Shape-Stabilized Phase Change Materials for Solar Energy Storage: MgO and Mg(OH)2 Mixed with Polyethylene Glycol

Abstract

Heat energy storage systems were fabricated with the impregnation method using MgO and Mg(OH)2 as supporting materials and polyethylene glycol (PEG-6000) as the functional phase. MgO and Mg(OH)2 were synthesized from the salt Mg(NO3)·6H2O by performing hydrothermal reactions with various precipitating agents. The precipitating agents were NaOH, KOH, NH3, NH3 with pamoic acid (PA), or (NH4)2CO3. The result shows that the selection of the precipitating agent has a significant impact on the crystallite structure, size, and shape of the final products. Of the precipitating agents tested, only NaOH and NH3 with PA produce single-phase Mg(OH)2 as the as-synthesized product. Pore size distribution analyses revealed that the surfaces of the as-synthesized MgO have a slit-like pore structure with a broad-type pore size distribution, whereas the as-synthesized Mg(OH)2 has a mesoporous structure with a narrow pore size distribution. This structure enhances the latent heat of the phase change material (PCM) as well as super cooling mitigation. The PEG/Mg(OH)2 PCM also exhibits reproducible behavior over a large number of thermal cycles. Both MgO and Mg(OH)2 matrices prevent the leakage of liquid PEG during the phase transition in phase change materials (PCMs). However, MgO/PEG has a low impregnation ratio and efficiency, with a low thermal storage capability. This is due to the large pore diameter, which does not allow MgO to retain a larger amount of PEG. The latent heat values of PEG-1000/PEG-6000 blends with MgO and Mg(OH)2 were also determined with a view to extending the application of the PCMs to energy storage over wider temperature ranges.

Preparation of a Sustainable Shape-Stabilized Phase Change Material for Thermal Energy Storage Based on Mg2+-Doped CaCO3/PEG Composites

“…The pure PEG has a melting enthalpy value of 221.3 J/g, while its freezing enthalpy is 201.0 J/g. Almost the same high enthalpy value has been reported by Liu et al [44] and Zahir et al [45]. The composite samples P-5-MCC, P-10-MCC, and P-15-MCC display an apparent melting enthalpy (computed considering the mass of the matrix) [13] or impregnation ratio (R) [22] of 70.94%, 80.43%, and 66.09%, respectively.…”

“…As a support material CaCO 3 alone is not suitable for encapsulation of PCMs because of the high supercooling. However, as per recently published studies [17,28,45], the encapsulation of PEG-6000 in CaCO 3 does not reveal the claimed characteristics and/or synergistic properties. Furthermore, literature indicates that the impact of PEG on CaCO 3 as a PCM has not been explored adequately.…”

Two-Step Triethylamine-Based Synthesis of MgO Nanoparticles and Their Antibacterial Effect against Pathogenic Bacteria

“…Figure 7 a shows the Fourier-transform infrared spectra (FTIR) obtained for the PM; the obtained signals correspond to those reported for the stabilizing PEI, the TEA base, and magnesium acetate. The sharp and strong peak at 3700 cm −1 is attributed to the stretching mode of the OH group [ 72 , 73 ]. There is a band from 3550 symmetric mode to 3120 cm −1 asymmetric mode which corresponds to the secondary amines of the PEI, an asymmetric mode of C–H at 2922 cm −1 (TEA), two symmetric vibrations of –CH 2 in PEI at 2843 and 2787 cm −1 , and two vibration peaks at 1656 and 1107 cm −1 associated to the secondary and tertiary amines of the PEI and TEA, respectively.…”

Design of three‐dimensional interconnected porous hydroxyapatite ceramic‐based composite phase change materials for thermal energy storage

“…26 Zahir et al used MgO and Mg(OH) 2 for supporting PEG to make a CPCM with an encapsulation rate of 60.9%. 27 Deng et al prepared PEG-Ag/EVM PCM, the thermal conductivity and latent heat of which were 0.68 W/mÁK and 96.4 J/g, respectively. 28 In general, the suitability of a material as a phase change material packaging matrix depends on its pore structure.…”

“…Zhang et al announced a composite phase change material (CPCM) produced by encapsulating PEG into Ag nanoparticle‐modified graphene nanosheets, which achieved photothermal conversion 26 . Zahir et al used MgO and Mg(OH) 2 for supporting PEG to make a CPCM with an encapsulation rate of 60.9% 27 . Deng et al prepared PEG‐Ag/EVM PCM, the thermal conductivity and latent heat of which were 0.68 W/m·K and 96.4 J/g, respectively 28 .…”