Number crunching

My adopted home town is on the high side of these averages, while still maintaining above average rainfalls, which means that if I ever retire I can follow the Amish advice of making sure that my garden is larger than my house.

The payback, of course, is autumnal storms and crushing humidity - but that's life in the deep South....

 

I just ordered an inexpensive DLI meter, or daily light integral meter, from Amazon. It is not made for PV panels but used more for plant propagation and gardening, but it should work for my purpose. With vast local weather differences, the average sunshine data for the state or city from the past records is not very reliable data for my solar analyses. I need actual sunlight measured on my roof.

Today, sun is out, unlike yesterday. For my second day of the PV operation, it has hit 8.8kWh already. And it's not noon yet. If no cloud moves in, the PV should generate close to 20kWh today.

 

Won't a 100w solar panel and an intelligent charge controller give you the same thing, for about the same money??

 

The PV system and app reports the total amount of kWh generated from the panels. I can even look up each individual panel's kW generating in real time. Theoretically, this number should be proportional to the total number of photon hitting the panel. But whole point is to confirm what is being reported by the panel (and app) matches the empirical observation of sunshine based total amount of photons received by the panel per square meter over the course of a day. I just want to confirm the daily mol/m²/d of photon changes closely follows the kWh production from the system over the course of a day.

 

The first full day of solar generation. The sun was out in the morning, but cloud moved in the afternoon and started snowing. Still managed to generate 23.6kWh total. That is less than what we usually use in a single day (our average is 34kWh/day). But 70% coverage on winter day is not bad.

 

You ae correct, sir.
HOWEVER (comma!)
Using a separate PV panel and controller and taking independent samples would yield the same data set at roughly the same price point as the TEMU-meter, allowing for monitoring and analysis of THAT SEPERATE PV panel's performance over time; essentially acting as a data logger independent from the system.
Since humans usually have 10 fingers, the 100w panel also makes for easy math.

AND.....
You would get to harvest the electricity WHILE you were taking your measurements.

 

Can you show me a link to your $47 100w solar panel and an intelligent charge controller? If it has a Bluetooth capability and data logging app for that price, I am going to buy one... More measurements are always better to verify the data.

 

Fair enough....

 

1 week of production from our 15kW system was just 93kWh. That's less than $30 worth of electricity.

3 days of no production with snow covered panels. But this should be the worst time of year.

 

$30 generated per week in mid winter sounds sorta OK to me.

@Salamander_King knows, but for benefit of readers, day length is only 9.5 hrs now. That will exceed 15 hrs in June and first half July.

PV at lower latitudes don't swing that much

 

I ordered snow rake like this for next snowy days. Should allow harvesting sunshine as soon as it stop snowing and sun comes out. After substantial snow, if waited till naturally melt, it can take days or sometimes weeks before the panels get exposed.

 

Yeah, short day is expected in winter. As long as sun is shining and no snow cover, the system can produce 30 kWh in a single day even this time of year. That's about $9 worth of electricity for us. The snow cover (after stopped snowing and sun came out) robbed at least half of that potential.

In future, if I install PV again in snowy region, I will do the vertical system.
Vertical rooftop PV performs better than conventional rooftop solar under the snow – pv magazine International

 

~Two decades ago I was at some rich guy's house south of Lake Tahoe in winter. Got there in something like a Tucker Sno Cat, so yes, rich. His PV panels were under feet of snow and clearing operations commenced. Ground team was buried by 'avalanche' but it was fluffy stuff and we dug them out no problem.

At that time battery storage tech was the largest 2-volt lead acid monsters that I had ever seen.

 

"Yeah, short day is expected in winter" Respectfully, your adverb is 'certain'.

Sorry, I have been editing manuscripts for the kids, and proper word selection is always a thing. This here is astrophysical certain, some notches above 'death-and-taxes' certain.

 

I learned it only takes coating of snow to stop the PV from harvesting photons. A few inches of snow was all I had to deal with. The problem was with temperature staying well below freezing, a few inches of snow will not melt and slide off the panel easily.

 

"I will do the vertical system."

So good in Oslo latitude 60 oN, but maybe not for your 'lat'. I wonder what is the lowest panel angle that will shed snow without intervention. It should be easy to find by tinkering, Incline panels thataway not vertically.

==
Having recently visited Norway and region, I'm quiet to not go off-topic.

 

The article does not say the advantages of vertical system in summer time in Oslo. But winter month advantage under snow is clear. The best system would be sun tracking PV panels but that would be prohibitively expensive for larger size home system. Vertical Bifacial PV are practical even in Colorado. I would think it works in my region as well.

As for "the lowest panel angle that will shed snow without intervention". I don't think there is easy way to find that out. Too many variables. Whatever the angle it is, it certainly will not work on all different types snow and weather conditions we tend to get. Powdery dry snow are easy to blow off if windy, but, being very light, it tend not to slide off easily. Wet sticky snow are hard to blow, but it can slide as a entire sheet at some point by its own weight. Then there is the problem of partially melt snow refreezing to become solid at night. Those are the hardest to remove without applying deicer such as salt or heat, neither of which are option on the PV panels.