Solar panel design

[Isetech]

I had my second fault on one of our installations, since we started installing solar.

F23 - AC leakage current is trans over current Leakage current fault
1.Check the PV module and inverter cables.
2.You may have a faulty PV panel (earth short)
3.Restart inverter

12.00 midday, click it went into a fault condition the red light started flashing and you could see on the app that the solar had shut down (went to zero) after about 4 minutes it the red light switched off and the solar started producing power again.

I reduced the solar to 1 kw and let it run until the following day.

I went to site the next day and carried out a number test, including L-N, L-E, N-E with all the switches off just the panel input, nothing seemd out of the ordinary, I also tested the voltage on the the SPD which I thought might be faulty.

Everything seemed normal, so I reset the sytem and cranked up the solar power to 8500 watts (slightly less than it was set prior to the fault). It has been running fine for the past 3 weeks. Returned to site a couple days ago, opened the DC control and checked the voltages again, it seemed fine.

I am wonder if it wasnt because the power was set to the inverter limit.
One thing I did find a bit strange, when I switch on the isolator on the side of the inverter, the voltage between N-E was constant at 247 Vdc however the L-E was fluctuating and then settled, it kept doing this every time put the test lead son the terminals.

I have read that it could have something to do with the MPPT adjusting itself.

Anyone else experienced this?

[Justloadit]

Can anyone tell me why the PV and MPPT range are not the same?

Solar panels are what we call a Current Source, as opposed to ESKOM being a Voltage source.
Voltage Source - Voltage remains constant and current can vary depending on load. Power is V x A
Current Source - Current remains constant and varies depending on the sun radiance, and voltage varies depending on load. Power is also V x A, however while the current remains constant and you load too much, then the voltage drops and the V x A also drops. There is a critical point where the current remains constant, but if you load it just right, you can get the maximum power out of the panel - Hence MPPT or Maximum Power Point Tracking. As the panel heats up or cools down, due to the nature of silicon which the panels are made from, this voltage point can go up (Cooler) or down (Warmer), so as the panel works so the temperature may change and the MPPT will track this change and readjust. If the panels are installed in an area where the panel is exposed to negative temperatures, then add an extra 5% to the open circuit voltage to accommodate the open circuit voltage during this period.

Another interesting fact about open circuit voltage and MPPT voltage, is that firstly they are referred to at 25°C, so the value will change with temperature. There is a percentage value that changes per °C, higher voltage when cold to lower voltage when hot. One also tends to forget that the power rating of the panel, also means that the panel is working at the power rating, so at midday it is say 500W, the panel is generating 500W, and hence the heating of the cells that in some cases the glass of the PV may be around 80°C and poses a dangerous temperature for human hands.

[Isetech]

Load shedding is taking a break, which is great news, back in 2008 the same thing happened, the generator industry went crazy, people started importing tons of generators and if you were in the petrol station market, man you were as busy as heck.

It looks like 2008 has repeated itself, there was a shortage of solar, prices went through, people made millions. IF you were in the petrol station industry you made a ton of cash again, now they all have a generators and a roof full of solar panels I am sure they are ready for the next wave, water tanks and booster pumps, if you are not already on this bus, you missing out. If not, you must be in the rock and stone industry, coining it, so much money to be made and I hear people complaining that work is quiet, really, which rock are you sleeping under, you need to wake up and make the dash for the money, it feels like we living a mad max movies, look for the opportunities and give it horns. Unless you have figured out which bus to get on in the domestic market or doing commercial solar, your bus is going to run out of fuel, quickly as they normally do.

[Isetech]

With the break in load shedding everyone is looking at the app on their phone/PC and reading their electricity accounts, that 65 % reduction in electricity bill people are still advertising on the radio doesn't seem to be happening, while there was load shedding the R100/200/300/400 000.00 plus investment seemed like money well spent.

The reality for many is that the municipalities are going to catchup sooner than later, systems will need to be registered (all SSEG's).

At this point in time, there seems to be a shortage of meters, if you register today, you will have to zero export your system until they can start rolling out the new meters and you will be instructed not to charge your batteries from the grid at more than 15Amps (25%) for a 60 amp supply.

So where to from here do you just disconnect your system and scrap it, or switch it off until load shedding starts again?

If your system was designed specifically for load shedding chances are you just going to be throwing more money at the system. These are the single inverter with 2 batteries and 6 panel type installs.

If you decide to continue with the solar, you are going to have to look at the ROI people keep telling you about.

During load shedding, 2 hours was all you had to consider, once you apply to register, you are going to have to take a whole lot of things into consideration, the cost of the system, the ROI, the municipal connection and monthly fee, the solar production capabilities, system maintenance, registration costs, COC's (if you didnt get one with the installation), the costs to upgrade your non compliant installation, if it was done DIY or by a green card or cardboard electrician.

We better hope the insurance companies dont catch on to what is going on, one of 2 things is going to happen, either they going to request a valid COC and check that they are filled out correctly or they going to increase premiums to cover for the risk. I am yet to see a valid COC that is filled out correctly.

[Isetech]

The question you sitting asking yourself right now, was it all worth it, if not how can we improve it.

The way I see it, you are going to have to take a good look at what you have and how you are going to improve it, starting with the panels on the roof.

If you only have an inverter and batteries, you might want to look at fitting panels on the roof. If you leave it plugged in, you are just going to be wasting electricity and if you disconnect the system and leave it unplugged, you will need to discharge the lithium batteries to around 50 % and recharge at least every 3-6 months. FLA batteries will need to kept fully charged.

If you have a load shedding solution, 5-6 panel on the roof, an inverter and 1 or 2 batteries, then you will need to look at the data and figure out how to improve it to a many saving system, this could mean more panels or more batteries.

If you have taken a loan or used money from and investment, you are going to have to take a look at how you can improve the system from a load shedding solution to ROI system.

IF you paid cash and just want to cover the additional costs that the municipality will add to your bill, then you might also want to pay attention.

[Isetech]

What is the ideal system:

1/ The solar panels produce enough power to charge your batteries, power the house during the day and feedback enough electricity to cover the additional municipality costs.

2/ Your batteries are never charged by the grid.

3/ The house can run off battery power in the evening, this people is where the fight starts.

4/ East, West facing solar panels, I can hear the experts screaming at their computer screens, but the data on the app is proving that systems we installed on east facing roofs may not be as efficient as perfectly position tilting North facing roof tops or ground mounts, but producing power from much early in the morning and still producing power late in the afternoon.

[Isetech]

The next thing to discuss is optimizers, do you need them or not.

I sort of looked in that direction, heard "expensive" so I didn't even bother wasting time going down that route, however, now that I have a long list of sites which are all different, which I can review actual data and not listening to the gibba gabba (which you need to do at times to learn).

However things are going change and the change is going to create a huge impact on the ROI, every single watt of power you can produce to optimize the system is going to pay off in the long run.

For example the location of the panels in relation to trees and how even a thin tree can reduce the power by as much as 80%, which may not even be a consideration in summer due the angle of the sun during the day, especially if the panels are facing in a certain direction.

Throw in the the winter losses, you could be down to zero, if it was one panel, it wouldn't be a big deal, however as we all know 1 panel in a string and the entire string is affected, hence the need for optimizers.

This is topic I plan to do a lot more research. the cost and the benefits.

[Isetech]

A quick question, does anyone find all this gibba gibba useful ?

The reason I ask, I plan to either employ someone or as I age gracefully to copy and filter all my content on this forum and boy there is a lot to compress into readable articles.

You will notice there are always errors in my content, they are there for a reason for it, I could write the posts in word, spell check and grammar check

It just seems such a waste spending so much time writing all this content for 100 people to read, so my thoughts are to copy it, review it, fact check some of the info and as we have learnt over the years so the content should have become more useable and accurate.

I believe that Because of my extensive experience in all the fields that I work, I could create a pretty informative data base focusing on specific information.

As my health deteriorates and it becomes more of a challenge to stand on top of a 14 ft ladder changing lights bulbs, getting a bit shaky, I might need to slowly starting finding a way to create an income from my knowledge and experience. I could still post threads here and add my personal opinion as I always do. Like or not it makes no difference to me.

Typing these threads helps me with my ADHD, while I post, I do other things like today, I am reviewing and updating customer projects, updating the firmware for the alarm systems, CCTV recorders and cameras and solar inverters and batteries, creating sketches for sites, single line diagrams for solar projects, material lists for quotes that need to be ready for Monday, messaging customer to inform them about the firmware upgrades and typing what is going on in my head with other. I know I said it is waste of my time, but is actually not really because the information I share here is normally directly related to my work.

Another half and hour and my 9 hour shift is done for today, then its time to go spend time with the family and allow my brain to process the information from today, while I relax and watch the grand kids experiencing life with so little to worry about at their age.

[Dave A]

A quick question, does anyone find all this gibba gibba useful ?

It certainly makes me think.
Unfortunately I don't always have the time to participate as much as I'd like at the moment. But that will change in the not-to-distant future.

[Dave A]

The next thing to discuss is optimizers, do you need them or not.

I sort of looked in that direction, heard "expensive" so I didn't even bother wasting time going down that route, however, now that I have a long list of sites which are all different, which I can review actual data and not listening to the gibba gabba (which you need to do at times to learn).

However things are going change and the change is going to create a huge impact on the ROI, every single watt of power you can produce to optimize the system is going to pay off in the long run.

For example the location of the panels in relation to trees and how even a thin tree can reduce the power by as much as 80%, which may not even be a consideration in summer due the angle of the sun during the day, especially if the panels are facing in a certain direction.

Throw in the the winter losses, you could be down to zero, if it was one panel, it wouldn't be a big deal, however as we all know 1 panel in a string and the entire string is affected, hence the need for optimizers.

This is topic I plan to do a lot more research. the cost and the benefits.

Here's a picture that paints a story on early morning partial shading losses in winter -



The string is 10 x Canadian Solar HiKu6 Mono PERC 455W (with 3 bypass diodes per panel to assist with partial shading issues).
The partial shading lasts for about an hour, and when there isn't much radiance to harvest anyway.
During the partial shading effect, the extent of the partial shading shifts from 3 of 10 panels (for about a half hour) to an individual vertical branch covering 1/10th of 1 panel (for about a half hour). The curious thing for me is that there is no visible change in gradient during this transition!

I'd estimate the loss at less than .75 kWh per day on clear days.
Is it worth installing optimizers to recover between 70% and 90% of a 0.75kWh loss per day?

[Isetech]

I am sitting with a situation on a site where the power drops from 5.5 kw to 100 watt due to one those Christmas trees. We didnt think it would have such and impact, so it was optimizers or the tree, the tree lost.