Creation sun power tower (Sevilla) in GC- equality between angles

Hello! My plan is to create something more or less like solar power tower in Sevilla but I have no idea what kind of script I have to use to obtain dependance on incidence angle and the angle at which light is reflected (which are equal).
The solar power tower is a type of solar furnace using a tower to receive the focused sunlight. It uses an array of flat, movable mirrors (called heliostats) to focus the sun's rays upon a collector tower. What I do not know is how to create a dependance between sunlight-mirrors-tower that really make sense moving only one point- the sun.