张泽    ZHANG Ze

Sunlight adjusts human physiological functions through various biochemical reactions and has preventive and therapeutic effects on many diseases. At the same time, proper lighting can reduce the carbon emissions generated by daytime lighting, which is conducive to achieving the goal of carbon peaking and carbon neutrality. There are about 219,000 old neighborhoods in China, and most of them have poor indoor light environments due to small building spacing and other factors, which will have a negative impact on the physical and mental health of residents when they live in such houses for a long time, especially for the elderly and children. At this stage, the natural lighting improvement measures for old neighborhoods are not ideal. The "smart mirror" is a device that automatically tracks and reflects direct sunlight to the target room for lighting with the help of built-in algorithms. The idea of this paper is to improve the indoor light environment by installing "smart mirrors" on the south wall of the building on the north side of a poorly lit house in an old neighborhood, reflecting daylight directionally to the north-facing room of the house and supplementing the south-facing light of such houses.
In order to verify the above idea, the corresponding "smart mirror" device was manufactured in this study, followed by a study of several residences in old neighborhoods in Xiamen from 1990 to 2000, and one of the residences in the old neighborhood was used as the research object. The target residence and the "smart mirror" were modeled in Rhino and grasshopper, and an automated simulation process was created according to the characteristics of the "smart mirror" model to conduct the simulation experiment of mirrored lighting. The experimental data are processed, and the indoor light environment is evaluated by illuminance distribution, illuminance uniformity, a modified self-defined effective luminosity, and daylight glare probability evaluation index; the indoor radiant illuminance data are processed and converted into average radiant temperature, which is used as the radiant heat evaluation of "smart mirror" reflected light. Through another workflow, we calculate the hour-by-hour radiation flux of the "smart mirror" during the lighting hours of the year, and summarize the law of smart mirror lighting from these data. Based on the experimental results and the law of mirror lighting, the design strategy is proposed, and finally, the retrofitting engineering design is carried out around the "smart mirror" in the selected old district, and the implementation path of the retrofit is proposed.
The simulation results show that the "smart mirror" has significantly improved the indoor light environment. The illuminance is significantly improved, and the illuminance of most areas is increased to more than 200lx; the effective illuminance, which meets the illuminance range of 300-3000lx and lasts more than 2 hours, is increased from 40% to more than 79%; the uniformity of illuminance is reduced due to the formation of too bright light spots by reflected light, and the probability of daylight glare at the evaluation point of glare is increased to 0.27, but it is still not easy to be detected, and the light-heat effect of "smart mirror" reflected light is obvious, and the temperature of indoor light spot area is raised about 25℃, while the temperature of other areas also increases to some extent. The higher the solar altitude angle is, the lower the cosine efficiency is, and the less radiant energy is obtained by the mirrors.
The above research results show that in old neighborhoods with poor daylighting, "smart mirror" reflective lighting is an effective means to compensate for this, and as a substitute for daylighting, it can transmit daylight to the interior of the house at a small cost, effectively improving its natural lighting.
This study has important implications for improving the living conditions in old neighborhoods.