How does latitude affect the solar energy that reaches the earth?

At equator sun rays drop at a 90 * angle - full power

at tropiques they drop at (90-23.5) * angle - ~70% power

at polar circles they drop at 23.5 * angle - ~30% power

at poles it's just 0 * that means they're tangent to ground - 0% power

(that's valid only at equinox)

the general idea is that the energy is proportional to cosy where y is the angle that sun rays make with the ground

the higher the latitude, the lower the angle = > less energy