Lead Performer: Oak Ridge National Lab – Oak Ridge, TN. Partner: Phase Change Energy Solutions – Asheboro, NC.
March 24, 2021
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Lead Performer: Oak Ridge National Lab – Oak Ridge, TN
Partner: Phase Change Energy Solutions – Asheboro, NC
DOE Total Funding: $1,200,000
Cost Share: $300,000
Project Term: October 1, 2020 – September 30, 2023
Funding Type: BENEFIT 2019 Funding Opportunity Announcement
Project Objective
This project will pursue a novel approach to microencapsulate salt hydrate phase change materials (PCMs) with a thermally conductive coating (i.e., 1.0–1.5 W/m•K) using a continuous process that is more controllable than conventional approaches (e.g., emulsification). The diameter of the encapsulated PCM fibrous structures can be controlled from 10 nm to 100 µm, which broadens the opportunities for optimization. The fibrous morphology of encapsulated material is expected to enable the PCM to have a faster charge and discharge rate because of its longer and continuous heat transfer paths when compared to commonly used spherical encapsulation morphologies.
The project aims to identify suitable coating material(s) and optimize the diameter of the fibrous structures that encapsulate the salt hydrates in order to achieve the targeted thermal conductivity of >1.5 W/m•K and energy density (volumetric and gravimetric) of > 100 kWh/m3. Additionally, the coating material composition will be optimized to minimize water vapor permeation and salt hydrate leakage to retain the PCM’s energy density for ≥ 5000 cycles.
Project Impact
Although salt hydrate PCMs are known to have higher energy densities and lower costs compared to organic PCMs (e.g., paraffin), the main technical challenge that hinders their widespread use is that there is no widely accepted encapsulation strategy. Encapsulation of salt hydrates by conventional approaches, such as emulsification and in-solution polymerization, are highly challenging because salts are hydrophilic in nature. Moreover, these approaches generally have low yields, the encapsulation material is a thick polymer with low thermal conductivity (i.e., ≈ 0.15 W/m•K), and the encapsulation process has few options for composition control. Our approach will address most of these challenges by using a coating with a higher thermal conductivity (i.e., 1.0–1.5 W/m•K), and enabling increased control of coating composition and thickness. This new approach to encapsulate salt hydrate PCMs could be a foundational technology that is applicable to the encapsulation of other types of PCMs.
Contacts
DOE Technology Manager: Sven Mumme
Lead Performer: Jaswinder Sharma, Oak Ridge National Laboratory