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Question: How is a solar panel orientated ideally?

Read first: "How can you orientate a solar panel?

Solar cells with a fixed orientation catch constant several amounts of light energy, because of the daily and annual movement of the sun to the sky. If we take the average over day and night, and over winter and summer during a year, then we find the average radiation.

Solar panels have been optimally oriented:

1) for the direct solar radiation:
The panel must be aimed to the South (therefore azimuth A=180°).
For the slope of the solar panels n (= usually the slope of the roof), a compromise angle between "b-e" and "b+e" should be chosen, with b the geographical latitude of the place where you install the solar panels (e.g. for Belgium: b=51°) and e the ecliptica (= 23.5 °).
From calculations, it becomes clear that for Belgium/the Netherlands, the optimum slope is n=37° (for the direct solar radiation(!) ).

2) for the diffuse solar radiation:
The optimum orientation is when the solar panels are orientated to the whole sky, in other words, the solar panels lie horizontally. The slope n is 0° (and of course, the azimuth A does not matter).

3) for the real situation with direct and diffuse solar radiation:
In a Belgian/Dutch climate, the contribution of direct and diffuse solar radiation are approximately just as important, therefore the ideal orientation is a compromise between 1) and 2).
For a geographical latitude of e.g. 51° (Belgium), the optimal parameters are:
A=180° (= aimed to the South)
n=35° (= slope roof)

Read further: “How bad is it if a solar panel is not ideally orientated?

Answer: to the South, with a slope of 35 °