Is the size of the reflected sun spot dependant on the distance the heliostat is from the target?
Sunlight diverges 1 foot over every 100 feet of distance, so as a general rule, the further the heliostat is from the target, the larger the reflected sun spot. However, by using Practical Solar’s mirror focusing technique during installation (tilting each mirror slightly in the mirror frame), the customer has some control over the size – and shape – of the reflected sun spot. Tilting the mirrors essentially creates a parabola that is tailored for a particular target at a particular distance away. However, the customer should be aware that the reflected sun spot may look different on a target a different distance away from the heliostat, since the focal length will have changed. The mirrors can also be de-focused during installation to diffuse sunlight. The most concentrated sun spot possible is about 15-18 inches in diameter. This is achievable from a heliostat-to-target distance of about 25-50 feet. From a distance of 100 feet, a 2-foot-diameter sun spot is possible. From a distance
