Core Daylighting: A New Approach for Non-Residential Buildings

There is a considerable amount of research currently being conducted on a variety of advanced core daylighting concepts, although much of the effort is still in the early experimental stages. This research encompasses a wide variety of advanced concepts ranging from selective glazing materials to direct beam daylighting and includes innovative interior distribution systems such as optic fibersand light pipes [1,2,3]. This paper focuses on only these advanced concepts, daylighting heliostats, because there is sufficient research to report and because some heliostat systems are already being used to illuminate the interior of buildings. Another new concept for daylighting buildings that is similar to heliostats is a polar axis rotating Fresnel lenses [4]. Concepts that are quitedifferent and do not track the sun include holographic optical elements [5], wide angle nontracking lenses with image collapsing subreflectors and reflective cylinders [6]. An advantage of the nontracking systems is that they usually require less moving parts; however, all of these systems in one form or another concentrate or reflect direct illuminance into the building by imaging the solardisc.