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Solar Power

As mentioned on the home page, I have a photovoltaic installation on my roof and I keep a close eye on it. The entire installation was done by a electric utility company. But  even though the system came with a monitor system and logs data to an online portal, I have written a few small programs in Python to log data into a database and display some of it. Since installation, I have been logging 10 different parameters every minute. The documentation for the inverter actually has the log file format explained so I could extract more parameters if I wanted. I also wanted to use a portal that the software in the inverter didn’t support so I wrote another script that exports daily numbers from the database and uploads them to the portal a couple of times each day.

This is a live graph of the output for the last 24 hours. Updated every 10 minutes between 05 and 22. I tried different graph modules for Python but ending up just feeding the kilowatt output data into RRDtool. 

Click here for a larger more detailed version with one pixel pr. minute.

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One of the programs generates a webpage for viewing on my smartphone so I can keep an eye on it from anywhere in the world where you can get a data connection.

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I also has this status monitor in the hallway / corridor. It’s a picture frame with a special USB key inserted. The key generates 5 images with data it gets wireless from a monitor box connected to the ethernet and the picture frame switches between these images. The monitor box can collect data from up to 10 inverters. 

Pictures from the installation

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The inverter with the front open. The electrician are installing the 3-phase 400 Volt output, connecting the DC input from the photovoltaic generator(the solar panels) and the ethernet connection for monitoring. 

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Only 3 more panels to go

Observations

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The two upper panels to the right of the chimney gets a shadow creeping across them in the afternoon around 16:00,17:30 18:45 and can be seen as a loss on the graph, marked with #1. Usually before it gets cloudy, the wind picks up and cools the panels better(#2) and when the sun breaks through, the panels produce better for a little while until they heat up again(#3). I am not sure what happened at #4, I am guessing it must be wind still cooling the panels. 

It could be fun to get a temperature probe on the panels, measure ambient temperature and wind speed and add those to the graph. Kostal has a add-on kit for the inverter that measures the temperature as well as a reference measurement of radiation from the sun. Maybe I can find that at a reasonable price somewhere.