Hi Everyone, have not logged in for sometime so hello. Hope someone can provide some advice. I had a crowd install a solar system for my Mom at her house in Tokai, the system is almost identical to mine (I Live in Pretoria) however her solar production appears to be quite a bit less. 

She has the following installed: 

12x Canadian Solar 405W Super High Power Poly PERC HiKU 
Victron MultiPlus II 48/5000/70-50 4000W Inverter 
Victron SmartSolar MPPT 250/100 
Solar MD 3.7kWh Lithium-Ion 
Solar MD Smart logger 
Victron Venus GX Communication

The system PV yield or Solar Charger PV Yield when checking on Victron VRM reports never goes above 2200W, daily KWh production on average is between 8-14KWh per day. I have the same setup except for the batteries and my System - PV Yield according to VRM often gets to just under 4000watts, my daily solar production is on average around 28kwh per day.

I have had the solar guys come out who did the installation and they indicate everything is working fine however i fail to understand how my Moms installation is getting almost 2/3rd less than mine. Her panels have no shade are on a tiled pitched roof and face North? Please can anybody advice what we can check? We have spent an incredible amount of the system and logic indicates something is not correct with my Moms installation? Please see below System - PV Yield from mine and my Moms systems. Not sure if any other VRM reports would be better suited to compare? Thanks in advance.

Can someone please recommend a good Solar company in Cape Town, i can send to my Moms house to check the installation etc that won't break the bank?

Maybe her loads on average are less and that's why the production is less?
The panels usually will only produce up to the max consumed.

Edited August 2, 20223 yr by WannabeSolarSparky

Thanks for the feedback, however i dont believe that isthe case checking for today between 11am and 12pm today consumption was 1.84kw, solar production was only 1.64kw

13 minutes ago, SheldonB said:

Thanks for the feedback, however i dont believe that isthe case checking for today between 11am and 12pm today consumption was 1.84kw, solar production was only 1.64kw

With the 1.84kw used and 1.64kw produced look like all in order. She should switch a 1-2kw load on and look again at the PV pruduction. All could be right on the install. Or switch the grid off so that battery can discharge and then switch the current load on. Always better to test in the peak time of the day. 11h30-13h00.

Thanks for the feedback Scorp007, why is her average Kwh produced per day so much less than mine? In addition on PV Yield if one checks on VRM my PV yield at height will reach around 4000Watts however hers never goes above 2200W give or take?

54 minutes ago, SheldonB said:

I have had the solar guys come out who did the installation and they indicate everything is working fine however i fail to understand how my Moms installation is getting almost 2/3rd less than mine. Her panels have no shade are on a tiled pitched roof and face North? Please can anybody advice what we can check? We have spent an incredible amount of the system and logic indicates something is not correct with my Moms installation? Please see below System - PV Yield from mine and my Moms systems. Not sure if any other VRM reports would be better suited to compare? Thanks in advance.

The ideal angle to horizontal would be different in the two locations, and at different times of year as the sun is higher in the sky in summer. If her panels are at a more shallow angle than yours then that might cause problems, especially in the winter.

Also are her panels clean?

What you're running into here is that there is no one thing as a PV system. Each household has different characteristics (including loads) and the same hardware can't be expected to produce the same results in two different locations.

23 minutes ago, SheldonB said:

Thanks for the feedback Scorp007, why is her average Kwh produced per day so much less than mine? In addition on PV Yield if one checks on VRM my PV yield at height will reach around 4000Watts however hers never goes above 2200W give or take?

Once again she uses less power per day than you due to loads connected. If the peak for her is so low then het daily total yield will always be lower than her load for the day.

One will need to know what het total power use is per day and what was supplied by PV and what from the grid. No clear answer based on the panels in use.

Edited August 2, 20223 yr by Scorp007

Thanks for the response, i checked for yesterday her between 8am in the morning till 4pm , her consumption was 15KWh, Production was 12KWh. 0.1KWh to Grid and 3.8KWh from Grid. Also just remembered COCT installed a compulsory prepaid meter in a number of months ago, she used to have the old wheel type meter if i remember correctly, the new meter i dont believe allows feedback to the grid could this be the reason why the overall KWh produced is so much less than prior?

Lastly does COCT have meters that allow feedback to the grid? If so how does one go about getting one and what do they pay back if feeding back?

12 minutes ago, SheldonB said:

Thanks for the response, i checked for yesterday her between 8am in the morning till 4pm , her consumption was 15KWh, Production was 12KWh. 0.1KWh to Grid and 3.8KWh from Grid. Also just remembered COCT installed a compulsory prepaid meter in a number of months ago, she used to have the old wheel type meter if i remember correctly, the new meter i dont believe allows feedback to the grid could this be the reason why the overall KWh produced is so much less than prior?

Lastly does COCT have meters that allow feedback to the grid? If so how does one go about getting one and what do they pay back if feeding back?

OK now we getting more info. Yes some makes of meters are set up to allow feed back but the normal ones will count export as consumption. Some meters might not count the export but merely record it in a register. Her inverter must be configured not to allow export to prevent paying for what you export. If the system is installed with all the paper work CoCT will charge a admin fee per month and not many houses have enough space for enough panels to overcome this fee.

11 minutes ago, SheldonB said:

Thanks for the response, i checked for yesterday her between 8am in the morning till 4pm , her consumption was 15KWh, Production was 12KWh. 0.1KWh to Grid and 3.8KWh from Grid. Also just remembered COCT installed a compulsory prepaid meter in a number of months ago, she used to have the old wheel type meter if i remember correctly, the new meter i dont believe allows feedback to the grid could this be the reason why the overall KWh produced is so much less than prior?

Lastly does COCT have meters that allow feedback to the grid? If so how does one go about getting one and what do they pay back if feeding back?

This probably explains it. With the spinning disc meter you could pump every bit of power back into the grid and make the meter spin backwards, and just see a net usage at the end of the day. If you now have 0.1kWh export to grid, that's probably the meter cutting the export out, so at times when generation capacity exceeds usage you will just produce less, and alternatively when usage exceeds capacity, the difference is drawn in from the grid. If you want to test your mom's generation, ask her to crank her usage up. Run a heater and a hairdryer at mid-day and see if her generation kicks up to near 4kW.

 

"Solar MD 3.7kWh Lithium-Ion"

The problem is likely to be the limited charging current of the Battery. The BMS will throttle the charge current from the MPPT to protect the battery.

This battery is significantly underspecified for the system.

Hi NigelL thanks for the feedback, sorry i am a bit of a noob when it comes to solar. So does this mean the battery itself is limiting production? If so should we look at replacing the battery with another make / model etc? If so firstly dammit, secondly what would you suggest and why?

Scorp, Greenfields thanks for the feedback will ask het to conduct the test.

11 minutes ago, SheldonB said:

Hi NigelL thanks for the feedback, sorry i am a bit of a noob when it comes to solar. So does this mean the battery itself is limiting production? If so should we look at replacing the battery with another make / model etc? If so firstly dammit, secondly what would you suggest and why?

The BMS in the battery will communicate with the Multiplus and MPPT to keep the charge current within sensible limits for the battery.

I see the max charge current for the battery is 100A, so you should theoretically be able to charge at around 5kW. Assuming there is nothing wrong with the wiring of the panels, then I would get the installer to check the BMS comms and ESS settings on the Multiplus.

Obviously Winter weather in Cape Town will also limit the max power output (I am getting about 65% of summer peak on a clear day).

23 hours ago, SheldonB said:

Hi NigelL thanks for the feedback, sorry i am a bit of a noob when it comes to solar. So does this mean the battery itself is limiting production? If so should we look at replacing the battery with another make / model etc? If so firstly dammit, secondly what would you suggest and why?

If it is a lithium battery then no need to change it. It just needs adding another. Provide details of the battery.

Further if she is not having the loads connected then this is the reason why the panels are not producing. If batteries are full and only DSTV and may be a light on and a fridge and this consumes say 1000W and battery is full you can have a solar farm of panels and they will just produce a bit below 1000W. 

Where must the power go and for what reason if the panels had to produce 1500W in the load scenario indicated above?

1 hour ago, Scorp007 said:

If it is a lithium battery then no need to change it. It just needs adding another. Provide details of the battery.

Further if she is not having the loads connected then this is the reason why the panels are not producing. If batteries are full and only DSTV and may be a light on and a fridge and this consumes say 1000W and battery is full you can have a solar farm of panels and they will just produce a bit below 1000W. 

@Scorp007 Is correct - you can normally add extra battery units in parallel to get extra capacity. Your installer should be able to advise you on this.

Note that you have a large solar array (4860Wp) and a small battery (3.7kWh). This means that the solar panels can possibly fully-recharge the battery by mid morning - long before the max power from the panels is achieved. After the battery is full, the solar panels will just supply the house loads (assuming no feedback to the grid).

It would be useful to see the PV-Yield over a 24-hour period (on a sunny day). See my PV-Yield from a few days ago (I have 9 x 330W panels = 2970W).

Edited August 3, 20223 yr by NigelL

Thanks for the feedback guys much appreciated. See below on the 29th May peak solar W was 3869W, so if i take the panels size 405w x 12 x 75% (Line loss etc etc)= 3645W Peak production? So i would assume they are performing as they should?

As a mater of interest how are the Solar MD batteries, ive checked the site and the web and have not found many reviews? Should i go for the same battery of can or would i be able to add a pylontech as an example to the existing Solar MD battery?

46 minutes ago, SheldonB said:

Thanks for the feedback guys much appreciated. See below on the 29th May peak solar W was 3869W, so if i take the panels size 405w x 12 x 75% (Line loss etc etc)= 3645W Peak production? So i would assume they are performing as they should?

Yes, looks like it's working fine technically, but it's maybe overkill for your mother's needs in terms of panels and generation capacity, and maybe under-weight on batteries relative to the amount of panels. But does it really make sense to add more batteries? How deeply discharged is her current battery in the morning? If she's not draining the battery it may make no sense to add more battery capacity. Maybe she should start baking during the day as a hobby.

Greenfields majority of power is consumed at at night with underfloor heating etc, also battery does not make the night especially with loadshedding. LOL i'll tell her to start baking. Will look at another battery when funds allow, any reviews on the Solar MD batteries??

Underfloor (well any area heating) is very inefficient powerwise and just gets worse the larger the area and increases power losses

You'd be better served using something concentrated like heated blankets and at worst - aircons with heatpump+inverter

PSYWulf i hear you!

25 minutes ago, SheldonB said:

Greenfields majority of power is consumed at at night with underfloor heating etc, also battery does not make the night especially with loadshedding. LOL i'll tell her to start baking. Will look at another battery when funds allow, any reviews on the Solar MD batteries??

OK... so all the pieces are starting to fit together now.

First, as noted, PV drops off once the batteries are charged. Her battery is smaller than yours, and so it gets charged earlier. Thereafter, during the afternoon, the system will draw just enough PV to service the load.

Second, she is consuming a lot at night - when it doesn't matter how many panels you have and how well they are working. 

3.7 kw/h is not a lot of battery, and a decision needs to be made on strategy. I'm not familiar with your inverter, but I'd be surprised if it can't be configured to save the battery for load shedding. This is not the strategy that saves you the most money, but something has to give here. You're very light on battery, for a start, and if your mother wants to use big loads like underfloor heating at night, then you'll need a very big battery to get you through the night. 

At my house we have 10 kw/h of battery. On a sunny day that gets fully charged during the day. Then once the sun goes down we try to be light with our usage. No electric heaters, no pumps or appliances. Our stove is full gas which helps us a lot.

We find that the the 10kw/h will easily get us through the night, and if the weather is good we start charging again in the morning. And we have something in hand in case of early morning load shedding.

I also have a rule set up on my inverter. Whilst there is a grid connection, it will not discharge the battery past 40% SOC. So no matter what, we always have 4 kw/h in hand when the power goes down. OK... we actually have 3kw/h because the batteries will shut down when SOC reaches 10%, but you get the point. 

There are different options available to you now. This depends a lot on priorities. If continuity through load shedding is more important than saving on the electricity bill then you have to get the battery charged and reserve it for outages. With 3.7 kw/h of battery, your hand is really forced anyway. If you had more battery, you'd have more options.

1 hour ago, SheldonB said:

majority of power is consumed at at night with underfloor heating etc, also battery does not make the night especially with loadshedding.

You could run the underfloor heating on the excess PV power during the day, it will heat the house and by night time it might not be noticeable when turned off. It should be automated to only switch on once the battery is fully charged and there is still excess power available on the panels, once loadshedding hits it should automatically switch off. That will probably yeild the biggest savings (assuming that there is plenty excess power going to waste)