Experimental analysis of a radiant floor system incorporating phase change materials: Thermal performance and energy efficiency

Abstract

The incorporation of Phase Change Materials (PCMs) in radiant floors has the potential to improve the thermal and energy performance of the system. PCMs can act as thermal batteries, providing additional thermal energy storage capacity to Radiant Floor Systems (RFS). However, in the case of wet construction, when PCMs are incorporated into the enveloping mortar surrounding the RFS water pipes, the resulting specific heat and thermal conductivity can pose a challenge to system performance. The objective of this paper is to evaluate the impact that the incorporation of microencapsulated PCM (mPCM) in the RFS mortar has on the thermal and energy performance of the system. To tackle this objective, an experimental setup was constructed consisting of two RFS specimens: one reference and the other with mPCM within an innovative mortar. The two specimens were then tested under different heating strategies controlled by: i) timer, and ii) floor surface temperature setpoint. The thermal performance of the PCM-RFS and operating time were compared with the reference RFS. Timer-controlled intermittent heating has proven beneficial when the heating strategy is established to combine renewable solar energy and off-peak electricity tariffs. Thermal fluctuation was reduced and the PCM phase change process was mobilized twice in 24 h, maintaining surface floor temperatures of the PCM-RFS within comfort levels throughout the test period. When the heat source is controlled by floor surface temperature setpoint, the thermophysical properties of the PCM-RFS led to longer operating times, however mitigating high intermittency of the heat source activations, resulting in more regular operation mode, easier control and avoiding peak heating loads.