Metal fibers-enhanced PCM thermal energy storage unit: An experimental approach on a composite roof application

• A galvanized metal fibers-enhanced PCM unit is investigated experimentally for roof application. • Roof maximum inner surface temperature reduction, attenuation coefficient, and time delay are analyzed. • Thin metal fibers are thermally better than thick fibers. • Up to 78 % attenuation coefficient, and 170 % time delay are attained for the PCM roof-based thin metal fibers. Integrating phase change materials (PCMs) into building elements considerably reduces energy demand and improves indoor thermal comfort. However, PCM's low thermal conductivity limits thermal cycles and slows the melting/solidification rate. Literature studies reported various solutions to enhance PCM performance, including nanoparticle dispersion, fins, shape and form stabilizing, metallic foams, and porous mediums, showing noteworthy advancements. Nevertheless, researchers highlighted some limitations in these enhancers, such as instability and agglomeration of nanoparticles, complex configuration of fins, design concerns, and limited shapes of foams. Therefore, presenting a novel thermal enhancer that could tackle the above limitations and benefit from recycled metals is essential. This research investigates the thermal advancements of immersing galvanized steel metal fibers with 0.1 % by weight into PCM units and shows their influence on a compact composite roof arrangement. To this aim, four experimental roofs are fabricated; one set for referencing, the second equipped with pristine PCM (PPCM), and two roofs equipped with PCM-enhanced metal fibres of different thicknesses (MFPCM1 and MFPCM2). The roof's thermal performance is analyzed in view of maximum inner surface temperature reduction, attenuation coefficient, and time delay for two hot days. Study outcomes showed that immersing thin metal fibers into PCM (i.e., MFPCM1) has improved the roof's thermal performance noticeably, wherein the maximum inner surface temperature reduction, attenuation coefficient, and time delay reached a maximum mark of ∼17 %, 77.8 %, and 170 % over the reference roof. Comparatively, MFPCM2 showed lower advancements than MFPCM1, achieving 16.5 %, 75.6 %, and 150 %, respectively.