A cycling study for reliability, chemical stability and thermal durability of polyethylene glycols of molecular weight 2000 and 10000 as organic latent heat thermal energy storage materials

Abstract

Summary In this experimental study, thermal aging test for investigating the variations in thermal and chemical properties of two selected organic phase change materials (PCMs) has been carried out. Polyethylene glycols (PEGs) of molecular weight of 2000 and 10 000 have been considered as potential latent heat thermal energy storage (LHTES) materials for investigation. The aim of this study is to identify the probable variations in thermal properties and chemical structures of PEGs after melting/freezing cycles repeated for 1500 times. The differential scanning calorimetry (DSC) technique was adopted for measuring the thermal properties such as melting point and latent heat of PCMs. In order to study the variations in PCM's chemical functional groups, Fourier transform infrared (FT‐IR) spectroscopy was used. Thermal durability property after the cycling test was investigated using thermogravimetric analysis. The DSC measurements indicated that PEG2000 experienced a maximum variation of about 4°C in melting point while the latent heat of fusion reduces by 16% after the cycle test. PEG10000 shows a variation of about 0.3°C in melting point and 15% of the latent heat of melting after the entire cycle test. The spectral investigation confirms that there are no variations in the functional groups of selected materials after cycle test, which can be inferred as chemical stability of them. The thermal gravimetric analysis curves show that both PEGs are thermally quite durable as well after such large number of melt/freeze cycles. Thermal cycling results and economic analysis confirm that both PEGs are potential PCMs for passive solar thermal management purposes. Highlights Synthesis of polyethylene glycol‐based binary eutectic mixtures. Accelerated thermal cycle test of eutectic mixtures. Binary mixtures were found chemically stable. Charging/discharging rates of PEG are controlled. Novelty Statement This paper presents the thermal performance of two polyethylene glycols, viz., PEG2000 and PEG10000. These materials were melted and solidified 1500 times for testing their suitability as thermal energy storage materials, and it was found that these materials are stable enough to store solar energy for five years. They found to be suitable for many solar energy storage applications.

Prediction of Thermal Properties and Reliability Testing of Binary Eutectic Mixture of Polyethylene Glycol 2000 and 10000 as Phase Change Materials

“…Since, this capacity is changing over thermal cycling, so as the shifting appears here. Similar deviations in thermal and chemical properties can be found in various literatures [20,[25][26][27][28] which support the integrity of obtained results. Figure 11 and Figure 12 show the TGA curves of EPCM 2 (PEG2000-20% and PEG1000-80%) and EPCM 6 (PEG2000-40% and PEG10000-60%) before and after reliability test.…”

“…[17][18][19] Apart from fatty acids, polyethylene glycols (PEGs) are another class of organic PCMs which offer excellent thermal energy storage properties. [20][21] They are available in various molecular weights and each one of them has a different melting point and latent heat of fusion. This property makes them very attractive to be used as thermal energy storage materials.…”

Development and characterization of form‐stable porous TiO 2 /tetradecanoic acid based composite PCM with long‐term stability as solar thermal energy storage material

“…Every parameter defining the thermal characteristics was measured three times and the average of these values was presented here for better accuracy. The uncertainty of these parameters was calculated by Equation () given in References 2 and 39 and presented in Table 2. where u is the value of uncertainty, x is the measurement of an individual parameter, and x avg is the average of these measurements.…”

“…The only problem with solar energy is its intermittent nature, which can be overcome by storing it in a suitable medium for later use. This can be done in two possible ways, sensible 2,3 and latent heat storage (LHS) 4 . The sensible heat storage devices require a larger space in comparison to thermal storage devices for storing/releasing the same amount of energy as they use phase change materials (PCMs) for storing the latent heat 5 …”

Lignin‐retaining porous bamboo‐based reversible thermochromic phase change energy storage composite material

“…Organic phase change materials with low corrosion and stable performance can be divided into four categories: paraffin, polyethylene glycols, fatty acids and polyhydric alcohols . For example, paraffin has been used as the PCM to prepare the glazed window, polyethylene glycols with different molecular weight has been discussed on the phase change properties, 3‐hydroxy fatty acids could be used as phase change material . And more, among these organic PCMs, polyhydric alcohols have the advantages of high phase change latent heat, high cycle stability and less severe super‐cooling, which have been used as latent heat energy storage materials, and its lower cost is conducive to its wide industrial application .…”