Enhanced thermal conductivity of waste sawdust-based composite phase change materials with expanded graphite for thermal energy storage

Abstract

Background: With the current rapid economic growth, demands for energy are progressively increasing. Energy shortages have attracted significant attention due to the shrinking availability of non-renewable resources. Therefore, thermal energy storage is one of the solutions that lead to saving of fossil fuels and make systems more cost-effective by the storage of wasted thermal energy. In particular, the application of phase change materials (PCMs) is considered as an effective and efficient approach to thermal energy storage because of the high latent heat storage capacity at small temperature intervals. Nevertheless, leakage problems and low thermal conductivity limit the practical applications of PCMs. Therefore, form-stable phase change materials with high thermal conductivity are urgently needed. Results:A novel form-stable composite phase change material was prepared by incorporating PEG into waste sawdust with 5% EG. In the composites, PEG served as a phase change material, while waste sawdust acted as a carrier matrix. EG was added to help increase the thermal conductivity of the composites. The melting temperature of CPCMs-4 with 5% EG was found to be 58.6 °C with a phase change enthalpy of 145.3 kJ/kg, while the solidifying temperature was 48.5 °C with a phase change enthalpy of 131.4 kJ/kg. The thermal conductivity of CPCMs-4 with 5% EG increased by 23.8% compared with that of CPCMs-4. Moreover, no obvious changes in melting, solidifying temperature, or latent heat after 200 heating-cooling cycles were detected. The supercooling extent of CPCMs-4 with 5% EG decreased by 19.2% compared with PEG. The volume change properties and wettability properties of CPCMs-4 with 5% EG are suitable for thermal energy in terms of practical application. Conclusions:The prepared composites have excellent thermal and form-stable properties and they can be recognized as potential candidates for thermal energy storage as form-stable composite phase change materials. Using simple impregnation techniques with waste sawdust as a supporting material, this study demonstrates an innovative technology for practically and markedly enhancing the adsorption capacity of phase change materials.

Activated biocarbons obtained from lignocellulosic precursors as potential adsorbents of ammonia

“…2b-d). As can be seen, biocarbons obtained from the sawdust maintained the channel structure of the precursor partially (Yang et al, 2017;Borhan et al, 2014). When the individual SEM images are analyzed, there can be seen differences in the structure of biocarbons resulting from different structures of different trees.…”

Use of phase change materials in wood and wood-based composites for thermal energy storage: A Review

“…In conclusion, the prepared PEG/WF composite has potential application as building material for heat storage. Yang et al (2017) impregnated poplar sawdust using PEG to obtain shapestabilized PCM. The resulting composite showed a high latent heat of fusion of 151.1 J/g and a fusion temperature of 58.1 °C.…”

Considering sawdust as a potential raw material for climate change mitigation in indoor environment

“…Sawdust has been shown to have a good structure suitable for water purification processes [15]. Waste sawdust has also been recognized as an absorbent for the removal of dyes, toxic salts, heavy metals, and waste oils from water [16]. According to International Agency for Research on Cancer (IARC) «Wood dust is composed mainly of cellulose (approximately 40-50 %), polyoses, lignin, and a large and variable number of substances of lower relative molecular mass which may significantly affect the properties of the wood» [17].…”