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My home's solar installation exhibits the curious behavior of producing its maximum overall single day output when there is summer morning fog which burns off
by danans 6y ago
My home's solar installation exhibits the curious behavior of producing its maximum overall single day output when there is summer morning fog which burns off around 9AM. This effect is clearly visible in the production graphs, which show a steeper energy production increase earlier in the day when these conditions are present.
My theory is that the fog moves the onset of generation earlier by reflecting low angle morning sunlight from the east down to my solar panels. The 9AM fog burnoff is critical to maximizing production because after that time, the fog begins to inhibit the production of electricity rather than enhance it.
- thdrdt 6y agoIt is also true that heat will add resistance to the electrical installation. So most of the time energy producten is way better when there is sun but it's cool. Energy producten can be much better in spring than in summer for this reason.
- spearo77 6y agoReduced heat might be the most likely explanation – https://www.renvu.com/Learn/How-Temperature-Affects-Solar-Panel-Efficiency https://www.renvu.com/Learn/How-Temperature-Affects-Solar-Pa...
- danans 6y agoI thought so initially too, but during the early hours of the day when the phenomenon occurs, the temperature is nearly always very cool regardless of whether there is fog cover or not - well below the 25°C (77°F) described in that article.
- coder543 6y agoAmbient air temperature is not the same as what a dark surface exposed directly to the sun will be at. The solar panels will be much hotter than the ambient air temperature if they're in direct sunlight.
- Retric 6y agoIn full sun panels can get up to ~150f, but they are not going to be that much above 77f ambient at 9AM.
- deleted 6y ago[deleted]
- lgats 6y agoThe panels could have a small amount of condensation on them?
- deleted 6y ago[deleted]
- saeranv 6y agoOther people are implying it, but to be more specific, the boost in cooling is the evaporative cooling impact of dew.
- hinkley 6y agoLong ago the World Solar Challenge competitors noticed that their cars had peak power output not on clear days but on overcast days. They explained it as having something to do with what frequencies get bounced back rather than radiating out into space. Later on while discussing a solar power result that sounded like Maxwell's Demon, someone pointed out to me that solar cell performance is affected by the temperature of the cell. Either or both could be in play here. Did you plot temperature versus output by any chance?
- danans 6y agoI didn't, but this is just after sunrise in the Bay Area, so the temperature is pretty low - not in the zone where solar panel efficiency starts to decline.
- dmoy 6y agoRight, wouldn't lower morning temperature be better for solar cell efficiency? It's been a long time since I took semiconductors, but I vaguely recall a decrease in voltage at higher temperature. You'd need to measure the temp of the actual cell, because it gets wonky. You can't just look at air temp.
- danans 6y agoIt would be surprising to see such huge difference in cell temperature in sun vs fog when the ambient temperature itself is about only about 60F, which is typical, or maybe even high for 7-9AM on the type of days I'm describing. Even if the cells were 80F on the sunny mornings vs 60F on the foggy ones (or a difference of roughly 10 Kelvin) that would result in about .5% to 1% drop [1] in efficiency, so I should see only slightly lower output on sunny vs foggy mornings. Instead what I see is that initial production on foggy days is several times higher than on sunny days. The only explanation I have for this is some kind of local effect where the fog reflects light that would have otherwise gone straight west in the morning down to my solar panels. 1. https://i2.wp.com/synergyfiles.com/wp-content/uploads/2017/01/Efficiency_PV_vs_Temperature2.png https://i2.wp.com/synergyfiles.com/wp-content/uploads/2017/0...