diy solar

diy solar

Solar Panel Tuning for maximum charge

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SirMichael

New Member
Joined
Mar 11, 2023
Messages
6
Location
Minnesota
I'm just setting up a 200w solar panel and 100AH SLA battery and considering adding a linear actuator to keep the solar panels turned toward the sun throughout the day.

What do I measure for maximum charge to the charge controller, the voltage or the current? Is there any reason that I can't do that measurement at the charge controller and send a signal up to the linear actuator (2 wires) the keep the panels at the maximum charge rate?

I'm planning on using an Arduino computer to measure the voltage/current at the indoor charge controller and activate the 12v linear actuator with a couple relays. (I've done this sort of thing before with remote antennas.)

The other thing that crossed my mind is to add some small solar cell at the panel (with 2 small plates on either side for better tuning) to block the sun for sharper tuning for the greatest voltage from the small solar cell (2 extra wires from the roof). Seems though that the voltage or current would be easier.

Suggestions?

Sir Michael
 
Sounds like a cool project. You'll need to use the current as the indicator of proper pointing. The voltage will not change that much.

So there is no reason why you can't do it but it seems complex for a small panel. Have you considered just adding another panel to compensate for decreased production either side of noon? You'll charge better throughout the day and won't have to deal with the arduino, actuator, etc.
 
I think current is the way to go but where does battery SOC fit in. If your battery is getting to 100% won't there be less demand and less current? SOC will need to be factored in so that the algorithm can decide if the dropping current is because the sun moved or the battery is charged. A fun project to be sure.
 
Thanks AmyG, those links were a great deal of help. I guess that I just didn't know that it was referred to as "solar tracker". Make sense though.
I'm actually surprised that tracking the sun doesn't make as much difference as I thought that it would.

TacomaJoe, you referred to the "SOC" which I had to look up. I'm assuming that the State Of Charge would be taken care of by the Charge Controller. I was hoping that I could use the voltage as opposed to the current, would be easier (less lossy) to measure.

Madco, you're right, it might be more cost (and complexity) effective to add a 3rd panel, or just use the two that I have in a stationary plane...

I gotta brew on this for a while...

Thanks All!

Sir Michael
 
SirMichael said:
Thanks AmyG, those links were a great deal of help. I guess that I just didn't know that it was referred to as "solar tracker". Make sense though.
I'm actually surprised that tracking the sun doesn't make as much difference as I thought that it would.

...
Click to expand...
Years of setups that were built to track the sun have fairly well proven that the gain does not offset the cost and complexity of going that route over fixed panel placement. Seasonal angle change (done manually) will provide the best gain.
 
Mattb4 said:
Years of setups that were built to track the sun have fairly well proven that the gain does not offset the cost and complexity of going that route over fixed panel placement.
Click to expand...
Yes, as @Madco pointed out, in most cases, if one has the space, it is more cost effective to just add panels in a different orientation.
 
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On the shorter days of the year with sun lower, when manually tracking my 30 degree panels and moving them three times a day towards the sun, I get perhaps 40% more power. This is less extreme in the longer days of the year.

That is just heresy, so if you want real data throughout the year use a solar calculator like in my signature block to compare output.

My gut tells me getting one more panel and pointing it SE and SW or two more panels and pointing them E, S, and W will make more power easier then a tracking system.
 
chrisski said:
My gut tells me getting one more panel and pointing it SE and SW or two more panels and pointing them E, S, and W will make more power easier then a tracking system.
Click to expand...
I am sure you have seen the numerous posts of Bruce on that other forum who has made numerous posts about how he keeps his inverter running at 100 percent most of the day. It helps that he is in rural Illinois.
 
Sir Michael is this for a home/cabin/shed installation or a vehicle installation? If it's on a vehicle and you travel in the winter, having the ability to tilt the panels once you arrive at the campsite can make a really big difference, and being able to do it without crawling onto the roof would be awesome. Still not a perfect solution as you have to be able to park the vehicle in the correct position, but I'd love to have auto-tilting panels on my trailer. Doesn't require an Arduino though, so that takes some of the fun out of the project :)
 
Mattb4 said:
Years of setups that were built to track the sun have fairly well proven that the gain does not offset the cost and complexity of going that route over fixed panel placement. Seasonal angle change (done manually) will provide the best gain.
Click to expand...
The majority of utility-scale installations now use trackers. Those economics don't really translate all the way down to a few hundred Watts, though. I classify home-built tracking as an interesting hobby and I agree the best way to get more kWhs is usually to just buy more panels.
 
We installed 4 dual axis Wattsun trackers 18 years ago. The reason for the trackers was that I could not get any more panels. So to get more power the trackers were the best option. I was allotted only so many panels from the factory. These trackers have been super reliable. I hope they last another 18 years.
Increase in power vs static ground mount is 25% to 40% depending on season. And when the grid power is out, the flat power curve provided by the trackers gives us power from sunup to sundown.

I would not bother trying to make a tracker controller. The ones on ebay from China look pretty good and are cheap enough.
 
Doggydogworld said:
The majority of utility-scale installations now use trackers.
Click to expand...
Some of the ones I see in California are capable of changing tilt but not orientation to the sun. Those systems are much simpler and may only require changing once a month with the season.
Interesting side note, many of the ones I see are also oriented West or WSW to produce more energy when rates are higher. Those may not be all utility scale installations, but large commercial installations.
 
Interesting discussion! This is a very small - at home - installation, 2-100 watt panels, more or less for hobby at this point (getting my feet wet). As I mentioned before, they will be roof mounted (very low slope, easy access). One problem is that we are in a Mississippi River valley coulee where the sun goes down behind a bluff to the west (about 25 angle) which will limit the afternoon/evening sun exposure.

I didn't realize that there where sun trackers on eBay (a lot of it is getting to know the lingo...) and other places. I doubt seriously if I would purchase a sun tracker, but rather build one, just for the fun and experience of it. For now, I think that I'll put it on the back burner and see how the system setup works for a while in a semi-fixed plane (V formation).

I've also seen fields of commercial solar panels in the area (Minnesota) that do have single axle trackers setup. I just need to pay more attention to the directions that they are tuning.

Again, Thanks!

Sir Michael
 
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Ampster said:
Some of the ones I see in California are capable of changing tilt but not orientation to the sun. Those systems are much simpler and may only require changing once a month with the season.
Click to expand...
Berkeley Labs latest report says 90% of utility-scale capacity installed in 2021 used single-axis tracking to follow the sun during the day. These systems typically have a single motor driving a long rack of panels. That adds very little cost. Tracking increases overall production, of course, but the bigger benefit is a much flatter output curve. This improves utilization of inverters, substations, wiring and connections, etc. which can comprise half of system cost. Power buyers also pay more for steady output vs. the "peaky" curve from fixed tilt, and buyers + grid operators especially like the late evening output.

Of course many of the installations you see when driving around are older and less likely to use trackers. They're also likely to be smaller, the really big farms tend to be in places few people drive.
 
Madco said:
Sounds like a cool project. You'll need to use the current as the indicator of proper pointing. The voltage will not change that much.

So there is no reason why you can't do it but it seems complex for a small panel. Have you considered just adding another panel to compensate for decreased production either side of noon? You'll charge better throughout the day and won't have to deal with the arduino, actuator, etc.
Click to expand...
Interesting using current. I just posted my single axis system I’m building with an arduino tracking solar radiance with LDR’s. Be interested to see how your’s turns out.
 
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