Artificial sky

The artificial sky is a daylight simulation device that replicates the light coming from the sky dome. An architectural scale model or 1:1 full-scaled aircraft is placed under an artificial sky to predict daylight penetration within buildings or aircraft that subjects to different situations, complex geometries, or heavily obstructed windows. The concept of the artificial sky was derived due to heliodon’s limitation in providing a stable lighting environment for evaluating the diffuse skylight component.
An artificial sky is primarily utilized in the field of architecture to analyze daylight in buildings and spaces. Architectural students, architects, researchers, lighting designers, lighting engineers, automotive and aerospace engineering use the simulation device for various purposes. Several versions of the instrument are used in laboratories of architectural schools and practice for daylighting studies and research. Lighting engineers and designers use the artificial sky to measure illumination levels. The instrument is utilized to examine the visibility of tools in the cockpit in automotive and aerospace engineering to improve flight safety.
Since 1914, Artificial skies were used by architects and lighting engineers to find ways to stimulate the sky from which physical models of buildings could be measured for interior daylighting.
Generally, interior daylighting of buildings is analyzed at the design stage using physical models by observation and evaluation of physical models of light levels under a real sky, but the luminance is constantly varying, and regular results are difficult to obtain, therefore artificial sky forms the ideal way to predict daylight penetration.
The artificial sky can replicate standard and statistical skies and are not restricted by the weather conditions of the natural sky. In general, the artificial sky is operational with lux meter heads, data logging systems, micro photo cameras and can be a manual or computerized system. The sky vault is partly or completely replicated. Three ways of replicating sky light are by direct lighting, by reflection, or by diffusion. Through reflection, spotlights directed under the model illuminate a white dome, the reflections on the dome illuminate the model. If the real sky emits a diffuse light, the most realistic principle is sky functioning by diffusion. Normally, the artificial sky has spherical forms. The most practical systems integrate the artificial sky with a mechanical Sun for reproducing the sunlight.
By measuring and estimating daylight penetration using artificial skies, building designers and engineers can reduce energy by controlling lighting, the simulation can provide a daylight design that reduces the environmental impact of buildings by decreasing the need for lighting, heating, and cooling. By analyzing issues of architectural light simulation, the simulation models which use artificial skies gives valuable advice to attain the best design solution for buildings and spaces. Daylight studies help in the design of passive houses, zero-energy buildings, and ecological building design.
To address readability issues that arise due to glare and faded screens under ambient lighting conditions in automotive displays, artificial skies provide a luminous environment that allows designers and engineers to handle any areas of concern.
The use of simulation aids in avoiding glare and reflected heat from building's facades mainly due to innovative design forms. Since the intense sun rays affect the surrounding urban environment, the heat and glare affect people on nearby streets and buildings. The simulation device will allow designers to avoid unexpected events that occurred in concave surfaces of the Walkie Talkie skyscraper and Walt Disney Concert Hall where it caused damages due to reflected heat and glare. To avoid overheating in outdoor areas and buildings from reflected sun rays, simulation using artificial sky for such types of building forms during design stages allows architects to avoid the high cost of retrofitting and damages.
Artificial sky types include mirror boxes, full-dome sky, virtual dome, and reflectors.
A mirror box is an artificial sky consisting of a luminous ceiling and mirrored walls, used to replicate uniform or overcast skies. In a mirror box, a consistent luminance distribution is created from reflections of the light from the mirrored walls and an appropriate estimation of CIE standard overcast sky is simulated. The light source is the white diffusing material illuminated by several lamps from behind to diffuse the light throughout the room with help of sensors. The walls of the room are surrounded by plane mirrors organized vertically on all sides, which produces an image of the luminous ceiling by reflection and inter-reflection.
A typical mirror box is a rectangular or octagonal box that can be installed in any laboratory. The mirror box is a simple, compact, and inexpensive artificial sky. But it can only replicate the standard overcast sky; therefore, it is suitable for Daylight Factor (DF) analysis.
Mirror box artificial type is used in universities such as:
The reflecting dome sky simulator is formed with a reflective opaque dome surface to reproduce uniform and non-uniform skies. The lighting system on the interior of the dome is formed to stimulate sky distributions that are different from a standard overcast sky. The artificial dome uses a reflective surface to illuminate sky distributions and evaluate daylighting on scale models placed on a rotatable tabletop. Also, it can be integrated with the artificial Sun to replicate sunlight. Compared to mirror boxes, reflecting dome skies are more adjustable in utilization and their variants are widely available in the market.
Reflecting artificial sky is available in university and research laboratories such as:
Virtual dome replicates the sky vault with a scanning process for any time and any location on Earth. This type of artificial sky is flexible due to its ability to replicate any type of sky. To limit cost and space, the virtual dome utilizes heavy robotic and fine control systems. The results of the simulation are measured only through a computer screen after a process of combinations of multiple simulations. It provides daylighting simulations on scale models on a rotating platform using an artificial sky and a Sun simulator. The artificial dome was found in the early nineties, and therefore it is the latest type of artificial sky.
Although it is the most precise tool, direct perceptions of the simulations are not achievable. Since direct perception is not possible in the virtual dome, the tool is largely used by scientists and not made for designers.
Virtual dome artificial sky is available in university and research laboratories such as:
A full dome is a type of artificial sky that can replicate any kind of sky distribution using dimmable luminaires. The simulation and obtaining daylighting metrics are performed through computers. When integrated with a heliodon, the device can replicate direct sunlight at any global location. The full dome is the most advanced type of artificial sky available. They are the fastest, most powerful, and highly expensive simulators. It is used by students and researchers for optimizing daylighting studies in architectural spaces.
Full dome artificial sky is available in the university, research laboratories and large lighting companies such as: