A Comprehensive Evaluation of Water Spray System on Transparent Roof Towards Optimal Operation Schedule

Indoor overheating induced by transparent roofs sharply increases the building energy consumption. Water spray offers a potential solution but requiring effective strategy to balance cooling effects and cost-effectiveness. Aiming at a spray system installed on transparent roof (63.2 x 24.6 m) of a mixed-use building in Guangz-hou, China, this study provides a comprehensive evaluation of multiple strategies including continuous and intermittent operation with different spray/interval time. In sunny weather, continuous spray reduces the exterior, interior surface temperature, and long-wave radiation by 17.5 & DEG;C, 9.6 & DEG;C, and 66.3 W/m2, respectively. Besides, the indoor air temperature, globe temperature, and mean radiant temperature are also lowered by 4.4, 5.2, and 5.7 & DEG;C, respectively. Comparatively, the intermittent spray produces worse cooling effect, the reduction of exterior, interior surface temperature, and long-wave radiation are 9.4-15.9 & DEG;C, 4.1-7.8 & DEG;C, and 24.1-47.7 W/ m2, respectively. The intermittent operating conditions, sorted according to the exterior surface temperature reduction, are ranked as 30/10 > 20/10 > 10/10 > 10/50 > 10/20 min, with the cooling effect not decreasing linearly with interval time, but increasing monotonically with spray time. The air conditioning electricity saved by continuous spray is higher than that by intermittent spray, but the water pump electricity and water con-sumptions are higher as well. Technical-economy evaluation indicates that water consumption is primary cost factor in spray systems and intermittent spray with 10/50 min is the optimal scenario. This study provides in-sights into the economical and efficient operation of transparent roof spray system, and lays a foundation for its smart control.