Abstract: There is provided a unit for light conversion in a building. The unit comprises a solar panel comprising photovoltaic cells without any light-absorbing or light-reflecting coating such as to be raw. The photovoltaic cells can have a wavelength range of conversion optimized for natural sunlight. The unit further comprises an enclosure surrounding the solar panel and preventing the exposure of the solar panel from direct light from outside the enclosure, the enclosure comprising an input. There is provided a light guide comprising an optical fiber and adapted for optical connection to the light collector, the light guide being connectable to the enclosure via the input, the light guide having an output end located by the input of the enclosure and directed toward a surface of the photovoltaic cells for illumination thereof. A light collector is provided outside the building for collecting sunlight and guiding the sunlight into the light guide.