A dynamic skylight for daylighting and assisting climatisation in a medium size room.

This work presents a dynamic skylight, for daylighting and assisting climatisation in a medium size room. Room’s dimensions (6 m x 6 m in plant and 4 m height) and lighting from above are compatible with uses as show-room of art gallery or museum, class room and lecture room. The device includes an heliostat with variable geometry, that can exploits direct or sky diffuse solar radiation as function of season and weather conditions. During the cold season the direct radiation, if present, is re-directed inside the room on diffusing ceiling. During the warm season the device modifies its configuration and allows to enter only to the fraction of sky diffuse radiation that is required for daylighting. This radiation comes from the North side of the sky-dome. The direct radiation impinging on the South side of the device is used to create in its interior a solar stack effect, that contribute to air extraction and natural ventilation. Dimensions of aperture on ceiling, device’s geometry and its control logic have been optimised by means of computer simulations, with the aim to minimise the total annual energy demand for climatisation and illumination. The software employed, Ener_lux, calculates the level of internal daylighting and executes a simplified energy balance of the room with hourly step. This balance takes into account solar gain and internal gains. Radiance too has been used for more accurate lighting simulations Two Italian climates have been examined: Venezia (44.5° N) and Trapani (39° N). For each of them device’s geometry has been optimised.