Experimental investigation of top lighting and side lighting solar light pipes under sunny conditions in winter in Beijing

Abstract

Natural light is very important element in the quality of vision. Solar light pipes are effective method to induce sunlight into the room need to be illuminated especially for corridor, some places natural sunlight cannot arrive. Solar light pipes are also effective ways to reduce electricity consumption for lighting; it can transmit sunlight from outdoor to the room without generating excessive heat. The performance of two top lighting solar light pipes and one side lighting solar light pipe were investigated at the same time under sunny conditions in winter in Beijing. The results showed that side lighting solar light pipes have better performance than that of top lighting one. Side lighting light pipe has better performance than top lighting light pipe if there are no shelters around the top dome under sunny conditions in winter in Beijing. Solar altitude is the main reason to give an effect on the performance of light pipes. The experimental results also showed that top lighting solar light pipes with snow type diffuser has better performance compare with the diamond type one. Solar azimuth can also affect the illuminance for whole day to all solar light pipes. So if the sunlight collector can following with the sun, this problem can be resolved, that is, automatic sun trackers are needed, but the cost will become too much at the same time. Different regions and different seasons had to select different types of solar light pipes to achieve maximum output of illuminance in the room. Design of the solar light pipes must adjust measures to local conditions. Solar light pipes will be popularized in the near future in China because have many advantages to improve energy efficiency in buildings.