Tubular light pipes （i.e., solar tubes） are modern daylighting devices, which are designed to let confined interior spaces benefit from natural lighting. In tropical country, the use of sunlight for lighting is a ma...Tubular light pipes （i.e., solar tubes） are modern daylighting devices, which are designed to let confined interior spaces benefit from natural lighting. In tropical country, the use of sunlight for lighting is a major concern due to the heat associated with sunlight, which has the potential to increase the cost of cooling, thereby reducing the energy savings from the reduction in lighting load. To investigate the thermal and lighting performance of light pipes, a case study for a seminar room, in which light pipes are installed, is presented. Temperatures for the solar tube （dome and diffuser）, window and room were monitored continuously for 24 h periods. Results from the study indicate that the diffuser was on average 6.68 ~C higher than room temperature on a clear day between 7：00 a.m. and 4：00 p.m., while dome temperature was on average 4.45 ~C higher than diffuser＇s temperature during the same period. This large thermal gradient in the day between dome, diffuser and room can significantly increase the cost of maintaining thermal comfort of 25 ~C, in the room. Another finding was the phenomenon of light pipes acting as a heat pumping the night, because it extracts heat from the room during the night between 7：00 p.m. and 4：00 a.m. This occurred because dome temperature is always smaller than diffuser and room temperature in the night. Therefore, for energy savings to be realized from light pipes, thermal performance must be taken into consideration in the analysis of energy savings from light pipes.展开更多
文摘Tubular light pipes （i.e., solar tubes） are modern daylighting devices, which are designed to let confined interior spaces benefit from natural lighting. In tropical country, the use of sunlight for lighting is a major concern due to the heat associated with sunlight, which has the potential to increase the cost of cooling, thereby reducing the energy savings from the reduction in lighting load. To investigate the thermal and lighting performance of light pipes, a case study for a seminar room, in which light pipes are installed, is presented. Temperatures for the solar tube （dome and diffuser）, window and room were monitored continuously for 24 h periods. Results from the study indicate that the diffuser was on average 6.68 ~C higher than room temperature on a clear day between 7：00 a.m. and 4：00 p.m., while dome temperature was on average 4.45 ~C higher than diffuser＇s temperature during the same period. This large thermal gradient in the day between dome, diffuser and room can significantly increase the cost of maintaining thermal comfort of 25 ~C, in the room. Another finding was the phenomenon of light pipes acting as a heat pumping the night, because it extracts heat from the room during the night between 7：00 p.m. and 4：00 a.m. This occurred because dome temperature is always smaller than diffuser and room temperature in the night. Therefore, for energy savings to be realized from light pipes, thermal performance must be taken into consideration in the analysis of energy savings from light pipes.
