What a nice solar day

Rory - 3 July 2025 - 13:53

Over the past days as we head down from the summer solosist the sun doesn’t get as high as it did the days before, each day, if memory serves, each day declines by around 3.52 minutes of solar production. There are many things that alter the power we get from solar and we recently “upgraded” to 500w bi facial panels

03.06.2025 Solar production

using our Home assistant and Growatt alternative we are able to view our power production on the small array.
So that it makes a little sense to you the top of this chart is 72% output. The array is easterly hence the start up in the mornings which will get later and later as the days go by. Usually in winter we have a start up time of around 09:35, today start up was at 05:35 and our peak power will be at 13:10, for those interested in the cut off time it was 22:10

Jumping back to our older system, on the 18.05.2025 our start up time was 05:00 and our off time was 19:00 and our peak time was between 11:00 and 14:00 we hit peaks of around 65.2% of course the panel angle was different as it was more flat and slightly south more so than what we have now.

Bi facial solar panels work differently than mono panels in that they gather power from the bottom, you could say they swapped out the back sheet to glass. which is pretty much what they have done, though they have redesigned the bus bars ( the wires that send the power around) to make them more like the front.
If you can imagine that the solar panel in our array is spaced from the surface so that as the west sun drops low it does shine under the panel. (off of our shingle roof too). So in part we have an east west solar array.

As you will see there are dips and bumps in the output as the MPPT tracks the solar production max power, you will notice the shading we have which for the most part is entirely across the whole chart. This shading is the lamppost outside, which is directly east of the array, so by 09:40 BST it is just clearing this summer array.
If you cannot see the image times, that the last jump in power.

The little bumps in the power are the diodes working as the shading passes over the panels segments.
Modern solar panels are half cells, they are parallel and series also, So you have two halves which are parallel; thats the top and bottom, and you have three series connections which are two groups of cells, These give you three sets (6) which cross the panels to make the voltage. Yeah not easy to follow unless you have a picture:

What you should take from this is how to lay the panels depending on your shading. ( and why tigo are a waste of time and money) as they were “invented” before didoes were largely installed in solar panels. This is not to say some cheap panels do not have them and a tigo would work in that scenario.

As you can now see some clouds are over head and we are also heating up the inverter so power is backing off. We peaked at 94% output from the solar panels. I think this illustates best that solar panels do not mean that they meet all of your power needs all of the time and it can be very much up and down.

We have always recommended batteries as this takes away the dips on power caused by clouds, therefore your inverter can supply the load regardless of how the solar is actually performing. This is a costly investment for solar, but it really does make a difference.

A small battery can act as a buffer for clouds provided it can make up the short fall in terms of capacity and output.
Small buffer batteries, for example the 5.12kwh battery can provide a 3.6kw inverter with full power and take up the slack left by the cloud. The excess power going into recharging the battery. The key here would be that the battery can run the inverter after the suns down, which is when most people use power.
Don’t take my word for it, check for yourself. go take a meter reading in the morning before you leave the house, take one when you get home and note the power use. then around 9, take another reading and see how much you have used.

Reading data.
Our system information is live, so we can see second by second what is happening, most inverter apps will show you over 5 minutes which can be a little misleading. We found some apps fake data. this means that you can really get the wrong info from your solar and how its working (or not).
Here is ours done to look like its super solar: