So, regarding to this part of the world, (Nigeria ). Good solar irradiance is said to be observed between the 10am to 4pm (6hrs).

You certainly know your onions, i recently witnessed an argument about this when a lady working with a solar dryer had no idea about the peak hours of solar irradiance.

Errm, with this your very clear and detailed explanation, I'm beginning to feel like a qualified technician. You're truly a master of the art. Well done.