or for all intents and purposes none at all. i could be wrong but given the relative sizes of the sun, the solar array, and the distances involved, the amount of sunlight that is blocked by the array from any observer's point of view on earth would be negligible.

for example planes flying at 35k feet don't cast visible shadows.

I don't think the distance really matters in the amount of blocked sunlight. The sun is very far away compared to the satellite. The atmosphere scatters the light so it would cast a more diffuse shadow than if it was closer to earth.

I've seen helicopters in films with shadows (due to the helicopter with the camera inside). But yes, that's not at 35k feet, but more like 200 feet.

That's a ~4 sq km shadow (spread out because of light scattering).