Diffusion of Shape Stabilized PEG-SiO2 as a Driver for Producing Thermoregulating Facing Bricks

Abstract

A novel form-stable phase-change material (PCM) based on facing bricks was developed by incorporating thermoregulating PEG-SiO2, synthetized by sol-gel method and based on polyethylene glycol as phase-change material and silica as stabilizer compound. The PEG-SiO2 in its liquid form (sol) is firstly adsorbed inside the porous brick and lastly stabilized (gel) by controlling its gelation time, obtaining form-stable PCMs with PEG-SiO2 contents within 15–110 wt.%. Kinetic adsorption curves of the sol into bricks having different porosities as well as maximum adsorption capacities were obtained. The effective diffusion coefficients (Deff) were estimated by means of Fick’s second law, it being possible to predict the adsorption of sol PEG-SiO2 by the brick as function of its porosity and the free diffusion coefficient. Finally, form-stable PCMs demonstrated an improvement in their thermal energy storage capacity (up to 338%), these materials being capable of buffering the indoor temperature during an entire operational day