1. Field of the Invention
The present invention relates generally to a light control apparatus, and more particularly, but not by way of limitation, to an apparatus for a skylight that uses solar radiation as the control parameter and as the power source for automatic adjustment of shade devices to control solar energy entering a structure through the skylight.
2. Brief Description of Related Art
Skylights were widely used to provide light to industrial and warehouse buildings before the widespread use of fluorescent lighting. Around 1995, “big box” retailers began to install skylights over product sales areas. The original objective was to improve the appearance of products by admitting daylight. Natural light has a color rendition index (CRI) of 100%. Thus, products were more appealing than when viewed under the weak fluorescent or high intensity discharge lighting then in use with CRI's of around 40-60%. In addition, natural light reduces the cost of artificial lighting, which accounts for 40% to 50% of the energy consumption in many commercial buildings. When sufficient natural light or daylight is available, a good daylighting system can significantly reduce artificial lighting requirements and the associated energy costs.
While skylights perform well in both improving the quality of store lighting and reducing the need for artificial lighting, they have a significant disadvantage. Daylighting is composed of the visible light spectrum plus direct solar gain. Direct solar gain increases air-conditioning loads resulting in increased utility costs.
The skylight industry does not have any advanced technology in the control of solar loading. The approaches used so far include adding tint to the skylight and thereby increase the shading coefficient. The problem with this solution is that it, in turn, decreases the light admitted into the structure. The window industry has also responded to government insistence in the form of low-e glazings and thermal blocking frames.
Technologies to provide active control, such as electro-chromic glazing (ECG), which has been in development for the past ten years and still not available to the mass market, are extremely expensive. While ECG will limit solar heat gain through windows it still will not optimize daylighting. Further, it offers no solution to the retro-fit market, nor does it offer any fire resistance.
To this end, a need exists for an apparatus for controlling solar energy entering a structure through a skylight which uses solar radiation as the control parameter. It is to such an apparatus and method that the present invention is directed.