Looking for help calculating daily solar PV insolation

[StevenMa]

I would like to write a simple (as possible) programme in Python for a Raspberry Pi that will calculate & display for each day the peak solar insolation +/- say 1 hour to display this 2 hour time window and a green LED or similar visual or audible indicator that now is a good time to run the dishwasher, kettle etc. to take advantage of the excess energy that would normally flow back into the mains electricity grid.

I have found solutions to switch on & off, for example, water heaters when excess energy is available but not devices such as the dishwasher which, when started, one doesn't really want to turn off just because the sun is behind a cloud. Typically, we set a delay on our dishwasher before we go out in the morning based on the insolation peak shown in pvoutput.org

The calculation will include the property location Lat/Lon co-ordinates, roof pitch angle and compass orientation of the roof in degrees.

What I've had difficulty finding help with is the mathematical calculation. I'm not a natural mathematician or programmer but I am probably determined enough to work it through with some help.

Thank you in anticipation of your help.

Regards, Steve

 

[haruspex]

I would think the main issue is the actual weather forecast. See http://laps.noaa.gov/solar/, and search the net for Opticast.

 

[StevenMa]

Thank you for your reply. Yes, that is a large part of it but, regardless of the weather, I still wish to compute the peak insolation time for each day. i.e. The time in the day when the sun is focused most directly on the solar panels.