine is ground mounted. (Less complexity - at least in regards to access to the array and the working parts which will also be accessible from terra firma.
  Quote   I try to steer clear of computer run tracking versions which require constant running & standby power, the power drain of which has to be taken off the potential tracking power gain.

Using 'conventional wisdom', I agree. However, using my 'perverted logic', I expect to get gains in other areas (like cloudy days, low insolation early and late in the day, derating due to higher panel temperatures etc.) that will more than compensate for running a small 5v processor.
  Quote  What I would *like* to do is to have one fixed panel mounted at the latitude angle, one identical panel on a timed tracker and a similar one on a continuous tracker, all in the same location. Only after logging the output of each for a season would real figures emerge if the various tracking methods do justify their respective complexity.

I have thoughts of trying a similar set of test conditions just to compare various scenarios. All I need to do is flick a switch (or two) to change from one set up to another. So I should be able to run any number of tests under all sorts of climatic conditions. (Just for the fun/curiosity of it.)
 
Tinker

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Posts: 1904
Posted: 02:22pm 08 Mar 2011
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  RossW said  
  Tinker said  

[quote]
I set the timing so that the panels move at the hour but the sun is in alignment at the half hour.
[/quote]

This one surprises me. Why is it that people think moving their panels every hour or two "wastes less power"? If you move the panels every hour, you probably need to run the actuator for 8-10 seconds. If you move them every 2 hours, you need to run for 20 seconds. Or 4-5 seconds every half hour.

You're doing *exactly* the same amount of work. Moving (x) mass (y) distance requires (z) watts. It doesn't matter if you do it every minute, 10 minutes or hour. It DOES have an impact on relay/contact wear (if your design uses them), but otherwise there is really very little to gain either way.





Yes, I get your point but you don't seem to see my reasoning behind the hourly movements.

1. off the shelf mains digital timer is used, modified to run off 24V which consumes far less running power since the timers electronics & relay run at 24V DC anyway.

2. Timing intervals (20 max per 24 hour period) is the limiting factor, half the intervals run the tracker in one direction, the other half back to the start which is done by a single timing disk with micro switches.

3.During the active tracking time the panel orientation is never worse than 7.5 degrees off perfect alignment. I do loose a bit early in the morning and late afternoon but from observation this is quite small. The battery bank gets fully charged by about 2PM at the latest (on cloudless days) so the late loss does not matter to me. On cloudy days I reduce the battery bank load.

4.the set up draws absolutely no power at all (the timer switches the control & movement voltage on and off) during the times the panels are stationary.
Klaus
 
Homegrow47
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Joined: 17/08/2010
Location: Australia
Posts: 31
Posted: 10:04pm 08 Mar 2011
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  RossW said  
  Tinker said  
However, having watched the Ampmeters connected to my solar panels on the tracker, I found that tracking at 15 degree intervals shows only a minute improvement in collected power at each panel adjustment.
[/quote]

Depends on your expectations I guess. 15 degrees off-axis is about 4% output loss. The losses rapidly increase after that though. 20 degrees 6%, 25 degrees 10%.


[quote]
I set the timing so that the panels move at the hour but the sun is in alignment at the half hour.
[/quote]

This one surprises me. Why is it that people think moving their panels every hour or two "wastes less power"? If you move the panels every hour, you probably need to run the actuator for 8-10 seconds. If you move them every 2 hours, you need to run for 20 seconds. Or 4-5 seconds every half hour.

You're doing *exactly* the same amount of work. Moving (x) mass (y) distance requires (z) watts. It doesn't matter if you do it every minute, 10 minutes or hour. It DOES have an impact on relay/contact wear (if your design uses them), but otherwise there is really very little to gain either way.


[quote]
Presently only 90 degree of tracking is done due timer interval restrictions but I since have found another timer that will allow 120 degree of tracking. This will be used on the Mk II model presently under development.
Your suggested 3 degree tracking might add much complexity for little observed (not theoretical) gain.[/quote]

Timers to do this need not be complicated. As you said, precise tracking for this sort of array isn't particularly critical. Perhaps you need a "gated timer"? One that free-runs for (say) 2 seconds, every 15 mins. (you can tweek this later). A second "sensor only". If it's bright (daylight), drive the panels west when the timer runs. If it's dark (night), drive the panels east. Couple of times a year, tweek the timer (either the interval, or duration, or both) to get a "reasonable" tracking rate. You could use two completely standard plugin timers cross-coupled to make an astable oscilator quite easily out of "over the counter" parts. Or one tiny little PIC could do it. One pot to set interval. LDR for "light" sense. Couple of lines of code.


[quote]
I try to steer clear of computer run tracking versions which require constant running & standby power,
[/quote]

I was lucky - the computer that controls it draws about 3 watts, and is already running (it's actually the touch-screen for the home-automation system), so there was zero "additional" power used.

[quote]
the power drain of which has to be taken off the potential tracking power gain.
[/quote]

I figure the actuators take about 9W each. To do a full 140 degree sweep (and return) on mine, thats 1620 watt-seconds per day. That would take less than 3 *seconds* of production of the panel to make up. Or to put it in terms more relevant - that 5% power loss you "can hardly see" - if you adjusted the panels so they were correctly aimed, you'd recover the ENTIRE DAYS ACTUATOR POWER in a mere 54 SECONDS simply by improving from being down 5% to being "on target".

[quote]
What I would *like* to do is to have one fixed panel mounted at the latidude angle, one identical panel on a timed tracker and a similar one on a continuous tracker, all in the same location. Only after logging the output of each for a season would real figures emerge if the various tracking methods do justify their respective complexity.


I have (as you would have seen in my last photo) a 12-panel seasonal-only adjusted array (ie, non-tracking but seasonally adjusted) and the power improvement - particularly early morning and late afternoon - is phenomenal. Eg, right now, I'm getting 1.8 amps (each half) from my fixed array, and 5.2 amps (each array) from the trackers (at 93V). That's nearly 300% more output from the tracking arrays. (it's only 8:40AM here at the moment)
 
Homegrow47
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Joined: 17/08/2010
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Posts: 31
Posted: 10:12pm 08 Mar 2011
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  RossW said  
  Tinker said  
However, having watched the Ampmeters connected to my solar panels on the tracker, I found that tracking at 15 degree intervals shows only a minute improvement in collected power at each panel adjustment.
[/quote]

Depends on your expectations I guess. 15 degrees off-axis is about 4% output loss. The losses rapidly increase after that though. 20 degrees 6%, 25 degrees 10%.



I calculate that Tinker only loses 0.2%,
by tracking every hour.
(reduction in proportion to cosine(3.75°))
Totally insignificant IMO.

Edit: sorry about previous post,
I hit the wrong key, and now cannot edit or delete the post.Edited by Homegrow47 2011-03-10
 
RossW
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Posted: 10:31pm 08 Mar 2011
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  Homegrow47 said  
I calculate that Tinker only loses 0.2%,
by tracking every hour.
(reduction in proportion to cosine(3.75°))
Totally insignificant IMO.


If he's moving 15 degrees at a time (going from 7.5 deg too far east, through "ideal" to 7.5 deg too far west), I'm not sure where you get 3.75 degrees error from. You appear to have halved the offset again?

At 7.5 degrees, the error is about 1% (but that's probably worst-case error). I hadn't twigged to that in the original post, and was working on a 15 degree error.

 
MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329
Posted: 10:36pm 08 Mar 2011
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Crew

I'm a little late jumping in, but better late than never, eh? Anyway, I was chatting with Oztules a while back on this very subject, to track or not to track and he made an interesting observation. He told me he had decided to merely over-purchase the panels.

His idea was to buy more panels than he needed and forget about all the losses. Of course, if you're not swimming in cash, this might pose a bit of a problem, but still, one could just continue adding panels as one's funds became available; it's no race, right?

Just thought I'd slip that in for anyone stuck on the fence.



. . . . . Mac
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
 
RossW
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Posted: 10:46pm 08 Mar 2011
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  MacGyver said  
His idea was to buy more panels than he needed and forget about all the losses. Of course, if you're not swimming in cash, this might pose a bit of a problem, but still, one could just continue adding panels as one's funds became available; it's no race, right?


I considered that and agonised over it for months.
Not withstanding I got the panels quite cheaply, I really want to get the "afternoon" sun to help minimise the depth of discharge overnight. Similarly, start getting power as early as I can in the morning to help the batteries out.

I could have done it with an east-facing and a west-facing array, but that didn't really appeal a lot.

The total gains over the day from tracking are roughly 1/3 over a fixed array. The cost of another 1.2kW of panels was significantly more than the incremental cost of making my arrays track.

The other thing that needs to be considered is - just adding one or two panels at a time may not be an option. Many people (myself included) run higher voltage strings in order to:
(a) minimise copper losses in the cabling
(b) maximise output in overcast days
(c) assist with MPPT flexability

If, like me, you run a "nominal" 100 volt system, you can't just add one or two panels. You need them in multiples of whatever you need to get your nominal voltage. In my case, thats 6 panels. (hence I have everything in multiples of 6. The trackers have 6 modules. The fixed frames have 12 panels (split as 2 sets of 6))

One should also consider the age and characteristics of panels. Getting them over a long period of time means they may not be identical, and may not "play nice" together. (or as nicely as identical units that age at the same rate may)
 
Homegrow47
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Posted: 01:19am 09 Mar 2011
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  RossW said  

If he's moving 15 degrees at a time (going from 7.5 deg too far east, through "ideal" to 7.5 deg too far west), I'm not sure where you get 3.75 degrees error from. You appear to have halved the offset again?

At 7.5 degrees, the error is about 1% (but that's probably worst-case error). I hadn't twigged to that in the original post, and was working on a 15 degree error.



So at the start of the hour he is 7.5° too far west, then sun moves though ideal, then ending hour with panels 7.5° too far east.
Doesn't this mean the average error for the hour is just 3.75° ?Edited by Homegrow47 2011-03-10
 
RossW
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Posted: 01:38am 09 Mar 2011
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  Homegrow47 said  
So at the start of the hour he is 7.5° to far west, then sun moves though ideal, then ending hour with panels 7.5° too far east.
Doesn't this mean the average error for the hour is just 3.75° ?


You'd think that, wouldn't you?
Reality is that the losses are not a linear function of the angle of error.
In the small differences we're talking about, it's close, but over greater variations, it becomes more pronounced.

Example: if I calculate a linear movement of the sun over 5 hours from -70 to +70 degrees, with 0 error in the middle, by your logic that's the same as a 35 degree error for the whole time.

35 degrees error is 81.9% output (down 18.1%)
If I calculate linearly (ie, 300 time points through the day) it's 76.9% (down 23.1%)

It's the same as saying if I have a wind turbine at a site that gets 30 kmh wind for 12 hours and no wind for the other 12 hours, it's equivalent to 15 kmh for the whole period. It's not - because the curve isn't linear. (You make WAY more from 12 hours at 30 than 24 hours at 15).

To answer your specific case though, as I said - makes little difference with only 7.5 degrees maximum error. Both are less than 1% output down on average over the hour.
 
Homegrow47
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Posted: 02:00am 09 Mar 2011
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  RossW said  
You'd think that, wouldn't you?
Reality is that the losses are not a linear function of the angle of error.


True the cumulative loses are not linear.
But the average angle error over the hour is 3.75°, not 7.5°.
You are correct in saying the loses will be more than simply cosine(3.75°)=0.2%
I used a spreadsheet to calculate the loss at each minute in the hour, and result was
0.29%
Insignificant.
I think Tinker's tracker is an excellent solution, and it has given me some great ideas.Edited by Homegrow47 2011-03-10
 
VK4AYQ
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Posted: 01:56pm 09 Mar 2011
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Hi All

If the complexity of the tracker is held at a DIY level with a gain of 20 - 25 % it is well worth while, when combined with a MPPT regulator for another 15 - 20 gain the exercise is well and truly worthwhile.

Discussing a few percent differences is academic as it does work, and is practical.

The fixed panels I have on my GT unit only produce 1/2 their potential power, so they will be going on a tracker this winter.

All the best

Bob
Foolin Around
 
RossW
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Posted: 10:28pm 09 Mar 2011
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  VK4AYQ said  
If the complexity of the tracker is held at a DIY level with a gain of 20 - 25 % it is well worth while
[/quote]

I think you will achieve that goal easily.

[quote]
combined with a MPPT regulator for another 15 - 20 gain the exercise is well and truly worthwhile.
[/quote]

Again, I think you'll get that gain easily if you take a "little" care in the details. Make sure your maximum "cold" open-circuit voltage doesn't excede your MPPT controllers input limits. Most of the MPPT controllers I've seen operate marginally more efficiently when their input voltage is close to the output voltage, however I seem to recover more power in early morning/late afternoon, and in haze, fog and high-overcast with my panels set for the highest voltage I can safely give the MPPT. (In my case, thats 6 "12V" panels in series. I usually see around 100V when they're making maximum power and still stay below the 150V max open circuit.

[quote]
The fixed panels I have on my GT unit only produce 1/2 their potential power, so they will be going on a tracker this winter.


I'm sure you'll be pleased with the outcome. I know I had great misgivings with mine in the early days (effort vs return) but once the bugs are all ironed out, I sure appreciate the extra kWh each day. Despite being a very heavy user of power (certainly by off-grid standards), I've easily managed 4 weeks without running the generator, where I used to have to run it for several hours, twice daily!
 
VK4AYQ
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Posted: 11:16pm 09 Mar 2011
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Hi Ross

Agree on all points mate, for a stand alone system it is important to get every watt you can as demonstrated by your reduction in generator usage. With fuel of all sorts becoming rapidly more expensive this is very important.

In the past I found that you needed at least twice the average usage in panels to get to a reasonable level of power as used in the modern home, while it is possible to cut back in some areas, but unless wife and kids cooperate it is hopeless.

I just wish I had the skills to make a real MPPT that could be used on different voltage systems by switching in panel configurations to suite. Say panel voltages from 35 volts to 120 volts, that would cover most battery operated systems.

Now the weather is getting a bit better I can start on the construction of my trackers.

All the best

Bob
Foolin Around
 
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