Core Sunlighting System

The Core Sunlighting System provides daylight to the core of multi-floor office buildings to substantially reduce the need for electric lighting and reduce green- house gas emissions.

The project aims to establish the cost-effectiveness of this core daylighting system through a variety of demonstration installations.

This technology has been extensively evaluated in a test facility and demonstrations in existing buildings are currently underway. The technology will be commercially available within the next few years.

The system, designed by UBC, consists of two sets of components:

Sunlight concentration panels

  • collect the sunlight on the exterior facade
  • act as integrated architectural design elements for the building
  • protect the interior optical elements from the weather

    The Dual Function Prism Light Guides

  • replace conventional light fixtures
  • distribute the collected sunlight within the building core
  • integrate standard dimming electric lighting fixtures
  • provide efficient electrical lighting when necessary

    This system is the first core daylighting system with potential for widespread adoption and tremendous reduction in greenhouse gas emission.

    The Core Sunlighting System is being developed and commercialized by SunCentral Inc.

    Project Summary

    Goal of the Core Sunlighting System

    All over the world, office buildings are illuminated with fluorescent lights, even when the sun is shining brightly outdoors. While effective, this lighting solution is extremely energy intensive, and accounts for more than 30% of the overall electrical energy requirements of the building. Since sunlight is plentiful in many parts of the world, and many people prefer sunlight over fluorescent lighting, wouldn't it be great if we could tap into this environmentally-friendly and free supply of light?
    Although the sunlight itself is free, the problem until now is that it has been too expensive to efficiently capture the sunlight and distribute it within the building. The goal of this research program, led by Dr. Lorne Whitehead at the University of British Columbia, is to develop an economically viable system that is capable of illuminating the interior of office buildings with sunlight.

    -Core Sunlighting System-
  • Provides useful direct daylight more than 20 metres into the building core
  • Reduces energy for standard commercial building lighting by at least 25%
  • Replaces electric lighting 75% of the time each day that the sun shines within six core hours
  • Outperforms the efficiency of photovoltaic powered electric lighting by a ratio of 7:1
  • Integrates readily into standard architectural designs for commercial buildings
  • Is the only core daylighting technology shown to be cost-effective through energy savings

    The Adaptive Butterfly Array

    A grid of thin, square mirrors for collecting sunlight.

  • Orientation of the mirrors adapts to changing sun positions by means of pulleys and inexpensive actuators.
  • Redirects and concentrates the light using a series of mirrors, and the concentrated rays are directed into the Dual Function Prism Light Guides.
  • The system is protected by a weather-proof enclosure with a transparent front window.

    The Dual Function Prism Light Guide

    The inner surfaces of the prism light guides are made very reflective, using a highly reflective film (such as 3M Multilayer Optical FilmTM/MOF) and a polymeric prismatic film (such as 3M Optical Lighting FilmTM/OLF). The MOF has a very high reflectance at all angles, whereas the OLF reflects light from certain directions using total internal reflection. Light incident on the film from other directions will be transmitted.

  • Concentrated sunlight entering the light guide is reflected by the MOF and the OLF
  • Total internal reflection allows sunlight to travel along the guide
  • Sunlight hits an extractor material
  • Extractor diffusely reflects the light so that a portion of it will no longer meet the angular conditions for total internal reflection
  • Sunlight exits the guide, illuminating the area below

    Electric lighting is provided by fluorescent lamps inside the dual function light guide. Most of the light from the fluorescent lamps will transmit through the OLF and will efficiently illuminate the room below when it is dark or cloudy outside.

    Using this system, we guide sunlight into the building so that it reaches areas away from the windows that would otherwise be dark. If both daylight and electric light are delivered by the same fixture, it is cost effective because there is no need to install two separate systems, and there will be adequate lighting in the room, whether the sun is shining or not.

    Benefits of Hybridization

    There are four specific energy-saving features that have been integrated to create this hybrid lighting system. The benefits of these features combine to make this system both energy and cost-effective.

    at high sun elevation, the canopy structure provides shade for the windows, which reduces both direct solar heating and glare.

    Photovoltaic Cells:
    some of the sunlight entering the canopy will not be used for illumination because of practical optical constraints (i.e. portion of sunlight that doesn't hit the ABA mirrors), but it can instead interact with photovoltaic cells to generate electricity for the building.Inexpensive photovoltaic cells can be used, since they are protected by the canopy structure.

    the canopy enclosure can be used to facilitate solar heating of the building, since the heat collected by the structure can be brought into the building during cold weather and rejected during hot weather.

    Dual Function Fixtures:
    the interior light guides used to distribute the collected sunlight are designed to also operate as efficient fluorescent light fixtures when the sunlight is insufficient to illuminate the work space.

    How Does It Work?

    For an overview on the technical details of the Core Sunlighting System, please take a look at our the ASME paper.

    Demos & Videos

  • Visit to view a recent lecture about "Bringing Daylight Indoors" : CLTC's inaugural Don Aumann Memorial Lecture in Lighting Efficiency held at the UC Davis Conference Center (Jan/2011)
  • Core Sunlighting System Demonstration Video

    Please Enable ActiveX Plug-in.

  • Weather Network Story

    Please Enable ActiveX Plug-in.

  • Knowledge Network Presentation -Sunny Side Up

    Please Enable ActiveX Plug-in.

  • Core Sunlighting System Demonstration Video

    Please Enable ActiveX Plug-in.