Experimental evaluation of the cooling performance of radiant ceiling panels with thermal energy storage

Demand-side management (DSM) strategies in buildings generally rely on short-term heat storage in structural thermal mass. However, the thermal storage capacity is limited by the available thermal mass as buildings are increasingly built using lightweight technologies. In addition, the structural thermal mass generally has a low heat storage and release rate, limiting the ability to manage building thermal loads. To overcome these limitations, we propose an innovative, flexible cooling system that can be installed in office buildings to replace conventional all-air systems. The system utilizes the high thermal energy storage capacity of macro-encapsulated phase change materials (PCM) discreetly incorporated below the serpentine copper coil of standard radiant ceiling panels (RCP). A walk-in dual climate chamber was used to evaluate experimentally the ability of the RCP-PCM system to shift cooling loads to off-peak hours. In addition, the heat removal capacity rate and the resulting indoor thermal environment improvements are assessed. The measured passive cooling power ranged between 11 W/m2 and 31.4 W/m2, with an average of around 17.3 W/m2. Results indicate that the RCP-PCM system can shift the cooling loads to off-peak hours while maintaining acceptable thermal comfort conditions during work hours (8:00 to 18:00). During the testing period, the system was able to passively absorb heat gains between 180 and 230 Wh/m2 during the day and operate actively only at night during unoccupied periods. This load-shifting capability of the RCP-PCM system can be of great help in planning DSM strategies for increased penetration of renewable electricity in building cooling applications.