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A dual axis solar tracker or mppt charge controller?

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Clarkdale44

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OK, it has been few months now since i installed my solar system. It is a small one but i want to extract every ounce of juice i could get from my solar pv's. I am already aware that the mppt charge controller can do it's wonders. Currently using a pwm one and the only i time i get full power(well not full 80% efficiency) is between 1200 to 1300 hours... the reason for that is, well you and i both know...

So i heard of these dual axis solar trackers which tracks sun's position in the sky for maximum power output from dawn to dusk.

Mppt and these solar trackers are both expensive as he**ll man, it's gonna take quite a while before i get my investment back....
I know buying both of these can be very good for me...
But, I can only afford one thing..

So which would be more beneficial for me..?
I am using 3x 150W panals total of 450w (max power output 320w to 350w). Using with 12v 40A pwm charge controller (pv connected in parallel configuration).
I might throw in one more 150w panal by the end of this year, making it 600w... currently using 150Ah battery.


Regards!!
 

MikeMl

Well-Known Member
Most Helpful Member
What problem are you trying to solve? Is the battery not fully charged at the end of a typical sunny day?
 

mab2

Member
if it were me I'd do neither and spend the money on more PV panels. Have some facing east-ish, some west-ish and some south. With solar so cheap now that's likely to be the best bang for your buck.

If that's not an option (limited space for e.g.), then personally I'd go for a single axis tracker. I actually have 470W of panels on a single axis tracker I built many years ago (when PV was >10x the price it is now). Is does have a manual seasonal adjustment but to be honest I don't bother adjusting it. The tracker allows the panels to operate at 100% f0r a large part of the day, but that's not the reason why it is useful - after all, if it is sunny all day then I've invariably got more energy than I can use and turn the tracker off to prevent the dump load boiling the water in my hot water tank. It is most useful on days when there is are a few sunny spells but it's generally cloudy (usual weather in these parts), as the tracker allows the PV to make good use of the sun regardless of the time of day when it appears, whereas a fixed south facing panel only makes good use of a sunny spell if it occurs late morning - early afternoon.

I don't use MPPT but then I use 30 cell PV panels which have a MPP around 30v which works well by direct connection to the battery (24v battery).
 

Clarkdale44

Member
What problem are you trying to solve? Is the battery not fully charged at the end of a typical sunny day?
Yeah that is another issue, but the maximum output i should be getting 23 amps from my 3x 12v 150w is only for a short time of 1 hour during the day, because during that 1 hour my pv's are facing the sun. I want at least close to 23 amps for few more hours.


if it were me I'd do neither and spend the money on more PV panels. Have some facing east-ish, some west-ish and some south. With solar so cheap now that's likely to be the best bang for your buck.

If that's not an option (limited space for e.g.), then personally I'd go for a single axis tracker. I actually have 470W of panels on a single axis tracker I built many years ago (when PV was >10x the price it is now). Is does have a manual seasonal adjustment but to be honest I don't bother adjusting it. The tracker allows the panels to operate at 100% f0r a large part of the day, but that's not the reason why it is useful - after all, if it is sunny all day then I've invariably got more energy than I can use and turn the tracker off to prevent the dump load boiling the water in my hot water tank. It is most useful on days when there is are a few sunny spells but it's generally cloudy (usual weather in these parts), as the tracker allows the PV to make good use of the sun regardless of the time of day when it appears, whereas a fixed south facing panel only makes good use of a sunny spell if it occurs late morning - early afternoon.

I don't use MPPT but then I use 30 cell PV panels which have a MPP around 30v which works well by direct connection to the battery (24v battery).
Yeah i thought of that, adding more panals, but there are problems in that plan. The first one you have already mentioned.. The space issue, the other one is my pwm charge controller... Adding more panals meaning i will have to switch to higher voltage(series connection), and it will also require a one more battery. And it is gonna be troublesome for me with everything already set up...

I think single axis tracker could be my thing. I just need to rotate panals from east to west, that should give me plenty of power in the day.
 

MikeMl

Well-Known Member
Most Helpful Member
I would add additional panels in parallel (not series), especially if some are facing east and others facing west. That way those panels that can make output will, while the ones that not facing the sun will just sit there. If you connect non-producing panels in-series with producing ones, then the non-producing ones will be reversed biased, and you will loose output voltage. With parallel-connected panels, there will be a time of day when currents from both panels will add, producing net more watts.
 

Clarkdale44

Member
I would add additional panels in parallel (not series), especially if some are facing east and others facing west. That way those panels that can make output will, while the ones that not facing the sun will just sit there. If you connect non-producing panels in-series with producing ones, then the non-producing ones will be reversed biased, and you will loose output voltage. With parallel-connected panels, there will be a time of day when currents from both panels will add, producing net more watts.
I don't think i can attach more panals due to very small area of space available. Currently my panals are in parallel configurations, so i will keep them that way. Virtual tracking is good if space is not an issue.
I think i am gonna look around for single axis tracker...
 

ericgibbs

Well-Known Member
Most Helpful Member
hi 44,
Have you seen this interactive Sun's arc calculator.?
If I was building a Solar tracker I would look at the feasibility of storing the known path of the Sun, say at 10 minute intervals, say between 09:00 and 15:00 hrs and driving the PV to face that stored position.

http://astro.unl.edu/naap/motion3/animations/sunmotions.html

IIRC this method is used for Solar panels.?

E
 
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Clarkdale44

Member
If I was building a Solar tracker I would look at the feasibility of storing the known path of the Sun, say at 10 minute intervals, say between 09:00 and 15:00 hrs and driving the PV to face that stored position.
Good material... But i guess i am gonna have to take the help of an expert.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi 44,
I live in the UK, where IMHO there is not enough Sunshine to justify me building a fully working unit.;)

I will scan the web for suitable sources/idea's.

E
 
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