Waste Thermal Energy Harvesting (III): Storage with Phase Change Materials

Abstract

In last two chapters, both methods to harvest waste thermal energy through the conversion to electricity. In this chapter, energy storage (ES) as an alternative method to harvest waste thermal energy, especially by using phase change materials (PCMs), will be presented.ES, as suggested by the name, is to store a certain form of energy, which thus be used later when necessary. A device that can be used to store any form of energy is generally called an accumulator. There are various forms of energy, commonly including kinetic energy, potential energy (e.g., gravitational or chemical), electrical energy, thermal energy, and so on. All these forms of energy could be stored by using an appropriate method [1,2]. For instance, mechanical energy can be stored by using hydrostorage, compressed air storage, and flywheels, while electrical energy is stored by using various batteries and supercapacitors. Thermal energy storage (TES) is the main content of this chapter.This chapter is arranged as follows. A brief description on various TES conceptions, together with a comparison, will be presented first. Among them, PCMs for TES will be emphasized. After that, PCMs with their classification according to their composition will be discussed. Design criteria, heat transfer phenomena, configuration of various PCM TES systems, which have been reported in open literature, will be summarized. Specific attention will be paid to the exergy analysis. The main applications of the PCM storage systems will be listed, analyzed, and compared. Strategies that have been used to improve the performance of such storage systems will be thoroughly evaluated. It will be ended with concluding remarks and perspectives of development of this technology.

Polyurethane/n-Octadecane Phase-Change Microcapsules via Emulsion Interfacial Polymerization: The Effect of Paraffin Loading on Capsule Shell Formation and Latent Heat Storage Properties

“…If compared to conventional sensible heat storage systems, latent heat storage is more reliable owing to higher energy density storage in the narrow temperature range and absence of heat leakages at any temperature [9]. Among others, certain organic PCMs, e.g., paraffins and fatty acids, possess high melting and freezing enthalpies, a wide range of phase transition temperatures defined by the length of the methylene chain, and durability of thermal properties [10,11]. However, the applicability of bare PCMs is limited, as they are prone to leakages during the solid-liquid transition.…”

Phase-Change Microcapsules with a Stable Polyurethane Shell through the Direct Crosslinking of Cellulose Nanocrystals with Polyisocyanate at the Oil/Water Interface of Pickering Emulsion

“…A significant advantage of latent heat storage with PCMs is a higher density of stored energy in a narrower temperature range, compared with conventional sensible heat storage [3]. Organic PCMs, such as paraffins and fatty acids, can store and release a large amount of latent heat during the melting and crystallization of long methylene chains with a wide range of phase transition temperatures and durability of thermal properties [15,16]. However, organic PCMs are hardly applicable as thermoregulating additives in the pristine form, as they suffer from leakage in the melted state.…”

“…The stable PU shell was achieved through the reaction of cellulose surface hydroxyl groups with polyisocyanate dispersed in the oil phase. Owing to its unique properties, such as large specific Young's modulus, small size (100-200 nm in length and 5-10 nm in cross-section), high aspect ratio (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and amphiphilicity, NCC appears as to be a promising reinforcing agent, rheological modifier and interface stabilizer [29]. Additionally, cellulose is a linear macromolecule composed of repeating rings of β-l,4-linked D-glucose units aggregated by numerous strong intermolecular hydrogen bonds [30].…”