Anidolic Systems – Prototypes

Several full scale prototypes of Anidolic Daylighting Systems (ADS) were built by the Solar Energy and Building Physics Laboratory of EPFL, in order to validate the principles of this novel daylighting approach with regard to visual comfort and energy savings. These prototypes were integrated in different construction types (test modules, experimental buildings, etc.); numerical simulations for integration of ADS within architectural projects were moreover used to complement the scientific knowledge gained on an experimental basis.


Anidolic Zenithal Collector

A 1:1 scale Anidolic Zenithal Collector (AZC) was installed in 1995 on the DIANE daylighting test modules (see Figure). This facility consists of three mock-up office rooms with the same geometrical dimensions (5.4 x 3.4 x 2.7 meters), which have been placed side by side on the EPFL campus.

The three modules are oriented due North and have an identical external façade, made of double insulated glazing, except the one equipped with an AZC (1.1 meter protrusion over the façade).


photo from inside daylighting test module, prototype anidolic zenithal collectors like boxes into the room

The DIANE daylighting test module equipped with an Anidolic Zenithal Collector (inside view).


test rooms diagram daylight distribution

Comparison of daylighting performances of the AZC versus optimally and poorly designed mock-up office rooms of identical dimensions

Monitoring of the daylight factors within the three mock-up office rooms confirmed the remarquable performance of the AZC prototype :

  • a 3.3 % daylight factor is observed in the deeper part of the room at a distance of 4.5 meters from the window façade;
  • a 60 % daylighting provision over the whole year is achieved by that way for the second part of the room (300 Lux required workplane illuminance);
  • a (2.85) multiplication factor of the daylight flux is observed in the deeper part of the room (see Figure …), in comparison with an identical room, optimally designed for daylighting but equipped with a conventional double glazings façade (a multiplication factor of 10 is observed compared to poorly designed office room regarding daylighting).

The DIANE mock-up office room was occupied for several years by scientific collaborators; its luminous atmosphere and visual amenity were greatly appreciated.

Anidolic Ceiling

The Anidolic Ceiling (AC) was built in 1996 and installed on a mobile daylighting test module (DEMONA modules), located on the EPFL campus (see Figure …).

It uses a light duct into a ceiling to guide a large flux of daylight into a 6.55 meters deep office space (3.05 x 6.55 x 3.05 meters). Its design had to meet the following requirements .

  • an Anidolic Zenithal Collector was designed (0.7 meter protrusion over the façade) and placed in front of the light guide to collect and concentrate the daylight flux at the entrance of the lightduct;
  • another anidolic device was installed at the end of the duct to distribute the daylight flux deep into the room and reduce glare risks.

All the internal surfaces of the AC were covered with highly reflective optical material (post-anodized alumium foils of 0.93 regular reflectance). The device is covered with an insulated double glazings at the entry aperture; a single pane, made of organic material, was placed at the exit aperture.

The entrance pane has a tilt angle of 25°, which contributes to to its clearing trough rainfall and constitutes a more favorable incidence angle for light rays coming from zehnital directions (brighter part of the sky). All the external parts of the system are thermally insulated to avoid heat losses and water condensation (thermal bridges).

The AC was installed on 1 : 1 scale mobile test module, placed beside a reference one equipped with a conventional double glazings façade and characterised by identical photometrical (0.8 walls and ceiling reflectance) and geometrical features (3.05 x 6.55 x 3.05 meters).

demona test module photo exterior with anidolic system above window

Front view of the Anidolic Ceiling, installed on a mobile test module, beside the reference one (conventional double glazings façade)


photos internal view workplace with and without anidolic system

Internal view of the mobile test module equipped with the Anidolic Ceiling

The monitoring of both modules confirmed the higher performances achieved by he Anidolic Ceiling for different orientations (mainly North and South), in comparison to the reference :

the average daylight factor of the deeper half room is multiplied by a (1.7) factor in absence of any external obstructions;

  • a (2.7) multiplication factor is achieved in the case of a urban environment caracetrised by 40° angle obstructions;
  • a 30 % energy savings was monitored on a 6-month period for the electric lighting system equipped with an “On-Off” control debice (300 Lux workplane illuminance requirement).

Assessment of the visual comfort conditions achieved within the test module by the way of the AC confirmed the pertinence of the approach.


Integrated Anidolic System

The Integrated Anidolic system (ADS) is intended to fit the requirements of building refurbishment and therefore takes specific architectural design imperatives into account and reduces the complexity of the setting-up process.

It was installed in 1999 on one of the DEMONA mobile test modules, located on the EPFL campus (see Figure).


photo external view anidolic integrated system prototype

External view of the Anidolic Integrated System, installed on a mobile dalighting test module, beside a reference module (double insulated glazings)

diagram daylight factor distribution with/without anidolic system

Daylight Factor profiles monitored for overcast conditions in the test and reference modules (DEMONA daylight modules)

Through the collaboration with a façade making firm, the following physical imperatives were considered :

  • the building outside appearance is kept unchanged by minimising the protrusion of the external collector (protrusion lower than 30 cm);
  • the thermal building envelope of the building is left in the vertical plane to reduce the overall system costs;
  • the fixed height of the existing concrete slab in the refurbished building is taken into account (generally 2.65 – 2.7 meters);
  • the height of the lowest point of the internal reflector must be higher than 2 meters for sake of users acceptance.

The monitoring of the test and reference modules was carried out during the 1999/2000 winter season (october through april). In comparisont to the conventional façade, the anidolic device is caracterised by the following daylighting performances :

  • the workplane illuminance over the whole depth of the office room is more even, in particular in the vicinity of the window façade;
  • a significant improvement of the daylight factor is achieved at the center of the office room (2 – 4 meters from the façade);
  • a slight improvement of the daylight factor is observed deeper into the room (0.5 % DF increase in absolute term);
  • the improvement of the daylight provision within the room reaches 10 % in absolute term deep into the room (50 % already achieved through the room daylighting optimal design)

The assessement of the visual comfort conditions confirmed that higher luminance values are achieved by the IAS on the ceiling and on the rear office wall.