Nanoparticle enchanced salt hydrate eutectic phase change material for thermal energy regulation in buildings

Abstract

Global energy storage trends are emerging as the energy market shifts from fossil fuels to renewable energy for electrification. Meanwhile, the indoor thermal conditions of buildings and offices are inversely proportional to the quantity of energy consumed and CO2 emitted. To reduce the energy consumption in thermal conditioning of buildings, phase change materials (PCM)s are predominant owing to their energy storage capability and passive operation. Inorganic salt hydrate PCMs are recognized as high energy storage materials with less toxicity, non-flammable nature and economically viable than organic PCMs. However, inherent thermal characteristics, low energy storage potential of PCM with low temperature, and degree of supercooling associated with salt hydrate are of utmost concern, which is resolved via tailored eutectic PCM. This encourages investigation and development of new type of inorganic-inorganic eutectic phase change material (EPCM). Nanoparticles are dispersed to enhance the thermal features and thermal reliability. Subsequently, substantial research is underway to investigate the performance of unique dimensioned nanoparticles in conjunction with PCM. Herein, the main objective of this research was to develop and evaluate the potential of an inorganic salt hydrate nanocomposite EPCM, intended for passive thermal regulation of buildings towards sustainable future. To achieve this objective, four inorganic salt hydrate with low melting temperature were selected to formulate 21 different combinations of EPCM adopting the Schrader equation. Among them, binary combination of 62% of sodium sulphate decahydrate (SSD) and 38% of sodium phosphate dibasic dodecahydrate (SPDD) displayed eutectic melting temperature of 27.6°C, eutectic melting enthalpy of 216 J/g and thermal conductivity of 0.464 W/m⋅K. Subsequently, 1D multi-walled carbon nanotube (MWCNT) and 2D graphene nanoplatelets (GNP); lab synthesised 2D nanomaterial MXene, 3D nano-sized tetrapods (thin-arms and thick-arms), and 3D ecofriendly coconut shell biochar were dispersed with EPCM individually to identify the suitable nanocomposite. Phase transition temperature, thermal conductivity, energy storage, degree of supercooling, chemical stability, optical absorbance & transmittance and corrosion analysis of the developed nanocomposite EPCMs are experimentally characterised. Nanocomposites EPCM improved thermal conductivity by 106.1% (0.956 W/m⋅K with 1.2 wt.% of GNP), optical absorbance by 746.15% (1.1 wt.% of MXene), reduction in degree of supercooling by 91.1% (0.9 wt.% of MWCNT). Thermal properties of superior nanocomposites EPCMs are used as input parameter via Type1270 PCM layer in TRNSYS simulation studio to analyse the variation in heating and cooling load of building integrated with PCM. On integrating 2 cm thickness of SSD/SPDD+GNP EPCM layer within the ceiling/roof of study space, cooling load for climatic condition of Kuala Lumpur and New Delhi decreases by 38.8% and 30.5%. Integration of nanocomposite EPCM with building structures assists passive thermal regulation with better thermal conditions for occupants. Furthermore, real-time experimental investigation on nanocomposite EPCM integrated constructions is needed to assess the real-time performance of building thermal comfort. Research presented in this thesis significantly contributes towards the sustainable development goal of SDG-07 (Affordable and Clean energy) in specific to target SDG-7.3 by facilitating improved energy efficiency; and SDG11 (Sustainable Cities and Communities) in specific to target 11.c by constructing sustainable and resilient building