Organic Salts as Intermediate Phase Change Materials
Abstract
The ever-increasing demand of energy storage devices for energy security and sustainability has made it vital to shed light on new technologies based on low-cost renewable resources. Thermal energy is easily harvested from a number of sources but requires storage wherever it is intermittent. Phase change materials (PCM), can effectively use the latent heat of a phase change to store and release large amounts of energy. These can be used as cost-effective, and highly scalable, thermal energy storage devices to provide thermal energy directly to processes, or to power refrigerator/air conditioning systems, hot water heating and space heating in commercial and residential areas. Coupled to Organic Rankine Cycle engines it can also be used to generate electricity. In order to function effectively in the decentralised commercial, domestic or remote area setting at an accessible collector temperature, inexpensive organic salts which typically melt between 150 ¡C Ð 200 ¡C and freeze quickly with minimal supercooling are of interest as phase change materials for this application. These salts are generally chemically stable, non-volatile and non-flammable. Less understood is the molecular features of the molecular anions and cations that give rise to high latent heats of fusion Ð the key property for use as a PCM. In our previous work we developed an ÒIce-like hydrogen-bonded structureÓ hypothesis based on observations of several high latent heat of melting materials that presented an ice-like hydrogen bonding network in their solid state (ice has one of the highest heats of melting known). Thus, we propose here to further investigate this hypothesis across several families of organic salts, in which the cations and anions have been selected to exemplify the role of an ice-like hydrogen bonded network. The properties of these salts can be altered by mixing them, fine-tuning the functional groups of cations and anions, or by increasing the number of hydrogen donor and acceptor sites, thus enabling the synthesis of a large family of PCMs. In order to gain a fundamental understanding of the molecular origins of the properties of these salts, their melting point, vapour pressure, crystal structures, crystallisation kinetics, thermal conductivity and thermal decomposition properties will be investigated and used to develop structure property relationships.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 23, 2018
- Source ID
- W911NF1710586
Entities
People
- Douglas R. MacFarlane
Organizations
- Army Contracting Command
- Monash University
- United States Army