Graphene aerogel-based phase changing composites for thermal energy storage systems

Abstract

Phase changing materials (PCM) release or absorb heat in high quantity when there is a variation in phase. PCMs show good energy storage density, restricted operating temperatures and hence find application in various systems like heat pumps, solar power plants, electronic devices, thermal energy storage (TES) systems. Though it has extensive usage in such a diverse range of systems, PCMs have some limitations like poor thermal conductivity, susceptibility to leakage during phase transformations. To overcome these shortcomings, phase changing composites (PCCs) were fabricated. PCCs are an amalgamation of filler material with PCMs to form a composite with those anticipated or desired properties. There are multiple factors like porosity, sealing performance, leaking holding capacity, shape stability, thermal conductivity that should be taken into consideration/account while fabricating PCCs. Having considered such factors, graphene, which has high thermal conductivity (2000–4000 W/m K) and high specific surface area (~ 2630 m2 g−1), acts as a suitable candidate for synthesizing an effective and efficient PCC. In its aerogel form, it is used as a conductive filler or form-stabilizer, to improve the thermal conductivity (~ 5.89 W/m K) and heat transfer of PCMs like reduced graphene oxide. Graphene aerogels, thus, are used in PCM as latent heat storage (LHS) for thermal energy storage systems. Many of the researchers have based their work focus on graphene aerogels in PCMs, significant roles of such PCCs, their advantages and disadvantages; this paper is an effort to elucidate those and provide further insight into TES systems in which LHS is explicitly used in PCMs and their practical aspect.