The Heliodome project: an innovative approach in assessing solar-optical properties of light-redirecting materials in combination with sun course simulations

The Heliodome is a new type of video-based goniophotometer to measure materials and coatings intended to be used for advanced fenestration technologies or energy-efficient luminaires. Using calibrated digital cameras combined with a light projecting surface (ellipsoidal mirror), the spectral, bi-directional transmission or reflection properties of these materials can be assessed to a reasonable degree of accuracy. Its major innovations compared to other devices are to enable an analysis of both the visible and the near-infrared portions of the solar spectrum, to provide spectral as well as photometric light distribution data, and to ensure a continuous investigation of the transmitted or reflected light in a time-efficient way. The rotating table also serves as a heliodon, an architectural design tool for visualizing sunlight distribution inside a scale model and performing analyses on appropriate sun control strategies. This automated setup is complemented by a portable, manual outdoor heliodon that uses the real sky and sun as light sources. The paper details current progress in the development of this dual use device, called the “Heliodome”, that includes an original methodology for using a Charge Coupled Device (CCD) camera and a near-infrared Indium Gallium Arsenide (InGaAs) camera to measure arbitrary spectra.