Solar Panel Tilt and direction

[Ridiq]

Good day, please assist me with the following:

Background: System installed December 2015, monitoring software installed April 2016. 3 x 305W Solar panels. Power output of the panels were very good until December 2016.. I initially thought all the cloudy days caused the system not to operate optimally. Solar peak use to be just after 12AM and @ 800 - 900W's. It now peaks at about 10AM and only 600W. The ouput Voltage of the panels is still about 119V. Thought that some of the cells might be dead. Measured my batteries individually and voltages seems fine.

Angle/ tilt of panels at about 28Deg

Direction - Just off North.

Question 1: Is it possible that the angle/ tilt of the panels can play such a big role in the effectiveness of the system?

Question 2: The inverter comes on for short periods to charge the batteries. Seems that the capacity of the batteries is not what it used to be. I change over to mains power on 47V. New set of Vision batteries installed in April 2016. Might this be because batteries are never really fully charged?

I would be glad if someone can maybe give me some advice.

Regards

[Guest]

When  last did you wash the panels?

[Ridiq]

I have not washed them since they were installed. They are on the roof of the double story and quite difficult to get to. More than one person have suggested that I should wash them, so would be doing that soonest and keep you guys updated if it made any difference.

[Chris Hobson]

 HI you need to give us a bit more info

1.  Inverter
2. SCC
3. Charge settings (Bulk  Amps and Volts - Float Volts).
4. A data sheet for your batteries - I fear they may be standby batteries not designed for renewable applications

[Ridiq]

Hi Chris

Some more info:

1. 5kVA Axpert Inverter
2. SCC?
3. Max PV charge A= 20A, Float Voltage 54 Max Voltage 56.4. Return to mains on 47V
4. Data sheet attached.

6FM200-X.pdf

[Chris Hobson]

Bulk charging should be between 57.6V and 58.8V according to the datasheet. I would opt for 57.6V since the datasheet mentions a low pressure venting system (not advantageous) and one is above gassing voltage at 25^oC. Float between 52.8V and 55.2V. That is well below gassing voltage so I am happy with that. Returning to mains at 47V is roughly a DOD of  60-70% so your batteries could last 300-400 cycles maybe a bit more.

At what voltage do you return to solar? I fear you batteries may have been chronically undercharged.

What monitoring software are you using? What sort of SOC are you achieving late afternoon? Does the middle LED come on and stay on for a couple of hours?

[Ridiq]

If I remember correctly the system goes back to Solar/ Battery at 54Volts. 

I assume from your :"  I fear you batteries may have been chronically undercharged" that i might have damaged the batteries? Is my DOD correct? I used 47V to save some cycles.

Should the mains power not fully charge the batteries? I cannot work out why my cycles are so short all of a sudden.

I used the Axpert WatchPower to set up the Inverter. Yes, as soon as the Solar detects sunlight it switches over to Solar Panel charging (Solar first). System is at 70-80% late afternoon. 

Middle LED - yes, during daytime yes, but only short stints when on Mains/ Utility.

[Chris Hobson]

If your back to solar is at 54V then one is doing very little grid charging. Once a battery is being charged its voltage rise quite quickly. So your batteries are depleted and you go to grid the grid charges for a while but your batteries are by no means charged and you switch to solar. This is all well and good if the sun is shining and solar can continue charging  the batteries. If it is still night or overcast one starts discharging without ever really having given the batteries a decent charge. That middle LED needs to be on for a couple hours at a time once or twice a week.

Your bulk voltage is too low. Make sure program 5 is set to USE(r) and Program 26 to 57.6V and Program 27 to 54V. Ensure program 31 is enabled.

Now to decide how you want to treat your batteries. Are you prepared to waste a bit of energy to make your batteries last? If so set program 13 to FUL of 57V at least so that the grid gives your batteries a good charge.

If you not wanting to charge from the grid then set  program 13 to 56V and program 16 to OSO (only solar). Under this regime you load will go to grid  but the batteries will wait till morning to be charged and your batteries will have been charge for a while (not fully charged) before your load is supplied by solar.

Others who have more experience optimising an Axpert with grid power may have a different approach. 

[Ridiq]

Chris, thank you very much for all your advise and help. I would have a look tonight and see that all my settings are correct. I have to say that we had a lot of cloudy days since December. Really hope that it would rather be the fault than anything else. I would keep you updated.

[SilverNodashi]

I would agree with TTT, wash those panels and see how much difference it makes. 

[Guest]

9 hours ago, Ridiq said:

I have to say that we had a lot of cloudy days since December.

Hold on, Centurion ... I would be very surprised if they are not clean. That place is flooding regularly. 

[Arandoza]

Hello Ridiq,

I too am based in centurion.

My panels were also at a fairly steep angle of about 28 deg also facing north. I too found that there was a notable top end drop from winter to summer.

I cleaned mine and found an improvement, maybe around 10%.

But the bigger issue I found was that if I lowered the tilt angle to nearly flat, the power improved once again, although with all the cloudy weather it's been hard to see via pvoutput.org daily figures. However if one loaded the axpert heavily at the same time of day, and compared what the panels would generate it seemed to make a drastic difference.

Also many of the tilt angle calculators on the web suggest that a horizontal panel in summer and slightly tilted in winter will give better results for the centurion / pta region due to the arc the sun makes during the year.

My own observation has been in winter the sun rises only till about the 11am position, if you face north. However in summer it appears to go to around the 1pm position, which when overhead at midday almost starts to shine downwards from behind the panels when at 28 deg. However when laid almost flat they still perform well.

I also find that in summer my west facing roof gets good late afternoon sunlight, in winter almost nothing, have been contemplating adding six panels to this portion of the roof to extend my sunlight hours in summer

A further thought. Is there possibly any new shading ? Trees that have grown ?

[SilverNodashi]

My own panels should be at about 83 degrees in summer for optimal results. Being on a tilted tiled roof, it's  bit difficult / costly to construct a structure that would allow it, and at the same time be wind resilient, and not take halve my roof with if a sudden gush of wind comes up. In fact, the sun is dead center on our veranda in the late afternoons.  In winter it drops down to about 28 degrees.

My neighbor across the street ended up building a solar tracker for 22 panels, some years ago, with full automation, but planted it in his front yard in the garden. I don't want that. He ended up not using it shortly after the first heavy winds in October that year due to it's dangerous nature. Imagine a couple 20Kg glass panels flying through the air! Instead he brought and installed 6 more panel to equalize the shortfall. 

So, yes, tilting your panels, if / where possible will definitely help. Otherwise see if you can add some more to make up for the shortfall. Clean them often, especially after windy days. A soft broom helps a lot.

[Ridiq]

Morning all

Well, I did the following:

Adjusted Bulk charge voltage to: 57.6V

Float Voltage to 54V, when I got home batteries were almost fully charged, even on utility power no Amps were drawn by the batteries. I left them in that state for a couple of hours. Still during the night with 180W load, the inverter came on every hour as the batteries reached 47V. Before December the system was able to just about run through the night on a single charge. These are 4 x 200AHr batteries that are not even a year old. Is it still possible that they were not fully charged?

With the 3 x 305W panels I only reached a maximum of 688W yesterday. I also think that the tilt angle on the panels is the biggest problem and not that the panels are dirty. The panels are installed on the second story roof and there is not a lot of space around them to maneuver and work. I'll be having a look at some bracket that can adjust the angle.

[SilverNodashi]

Just now, Ridiq said:

Morning all

Well, I did the following:

Adjusted Bulk charge voltage to: 57.6V

Float Voltage to 54V, when I got home batteries were almost fully charged, even on utility power no Amps were drawn by the batteries. I left them in that state for a couple of hours. Still during the night with 180W load, the inverter came on every hour as the batteries reached 47V. Before December the system was able to just about run through the night on a single charge. These are 4 x 200AHr batteries that are not even a year old. Is it still possible that they were not fully charged?

With the 3 x 305W panels I only reached a maximum of 688W yesterday. I also think that the tilt angle on the panels is the biggest problem and not that the panels are dirty. The panels are installed on the second story roof and there is not a lot of space around them to maneuver and work. I'll be having a look at some bracket that can adjust the angle.

how cloudy is it there for the past two days?

[Mark]

Why don't you set the Axpert to UTL and just run like that for a few days and let the batteries charge and also be held at 54V.  ie no load on batteries for a few days.  The see if that changes the situation.

I don't think you have enough panels to keep the batteries charged.  Do you have a battery monitor (Victron BMV 700/2) - that would allow you to actually see the state of the batteries.  Search for BMV on the site.  Lots of discussion on this issue.

[Ridiq]

According to the graph we started out quite cloudy yesterday but had some good sunshine between 11AM and 1PM and became overcast again. Not sure about the day before. Before December I had peaks of up to 1100W's input from the 3 x 305W panels. I still measured 119V input from the panels at 5PM yesterday... I'm a bit frustrated at this stage as I am worried that my batteries are not at their best at the moment. The cost me a arm and 

[Ridiq]

22 minutes ago, Mark said:

Why don't you set the Axpert to UTL and just run like that for a few days and let the batteries charge and also be held at 54V.  ie no load on batteries for a few days.  The see if that changes the situation.

I don't think you have enough panels to keep the batteries charged.  Do you have a battery monitor (Victron BMV 700/2) - that would allow you to actually see the sate of the batteries.  Search for BMV on the site.  Lots of discussion on this issue.

Hi Mark, yes imagine that I should try that by leaving them on charge for a day or so. 

Unfortunately don't have a BMV 700/2.

During winter and Spring the panels easily charged the batteries, didn't had any issues, only now in summer.

[Chris Hobson]

43 minutes ago, Ridiq said:

I'll be having a look at some bracket that can adjust the angle.

On a second story roof I would leave them alone. Add panels sort out the batteries but don't have a tilt mechanism that high off the ground - hospital food tastes awful.

[Chris Hobson]

46 minutes ago, Ridiq said:

Still during the night with 180W load, the inverter came on every hour as the batteries reached 47V.

Centurion we have a problem! With 180W load the batteries (assuming you have four batteries) should last through the night and the next day and still be above 48V. Is yours a DIY install? If not get the installer back and get him to sort it out. If it is a DIY install maybe someone on the forum can come to your rescue. Fortunately TTT is on the other side of the country .

[SilverNodashi]

26 minutes ago, Ridiq said:

According to the graph we started out quite cloudy yesterday but had some good sunshine between 11AM and 1PM and became overcast again. Not sure about the day before. Before December I had peaks of up to 1100W's input from the 3 x 305W panels. I still measured 119V input from the panels at 5PM yesterday... I'm a bit frustrated at this stage as I am worried that my batteries are not at their best at the moment. The cost me a arm and 

So you got 1100W out of a 915W array and wonder why it's dropped? Very few solar panels will delivery close to their specs, continuously. On some days you might get over production like you see, but generally you would have about 20% loss. The tilt angle, length + thickness of cable + MPPT charge controller, etc, etc all play a BIG role in the production as well. December was rather cold last year so production might have been a bit better than normal. 

[Don]

21 hours ago, Chris Hobson said:

I fear you batteries may have been chronically undercharged.

I agree with Chris.

Ridiq, you have been draining your batteries over a period of time and at the same time not fully charging them. I think it would be fine to run from solar during the day from 7h00 to 17h00, but then you need to switch to grid and ensure the charge priority is set to UTL as @Mark suggested. You need to charge your batteries from grid during night time without load for 12-14 hours. Hopefully, you can fully recover them over time. 

You spent a lot of money on those batteries. I recommend you get a BMV 702 so you can look after your batteries and get the maximum cycles out of them. 

[Chris-R]

I noticed that you've also got a solar geyser installed. Does that also produce less heat in summer? Just thinking, if your problem is connected in any way with the weather / sun, you should have the same effect on the geyser?

[Ridiq]

2 hours ago, SilverNodashi said:

So you got 1100W out of a 915W array and wonder why it's dropped? Very few solar panels will delivery close to their specs, continuously. On some days you might get over production like you see, but generally you would have about 20% loss. The tilt angle, length + thickness of cable + MPPT charge controller, etc, etc all play a BIG role in the production as well. December was rather cold last year so production might have been a bit better than normal. 

They only peaked at 1100W after cloud cover and after panels cooled down.

[Ridiq]

@Chris Hobson It is a DIY installation Chris.

@ Chris-R Doesn't seem as hot as it use to... 
@Don Thought I could get away without buying a BMV, but seems I do need one.