Innovations in direct-beam daylighting systems

Larry Kinney and Tony Burnett, E SOURCE, USA

Keywords

Daylighting, active daylighting systems, direct beam, natural light fixtures, ASZEN, DayTracker

Abstract

Two practical daylighting systems are being developed that use direct-beam sunlight to provide controlled natural lighting to the interior of buildings. One, the Aszen system, can be employed in either of two modes.

In its non-concentrating mode, the system sweeps controlled sunlight across a light-colored ceiling, from which diffuse light is distributed onto surfaces below.

In its concentrating mode, the system directs concentrated sunlight into a rectangular light pipe that resembles a small air duct. It delivers useful levels of sunlight over a distance of 30 meters within a structure. Both versions of the system employ an array of automatically or manually adjustable vertical and horizontal mirrors to control beam sunlight.

The other system is known as Daytracker. Installed on the rooftop or sidewall of a building, this system system uses a pair of parabolic mirrors to form a concentrated beam of sunlight that is directed down a cylindrical light pipe by a third, optically flat mirror. The three mirrors rotate around the light pipe on a “lazy Susan”–style bearing.

Both systems are steered by a pair of stepper motors that are actuated by a dedicated micro-controller. At the point of delivery, beams are typically redirected onto a white ceiling via “natural” light fixtures, thus allowing soft, diffuse light to illuminate the space below. Simple schemes for controlling lighting levels and bringing efficient electric light up to whatever level is needed are integrated into both systems, as are filters to eliminate most of the infrared and ultraviolet portions of the spectrum.