What is the lowest latitude for which if the ideal solar energy received each day for a year is graphed, the graph would contain one peak?

Question

I asked a question with the same meaning on Quora, but it seems no one got it, so I'm asking it here with a very different wording. I'm actually not sure if this would belong here or on the Astronomy stack exchange, as though it deals with the Earth, it is an extremely pure question with almost nothing to do with its atmosphere or complicated innards. Real-world topographic and atmospheric moisture conditions that may affect the results are to be ignored.

For all latitudes outside the tropics, as I'm sure we know, the summer solstice is the date where the sun culminates the highest in the sky, having the highest solar angle and insolation. This angle is 90° at the tropical circles. Closer to the equator, this 90° angle is experienced in 2 Lāhainā noons moving further from the solstice the lower the latitude is until reaching the equinoxes at the equator.

However, at all locations except the equator, the summer solstice is the longest day of the year and the winter solstice the shortest. Hence, down to a certain latitude within the tropics the summer solstice should still experience the most total solar energy, as the effect of the longer day would be stronger than that of the lower solar angle. As you get closer to the equator, the day length gets more consistent and the angle at the solstice becomes still further from that at the subsolar point, until eventually the solstice no longer receives the most total solar energy and two "humps" emerge.

So, what is that latitude?

Note: This answer can depend on if the eccentricity of the Earth's orbit is taken into account, in which case the values for the Northern and Southern hemispheres will be different. Answers may choose to take this into account or not (ideally I'd like both).

Answer 1

Any area south of the northern polar circle will have one peak per day,and the same goes for the southern polar circle any area north of this will have one peak per day,the polar circles is at 66,33 north/south.

The areas whitin the polar circles will have only one peak per year but it will last for half a year.

A solar panel will only produce significant power for a maximum 12 hrs even in the area of the midnight sun,This is due to the very low angle of the sun during the "night",or at the poles it will produce energy for 24 hrs but due to the suns angle a solar panel will produce a lower level of power than if the solar panel was at the equator.

Solar panels will be most effective if placed close to equator and less effective as you move away from equator,The suns rays have to penetrate less atmosphere at equator and a lot more closer to the poles.