🪞 Heliostat Mirror: Normal Vector, Cosine Efficiency and Spillage Over the Sun Path (2D)

Side view of a heliostat reflecting sunlight to a receiver on a tower. Set latitude, day of year, solar time, tower height, the mirror position, tracking error and receiver radius, and see the mirror normal bisect the sun and receiver directions. Cosine efficiency, spillage and the daily sun path are computed, with four in-page numerical checks. A geometry companion to the 3D heliostat lab.