A self-regulating glare protection system using concentrated solar radiation and thermotropic coating

A static, non-mechanical, self-activating sun protection system affecting the direct sunlight but not the diffuse skylight is described. It is based on the selection of direct sunlight by concentration. A lens array in front of a glass pane concentrates the direct light onto a thermotropic layer where it increases temperature beyond the switching temperature and causes the thermotropic layer to become locally quasi-opaque. Most parts of the glazing except for the small focal regions remain transparent and contribute to the illumination of the room behind. The system performance is theoretically analysed by a numerical solution of the equation of heat conduction, giving the temperature distribution within the system. Different samples of the sun protection system, using different thermotropic materials and other system components have been constructed and measurements of various temperature and transmission properties have been performed.