I don't think the equinox is special in this regard - as the days at one point get longer, they shorten at the antipode. As a practical matter insolation at da

I don't think the equinox is special in this regard - as the days at one point get longer, they shorten at the antipode. As a practical matter insolation at dawn/dusk won't be able to power much, without a PV array that would be quite oversize during the day. Lots of interesting optimisation problems in this area. But at this scale batteries and solar panels come in discrete sizes, so it's a bit academic.