Our family recently bought a vacation/future retirement home in the country and one of the nifty features it came with is a pretty substantial solar array that generates enough power to keep the house net-zero each year. There is, of course, an app that comes with the system so that you can monitor the performance of the solar array down to the 15-minute interval and compare with previous days or years, and allows exporting to Excel. As we’ve been busy moving stuff into the house and getting it ready for regular occupation, I haven’t paid too much attention to the system, but the fact that they panels hadn’t been washed since well before it was sold to us had been nagging me for a while, so I finally got around to giving them a good scrubbing the other day.
Uh-oh! I made a clean spot. Now I’ll have to do the whole thing.
And that’s what triggered my data geek nature. Because, of course, one needs to know how much cleaning your solar array actually affects performance.
The graph above represents the solar generation performance of our array on the day I washed the panels, with additional lines for the previous day performance and the year-before performance. All the days represented completely clear sunny days, so the panels were pretty much maxing out what they could do.
The cool thing is that you can see, around 10:30-11:00am, when I washed the panels, because the generation performance suddenly jumps above the lines for the previous day and previous year. We now have hard data to prove that washing your solar panels makes a difference! How much, you might ask? Well, as compared to the previous day, the wash day performance was 100*(81.3-77.6)/77.6 = 4.77% better. That’s a pretty significant jump! And that also doesn’t cover a full day of power generation, as well as the fact that since we’re on the downhill side of the Summer solstice, each day is a little shorter and generates a little less power.
Sadly, the following day had a lot of overcast, so I haven’t been able to get a full day-to-day comparison yet, but you know I’ll be checking my app. All the time. Over and over again. DATA!
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