When it's super hot are solar panels more effective, or is it just a matter of direct sunlight from a cloudless sky gives the same amount of energy in winter as in summer?
Direct sunlight is needed, or preferred at least to get the most power generated.
Direct sunlight in winter is less useful as it is less intense due to the angle in incidence. Same as why it's colder in winter than summer. Earth tilting away from the sun rather than towards the sun. Same light beams spread further. You obviously also get less hours of daylight in winter, but that's got nothing to do with the intensity of the light.
Still generate some whilst cloudy, just nothing like a clear sunny day.
