We spent a long day today in 41-degree bright Mediterranean sunshine rearranging our solar arrays. Let me start here with a statement earned from direct experience: Any marketing guru who waxes lyrical about the advantages of Solar and self-sufficiency should retire (that's the mild version). Given modern living habits, you can only expect Solar to be a partial power provider.
So, how did we become aware of this? Niaieve me installed a 6kW solar array; by most standards, that is huge. Reviewing the performance showed we generated 1.0kW for 6 hours a day or thereabouts. There was a lot of messing around later, and it's 1.4kW, but it still needs to be more. Vanguard can use 5kWh all day unless we look at more economical operating options.
So, investigate the shading of the solar panels; it is the biggest target but also one of many. Two things happen. We realize that "unshaded" panels have been linked with commonly "shaded panels." This renders both useless. Secondly, two smaller arrays often do not attain the "firing" voltage for the MPPT controllers (25Voc). That also renders them useless; they may look impressive but need help to do something.
We then spent several days mapping the movement of shadows across the panels. While it's not an exact science, given Vanguard's stationary position, it's a good starting point in a world of infinite possibilities. Our goal was to group panels that behave similarly. Those that shaded in the morning were linked, as were those that shaded at noon and in the afternoon when the sun was on the other side. We made sure to avoid connecting a 'good' panel with a 'suspect' one, so to speak.
I'd refer to the plan below. It is color-coded, so the linked panels are similar in color. We must link two in series, as the Victron MPPT charge controllers have a starting voltage of 25Voc, and a single 160W panel has a Voc of 19.5 (too low to fire the MPPT). So, two are linked in series, and the series arrays are connected in parallel. Some smaller panels get a different treatment, but that's an unnecessary complication for this story.
After all this, we woke up to another scorcher of a day in the eastern Mediterranean. Fully charged house batteries kill the solar charge current, so we turned off the shore power and started draining them with our air-cooling loads. You can see this as the blue line in the graph below.
We checked the MPPT and confirmed all panel groups reached the firing voltage of >25 Voc. Shadows were still playing havoc as the sun rose in the sky and began its celestial circle. Vanguard is moored as effectively stationary. You can see that as the Voc collapses, the panels become shaded. Two groups are shown below. The Left is affected by shadow mid-day, and the right is mainly unshaded.
At first, there did not appear to be much of a difference, but as the day wore on, it became apparent we had improved performance by around 20%. Not bad for shifting some wires. From the nearest equivalent day of 8.8kWh total to today's 10.45kWh (I added 250W for the late start in killing the shore power).
There was no increase in panel efficiency; the maximum still hovered around 1.2/1.4kW, but we did see an increase in the duration of this production with a steeper rise and fall at the end of the day.
Our next exercise is to try to lift the efficiency. My suspicion is we have something in there that is self-limiting. I'm still trying to figure out what, but don't confuse me with someone who knows much about solar. That work will have to wait until we get to Palma. Due to depart Turkey on Wednesday 25th.
Regards to all.
Chris