How much do your panels produce when it is overcast and raining?
- Thread starter Mattb4
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HighDesertOffgrid
Solar Addict
- Joined
- Sep 15, 2022
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- 628
My panels only have 2 modes of efficiency.
Can make coffee at 5am.
Need more Gas for Genny.
Can make coffee at 5am.
Need more Gas for Genny.
I dance the dance of astonishment! Very interesting to see the relative efficiency curve as irradiance drops. One would have thought it was more of a straight line decrease.
That actually would be nice to see for the various panel types.
seneysolar
Solar Enthusiast
Does anyone have a light meter they can recommend to measure irradiance? I see them online but never used one. Would be handy when comparing panel outputs rather than saying "it was sunny out"
Ron Asbury
New Member
I just received some new panels last week. 415Watt Mono PERK 1/2 cut with STC VOC of 38.82
The next morning I opened a pair to test the voltage. Cool temps 38F and clear skies. At 11:00 am and a 30 degree angle the VOC was 36.2.
Three hours later a front had moved in and I retested. Overcast and a light rain/mist, temperature remained the same. VOC - 26.1.
The next morning I opened a pair to test the voltage. Cool temps 38F and clear skies. At 11:00 am and a 30 degree angle the VOC was 36.2.
Three hours later a front had moved in and I retested. Overcast and a light rain/mist, temperature remained the same. VOC - 26.1.
chrisski
Solar Boondocker
- Joined
- Aug 14, 2020
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- 5,208
I’m sure some are better on cloudy days. Too hard to quantify.
Even with a 100% improvement, you’d just get 260 watts . Generator comes on or utility still has to help.
My q cells outperformed a coworker, but the next cloudy day he did better.
Cloudy with shadows, cloudy with no shadows, cloudy and rainy, cloudy and pouring, etc. Too many variables.
Even with a 100% improvement, you’d just get 260 watts . Generator comes on or utility still has to help.
My q cells outperformed a coworker, but the next cloudy day he did better.
Cloudy with shadows, cloudy with no shadows, cloudy and rainy, cloudy and pouring, etc. Too many variables.
HighDesertOffgrid
Solar Addict
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wpns
Solar Joules are catch and release
Not only what I like to see that graph go all the way down to zero, I’d love to have that curve in numerical format, so I can try to correspond insolation as reported by my WeatherStation to solar power
wattmatters
Solar Wizard
You'll need the temperature coefficient as well.
I don’t think that’s broadly possible …….without some extreme number crunching, data and computations to be meaningful. There’s just a lot of things that affect things they can’t know .
I have seen great sunny days and only 80%…. and gaggy days with 35% …..???? But that’s not normal…
I think they are telling us what’s possible at STC , but what you get ,will be what you get, depending on many variables……
I understand what your saying , and it’s cool , but I think after a while we get a good feel for what is in store +/- 10% by lookin at the sky and thermometer…
.and considering what month it is….
.J.
Ampster
Renewable Energy Hobbyist
i just use the output of the panels as a crude measure of solation. My Davis weather station sells a meter but it does not seem worth the expense because I use Solar Assistant and get lots of data about Amps, volta and Watts from my panels.
hwy17
Anti-Solar Enthusiast
I have an Ambient Weather weather station and it reads irradiance in Wm/2. I don't know if it's super accurate, but it does. I have mine connected to weather underground publicly so I can go to my station on there and look at historical data and graphs.
labeeman
Solar Enthusiast
wattmatters
Solar Wizard
This month's daily production and forecast by Solcast:
wpns
Solar Joules are catch and release
I’ve just looked at the last few days of production om my ~15KW array, and in 3 of the last 4 days I could have sustained a 2KW load from 7:30AM to 4:30PM. And this is a pretty sunny place! I would not want to depend on this.
wpns
Solar Joules are catch and release
AI, when you have to have an authoritative, unambiguous, and potentially wildly wrong answer immediately! I’d rather get my hallucinations from the Internet, at least then I know what to expect!
Checkthisout
Solar Wizard
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- Nov 14, 2021
- Messages
- 4,819
Rain = 2-5% of nameplate rating at high noon, then combine that with day length during December and January and Ethanol-free is getting burned in the backup generator.
In my case light overcast sometimes assists in getting better numbers because I have shadowing from trees.
In my case light overcast sometimes assists in getting better numbers because I have shadowing from trees.
Q-Dog
¯\_(ツ)_/¯
On a good sunny day my 2200 watts of panels can make 11.8kWh. On the darkest rainy day they made .36kWh, so about 4%?
Hmmm... seems 4% might be a good figure for what you can expect from regular solar panels on a dark and gloomy day.
