1 months worth of dust equals 4% of lost production where I live.
I wonder what the detail data looks like. For example, what was the gap on the day after they were cleaned? Basically how fast does the dust/soiling start affecting the production and when does it start leveling off.
I've also wondered if the dust affects production in a small measurable positive way when the sun is perfectly perpendicular to the panel. Does the dust act as reflector for light coming in at off angles and reflect it back on to the panel thus reducing the penalty for soiling.
If the measurement were taken right after they were cleaned, it would be nice to see a comparison a day or two later. Especially if a moderate amount of water was used, the panels that were cleaned would be somewhat cooler than the uncleaned panels, as cooler panels can cause a few percent higher production for a short period as well.
I love data! I unfortunately don't have module level instrumentation to perform this experiment. Thank you for doing this!
As one who seems to have almost always lived in hard water areas, I am sure you are aware, but soft water can still have minerals in it. Rinse agents help. You might want to wait for a foggy night when you have condensing water to do a "final rinse", like @sorka.It's tree pollen season where I live and I have noticed about a 10% reduction in production over the last week. So in a few weeks, once the trees are done doing their 'thing', I am going to wash all my solar panels off with soft water and the special 'water broom on a pole' device I bought last year for this reason.
I will then have a pretty good idea how much of a difference it makes.
In my area, Sierra foothills, I'll be waiting until November.
have found that after occasionally cleaning panels on my homes in different areas over the last 15 years, it really made absolutely no difference what water I used. And 4%, plus or minus a couple percent is about what I experienced with various levels of dust and dirt.
Nice, I'll be looking forward to more data over multiple days.They were cleaned the night before. I'd never do this during the day when the sun is up. I also rinsed with deionized water and did so the night before as condensation was starting to form. This prevents even the soft water I rinsed with from forming any mineral deposits on the glass as all that water will be displaced through the night be condensation which is mineral free.
Well, the experiment is not so simple. The panel 2 and 5 have a difference of 1.3% in that picture. How do those two compare over historical past, always a 1.3% difference? Or there is a variance?
Then panel 3&4, the clean one have 2 decimal equivalence. Have they always be equal in production in history or there are time when they vary?
Number 5 is also on the outside, more ventilation, will that mess up the experiment?
Perhaps if that 4% difference can track over time, it may have some relevance?