Improvement of the Performance of Solar Underfloor Heating System Integrated With Phase Change Material

This theoretical study presents a detailed analysis of a solar-assisted underfloor heating system integrated with a phase change material (PCM) model—Type 1991, applied to the internal wall of a residential building. The objective is to evaluate the thermal and energy performance improvements achieved through PCM integration as compared to traditional systems. To determine the most efficient setup, the simulations are performed using TRNSYS software under various system configurations by adjusting the solar collector area and storage tank volume. The proposed system consists of a flat-plate solar collector, a thermal storage tank, an auxiliary electric heater, and a multizone building fitted with underfloor heating pipes and PCM-treated walls. The PCM model accounts for temperature-dependent thermal properties including specific heat and thermal conductivity, allowing it to absorb and release latent heat and thereby regulate indoor thermal conditions. Simulations are done based on a 100 m² house in Mosul, Iraq using the data of December, January, and February, revealing that the optimal collector area is 24 m², beyond which further increases provide only minimal energy savings. The addition of PCM leads to an increase in indoor air temperatures by 2°C–3°C and hence, improves thermal comfort during cold periods. The results displayed that there is a 30% average reduction in electrical energy consumption. The use of PCM on the floor leads to a reduction in the useful solar collector energy by 15%. The overall solar fraction is increased and thereby, reduces the dependency on external electricity sources. The findings demonstrated that the use of PCM enhances both energy efficiency and thermal comfort, making it a viable approach for sustainable heating in residential buildings.